engine and drivetrain Rough Idle

[jjbunn]

Here's another idle problem video 

 

1) New plugs

2) New wires

3) New distributor rotor

4) New distributor cap

5) Valve lash adjusted .007

6) Timing set static

7) Carb refurbished 

 

The valve lash was adjusted with the engine cold.

 

The idle rate and idle mixture adjustments on the carb were set as best I could given the unevenness of the idle.

 

The wires are in the correct order: 1-3-4-2 going clockwise looking at the top of the dizzy.

 

I checked for vacuum leaks around the intake manifold, but can't detect any. The vacuum gauge on the manifold shows good vacuum (around 20 mmHg).

 

I've tried rotating the dizzy to try to improve the running, but with no luck.

 

If it's not clear from the video, the idle is hunting up and down, from about 1000rpm to 1500rpm. The engine is shaking, as if there is a misfire (perhaps there is).

 

I'm struggling with this - the engine used to run reasonably smooth when I first got the car, as far as I remember (it's been a while!).

 

[Mike Self]

At least in your video, the valves sound kinda noisy...given that (slightly) noisy valves don't burn, what did you adjust 'em to?  The standard is .006-008.  I use a "go/no-go" routine--I use a .007 gauge to set the clearance, then try an .008 feeler; if it won't pass through the gap, I have it right.  If it does, I adjust it again. 

 

But as my late and much-missed father-in-law used to say, "Mike, 90% of your carburetor problems are in the ignition"  so make sure the whole ignition system is up to snuff before delving into the fuel system.

 

cheers

mike

[jjbunn]

At least in your video, the valves sound kinda noisy...given that (slightly) noisy valves don't burn, what did you adjust 'em to?  The standard is .006-008.  I use a "go/no-go" routine--I use a .007 gauge to set the clearance, then try an .008 feeler; if it won't pass through the gap, I have it right.  If it does, I adjust it again. 

 

But as my late and much-missed father-in-law used to say, "Mike, 90% of your carburetor problems are in the ignition"  so make sure the whole ignition system is up to snuff before delving into the fuel system.

 

cheers

mike

Thanks, Mike - as said in my post, the clearances were set to .007. Maybe I should re-check them.

 

I'd like to eliminate the ignition system, which is why I did all the replacements mentioned (plugs, coil, rotor etc.) (But I haven't replaced the coil.)

[Roland]

Here's another idle problem video 

 

1) New plugs

2) New wires

3) New distributor rotor

4) New distributor cap

5) Valve lash adjusted .007

6) Timing set static

7) Carb refurbished 

 

The valve lash was adjusted with the engine cold.

The idle rate and idle mixture adjustments on the carb were set as best I could given the unevenness of the idle.

The wires are in the correct order: 1-3-4-2 going clockwise looking at the top of the dizzy.

I checked for vacuum leaks around the intake manifold, but can't detect any. The vacuum gauge on the manifold shows good vacuum (around 20 mmHg).

I've tried rotating the dizzy to try to improve the running, but with no luck.

 

I'm struggling with this - the engine used to run reasonably smooth when I first got the car, as far as I remember (it's been a while!).

 

 

Following MIke's hypothesis, what do your plugs look like and what heat range are they?  Static timing is only helpful as a starting point and does not address potential distributor problems, including the condition and overall function of your advance mechanisms.  As your distributor's advance is or should be dynamic, unless you know all of its variables, it should be tested dynamically.  (But, as nice as it would be to have a distributor machine or even a timing light with advanced features, neither is absolutely necessary.)  

 

This leaves 10%.

 

Decent vacuum readings suggest no compression issues.  This being the case, your idle mixture is probably too lean.  If plug reading is not revealing enough for you, exhaust sniffing is always a good idea.  But as with dynamic timing, exhaust analysis is helpful but not absolutely necessary.

 

There are a lot of variables when it comes to  - carburettors.  Refurb sounds like pure puffery.  It tells me nothing, other than the fuel bowl may contain less contaminants than it once did and the exterior is probably clean.  Even if the refurb was perfectly performed by Edoardo Weber, unless the carb is jetted properly for your application, you still may have operational complaints.

 

What jets are you running?  If you want to try a shortcut, What is your idle jet number for the primary side of the carburettor?  Sight unseen I would consider going one or two steps larger.  This may resolve your idle issue without addressing other unknown mixture issues.

 

hth

[jjbunn]

Following MIke's hypothesis, what do your plugs look like and what heat range are they?  Static timing is only helpful as a starting point and does not address potential distributor problems, including the condition and overall function of your advance mechanisms.  As your distributor's advance is or should be dynamic, unless you know all of its variables, it should be tested dynamically.  (But, as nice as it would be to have a distributor machine or even a timing light with advanced features, neither is absolutely necessary.)  

 

This leaves 10%.

 

Decent vacuum readings suggest no compression issues.  This being the case, your idle mixture is probably too lean.  If plug reading is not revealing enough for you, exhaust sniffing is always a good idea.  But as with dynamic timing, exhaust analysis is helpful but not absolutely necessary.

 

There are a lot of variables when it comes to  - carburettors.  Refurb sounds like pure puffery.  It tells me nothing, other than the fuel bowl may contain less contaminants than it once did and the exterior is probably clean.  Even if the refurb was perfectly performed by Edoardo Weber, unless the carb is jetted properly for your application, you still may have operational complaints.

 

What jets are you running?  If you want to try a shortcut, What is your idle jet number for the primary side of the carburettor?  Sight unseen I would consider going one or two steps larger.  This may resolve your idle issue without addressing other unknown mixture issues.

 

hth

A lot of useful advice here: thanks.

 

1) Vacuum advance mechanism on the dizzy is working in that I can suck on it and the plate moves 

2) The plugs are brand new NGK BP6ES ... I haven't extracted them since gapping and installing them, but will take a look.

3) For the carb, I bought a refurb kit from Weber, completely disassembled the carb, cleaned, and replaced all the parts from the refurb kit.

4) I don't know what jets are in there, and haven't changed them. Since the engine used to run alright before, then unsuitable jets seems a long shot.

 

Having said all that, I do suspect I've screwed something up carb-wise.

 

Can I still dynamic time the ignition (with my adjustable advance timing light) with the idle hunting around as it is? I haven't tried, because just experimentally slowly twisting the dizzy doesn't improve the idle at all.

 

Thanks again for the advice. 

[Roland]

A lot of useful advice here: thanks.

 

1) Vacuum advance mechanism on the dizzy is working in that I can suck on it and the plate moves 

2) The plugs are brand new NGK BP6ES ... I haven't extracted them since gapping and installing them, but will take a look.

3) For the carb, I bought a refurb kit from Weber, completely disassembled the carb, cleaned, and replaced all the parts from the refurb kit.

4) I don't know what jets are in there, and haven't changed them. Since the engine used to run alright before, then unsuitable jets seems a long shot.

 

Having said all that, I do suspect I've screwed something up carb-wise.

 

Can I still dynamic time the ignition (with my adjustable advance timing light) with the idle hunting around as it is? I haven't tried, because just experimentally slowly twisting the dizzy doesn't improve the idle at all.

 

Thanks again for the advice. 

 

More advice, but of questionable usefulness.

To recap, your only concern was idle and you did not mention part or full throttle operation.  Sounds as though you have most of the bases covered.  As you know, it takes only a tiny turn of the mixture screw or a leaky spark plug lead to significantly impact engine performance.

When you mentioned static timing I took that to mean not using a timing light.  Sure, you can use a timing light if the engine is "under the weather."  Your results may be problematic, because an ignition issue could cause misfiring and erratic timing marks.  That said, I doubt your problem is specifically ignition timing related and as things progress it's easy enough to recheck and adjust.  It is good that your vacuum advance holds a vacuum, but that is separate from a worn or poorly adjusted vacuum advance linkage, or a loose/worn points plate or any defects or wear in the centrifugal advance mechanism.  While a worn or maladjusted distributor can affect idle, I do not think that is your problem.

Conventional wisdom also agrees with BP6ES is a good start.  Plugs gapped correctly?  (Hint: a wider gap places additional stress on the system, but wider gaps also tend to better ignite lean mixtures.)

Since the only thing you made any major mods to is the carburetor, I would look there.  You did not disclose how far you went in your carb rebuild.  Interpretations vary, but some think removal or replacement of the top or bottom gasket constitutes a rebuild.  Others contend the complete carb needs disassembly, including the throttle plates and shafts, and all jets and emulsion tubes.  My guess is that you used most of the parts in the kit, and this typically includes gaskets, needle and seat, and a power valve (at bottom of bowl.)  Webers are pretty forgiving, but if you left some debris in the circuitry or a jet was inadvertently switched, or the float settings were dramatically changed, any or all of these things can affect the carb's calibrations and engine performance.  Likewise, if the kit contains a slightly different gasket than the one with which you started, or a gasket is designed to fit one way, but it is flipped, this can also cause difficult-to-diagnose running issues.

You mention using a vacuum gauge.  If the engine is hunting I would expect to see an unsteady vacuum reading.  If the vacuum is high despite the hunting, I wonder if your throttle plates are open beyond where they should be at idle.  This could cause the engine to bypass part of the idle circuit.  Also, while I haven't consulted the recommended instructions for many years, the rule of thumb was that the mixture screw should be set to approximately 1.5 turns out.  A significant deviation generally indicates the wrong idle jet size.  A mixture screw setting more than 2.5  turns out generally indicates an idle jet that is too small - causing a lean condition.  Conversely, when the best idle is achived with the mixture screw at less than 1.5 turns out, the jet is probably large, causing a rich condition.  Is your mixture screw turned out more than 1.5 turns?

Still another possibility is that you have everything squared away, exactly as before - but you only think the engine idled smoother than it does now.  I was recently at a gathering of exotic car buffs where a new owner was describing how great his car ran.  It did run great until he had a chance to compare it with a simiilar car.  He was shocked to discover how much smoother another engine ran.  My point is that you may have always had a fair running car that still had a decent but less than perfect idle.  A hunting and rough idle can be caused by many things mentioned, but it is primarily symptomatic of a lean mixture.  The proof might be increasing the size of the primary idle jet which affects both idle and part throttle running.

Most, but not all Weber 32/36 DGV carbs are equipped with idle solenoids. Since I don’t see either the solenoid or a wire protruding from the side of the carb in your picture, I am assuming you do not have one.   If you are not using an idle solenoid, this would suggest the same style idle jet is employed in both the primary and secondary side of the carb.  Most often the 32/36 DGV's are equipped with the same size idle jets for both barrels.  However unlikely, it is possible to have different sized jets and maybe, you mixed the two.  If you are using an idle solenoid, you didn't/couldn’t confuse the two idle jets.

Best of luck.

Edited August 9, 2013 by Roland

[jjbunn]

More advice, but of questionable usefulness.

To recap, your only concern was idle and you did not mention part or full throttle operation.  Sounds as though you have most of the bases covered.  As you know, it takes only a tiny turn of the mixture screw or a leaky spark plug lead to significantly impact engine performance.

When you mentioned static timing I took that to mean not using a timing light.  Sure, you can use a timing light if the engine is "under the weather."  Your results may be problematic, because an ignition issue could cause misfiring and erratic timing marks.  That said, I doubt your problem is specifically ignition timing related and as things progress it's easy enough to recheck and adjust.  It is good that your vacuum advance holds a vacuum, but that is separate from a worn or poorly adjusted vacuum advance linkage, or a loose/worn points plate or any defects or wear in the centrifugal advance mechanism.  While a worn or maladjusted distributor can affect idle, I do not think that is your problem.

Conventional wisdom also agrees with BP6ES is a good start.  Plugs gapped correctly?  (Hint: a wider gap places additional stress on the system, but wider gaps also tend to better ignite lean mixtures.)

Since the only thing you made any major mods to is the carburetor, I would look there.  You did not disclose how far you went in your carb rebuild.  Interpretations vary, but some think removal or replacement of the top or bottom gasket constitutes a rebuild.  Others contend the complete carb needs disassembly, including the throttle plates and shafts, and all jets and emulsion tubes.  My guess is that you used most of the parts in the kit, and this typically includes gaskets, needle and seat, and a power valve (at bottom of bowl.)  Webers are pretty forgiving, but if you left some debris in the circuitry or a jet was inadvertently switched, or the float settings were dramatically changed, any or all of these things can affect the carb's calibrations and engine performance.  Likewise, if the kit contains a slightly different gasket than the one with which you started, or a gasket is designed to fit one way, but it is flipped, this can also cause difficult-to-diagnose running issues.

You mention using a vacuum gauge.  If the engine is hunting I would expect to see an unsteady vacuum reading.  If the vacuum is high despite the hunting, I wonder if your throttle plates are open beyond where they should be at idle.  This could cause the engine to bypass part of the idle circuit.  Also, while I haven't consulted the recommended instructions for many years, the rule of thumb was that the mixture screw should be set to approximately 1.5 turns out.  A significant deviation generally indicates the wrong idle jet size.  A mixture screw setting more than 2.5  turns out generally indicates an idle jet that is too small - causing a lean condition.  Conversely, when the best idle is achived with the mixture screw at less than 1.5 turns out, the jet is probably large, causing a rich condition.  Is your mixture screw turned out more than 1.5 turns?

Still another possibility is that you have everything squared away, exactly as before - but you only think the engine idled smoother than it does now.  I was recently at a gathering of exotic car buffs where a new owner was describing how great his car ran.  It did run great until he had a chance to compare it with a simiilar car.  He was shocked to discover how much smoother another engine ran.  My point is that you may have always had a fair running car that still had a decent but less than perfect idle.  A hunting and rough idle can be caused by many things mentioned, but it is primarily symptomatic of a lean mixture.  The proof might be increasing the size of the primary idle jet which affects both idle and part throttle running.

Most, but not all Weber 32/36 DGV carbs are equipped with idle solenoids. Since I don’t see either the solenoid or a wire protruding from the side of the carb in your picture, I am assuming you do not have one.   If you are not using an idle solenoid, this would suggest the same style idle jet is employed in both the primary and secondary side of the carb.  Most often the 32/36 DGV's are equipped with the same size idle jets for both barrels.  However unlikely, it is possible to have different sized jets and maybe, you mixed the two.  If you are using an idle solenoid, you didn't/couldn’t confuse the two idle jets.

Best of luck.

 

Thanks for sticking with me on this!

 

Update: something surprising that makes me think I have something wrong in the ignition after all. I swapped #3 and #2 leads at the distributor cap, as an experiment (suggested in the Weber troubleshooting guide) - and the engine ran (much to my surprise) but idling somewhat more roughly than before and at lower revs (about 1000rpm). 

 

How can this be?!

 

Somebody told me I have a "reverse points dizzy", I'm not sure what that means, but does it affect how static timing is performed?

 

What to do next? I'm losing all confidence 

 

(BTW I did look at the jet sizes: the idle jets are both 50. The primary air corrector jet is 170, and the secondary is 175.)

[Roland]

Thanks for sticking with me on this!

 

Update: something surprising that makes me think I have something wrong in the ignition after all. I swapped #3 and #2 leads at the distributor cap, as an experiment (suggested in the Weber troubleshooting guide) - and the engine ran (much to my surprise) but idling somewhat more roughly than before and at lower revs (about 1000rpm). 

 

How can this be?!

 

Somebody told me I have a "reverse points dizzy", I'm not sure what that means, but does it affect how static timing is performed?

 

What to do next? I'm losing all confidence 

 

(BTW I did look at the jet sizes: the idle jets are both 50. The primary air corrector jet is 170, and the secondary is 175.)

 

Hang in there.

 

I am not familiar with the Weber Troubleshooting Guide, but I can only guess that the purpose of lead swapping is to possibly determine whether each cylinder is firing or a hit or miss attempt to establish whether the distributor leads are in the correct firing order.  It seems as though you established that you started with the leads being in the correct order and you should return to that setup.

The fact that the engine runs with two wires crossed is not that surprising.  You have two other cylinders that are working to turn the engine.  You may be getting partial combustion in the crossed wire cylinders.  Bet you would not be happy putting the engine under a load and driving it on two or three cylinders.  As I said before, it does not take much to alter a decent running engine.  

Reverse points distributor?  Guess it depends upon who’s asking and the style of distributor they are using.  Timing is not affected.  There were many different variants to the Bosch 4cylinder points-equipped distributor, and among other things this involves the design and mounting of the ignition points.  To the best of my knowledge, points came in two different hand shakes (below).  However configured, they peform the same basic function being activated by the distributor cam.  Timing is set the same, regardless of point style.  (see below)

 

 

What to do next?  Reinstall the plug wires in the proper sequence, so that the engine is running moderately well.  You can always go back to basics and recheck your settings as you would with any major tune up.  For a rough idle with a properly jetted carb, I might be inclined to use a larger valve lash setting of .008".  But my hunch remains that your idle will improve by increasing the primary idle jet size to 55 or 60. (In the good old days you could drill the jet larger, but that was also when replacement jets were plentiful and very inexpensive.)   Each engine is a little different, and that includes different states of tune and condition, so there is plenty of room to maneuver.  But as a baseline, Creighton’s jetting recommendations are a good place to start.

Primary barrel: idle jet 60  main jet 140 air correction jet 145

Secondary barrel: idle jet 55; main jet 170; air correction jet 175

Float level: 40mm

Edited August 10, 2013 by Roland

[mike472]

Here is something to try. Tighten the screw holding your condenser to the body of the distributor. I had a problem with a general misfire that drove me crazy that sounded for all intents and purposes like your video and I spotted it by poking my screwdriver into the space between the condenser and distributor body and low and behold, I sees a spark! Engine immediately stops misfiring while I'm holding my screwdriver jammed in there. Now I had to turn the distributor around to access the screw, but once tightened, the misfire went away and the was engine running smooth again. Like Mr Pugh says: 90% of your carb problems are in the ignition

Mike

[jjbunn]

Hang in there.

 

I am not familiar with the Weber Troubleshooting Guide, but I can only guess that the purpose of lead swapping is to possibly determine whether each cylinder is firing or a hit or miss attempt to establish whether the distributor leads are in the correct firing order.  It seems as though you established that you started with the leads being in the correct order and you should return to that setup.

The fact that the engine runs with two wires crossed is not that surprising.  You have two other cylinders that are working to turn the engine.  You may be getting partial combustion in the crossed wire cylinders.  Bet you would not be happy putting the engine under a load and driving it on two or three cylinders.  As I said before, it does not take much to alter a decent running engine.  

Reverse points distributor?  Guess it depends upon who’s asking and the style of distributor they are using.  Timing is not affected.  There were many different variants to the Bosch 4cylinder points-equipped distributor, and among other things this involves the design and mounting of the ignition points.  To the best of my knowledge, points came in two different hand shakes (below).  However configured, they peform the same basic function being activated by the distributor cam.  Timing is set the same, regardless of point style.  (see below)

 

 

What to do next?  Reinstall the plug wires in the proper sequence, so that the engine is running moderately well.  You can always go back to basics and recheck your settings as you would with any major tune up.  For a rough idle with a properly jetted carb, I might be inclined to use a larger valve lash setting of .008".  But my hunch remains that your idle will improve by increasing the primary idle jet size to 55 or 60. (In the good old days you could drill the jet larger, but that was also when replacement jets were plentiful and very inexpensive.)   Each engine is a little different, and that includes different states of tune and condition, so there is plenty of room to maneuver.  But as a baseline, Creighton’s jetting recommendations are a good place to start.

Primary barrel: idle jet 60  main jet 140 air correction jet 145

Secondary barrel: idle jet 55; main jet 170; air correction jet 175

Float level: 40mm

 

Thanks, Roland. I'm going to go with your hunch and order a couple of idle jets: 60 and 55.

 

While waiting for those, I set the timing with a timing light on #1 plug wire - I got the ball lined up at 1400 rpm with the dizzy vacuum plugged, but it was dancing around.

 

At that point I decided to pull the dizzy and take a look - I'll post about what I found in a separate thread 

Here is something to try. Tighten the screw holding your condenser to the body of the distributor. I had a problem with a general misfire that drove me crazy that sounded for all intents and purposes like your video and I spotted it by poking my screwdriver into the space between the condenser and distributor body and low and behold, I sees a spark! Engine immediately stops misfiring while I'm holding my screwdriver jammed in there. Now I had to turn the distributor around to access the screw, but once tightened, the misfire went away and the was engine running smooth again. Like Mr Pugh says: 90% of your carb problems are in the ignition

Mike

Thanks, Mike.

 

I'm running a Pertronix, so no condenser. But your suggestion made me think, and so I pulled the dizzy to take a closer look - subject of another thread.

[jjbunn]

I cleaned up and fixed the distributor issues, replaced it in the same orientation, and ran the engine again.

 

No noticeable change. I was hoping that I would at least get some improvement!

 

I ran the engine for about 20 minutes, revving it up and down, and then pulled the plugs. These are new plugs, and they all look like this:

 

 

I'm not any good at reading plugs, but doesn't this look like too rich a mixture? Somewhat sooty and wet.

[Guest_anonymous]

http://www.4secondsflat.com/Spark_plug_reading.html

 

http://www.4secondsflat.com/plug_chart.html

Edited August 11, 2013 by daron

[Guest_anonymous]

Fix the distributor first. the ball should be steady. the distributor post shows your dizzy needs a little internal R&R. maybe a hotter plug like a BP5ES. a longer video with a fixed position camera. Cam or no cam ? Vacuum gauge pressure- what is the rhythm of the vacuum ? coupled with compression and leak down tests. Is the carb float correct height? break booster check valve correct orientation? can you narrow it down to a particular cylinder by removing an HT lead one at a time.

On "reverse" points...as you see the PO didn't purchase the correct pertronix unit and had to wrap the wires around the center shaft causing a potential long term viability issue of the pertronix issue. Last time I pointed this out to someones dizzy picture I had the response..."It works"

but now I searched and realized that was your post from March http://www.bmw2002faq.com/topic/138580-pertronix-sensor-wire-rub/

[Roland]

I cleaned up and fixed the distributor issues, replaced it in the same orientation, and ran the engine again.

No noticeable change. I was hoping that I would at least get some improvement!

I ran the engine for about 20 minutes, revving it up and down, and then pulled the plugs. These are new plugs, and they all look like this:

 

I'm not any good at reading plugs, but doesn't this look like too rich a mixture? Somewhat sooty and wet.

 

 

To my tired old eyes, your plug looks fouled with a combination of oil and fuel deposits, in other words, incomplete combustion. This could be caused by a lot of things, including retarded ignition timing, lugging an engine in high gear and improper spark plug heat range.  This occurance is also not unusual if you have been doing a lot of tinkering, and this includes swapping spark plug leads and squirting carb cleaner in every direction.   Since you have not fully disclosed the condition of your engine, at least not in this thread, is it possible the combustion chambers are laden with deposits that have been loosened up with your latest handiwork?  (I might have suspected a crankcase blow-by issue, but for your picture showing no connection from the valve cover breather and the carb.)  How did the the plugs you replaced look?  Dry and worn or wet with deposits?  Those old plugs may be able to tell you a lot.    How many miles on your engine?  Does it consume any noticeable amounts of oil?  Do you have any recent compression numbers?  (None of this information is a necessity, but the more you know, . . . is generally a good thing.)

 

Looking at the plugs after twenty minutes of spirited driving might give you a fair indication of engine health.  So might a .25  mile run, if the engine was built specifically for that purpose.   But you mention twenty minutes of engine "running."  That is not necessarily the same thing,  If you are constantly throttling up the unloaded engine, you are engaging the accelerator pump and flooding addiitional fuel to the cylinders - which is a naturally rich condition.       

 

I just read Daron's post and agree with his suggestion about double checking the distributor and the possibility of low temperature fouling, meaning you might consider a hotter heat range plug - as suggested a BP5ES.  (I have run both numbers on my '02s going mostly with the "5s" when the majority of the driving is city traffic as opposed to the open road.  The '5s tend to look extremely white (as in overheated) on my cars after long hightway trips.  The "6s" tend to look tan and the engines are less prone to pinging on pump gas with the cooler plugs.)  There is no question that a worn distributor, or one with a gummed up centrifugal advance can impact the full range of engine operation.  To be clear, I was only focusing on your rough idle, as you did not mention any other engine issues.  Of course you should have a rock steady timing mark, but if misfiring is present, it can cause an erratic mark.  Since the idle circuit affects idle as well as low speed part throttle operation, inclusive of 1400 rpm, some mark jumping is understandable.  However, the mark should be stable at higher rev ranges.  Did you have a rock-steady timing mark before the tuneup and carb rebuild?

 

if your engine is past its prime, (not saying that it is) and carburetion is determined not to be a primary issue, you might consider employing the "Big Dog" timing method mentioned early on in this forum.  Recommended timing settings are great as a baseline for most fresh, up-to-spec M10 engines,  but so many engines in 40+ yo cars can't claim that mantle.  

 

hth

 

http://www.bmw2002faq.com/topic/44252-retarded-newbie-sees-the-light/

Edited August 11, 2013 by Roland

[jjbunn]

Fix the distributor first. the ball should be steady. the distributor post shows your dizzy needs a little internal R&R. maybe a hotter plug like a BP5ES. a longer video with a fixed position camera. Cam or no cam ? Vacuum gauge pressure- what is the rhythm of the vacuum ? coupled with compression and leak down tests. Is the carb float correct height? break booster check valve correct orientation? can you narrow it down to a particular cylinder by removing an HT lead one at a time.

On "reverse" points...as you see the PO didn't purchase the correct pertronix unit and had to wrap the wires around the center shaft causing a potential long term viability issue of the pertronix issue. Last time I pointed this out to someones dizzy picture I had the response..."It works"

but now I searched and realized that was your post from March http://www.bmw2002faq.com/topic/138580-pertronix-sensor-wire-rub/

Yes, the wires had rubbed, as shown by the photo in that post, and it's true that it works   The dizzy is now sorted, at least temporarily until I get a replacement from Ken. At that point I may replace the Pertronix.

 

I'm afraid I don't always understand some of the jargon, like "reverse points". E.g. I'm not clear what you mean by "cam or no cam"?

 

The vacuum rhythm: do you mean the frequency at which the idle speed drops and rebounds? I'd say it's about every couple of seconds.

 

Yes, the brake booster valve is in the correct way (and there is a good vacuum on the brake booster).

 

I need to:

a) check the float height in the carb

check each HT lead in turn

c) take a longer, steadier video

d) take another look at the timing since the distributor was repaired.

 

Do you think re-gapping the plugs to, say, 0.035 might improve matters - I saw reports of improved running with Pertronix if the plugs were gapped wider?