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1976 2002 Rough Idle / Rich with new Weber 32/36


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Recognizing that the topic title is a classic around here, I can assure you I have Googled the issue like crazy and have read many forum posts.

 

Background: 1976 2002 not tii that has not been on the road since 2000.

 

Situation now: very rough idle, missing. Smooths out at 2000 rpm-3000 rpm, with occasionally missing.

 

Spark Plugs: NGK Standard BP6ES gapped at .037, .030 plus .007 for Pertronix. Removed aluminum threaded caps.

Coil: Bosch Blue 3 ohms

Plug Wires: New and tested

Compression: 140 across cylinders, have not done a leak down

Head: it appears the head was rebuilt as it is a really clean valve train

Carburetor: new Weber 32/36 - the old 32/36 had a barb snapped off the water choke plus really sticky

Linkage- currently disconnected to eliminate binding as an issue

Distributor: Cardone re-manufactured distributor. The original had a ton of vertical play. I installed new Bosch cap, rotor and Pertronix. I paid attention to position of sensor vs. magnet and it did not need the spacer

Plug Wires - correct order

Fuel Pump pressure - 4.5 psi

Valve train - adjust valves to spec, which I don't remember what it was, but to spec.

Tailpipe - a little white smoke, some condensation

Misc: re-cored radiator, new water pump, new mechanical fuel pump, tank drained twice but still smells like bad gas, new filter, new fuel lines, new thermostat. There is an exhaust leak under the manifold, but not sure where yet.

 

Timing history - as it is a 1976, I believe the timing is only at the back of the engine. The "shiny ball bearing" is completely un-seeable. I removed plugs, valve cover and turned engine from crank nut until #1 was at TDC. Both valves closed, can move the rocker fore and aft (no tension). The cam gear line matches perfectly with the oil line. The distributor initial advance is 2 degree-ish BTDC based on rotor alignment just before the engraved line. I made a paint mark at this point through the little observation hole. With timing light, this shows. Rotating the distributor changes the idle a little, but not a ton. If I move timing light from cylinder to cylinder, they are all firing and appear similar with no noticeable drops or missing flashes.

 

Vaccum - At idle, manifold vacuum bounces between 12-14. currently, I have all vacuum lines plugged on the intake manifold. I have plugged the vacuum advance on carb.

 

Plugs - black, sooty, a little wet, stink like gas

 

Carb - I really tried to not touch the carb from original spec. I really wanted to make sure the ignition was correct and wanted to make sure I had that as dialed as I could get it. I am just a shade tree mechanic and I know the bias is to start turning carb screws when the issue is ignition. I have set it to spec - 1.5 turns on idle stop and 2 turns out on mix screw.

 

If I pull a vacuum cap off the manifold, RPMs go up probably 400 RPM, it evens out some, generally runs better. If I screw in the idle mixture screw all the way (lightly! not to damage the seat!) it doesn't terrifically affect idle performance.

 

So, those reading along, have no doubt yelled multiple times "It's too rich!" and I agree. I have yelled too! I assure you.

 

Question:

 

Before I buy a Weber fuel regulator, do the kind FAQer's agree that 4.5 psi fuel pressure is really too high? I know what Weber says, but I also see comments of people running 5psi+. 

 

Or, do I have a jet issue?

 

Or, do I have a combination of the problems or another problem all together?

 

Thank you kindly in advance and especially for reading to this point.

 

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Definitely do not be afraid to try more or less turns on the weber screws. Those weber screw specs are more of a guideline than a rule especially since you dont know the jet situation.

 

Also dont be afraid to twist the distributor a few degrees left and right to see if there is any improvement since you arent really timed off the ball.

 

Has the resistance wire been removed from the wire harness in order to use the blue coil? The original resistance wire in the 76 harness has to be removed in order to use a blue coil.

1976 BMW 2002 Chamonix. My first love.

1972 BMW 2002tii Polaris. My new side piece.

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Quote

I also see comments of people running 5psi+. 

...and then 3 or 4 of us saying that many Webers flood over 2 psi...

You'll prolly want a regulator.

 

What Steven said.

 

From the sound of it, you need to find or make a timing mark, either on the flywheel

or on the front pulley.  If you have an advance timimg light, it can be tdc.

 

Tuning tends to be iterative, as in, you adjust one thing, it helps, you adjust a second, a third-

and then you recheck the first, and so on.

 

Where did your carb come from?  Unless you got it from a vendor who jetted it for a 2002, it's not jetted properly...

 

And no idea what your distributor has in it.  BMW changed them almost yearly, so you probably would have had an advance/retard unit.

But what Cardone gave you, there's no way of knowing without Tom's tester.  Most work- but the inital setup varies a bit.

There's no static timing spec- you'll need to play with it to see.  And usually, the vacuum advance wants ported vacuum off the carb.

 

Lots of variables.  You'll sort it out.  Start with getting the idle speed to 800, then adjust timing for best idle, and see what happens...

 

t

 

"I learn best through painful, expensive experience, so I feel like I've gotten my money's worth." MattL

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If you're running a 4.5psi fuel pump without any regulator or fuel return back to the tank, then yes I suspect this is too much for the carb and you have extra fuel seeping past the needle seats and dribbling into the intake, leading to a rich condition.  This would also explain why removing the vacuum cap helps: it adds additional air without drawing additional fuel, thereby leaning things out.  If you do have some sort of fuel overflow return system, I'd suggest making sure it's working properly and then move on to the idle jets.  Also agree with Steven to not be afraid to play around with mixture and timing to try to improve things by ear, but from your description it definitely sounds more like a mixture problem than a timing issue.

-Carl

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8 minutes ago, TobyB said:

But what Cardone gave you, there's no way of knowing without Tom's tester. 

UNLESS

9 minutes ago, TobyB said:

... you have an advance timing light ...

 

I would highly suggest buying one, because it will let you see what the total mechanical advance is for your new Cardone unit and set the timing accordingly, for all-in advance.  You can even plot the advance curve with an adjustable light.  (I like the Innova 5568 and an online purchase will get it to your door, for $100).

 

I recently swapped in a distributor with a flatter curve, which allows me to have the all-in advance where I want it, without getting pinging at the lower rpms.  I'd like to know what the Cardone curve looks like.

 

+1 for popping the top off of your carb, to see which jets are in it.  c.d.'s jetting prescription for the 32-36 is working well for me, it seems.  Take the cover off the old one too, since it may have jets you need to correct the new one.  Check the float height while you are in there.

 

Don't toss your original Bosch distributor.  Vertical play happens.  Shim kits are available for $15ish and will allow you to correct the vertical slop... if you are so inclined. 

 

Tom

     

 

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From one new BMW 2002 owner to another.  The trick with these is to set the timing correct and use the 32-36 jetting prescription.  My 2002 would barely idle, now I jetted it correctly it purrs like a kitten.  I do have an issue with cranking it over for a long time, but that is due to fuel siphoning, which will be addressed shortly.  I had the same problem finding the timing BB. I am having a great local guy help me out with that. 

"Goosed" 1975 BMW 2002

 

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Cant say enough about the jetting issue.  Don't know the Weber factory jets, but mine were way off.  When I did c.d.'s prescription, it made a huge difference.   take out the emulsion tubes and clean those well too.  Mine had some build up.  Finally, set the float correctly.  The brass float from Piece was dead on upon install, but I bought the float guide from them just to make sure and make the measuring job easy for next time.  The Weber book from Pierce was very helpful. 

Mike

76 Malaga (Molly)

Mods:

Weber

Recaro

Eibach

Bilstein

Panasport

Ansi

Parker

Ireland Eng.

'72 Tii Project

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  • 2 weeks later...

Thanks so much for the help and apologies for the late update.

 

I have limited time to work on the car. I was busy before, but now I am taking engine rebuilding at Pasadena City College.

 

Some progress, clarifications:

 

I got the timing set off the ball. I found my adjustable timing light and that made a world of difference. I got the timing to running condition by TDC and looking at the rotor. Then I was able to position the timing light and turn the adjustment until the ball appeared. That way I could see how far off I was, move the distributor until the ball disappeared, change the adjustment, repeat. Just to be a thousand percent sure - the ball is the correct advanced position, right? Vacuum plugged, timing light set to 0, the ball will line up, right?

 

Running a little smoother, but still rough. I bought the Weber regulator and set for 2.5 psi but that didn't make a difference.

 

stevenc22 - points out that blue coil would need elimination of resistance wire. I just went back to the old coil. I had no reason to doubt the old coil, I just thought I would upgrade as part of Pertronix.

 

tobyb - I got the carb from WorldPac and it is a new, for BMW 2002 application. I compared the stated jet sizes to the 'prescription' and it is not very far off. But, I got the jet kit and will change to the prescription.

 

Next step is to change the jets. I will do that this week I hope. I love hearing from you guys that the jets made such a difference and I am grateful there is a prescription available.

 

For the guys that did the prescripton, did you block that circuit that C.D. references? If so, how? JB Weld?

 

Thanks again!

 

 

 

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36 minutes ago, misterjalopy said:

the ball is the correct advanced position, right? Vacuum plugged, timing light set to 0, the ball will line up, right?

And engine spinning at the correct rpm, 2000? Somebody help me if that isn't right for a carb.

A radiator shop is a good place to take a leak.

 

I have no idea what I'm doing but I know I'm really good at it.

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1 hour ago, misterjalopy said:

Vacuum plugged, timing light set to 0, the ball will line up, right?

Try it this way.  

 

Set your timing light to 13 degrees of advance.

Disconnect vac pod and rev engine to 3500 rpm, while turning the distributor body, until the ball (BB) is in the hole.

Tighten distributor there and then reset the light's advance to ZerO.

 

Now rev the engine and see what the rpm reading is when the BB appears in the hole.

Write that info down.

 

With the engine idling, shine the light down the hole and bump the advance setting up, until the OT line shows up.

That will be your advance at idle.

 

If you are so inclined, you can set the gun at 2 degrees and rev until the OT appears, then 4*, then 6* and before you know it, you have plotted your advance curve.

 

I am curious what those two readings will be.  (BB rpm and Idle advance)

 

Do you have the distributor model # ending in 164?

 

 

     

 

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