Dead cylinder in 1972 2002tii

[Pablo M]

This is a bit of a frustration rant, bit advice seeking. Apologies in advance if this gets too long. I’m coming up on owning this tii a full year now.  
 

I’ve been chasing vacuum leaks and other issues with my car, which sat 10 years,  over this year and have been making some progress. Feeling I needed a good baseline tune up to eliminate those elements as variables I decided to throw money at it and took it to a local, very respected shop specializing in BMW and 2002’s particularly. 
They just called today to tell me I have a dead cylinder. They did not do any further diagnosis to determine any causes. When asked, they responded “I don’t know.”  
Spark plugs show #2 wet, all the rest very sooty. Plugs are new, as are wires, distributor cap/rotor/condenser.
Idles a bit rough but I was previously able to get it to run surprisingly smooth 4-5 months ago/750 miles ago. At idle you can hear a misfire in the exhaust. But sings above 5000rpm-I drove it to the shop doing 70mph for a spell. Felt good and thought that’s what I had more to look forward to. Still though, feels

down on power as didn’t feel it had much more to give above 70. 
Oil looks dirty but no presence of coolant. At idle there’s a tick like the valves need adjusting. And it does blow blue smoke when I rev it highly in my driveway. 

Original plugs I pulled out:

 

 

Current plugs (non resistor type):

 

 

This is idle currently. 

 

 

So, what diagnostic steps should be taken next (by shop or me)? 
I have not checked compression yet.

Pull valve cover and/or head to check valves and pistons?

 

I’m feeling overwhelmed by all this now. 

[Mike G]

Find a different shop. No reputable shop would answer any question with “I don’t know”.  If you want to go it alone do a compression test and leak down test, set valves then start down one of the many tii tuning guides. An afr gauge will be invaluable. 
 

all your plugs are very rich. 

[OldRoller]

Second that... if they found #2 "dead", the first thing they should have performed is a comp/leakdown check. 

Sounds like a vacuum leak at idle, one of many causes to a rough idle. 

 

As Mike G said, start with tuning basics, go from there before chasing deep ghosts.

 

 

[resra]

Injector on that cylinder is not spraying properly. Switch the injector from a good cylinder to see if it changes. This can happen from letting a tii sit around for many years. Happened to me.

Hint, comes alive at higher rpm.

Edited August 9, 2023 by resra

[dlacey]

Firstly, the fact that the No2 plug is wet indicates that fuel is being injected...this is unlikely to be a check valve or injector issue. We're assuming the WUR is warmed-up and inactive.

 

I dunno if this helps, but here's my mental model for how that Kugel should be tuned.

 

1) the cone inside is the fuel map, that can't be changed and it responds to engine speed and throttle position. But although the shape of this 3D Fuel/Speed/ThrottlePosition map can't be changed, the two corners of the map can be tuned.

 

2) the high rpm, full throttle end of the 3D map is set with the verboten screw (it is an adjustment of the fuelling)!, that should be trusted to be correct unless you know for sure someone has messed with it before... In that case get the full throttle high revs tuning set first with verboten adjustments (in your case, you say it ran well at 5000 rpm, so I would say this is fine...don't touch it). Exact throttle position isn't so important here, as the butterfly angle has minimal effect to flow at close to fully open.

 

3) the low RPM, idle throttle end of the map is set inside the tuna can (it is an adjustment of the airflow). The tii setup is very sensitive to throttle butterfly  position at this end of the map. That's why there is such a concentration on air leaks.. small leaks at idle contribute to a significant proportion of airflow in the plenum...if you attempt to set the tuna can in this situation the throttle butterfly will be almost (or even fully) closed as the air is coming into the plenum from elsewhere... In this situation, at low revs and part-throttle it will be far too rich because the leak is rather constant...making-up , say, 50% of the airflow at idle but only ~10% at 2000rpm ... So by setting the idle "right" with the leak, as soon as you move off-idle the butterfly is not open enough to match the fuel and it's way over rich.

 

So given your description and the sooty plugs, the issue is with the part-throttle fuelling and that's likely (3) above, tuna can setting...maybe with a background leak, certainly too rich.

 

In the tuna can there are two settings, the mixture screw adjusts airflow/throttle position completely independent of fuelling. The outside idle screw moves both the throttle position AND the pump throttle lever - so as you back-out the idle the fuelling is reduced in sync with the airflow reduction.

 

That's how my brain sees it, anyway....

[Stevenc22]

Doesnt sound like a dead cylinder to me. Sounds like all 4 are running.

 

Just pull the spark plug wire as the car is running and see if the idle changes or not. If it doesnt change, the cylinder is dead. If it does change, the cylinder was firing. It might have other problems but at least its firing. 

[tech71]

11 hours ago, Pablo M said:

So, what diagnostic steps should be taken next (by shop or me)? 
I have not checked compression yet.

Do you really have to ask?

Check compression yourself or instruct shop to determine cause

As far as the shop goes... maybe they "dont know" because as soon as they found a low cylinder they stopped to keep your bill as low as possible? Just a guess but seems plausible. Unlike some, I cant really condemn them on info available.

Edited August 9, 2023 by tech71

[Pablo M]

10 hours ago, Mike G said:

Find a different shop. No reputable shop would answer any question with “I don’t know”.  If you want to go it alone do a compression test and leak down test, set valves then start down one of the many tii tuning guides. An afr gauge will be invaluable. 
 

all your plugs are very rich. 

Thanks. I feel he just can't be bothered with such a project car. He generally builds high dollar projects. I feel, even in his demeanor to me, that this is below him. I'm going to stop by the shop, maybe tomorrow, and talk to him in person. It's very disappointing to be treated like this. I would have expected some further diagnostics at the very minimum once they discovered the 'dead cylinder'.

 

 

5 hours ago, OldRoller said:

Second that... if they found #2 "dead", the first thing they should have performed is a comp/leakdown check. 

Sounds like a vacuum leak at idle, one of many causes to a rough idle. 

 

As Mike G said, start with tuning basics, go from there before chasing deep ghosts.

 

 

Exactly! Further diagnostics is what I would expect, so they can confirm it or give further action items.

Ironically, I took it to him to get professional tuning basics taken care of by someone who knows these cars well.

 

 

5 hours ago, resra said:

Injector on that cylinder is not spraying properly. Switch the injector from a good cylinder to see if it changes. This can happen from letting a tii sit around for many years. Happened to me.

Hint, comes alive at higher rpm.

It could be this too. Car sat very long and lots of dry rot present. I've been taking care of a bunch of things (fuel lines, brake system, vacuum leaks, etc) over the year I've had it.

 

 

5 hours ago, dlacey said:

 

In the tuna can there are two settings, the mixture screw adjusts airflow/throttle position completely independent of fuelling. The outside idle screw moves both the throttle position AND the pump throttle lever - so as you back-out the idle the fuelling is reduced in sync with the airflow reduction.

 

That's how my brain sees it, anyway....

See, I've messed with the tuna can outside idle screw to no avail, and that was the last straw convincing me I needed someone familiar with the car to set the basics right.

 

 

4 hours ago, Stevenc22 said:

Doesnt sound like a dead cylinder to me. Sounds like all 4 are running.

 

Just pull the spark plug wire as the car is running and see if the idle changes or not. If it doesnt change, the cylinder is dead. If it does change, the cylinder was firing. It might have other problems but at least its firing. 

Thanks. I'll try it.

[Pablo M]

1 minute ago, tech71 said:

Do you really have to ask?

As far as the shop goes... maybe they "dont know" because as soon as they found a low cylinder they stopped to keep your bill as low as possible? Just a guess but seems plausible. Unlike some, I cant really condemn them on info available.

I'll give you that. Good point about the bill. When we talked he did not give the option to do further diagnistics, or what the next steps were. He simply said to give him a call when I know what I want them to do with it.

Yeah, I know...compression test. Surprised they didnt do that or offer to do that or offer to do any further diagnostics. I'll definitely do it once I get the car home.

[tech71]

Your idle is a bit rough but it would be a lot more lumpy(across RPM range) if it was running on only 3 cylinders.

OK, shop telling you that you have a "dead" cylinder without further explanation is a bit odd. That could mean different things I guess.

As mentioned above, a clogged injector(not atomizing fuel correctly) or a vacuum leak could be the cause of a rough idle.

Vacuum leaks are common sources of trouble.

By the way your engine bay looks good! Squared away nicely.

Dont get discouraged, think of the wealth of obscure knowledge you are acquiring 😉

 

 

Edited August 9, 2023 by tech71

[Mike Self]

Having been forced to drive a 2 cylinder 2002 (blown head gasket between 2 cylinders) for several miles, I can state for a fact that your video sounds like all 4 cylinders are reporting for duty.  And if you drove it to the shop at 70 mph, even an occasional misfire on one cylinder (not to mention a completely dead cylinder) would have been immediately evident.  From the video I can hear some slightly loose valves (better too loose than too tight) but not a dead cylinder.

 

However, if you're getting blue smoke when the engine is revved, that's usually a sign of worn rings--so as has been stated, a compression and leakdown test is definitely warranted.  Smoke on the overrun is usually worn valve guides/stem seals.

 

One more thing:  those plastic runners are known to warp, crack and leak (why the factory switched over to cast aluminum ones early in tii production) so carefully examine the runners--especially #2 to make sure it isn't leaking air, thus upsetting the engine's vacuum.

 

And finally...before messing with any of the above, make sure the offending cylinder is getting a spark.  That's an easy test as has been stated previously.  My late F-I-L, who began wrenching on Model Ts, when teaching me how to work on cars used to say, "Mike, 90% of your fuel problems are in the ignition, so check it first."

 

Keep us apprised of your progress...

 

mike

[Pablo M]

17 minutes ago, Mike Self said:

One more thing:  those plastic runners are known to warp, crack and leak (why the factory switched over to cast aluminum ones early in tii production) so carefully examine the runners--especially #2 to make sure it isn't leaking air, thus upsetting the engine's vacuum.

 

Thanks Mike. Will do.

Ugh, those runners. Its even worse, as mine were replaced with the TEC metal aftermarket runners. The couplings were giving me constant vacuum leaks.

I ended up replacing the whole thing, plenum/log, intake runners, runner manifolds with ones from a 74tii. In the video above you can see it doesn't have the plastic ones. I painted the aluminum runners black to give it the original look though. This swap definitely helped.

[SydneyTii]

I had a dead cylinder on my Tii that idle does not have one by the sound, all plugs look rich so fuel is there, if you want to double check, start it and crack the allegedly dead cylinder injection pipe at the pump, the engine tone will immediately change if it is sending fuel to the injector, in fact if test each one whilst youre there.

When you change plugs, cap, leads all at once you introduce too many new variables.

I put everything back when I did the same and started sequential fault finding, in the end I realised I’d moved the shaft magnet for my Petronix when I changed the cap, such a small thing but it ran like a dog.

if you don’t have the Kuglefischer injection manual get it from this site, the Tuna can is a juggle between the idle mixture screw on the inside and the external screw on the outside, you have to go back and forth between the 2.

if you have Mike Mcartneys resto guide he explains it well.

Good luck, best thing you can do is learn the injection system back to front, it’s not too bad, once you have it you won’t look back!

Edited August 10, 2023 by SydneyTii

[Pablo M]

On 8/9/2023 at 9:22 PM, SydneyTii said:

if you don’t have the Kuglefischer injection manual get it from this site.

if you have Mike Mcartneys resto guide he explains it well.

Good luck, best thing you can do is learn the injection system back to front, it’s not too bad, once you have it you won’t look back!

Thanks. I do have the Kfisher manual as well as the Mcartney's resto guide! I was hoping a knowing professional would do all that for me though.

 

UPDATE:

I went to talk with the shop owner in person. He did, in fact, do a compression test. Couldnt remember off hand what the numbers were or what cylinder it was (I was guessing based on the plug condition). Don't think he wrote that stuff down either. That's the extent of what he did. No further diagnosis, and recommends an engine rebuild.

So I'll go back to get my car, bring it home and start doing my own diagnosis. A friend has a borescope so I'll borrow that to inspect the cylinder walls for damage. I'll do the diagnostics mentioned in this thread. If I need a rebuild I'll pull the motor and have it done. Disappointing 4 weeks dealing with this (appt to bring it in 2 weeks in advance, 2 weeks they sat on it).

[Mike Self]

Sounds like it's time to find another shop....