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My car is exhibiting a peculiar mode of operation... maybe someone can shed some light.
The car is a 1982 turbo; it is water-cooled and intercooled. M46 transmission. 293,000 miles. Other than the later style turbo, everything is factory stock.
It appears that I've got a problem with the idle circuit. It's been doing this (showing this anomaly) for a couple weeks. The symptoms:
1. It starts easily and runs fine while under load (accellerating or just driving down the road). However, while at idle (car is stopped, like at a light), the engine speed either "oscillates" between about 600 rpm and 1500/1800 rpm... or it just idles "smoothly" at 2000 rpm. I've noticed that when it's at the high idle, if I shift into 1st gear, and let the clutch out just a little (loading the engine), the idle speed will be reduced to about where it should be (800/900 rpm). However, this last only a short period of time; it (usually) then goes back into the "oscillation" mode.
2. While driving, when I shift from one gear to the next, the engine speed (generally) does NOT decrease... in fact, sometimes, it actually INCREASES. For example, if I make the 1st-gear-to-2nd-gear shift at about 3000 rpm, the engine may race to about 3200/3300 rpm until I let the clutch out. Naturally, at that point, the engine is forced to a lower rpm; I can then continue accellerating. Same thing happens at the 2nd-to-3rd shift and 3rd-to-4th shift.
3. This one just revealed its ugly head a couple days ago... the engine backfires through the exhaust. This happens when I'm decellerating, in a particular gear. The scenario is: I'm coming to an intersection where I need to turn. I let the car slow itself a bit (it's still in gear; no brakes yet). When I apply the brakes, at the point just a little before the engine would die, it backfires. Quietly; maybe two, three, four times... but it's definitely a backfire. I engage the clutch, downshift, accelerate, up-shift, and... then it does the "engine race" thing I mentioned above.
So... any thoughts?
As always, thanks.
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Hi Les,
I also have an '82 242t that I had a similar problem with. I took mine apart over the summer and did many repairs & maintenance to it such as new harness, all new vac lines, h2o turbo & intercooler, t belt and on and on and on. Long story short, after final reassembly over this weekend I couldn't get the idle to drop under 3k. I even pulled the intake off again to see if I missed a vac line but I did not. I tried setting the base idle per Bently but still had 3k idle. Just on a hunch i swapped in a spare idle brain that i had and the idle dropped down to around 900. The idle brain is in the passenger footwell behind the footwell outerwall trim(kickpanel?). It is a black box with the #0 280 220 005 on it and has two plugs going into it. I'm guessing the bad harness i took out probably cooked the brain.
hope this helps,
Dan
p.s. When I reassembled the wiring harness i wrapped the grey connector in a heat resistant cloth(header wrap) that I got at a speed shop to protect against the high heat on the turbo side of the engine compartment. Time will tell if it's effective.
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All Monday evening posts never appeared to make it to the board so I reposted Tuesday a.m. please ignore all 10/11/04 posts.
Dan
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Hi Les,
I also have an '82 242t that I had a similar problem with. I took mine apart over the summer and did many repairs & maintenance to it such as new harness, all new vac lines, h2o turbo & intercooler, t belt and on and on and on. Long story short, after final reassembly over this weekend I couldn't get the idle to drop under 3k. I even pulled the intake off again to see if I missed a vac line but I did not. I tried setting the base idle per Bently but still had 3k idle. Just on a hunch i swapped in a spare idle brain that i had and the idle dropped down to around 900. The idle brain is in the passenger footwell behind the footwell outerwall trim. It is a black box with the #0 280 220 005 on it and has two plugs going into it. I'm guessing the bad harness i took out probably cooked the brain.
hope this helps,
Dan
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Hi Les,
I also have an '82 242t that I had a similar problem with. I took mine apart over the summer and did many repairs & maintenance to it such as new harness, all new vac lines, h2o turbo & intercooler, t belt and on and on and on. Long story short, after final reassembly over this weekend I couldn't get the idle to drop under 3k. I even pulled the intake off again to see if I missed a vac line but I did not. I tried setting the base idle per Bently but still had 3k idle. Just on a hunch i swapped in a spare idle brain that i had and the idle dropped down to around 900. The idle brain is in the passenger footwell behind the footwell outerwall trim. It is a black box with the #0 280 220 005 on it and has two plugs going into it. I'm guessing the bad harness i took out probably cooked the brain.
hope this helps,
Dan
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Hi Les,
I also have an '82 242t that I had a similar problem with. I took mine apart over the summer and did many repairs & maintenance to it such as new harness, all new vac lines, h2o turbo & intercooler, t belt and on and on and on. Long story short, after final reassembly over this weekend I couldn't get the idle to drop under 3k. I even pulled the intake off again to see if I missed a vac line but I did not. I tried setting the base idle per Bently but still had 3k idle. Just on a hunch i swapped in a spare idle brain that i had and the idle dropped down to around 900. The idle brain is in the passenger footwell behind the footwell outerwall trim. It is a black box with the #0 280 220 005 on it and has two plugs going into it. I'm guessing the bad harness i took out probably cooked the brain.
hope this helps,
Dan
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If your car is equiped with the K Jet continuous injections system as the Haynes manual suggests it is, then here is another area for you to consider.
The fuel metering rod (plunger, piston whatever you prefer) in the fuel distributor may be hanging up.
I managed to induce the kind of problems you are describing after cleaning up the entire intake sytem from the airbox to the head on my 82 GLT B23E. However, I did not disconnect the fuel distributor body from the air sensor housing and clean the fuel metering rod. The air sensor housing was full of gunk and I suspect that in the process I disolved, but did not completly clean some this stuff from the part of the rod that makes contact with the air sensor lever. Upon reassembly and start, I had a baseline idle of 2500 that I was unable to reduce. The next day I took the car for a test run and upon start the idle was in the 1500 RPM range and could be varied a bit using the idle throtle control on the throttle body. But, after stoping and restarting, idle goes to 2700 and the car drives along at 60 kms per hour with no throttle applied.
After learing a bit more about how the CIS system works (see my earlier posts and the great replies)I took it all apart again and very carefully extracted and cleaned the rod.
The fuel ditributor is attached to the air sensor casting with three slotted machine screws that can be seen beneath the injector line hoses coming off the distributor. I did not remove any of the fuel lines and found the 3 srews to be very tight but with care managed to get them loose without damaging the slots. When separating the distributor from the air sensor housing take care that this rod does not fall out on its own and get damaged. Mine was stuck but yours may not be. This is a very high precision machining and care must be taken not to scratch the surface. To clean, I used cotton swabs, the residual fuel left in the fuel distributor and lots of elbow grease and time. Do not scrape tarnished or varnished areas - just rub.
After putting it all back together again, the idle is back were it should be and the rate of decline of engine RPM between shifts is as it used to be.
I hope the suggestions of vacuum leaks turn out to be the problem as this repair is time consuming and hard on the hands.
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posted by
someone claiming to be Jay Fiedler
on
Mon Oct 11 03:55 CST 2004 [ RELATED]
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this happens if you let the car sit. to check pull disk up full, push down quickly. rod will fall at consistent rate- you feel it bump down. takes about a second
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"This happens if you let the car sit."
Ok, but I drive the car daily... any other thoughts?
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Thanks for taking the time to document such a thorough description.
I didn't get a chance to attach the beast over the weekend; hopefully I will next week.
Meanwhile, I guess I'll just have to idle my time away..!
Ok, sorry. That was REALLY a reach and a pretty rotten pun.
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My '81 245 B21F (non-turbo) surges at start, usually up to around 2,000-2,500 rpm, then immediately settles down to proper idle. I've seen other posts that surging on start is typical of the CIS system, but I find it annoying, could this be due to the same rod being slightly sticky? Idle is a bit rough, but otherwise not a problem. I was going to try to clean out the IAC this weekend, however.
I will take off the intake manifold when I can get a new wire harness, sounds like this is something to add to the ever growing list of to-do's.
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Had your car been parked for a while? It seems as though the fuel distributor is the first to feel the effects of gum and varnish due to the custom fitted close tolerances. And, yes, thanks for including that bit about dropping the plunger. If that hits the concrete floor you'd be in the yards looking for a another AFU.
--
Art Benstein near Baltimore
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I'll bet it's a vacuum leak somewhere as Art said below.
Replace any of those vacuum lines that seem worn.
Might also be a good time to remove and clean out the throttle body.
Good luck!
--
If you listen to the radio in Portland, OR, you may know me as "Portland's Favorite Soul Brother!"
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posted by
someone claiming to be art
on
Fri Oct 8 08:13 CST 2004 [ RELATED]
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Les, I'd immediately look for a split hose at manifold vacuum. First thought was the microswitch on the TB, or sticky IAC, but then you said backfire on decel. Seems like air is entering past the throttle plate. What does the pressure gauge show under boost?
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"What does the pressure gauge show under boost?"
Well, that's the odd thing... Vacuum gauge has continued to look normal thru all this...
The split vacuum hose is a good call. Hopefully it's something simple like that. Actually, considering the problem is only present at idle, I'm pretty sure it's going to be something uh, "relatively" simple.
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