Audi 100 '89 No Power.

Hi,
My Audi 100 '89 (manual transmission) has Abruptly developed a problem while my wife was driving uphill and was changing to a lower gear. This happened about 3 years ago.
Description of problem: - The car runs very rough as if only 3 or 4 of the 5 cylinders were firing during idle and attempted ride on the road. - It always starts OK even after not being started for months. - When I try to rev up the engine the car struggles to increase the RPM, however when I release my foot from the gas pedal the RPM seems to pick up. I can then sort of pump the gas pedal and get the RPM quite high, as high as I want to. - I sometimes attempt to drive the car but it has consistently very low power!!!
I have been trying to get to the bottom of the problem with no luck trying various things over the last three years. I have done the following (don't remember all the things I've done): - replaced fuel filter, - cleaned air filter, - tried different spark plugs, cables, distributor cap - I have looked extensively for a bad ground connection. I have actually had a problem with my 85Audi5000 which closely resembled this one where the problem was a broken ground wire. - I have checked various wiring from the Fuel injection Control unit and from the Ignition Control Unit. - I have removed the ICV and made sure it is not stuck - I have looked extensively for vacuum leaks.
The problem has never budged. The problem happened from one second to the next and subsequently never subsided regardless of which cables I touched while the engine was running.
I hope that someone has seen such problem before and had more luck than me dealing with the problem.
Thank you for any hints or advice,
Andre
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Andre, Please say that you have pulled the diagnostic codes from the engine control unit: http://www.sjmautotechnik.com/trouble_shooting/10naecu.htm Don't just buy/replace parts without using the onboard diagnostic first. Failing that, could you have an obstruction in the exhaust system, like a plugged catylitic converter? - try disconnecting the exhaust before the cat and seeing if the power returns - the car will be super loud, which, apparently, is cool these days ;-) Scott Mockry's site is an excellent one to review for trouble shooting - so is www.audifans.com and the newsgroups at www.audiworld.com Cheers! Steve Sears 1987 Audi 5kTQ 1980 Audi 5k 1962 and '64 Auto Union DKW Junior deLuxes (SPAM Blocker NOTE: Remove SHOES to reply)

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Thank you all for your responses. It is my first time asking for help through an internet group and I truly appreciate the quick response. Some of the ideas I have already tried or considered but some of the suggestions I haven't tried yet and the information is very useful to me. I will not be able to work on the car in the next couple of days but when I do, I will let you know what I have accomplished.
Thank you again,
Andre
Steve Sears wrote:

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Since the engine appears to be missing on 1 or 2 cylinders, the first order of business is to determine which cylinders are missing. Using an insulated spark plug wire puller and with the engine running remove one wire at a time to determine which cylinder(s) are dead. Once you have determine which cylinder(s) are dead remove the spark plug and inspect them. If the are really black with soot then you have a fuel problem (way too much fuel), but if they clean and wet with gas then you have an ignition problem.
Andre wrote:

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After reading all the responses my primary suspect right now is in the area of ignition with the ignition coil topping the list. e-mail#6 reinforces my theory. My brother has at some point tried to investigate the cylinders that are misfiring. It was not clear that these were always the same cylinders. We replaced a spark plug in cylinder #1 which seemed to make no contribution to running the engine (pulling cable #1 didn't make a difference). Replacing the spark plug seemed to help but not for long. In any case I do remember that the spark plug was wet rather than covered with cids.
I have also tried to read the codes using an LED jig that I made. The readings were not consistent. At one point a bunch of codes were reported but none led me anywhere. One of them was a "full throttle switch failure". I checked the switch and the wiring and couldn't detect any failure.
Unfortunately this weekend doesn't look too good for me in terms of having time "for my Audi 100". I will keep you posted of any progress I will be able to make with this car. The car is in good condition (apart from the problem of course) and it is a niec editions of that model, leather seats and all... I am rather determined to put this car back on the road.
Many Thanks,
Andre
upallnight-two wrote:

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Good work on pulling the codes.
The 'full throttle switch failure' that you were checking is a common problem with the I5 engines. As you know the switch is in the throttle body and includes two switches: WOT - wide open throttle and another switch for closed throttle.
The wires from the switches go to a three conductor plug at the back of the TB. Ohm out these wires while operating the linkage should show changes from open to closed circuit at each extreme.
Even if this ohms out OK there could still be an intermittent failure due to cracked solder contacts on the switches. Removal and re-soldering will correct this in most cases.
Andre wrote:

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Here is a link to Scott Mockry's Site on the throttle switch.
http://www.sjmautotechnik.com/trouble_shooting/10vthrot.html
You should also do a compression test on all cylinders to determine if you might have a burnt/crack valve(s).
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Try changing the distributor rotor if you can't remember when it was last changed.
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I have tired my old ditributor cap and rotor which "worked" OK when I replaced them. I also tried cleaning the contacts.
I am tempted to replace the coil to resolve the coil question. I can get a good used one for about $70 with shipping.
Andre
upallnight-two wrote:

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Hi Andre,
I am chasing a similar fault right now myself! I have not yet got around to half the things that you have and I only hae a mis on one cylinder which appears to not be an ignition problem. The reason I am writing this is just to save you a few bucks - go to u-pull-it and buy a coil from any car with 6 cylinders upwards and electronic ignition... I grabbed one from a truck that had had a recent ignition upgrade before getting scrapped... It cost me $2.50 and made NO difference whatsoever. A coil for the most part is a coil, so it was a very cheap way of testing the component I already had....
I will continue to post on here as I diagnose the issue...
Dan Andre wrote:

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Try changing the distributor rotor if you can't remember when it was last changed.
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Coil might be worth swapping, especially if runs worse under load. See if there's any oil dripping from the coil. Note you can't rely on just measuring the coil resistances.
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I previously owned four T44s NA 5 spd.
The problem you describe sounds a lot like a clogged fuel filter but I see that you have already changed that.
Another source of fuel problems can be due to the lining of the tank flaking off and clogging the inlet screen on the fuel pump. This was corrected in the later years of the T44s so may not be the cause. If it is the problem the factory recommended fix is to cut off the fuel pump inlet screen and let the fuel filter catch the crud and change it more often.
Bad ECU ground on the head?
Clogged cat? Quick test is to pull off the blue cover from the steel line that runs to the down pipe (for testing O2) and if there is a lot of pressure forced out then probably clogged cat.
Hall sensor loose connection in the distributor?
The fusees along the side of the main relay box are for engine management and ICU. They look like spares but aren't. Any bad?
Good luck.
Andre wrote:

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Andre wrote:

A clogged catalytic converter will cause the symptoms you describe. Only way to find out for sure is to take it apart. -- C.R. Krieger (Been there; done that)
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