1997 A4 1.8T Quattro rough idle problem
 

My car: 1997 Audi A4 1.8T Quattro

Hi, this is my first post! Anyway, my problem is my car isrunning really rough under 1000 rpms (and while idling), check engine light is on,but runs fine otherwise. I bought the car about 2 months ago and the turbo blew about a week after owning it. I took it to a shop and it's got a brand new turbo and new spark plugs now (expensive fix), but the engine was idling rough after the fixand the guy said to take it to an audi dealer and they can program the ECU. So I took it there and he said the coils and plugs are in good condition but the aftermarket power output stage (ignition control unit/module, by Huco)might be bad. He said they tested a known good ICU in there and the engine ran much better. He also said they couldn't verify if the ECU was working correctly. Apparently it had been replaced sometime before I owned the carand is not the identical unit # to the OEM unit. The ECU in my car right now is part # 8D0907557N. From my searching online I can't tell if that's the right part number or not, I guess just the last letter "N" is confusing me. There appear to be ECU's that end in P, etc. Anyone know if that last letter makes a difference?

Anyway,I declinedthe repairsand bought the oem BoschICU (toreplace the supposedly bad Huco one)from online for about $140. I plugged it in and my engine is still idling rough (exactly the same, bummer). Took it for a spin around the block a few times and stillonly runs bad when I get to a red light, feels like it's going to die. Also the check engine light is on, although not flashing. I'm going to pick up a multimeter tomorrow to test both ICU's to see if one or both are defective. If so, then I'll have to get a replacement ICU, otherwise it's something else. Let me know if anyone's had similar problems but something else besides the ICU causing these symptoms. Thanks!

RE: 1997 A4 1.8T Quattro rough idle problem
 

Why don't you READ THE CODES? Chances are, the answer is in there. You might have something as simple as a unplugged sensor, a boost leak, bad/dirty MAF.

RE: 1997 A4 1.8T Quattro rough idle problem
 

Agreed...It will save you money

RE: 1997 A4 1.8T Quattro rough idle problem
 

Thanks, I ordered ausbVAGcable and downloaded theprogramfrom Ross-Tech. Should be here sometime next week, then I can get the codes and post them on here too, hopefully pinpoint the problem and fix it so I don't have to ride the bus haha.

RE: 1997 A4 1.8T Quattro rough idle problem
 

Ok, got my vag-cable today and finally got the error codes. While I was waiting for the cable to get here I decided to clean the MAF, I only had 70% isopropyl alcohol but did it anyways, didn't fix my problem though. Ok, the only faults I got were for my engine:

5 Faults Found:
18089 - Control Module Programming Not Finished
P1681 - 35-00 - -
16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 35-00 - -
16687 - Cylinder 3 Misfire Detected
P0303 - 35-00 - -
16688 - Cylinder 4 Misfire Detected
P0304 - 35-00 - -
16686 - Cylinder 2 Misfire Detected
P0302 - 35-00 - -

I tried running the throttle body alignment using vag-com but that didn't fix the idle problem.

Could there be something wrong with my ECU? I opened up the ECU and it looks stock, I can't tell if it's chipped, but there's nothing indicating it is chipped, and as far as I can tell the soldering looks ok. Also when I took my car to the dealer the guy said the part # for the ECU isn't correct, but he wouldn't give me the correct part #. The car was idling fine when I first bought it(for about 2 weeks before the turbo blew), so the ECU should still be ok right? I've only had this problem since the turbo and oil pump were replaced. I've read that audis can have idling problems after disconnecting the battery and ECU, both of which I have done. Also tested my old and new ICU with a multimeter and they are both fine, so that's not the problem. Let me know what you think I should do next to fix this problem. Thanks for the help!

RE: 1997 A4 1.8T Quattro rough idle problem
 

Swap the coil from cylinder 1 with another one, to see if that one
is the only good one.

RE: 1997 A4 1.8T Quattro rough idle problem
 

I think that is your best bet, swapping out coil packs to see if you get rid of any codes, the misfires are mostlu due to coilpack plug or wire going bad, check the plugs make sure there not fouled reset your codes and take it for a spin. That will tell us better whats wrong with yyur whip

RE: 1997 A4 1.8T Quattro rough idle problem
 

Ok, I switched the ignition coils from cyls. 1 & 2, cleared the fault codes, then ran the engine for a couple minutes and checked the fault codes again. Here's what I got:

Control Module Part Number: 8D0 907 559 C
Component and/or Version: 1.8L R4/5VT MOTR AT D03
Software Coding: 06251
Work Shop Code: WSC 10001
4 Faults Found:
18089 - Control Module Programming Not Finished
P1681 - 35-00 - -
16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 35-00 - -
16688 - Cylinder 4 Misfire Detected
P0304 - 35-00 - -
16686 - Cylinder 2 Misfire Detected
P0302 - 35-00 - -

So, cylinder 1 didn't show misfiring before or after the swap with cyl 2. And the cyl 3 misfire didn't show up for some reason this time (I didn't touch that one). Ichecked out meas. blocks 015 and 016 (misfire counter) and it looked like cyls 2 and 4 were counting up fastest (up to about 22-25 before resetting to 0), and cyls 1 and 3 counted up slower to about 8-11 before resetting to 0. So I'm still not sure if the coilpacks are bad or if it's a wire or sensor problem. Let me know what I should do next.

Also, vag-com says the Control Module Part Number is 8D0 907 559 C, but the ECU in my car has part number 8D0 907 557 N on it. Could that be causing a problem? Is vag-com recognizing my ECU as a different part number than the actual part in my car? Thanks again for the help.

RE: 1997 A4 1.8T Quattro rough idle problem
 

There is a computer problem, what it is, I have no idea. Notice the first code, that's not a good one.

I thing you a few bad or going coil packs.

RE: 1997 A4 1.8T Quattro rough idle problem
 

hmmmm.........well VAG gets the ECU # from the ECU so its the one that VAG says. Did someone take the brains out of a 559C and put them into your 557N body I don't know. I'm fairly sure your supposed ot have a 557 in your car. I can't tell you if that is a problem but I really don't like that the VAG # and your sticker don't match. find out what # your car came with (call audi) and then search the forums or ebay for the correct #(maybe get one thats chipped)