alpinab7

Check eng light is OK. If I disconnect the ecu and plug it back in the light comes on for a sec. Had a Vag-com on it last week (thanks Scott from Boston) and it pulled codes just a couple times out of about 20 times. I managed to get a 2231 code out of it the other day but can't pull any more codes. Car has a stumble at 3500-5000 rpm. In boost, out of boost, hot, cold. All sensors check out. Do I have a bad ECU?

Suffolk

<center><img src="http://www.quattro123.com/Photos/200/MVC-294F.JPG"></center><p>
Watching for the answer...........

Additional info:
Vag-Com on really old Laptop with super slow, like Audi likes, baud rate.
Offical 2x2 ugly cable. Hex-Com
able to pull codes and monitor Engine Channel 1, measuring blocks at: "000" occassionally.

Worked well as a test on another 200 20v in the driveway.

Codes (extrapolated data from Engine 1 as the Vag-Com could talk to the ECu "controller"/"motor", but wouldn't register a fault code (DTC)).

Channel "000" were O2 sensor readings flat &amp; steady low 15 &amp; 7 in fields/channels 8 &amp; 9
and channels 4,5,6 were 1/2 the 120 or so value they needed to be 57. 60 -ish. this leads towards the ISV (air leak). He checked this and carb cleaned the ISV valve.
Check the Bentley Volume 1, reference tables in trouble shooting, in the back: D2-Page 440 for chart for above fields of data.<ul><li><a href="http://www.quattro123.com/200ECUscanningIssueJohn.htm">Story here:</a></li></ul>

alpinab7

I replaced the ISV with a known good unit. No change. Found some frayed Knock sensor wires. Discon knock sensors. No change. Coolant temp sensor registers OK. Maf:OK. Went through all the Bently tests. OK. I had this hesitation 6 months ago and brought it to a mechanic. It was returned fixed but they had no idea why. Removed the ecu harness connector last week and bang, it's back. All the pertinent wires test Ok. Connecters are ok. As in Scott's post, values for O2 sensor are low and ISV are low and both are steady. I plugged in an old 02 sensor and it didn't change. Is it my ECU? I'm ready to just buy a used one and give it a shot.

boxerfan

The region that you are experiencing a stumble is in the peak boost region. Are you running higher boost? Are you always mashing the throttle when testing or are you also doing gradual acceleration too?

Sounds to me like you are running lean, activating the knock sensor and the ECU is retarding the timing. Alternately, are you hitting the fuel cut out?

alpinab7

Stumble happens when accelerating, mashing the pedal or accelerating very slowly. It also gives me a little "buck" sometimes while cruising. A fuel pressure gauge hooked to the front of the fuel rail shows not spike or drop in pressure while driving. I disconnected one knock sensor and it still does it. I'm not sure if it is ok to disconnect both. What is the fuel FV?