http://home.adelphia.net/~sabre81/st...e81- 94z28.zip

thanks

im having a high rpm stumble. Still good amount of power until i hit about 5000-5500 rpms then it shifts and the power is back.

 

Your getting a lot of knock retard from 3600 with a max of 10 around 4400. But, your 02s look good. I can't see the power loss by the chart so maybe your valve springs are weak?

Hal

 

I've downloaded the file so I can take a look at it.... it is HUGE - more than 250,000 data points!!! You've got a few things in there that can be eliminated, in the interest of reducing the volume of data. For example, you don't need both TPS voltage and TPS %. Just the % is adequate. Same with "coolant volts" and "coolant temp"... you only need the temp.

Some quick observations.....

It appears to take quite a while to go into closed loop. During the warmup, O2 mV's appear to behave a liitle oddly.

At record #2876 your knock retard hits hard, peaking at 10.5 degrees. You get more knock a little later, 8.8deg, and you are only at part throttle. Seems odd, particularly with the very cold coolant temperature. There seems to be a trace of knock retard any time the throttle is open more than 10-15%. And 100% throttle always gets you 10+ degrees retard.

Your coolant temp seems to take an awful long time to warm up. That may be why it takes so long to go into closed loop. Its about 140degF (60.5degC) when it does. Do you have a thermostat installed?

 

I notice the high lower rpm knock as well. This is the period the car is under peak load. I'm wonder if he is using permium gas?

Hal

 

im running a 160deg hypertech themo.

premium gas of course.

 

Oh, wait, you said stumble. A stumble is usually only one thing, spark, right?

Hal

 

Knock retard........

Could be th infamous exhaust leak. Very popular for knock during heavy loaded situations.

Just a thought....

D Moss

 

Could you give more info on the "infamous exhaust leak"? I get knock when I first nail the throttle, then its gone the rest of the run. Does that sound like it?

Hal

 

um, no.

The exhaust leak would be there for longer than the initial surge. It would be there pretty much the whole time you are under a loaded condition.

Check your motor mounts and tranny mounts. If they are shaking hard, you could be making the knock sensor pick that up. I know some people see knock when they shift hard with a M6

Just a thought.

D Moss

 

Thanks for the reply.

I have an A4 so its not the mounts I guess. I have seen it only with the obd1 pcm, not the stock obd2 even though I dropped the advance to well below a believable factor (like 26 degrees) and even have a desensitize circuit hooked on the knock sensor (which is the 100k obd2 with pcm resistored). I'll just keep working on it, thanks.

Hal