Well I've been having this problem for a while, I've replaced the opti, plugs, wires, coil, coil wire, and 02 sensors and nothing fixed it. I ran the car today and got some data logging. I don't have the logs, but i was reading the laptop as the car was run through the gears.

The first time out, we got a trouble code. Code 48: Mass Air Flow system failure. So we swap out the maf for my friends which we know is good.

Took the car out again, the code is gone. No other codes come up. But here is the puzzling part. The car was showing 0 degrees of KR at idle, but at WOT it showed as much as 8 degrees. The 02 readings were all over the place as well, jumping from .0 up to 1.1 or so.

Describing the miss: Before the maf swap, the car would miss past ~4k in 1st and 2nd. After the swap, the car pulled pretty smoothly in 1st with only a slight miss, but once into 2nd the miss was pretty bad again.

Could this be a bad knock sensor? Do you think the problem could clear up once the car is used to the new maf? If it is real knock that i'm getting, am i screwed?

Oh yeah I'm only getting around 13 mpg as well, I'm sure that was mostly maf related though.

Thanks for the help.

 

8 degrees of knock retard will make the car feel slow, that's for sure. I'm guessing it may be the maximum allowed KR on your tune.
Either way, you might have some other problems as well. (ignition/fueling)

I'd recommend saving the logs next time so we can take a look at them.

 

The logs are saved, just the laptop wasn't mine. So I don't have the files. I'll see if I can get ahold of them though.

Also, the car doesn't feel slow at all, up until it starts to miss that is...

 

Well yes, but what I was saying is that you are losing a significant amount of power with 8 degrees of knock retard.
You mentioned that you've seen 1.1V at the o2. Was this on both sides or did it tend to predomine one of the sides? Also, was this just like for a flash, or have you seen it for a while at that value?

 

I ran the logs on this car and still have them saved; however I only ran them before we replaced the MAF. Tomorrow I'll run more and mail'em to anyone. The problems w/ this car go pretty in depth since the problem seemed to go away after the opti/plugs/wires/coil swap (opti showed signs of rotor burns and also water damage in the electronics part). Then when it came back, the plugs looked horrible (2-3 weeks) and I replaced the ESC module with a "good" one. The car promptly fried the ESC after about 4-5 days of good running conidition, then we simply put the old one back on because it hadn't tested "bad." Now, I'm not the type to fix a problem by the "lets replace this and that and see if it's fixed method," but this car keeps on throwing me off track.....The MAF wasn't the problem @ one point because it tested fine and misfired in limp home mode. Then it ran great after the new plugs I put in the second time until in burned up the ESC. Then it ran great on the old ESC for another week or two. So far we've detected no problems w/ the new plug wires. I think that it is also important to state the condition of this car. The car has WAY over 100K mile (mike give us the exact #) and has unquestionably had nitrous before the current owner owned it.

 

it could be a catch 22 effect. You could be getting KR because of the miss... But thats a maybe.... ICM is about the only thing left, try to swap that out with your friends. Good Luck

 

run some race gas and see if the knock goes away... if it does then your getting real knock, prolly something to do with the miss as said above... if it DOESN'T go away then it's time to bypass that stupid knock sensor... i got MAD false knock with that lame thing so i just have it bypassed all together now

 

How did you bypass it? Manually or was it programmed out?

 

Running on 100 octane gas doesn't always mean you won't have real knock. If for instance, you have too much timing, or you're running too lean, no 100+ octane gas will cure that. Bypassing the knock sensor is a pretty desperate measure in my opinion and should be used only as a last resort, especially on a daily driven car...

 

From what I could see the 02 readings were jumping all over the place in that range, they were never in one place for long. When brett posts or emails the logs, you'll see in better detail of course.

 

A false reading from the O2 sensors could create a lean air/fuel mixture which could cause a misfire. Again, is it a steady value or a flash?

 

Well since the maf was replaced the car will not miss unless it is warmed up. This could be either a closed-loop issue of some kind, or the ICM could be getting hot i'm told. BTW, I've done the ICM cooling mod already.

Any other ideas?

 

All things considered I would have to say that the ICM getting hot sounds like a valid solution.

 

Like I stated above, you should try to swap your ICM with your friends to eliminate that as a cause, before you spend any more money.

 

This is sad I'm posting this after owning LT1s for the last 6 years, but.. what is a ICM?

Just wonderin if this could be my problem too. Though seems like regardless I'm getting the miss with the car being cold or hot..

Jason