My EVO has been running bad. Lots of power loss, and miss-fires at 4.5kish in 3rd and 4th sometimes. I did a boost leak test, felt turbo for play, checked plugs, checked for vacuum leaks and I've found nothing so far.


I am just starting to learn about logging, and this log doesn't indicate anything abnormal to me, but I was wondering if some of you more knowledgeable people could take a look. I have a wideband, which is not hooked up to my computer yet, but A/F seems to be about where it should be - about 14.7 cruising, and 11ish WOT. Because the A/F seems about right, it seems like it probably is not a fueling issue. I am also wondering if the sensors with the 0 readings are supposed to be 0, and is there any way to tell if the cam sensors are bad since I read that could be a possibility?


Any other troubleshooting advice would be appreciated.

 

MAF sensor? O2 sensor?

crank angle sensor?

 

A. You're logging too much stuff.
B. Have you tried replacing your plugs?
C. I would think if you had a bad crank or cam sensor, the problems would be all the time, not just WOT. I would think anyways. I would personally start off with plugs. If the simple stuff doesn't fix it, then start looking elsewhere. Just my opinion though. WOT misfires are usually ignition related. I'm dealing with the same issue right now as a matter of fact, and I just ordered a nice COP system.

 

As far as I can tell, MAF readings look OK in the log, and o2 look fine as well.

I do not know what to look for regarding the crank angle sensor. If anyone could help me with that I would appreciate it. Can anyone explain what the 1s and 0s are in the crank column?

A. Thanks, and I realized I should have cut some stuff out. Will log less things next time. I left a few things that I did not understand on the log just because I wouldn't know if they were abnormal.
B. No, but they looked OK when I took them out. I guess they might be bad and look ok still? I plan on checking plug wire resistance today and coil packs as well. Maybe I'll also buy new plugs.
C. From what I have read it seems that if I had a bad cam sensor, the rpm readings in the log would be off. They seem OK, so wouldn't this indicate that it isn't the problem, or is that not the case?

 

Spark plugs don't have to look bad too be bad. After 9 years of fixing Vw's and Audi's, I've learned that if it's a mis under load, then it's 99% chance that its ignition related.

From your logs, Id say your sensors are doing just fine. If you had a bad crank sensor, I'm pretty sure the car wouldn't start...if you had a bad cam sensor you may see the same issue or even weirder timing numbers and other things across the board, not just under load. Cam and crank sensors don't "care" about load.

 

Good info.

There's a twist now. The misfire is because the car spikes lean. Keep in mind I only installed the wideband a couple days ago. I should have played around with it more before jumping to the conclusion A/F was fine. This evening under WOT in third it was rich like it should be around 11ish, but then at 4-5k it shot up to 16 and misfired.

Am I correct when assuming now that the issue most likely is something with the fuel system or possibly a vacuum leak? Or, would an ignition problem cause a lean condition as well? Also strange how it wasn't a constant lean condition, it just hit all at once. I'm not sure why that would happen.



Now more logging, connecting wideband to computer, and researching more...