tylerwerrin

Hi guys,

The never ending saga of getting this engine working good continues. The other day while I was driving, the car started shuddering and acting very weird just as it was about to enter "Closed Loop" (educated guess) I noticed that after driving a bit more, it smoothed out enough, and I got to work OK.

I decided to scan the engine, and this is what came back:

http://dl.dropbox.com/u/24984984/Jun...Test%20Run.uni

The results are kind of disturbing -- the engine is running extremely lean, and you can see where the engine changes from Open to Closed loop, the STerm BLMs drop to 87! (Rec 2057) While driving around, the engine seems to stay around the 140 range. I'm not sure what to do. I did notice that the Left O2 bank seems to be hovering only around the lower numbers (under 500, which was different from what it was doing at my last tune) where as the right side seems to be doing ok, or at least doing what it used to do. Perhaps that is my problem? However, the O2's are relatively new -- they probably only have 2500 miles on them.

Can anyone help me out? Should I change the oil? This just started randomly one morning -- I'm completely stumped.

tylerwerrin

i should also note:

the injectors were cleaned last year, i haven't tested them to make sure they ae all functioning but i assume (for now) that they are. I was also thinking this could be a fuel issue, but it doesnt explain why the car runs so poorly getting up to closed loop and then runs "ok"

Injuneer

Are we looking at the same file? It goes into closed loop at 206 seconds, exactly when it's supposed to. That is record #1524. Nothing happens to the ST's.

Most of the time in the first 1/2 of the log your left O2 sensor is static at 453mV, indicating it's unhooked or simply dead. But other times it bottoms out in single digit mV's. When it stays at 453mV too long, the PCM drops out of closed loop. See record #1847. At record #1862 it drops back to single digits, and the PCM goes back into closed loop. Happens again at record #2087.

If I go to record #2057 it's in closed loop both before and after, but the LT and ST fuel trims on the left side are dropping like a rock. But the O2 sensor is stuck at 453mV. The PCM should only drop the ST's in response to a very rich O2 reading. You don't have that. Later in the log, the LT is dropping and the ST is rising, in response to very low O2 sensor readings.

In your earlier post regarding the 15MPH problem, bobdec posted that in another forum, it was determined that the PCM program was corrupt and that reloading a stock program solved the problem. Was he specifically referring to your car, or was he referring to a similar problem on someone elses car?

Basically, the left O2 sensor seems to be bouncing back and forth between very low readings (short to ground?) and the 450-ish reading that indicate its either not connected or not working. That leads me to believe you have a major wiring problem. But then I see the PCM making changes to the LT's and ST's that are totally illogical, and I wonder if the PCM is corrupt.

You also have a lot of "data errors". Have you read the comments on the TTS website regarding that problem? Could be interference on the data wire.

tylerwerrin

hi fred,

thanks for looking at the file! Yes, it is the same car as the one I was having the issues with last week. I was having this issue with the crazy shuddering going from open to closed loop before I tackled the 15mph problem. This PCM is the same that has always been installed -- i do have a couple spares which I could try out.

As for the PCM going from open to closed loop, and where the problems start, i thought that was what was happening -- i guess in reality it is just AFTER i went into closed loop that the problems started happening, in what is looking like a bad 02, or some other problem.

Indeed, I re flashed the PCM to see if I could fix both problems -- I did manage to fix the speedometer problem with the new flash, but the shuddering remains. I then data-logged it today, and when i saw the results, i immediately decided to post here for some guidance.

I assume that one of the o2 sensors is dead like you say -- however, like you said, what the PCM is doing doesn't make any sense. I'll try swapping in a new O2 sensor and see what happens, but what makes no sense is that this issue arose seemingly out of the blue -- hadn't made any changes to the system, and the wires are in the same shape as they were before. You've seen some other datalogs that I posted before when i was running rich a few months ago, and there was nothing like this showing up.

The errors are because I have the data transmission up too high, I think. At least that's what Ive come to gather. It could be caused by noise on the aldl wire as well. Thanks for the input, if anything else comes to mind would you mind posting back to the forum for me?

oh and the DTC error is only present because i haven't tuned the "Skip Shift" error code out yet....

thanks!