Hi guys,

Finally got the car back together this last weekend, and I took her out for a spin and logged the drives. The car runs poorly in open loop -- backfired once and generally ran like a dog. Once it kicked over to closed loop, the performance was alot more responsive -- like how it used to be.

However, when I went over my log, i noticed some things stand out -- for one, i had moments of spark retard (which i didnt have before) and secondly my fuel cell trims only stay near 128 on deceleration -- the rest of the time they are showing as "lean" so the computer is adding fuel to compensate.

Can anyone help me interpret this data? Below are the links to my files, they are stored on my drop box:

TEST 1

TEST 2

On test 2, I had no spark retard, although the fuel cell trims remained. What can I do to amend this?

Thanks!

Tyler W.

 

The run labeled "JUNE 30TH 2013 RUN 2" is a disaster. When you go into PE mode the O2 sensor readings drop to dead lean 44mV left/4mV right and in response, you start getting lean knock and knock retard. It's so bad the PCM is using Cell 18 for accel, and when it sees the very low O2 readings in PE mode it starts jacking up the short term counts to try and fix it. I'm looking at Rec #703 and left O2 is 44mV, right O2 is 4mV, both long terms are maxed out at 160, and the short terms have been bumped up to 149/150 and it never richens up. It's adding 46% extra fuel and the O2 sensors are reading lean????

The log is also full of a huge number of data errors.

That was just a quick look, all I had time for. I'll look more later, but it is probably one of the worst data logs I have ever seen.

 

Hi Fred,

Thanks for looking at the file -- i always seem to get a bunch of data errors when I'm logging -- i think it might be due to noise in the wires down stream, but I can't be sure. Possibly a slow laptop could be the culprit. I have set the RECS down to 8 p/s down from 10. Maybe I need to reduce that number further.

As for the horrendous log, I don't know why it would be so horrible. I did notice that in open loop, the car runs like absolute crap, and once it gets into closed loop it seems to run better. The o2 sensors are new; one thing I thought could be possible is that the o2 sensors connectors are swapped. I wasn't sure which was which when I was reattaching everything. I think they are set up correctly now, but if the readings are this far gone then perhaps they are switched. I recently got the heads rebuilt (stock), which is why i'm doing some logging before getting it out on the road. It sounds like I made the right choice in not driving it back the 100+ miles to the city before further diagnosis

Since the PCM was dumping 46% more fuel into the engine, should I immediately change my oil before driving it anymore? I only drove about 6 or 7 miles while testing it. Hopefully the engine hasn't been damaged. Thanks for agreeing to look over the log with me; it's a very big help.

 

Shouldn't be.... In theory, the PCM is adding all that fuel to make up for a lean condition at WOT, and the O2 sensors say its not enough to kick them above 250mV (I think that was the highest I saw). But check your oil and see if is smells of fuel or feels thin.

I can't understand it - everything is running fairly normal (but the BLM's are way high on both sides, I don't think its a problem with the harness being switched). But when the throttle position percent exceeds the threshold to kick it into power enrichment mode, the O2 sensors go south immediately.

Did you buy commercial harness extensions - if you needed them - or make your own? Or did you possibly build your own harness? It's almost like the polarity on the sensors is switched. If it was actually running as lean as the sensors indicate, it would be detonating a lot. But the knock retard appears to come largely from the knock counts, which increase based on engine operating conditions, and the PCM seeing such lean readings would probably cause it to increment the knock counts and pull timing.

Another odd thing - if the PCM sees the O2 sensors very lean in power enrichment mode for 3 seconds it should set DTC 55. Maybe the PCM isn't in PE mode for that length of time with the brief acceleration runs you are making.

This looks so screwed up that I almost thought I had opened a 93 file with the 94/95 version of DataMaster.

I noticed less errors in the other file, but the error was almost always related to DTC 43 (knock sensor), but the indicated MPH in that frame would change to 43 as well.

I need more time to work on it, but it's been a very busy day at work.

 

Thanks for the detailed response; here's what I can offer up:

No on the custom harness or harness extension -- The harness is from a 1996 Impala harness and modified; I removed the ABS stuff, the rear 02 sensors and a couple other things I don't need for the jag. I used it for about a year until I redid the heads. The only problem I've ever had has been the log errors, which according to the TTS documentation is

in the file called "JUNE 30TH 2013 RUN 2", the 02 sensors seem to fluctuate higher and lower than you described. While in open loop, the 02 sensors are fluctuating semi-normally. At REC 1488, I can see both 02 sensors are in the 800mVs. I don't see where you are seeing the max of 250mv?

At REC 1489, when the PCM goes into closed loop, and the 02 sensors begin to fluctuate in a normal enough fashion, correct? I also don't see any spark retard in this file; in the file "JUNE 30TH 2013 RUN 3 TOM", there is some spark retard which shows up in the higher RPM registers.

In the original file though it seems as though the LTerms are always in the 140s-160s and the S terms only show as 128 on deceleration. Do any of the other stats look abnormal? I'm not sure where to investigate next

 

hi fred,

did you get a chance to take a peek at the datalog? Bobdec took a look at it too, i'm waiting to hear his detailed response too. Sorry to press the issue, i'm just curious as to what to trouble shoot down when i go out to the desert in a week or so to work on the car again.

 

Seemed like you didn't agree with the data I was quoting, appeared one of us was looking at a different file, so I didn't do anything more.

 

Hi Fred,

I wasn't trying to disagree, I was just confused as to what you were seeing versus what I was seeing -- I can take some snap shots and post those?

would it make a difference which version of datamaster you or i was using to observe the data? I recorded the data with version 3.5.1, and I was using the latest version (i think 4.0) to read the data.

When I'm looking at the data I can see that the L term is very very lean at almost all times, and the S terms are high for 70% of the run, like you said

RUN 2

Here's the "June 30th 2013 Run 2" uni file again. If you have gmail, I could just email it to you. Maybe the dropbox link is what's messing it up?

 

Let me refresh my failing senior citizen memory........

 

Thanks! Let me know if I need to upload the file a different way.

 

nothin?

 

Fred is there anything else I should check other than fuel pressure and spark? i'm heading out to the shop this weekend to try and figure out what the heck is wrong with this car.