Hey,

I hope some one can head me in the right direction here.

Link to a zip folder of my data logs taken with the Innova scanner:

http://ftp.covingtonhill.com/Covington/innova.zip

Here are the first emissions results:

2060 RPM
hc limit 55 reading 15
co limit .31 reading .03
no limit 408 reading 251

Idle
hc limit 200 reading 224 FAIL
co limit 1.00 reading 0.88

I took the old girl home, figuring I had a misfire which seemed to be the case - I found a split MSD spark plug boot and very sooty plug in cylinder 7. While I was changing all the plugs and the bad boot, I took the opportunity to replace the coil and IAT sensor with GM units. I also cleaned the MAF with the correct spray cleaner and did not touch the filaments.

Second emissions test:
2054 RPM
hc limit 55 reading 55 PASS - Barely
co limit .31 reading .71 FAIL
no limit 408 reading 119

Idle
hc limit 200 reading 47 PASS - big improvement over test one
co limit 1.00 reading .04 PASS

It was during this test that the service engine light came on and generated the two codes mentioned in the title.

Given that these two codes came up at the same time, we must be looking at a common cause. The MAF readings appear correct, though I have not tried to disconnect it yet.

Is it possible I mangled the PCM ground near the starter when I was working around there and that that might cause what I am seeing?


I have seen in the shop manual that an O2 sensor heater circuit short might cause this, but since both codes appeared at once, I figured the solution must be quite simple.

Many thanks.
Any other direction would be most appreciated

 

I know that the O2 sensor graphs from the Innova software are useless (Ugh) so I jotted down the front O2 sensor readings (left and right) in a couple of ranges.

These were taken from the same data log that was used for the previous graphs.

http://ftp.covingtonhill.com/Covington/Readings.jpg

Pardon my awful writing.

From my limited knowledge, it seems that the O2 voltage readings are pretty normal. They are taken about 2 to 3 seconds apart during the data record.

Also, the scanner shows that the O2 monitor has not run yet (because I only hooked up the battery and started it shortly before taking it in for the E-test).

Or perhaps the monitor has not run because of the two codes??

I wonder if the problem might be that I just need to drive the car more to give it a few drive cycles? I know - that sounds like a very optimistic possibility.

But the two codes must have a common cause, I would think.

Thx.

 

Both those codes set when the pre-cat O2 sensor voltage is above 775mV for an extended period of time, indicating a rich condition.

I took a look at your jpg's, but it would be a lot more useful to have a frame-by-frame data log in .csv or excel format. Does the Innova support "export as...." alternative file types? The format of the graphs is not clear, compared to the logs that I've seen from AutoTap, DataMaster, Freescan, etc. O2 sensor voltage shows as "0" with grid lines of +0.4, +0.2, 0 -0.2, -0.4. And the graph is a straight line at "0". The TPS %, engine RPM and the MAF flow are all consistent. But it's hard to make out what they are graphing for O2 sensor voltage.

Your handwritten O2 voltages appear to indicate the sensors are working normally, with no evidence of them sticking above 775mV.

 

Thanks for the response.

From what I can discern in the Innova software, there is no way to export the data as an excel file - as crazy as that sounds.

I realized that the o2 voltage reading graphs were completely useless (and there does not appear to be a way of resetting the scale on the Y axis to make it meaningful). I have had a quick look at the data log, but that was at idle for the most part. The wacky behaviour seems to take place above idle, based on the results of the most recent E-test.

I can input a longer stretch of the existing O2 sensor readings (as I did in the last post). In your view, are they swinging back and forth as they should?

Based on the MAF graph, would you say that sensor is operating properly?

Maybe I will reset the code and go for a drive and see what happens.

I can set the Innova to do a data log 50 frames before and 50 frames after a code is set by the PCM. Hopefully, that will shed more light.

Have you seen anything like this caused by a poor PCM ground?

Merci.

 

If your O2 sensor readings are 2 or 3 seconds apart, you're not capturing much data due to a low sample rate. The PCM does about 9 frames per second. But what you hand wrote appears to indicate they are moving like they are supposed to.

 

I believe I am able to reduce the PIDs to be sampled such that it will record only the O2s, perhaps along with RPM or MAF for a reference. I would expect that the sample rate will be higher if I lighten the load on the scanner's CPU.

I will report back.

Thx.

 

More data logs:
http://ftp.covingtonhill.com/Covington/carScan.zip
http://ftp.covingtonhill.com/Covington/4Scan.jpg

I have been driving the car quite a bit over the last several days and cannot get it to throw either (or both) of those codes again. I have done a number of sustained 2K rpm cruises, the conditions that set the code before.

If you look at the O2 readings (hand-written scan) the sensors still seem to be moving as before - though at times they seem to linger in the higher range before dipping back down below the 450mv point. Though conceivably, these readings could be due to the fact that the sample rate is low, compared to what the PCM is actually putting out. Even if I reduce the number of PIDs to be just the O2 output volts, the Innova scanner only samples every 2.5 to 3 seconds.

Based on the rest of the data output and the fact that it is now running squeeky clean at idle (according to the last e-test), is it possible to make an educated guess that it will now pass the 2K rpm smog test?

It is driving very well and showing great throttle response, though that is of course subjective.

If this does not sound too much like wishful thinking, I believe I just took the thing in too soon after reconnecting the battery (I did some idling and drove it directly to the testing station, 5-10 minutes away) and it had not had a chance to re-learn after the LTFTs were dumped when the batt was disconnected.

Opinions?

 

Follow-up

I drove the car for ~900 kms, it never threw the originally mentioned or any other codes and never generated any pending codes.

It seemed to be driving as strong as ever and I did not get any indication that either of my data logs were out of whack so I brought it back in for a third E-test, thinking that the disconnected battery had caused the loss of the LTFT info and had led to the failed emissions on test 2.

Well, it passed the 2525 RPM test with flying colours (a big reduction in these numbers, as compared to test 2), but it only barely passed the idle test (the idle emissions numbers had been far below allowable on the second test).

No idea why this would happen, I did nothing to the car in the two weeks since the second test, other than check for codes and gather data logs.

In any event, I am now licensed and the top is down. I will have to monitor it's data to see what else I can glean.

Test three emissions results:

2525 RPM Test

HC limit 55 reading 16 (big improvement)
CO% limit.31 reading.04 (big improvement)
NO limit408 reading 231


Idle - 910 RPM
HC limit 200 reading 164
CO limit 1.00 reading .99 (WTF?)


As you will have seen earlier, the idle readings for the previous test (#2) were:

HC reading 47
CO reading .04

That is a huge difference for having done no changes to the car, and having the test conducted on the exact same machine.

I hope the info helps someone else.

Thanks to all those who followed along and offered their views.