AC Delco/Delphi. Do not use Bosch.

Yes, an O2 sensor can give faulty readings without setting a code. Or the wiring can be shorting out, causing a bad signal, and not set a code. But that problem would most likely not affect both sides of the engine, unless the problem is due to contamination with lead from the fuel or silicates/phosphorus from the coolant.

 

No significant exhaust leaks found after an shop inspection today. Next up: two new O2 sensors which are on the way. I'll update again after that.

Feedback always welcome!

 

Another thought also, check your intake manifold gasket. Just spray some carb cleaner around the seal, and if the motor revs up some then its bad. I say this because it happened to a friend of mine. Car was pulling air in and showing a lean code on one side, and then wasn't properly burning the extra gas being put in. I don't know how much of a problem that is on these cars though because of the reverse cooling system. But only costs about 5 dollars to check.

 

The new o2 sensors have been installed. One of them was a major f@#king PITA! (passenger side).

The car hits closed-loop right at 205 seconds. I've recorded some new data, but don't yet know if the HC problem/extra-fuel at idle/false-lean condition problems have been corrected. I hope to know more soon. Love the feedback.

 

Still adding extra fuel at idle, with Cell 16 BLMs of 142 (+10.9%) left and 146 (+13.3%) right.

Under load, left side is still bad in cells 9 and 14 with 14x BLM's, while the problem minimizes on the right side. 15 and a couple of others are close to 140 on the left, not on the right.

That MAP still looks high at idle - 50kPA at idle in middle of the log (idling in gear), and then drops to a more reasonable 40kPa in the idle period toward the end of the log (idling in neutral). The TPS looks steady closed throttle at 0.61V, so that issue is gone. Still some signs of knock retard, but not as bad as before.

I'm surprised it went into closed loop at 206 seconds. The coolant temp was only 109.9. The coolant seems to take a long time to warm up - took 10 minutes to reach 180*F. Low coolant temps will elevate HC and CO.

 

Invaluable feedback. Thanks, Fred!

A couple of things:

It looks like I need to completely rule out ANY exhaust problems. Although there isn't a leak deemed noteworthy by the local guy, there is evidence of a small damage to one of the exhaust manifold gaskets. It probably best to replace the exhaust manifold gaskets before moving too far forward to 100% rule out anything there affecting the car.

I did get a couple of misses early on in the road test when giving gas at low speeds or from stop. Probably need to check the plugs for any problems - though they are new within the past 6 mos or so (as are the wires).

Based on the ScanMaster tutorial (http://www.injuneer.com/ScanMast.html) it says:

"You engine can not run lean or rich in closed loop, unless the control system is not working, or the oxygen sensors are providing incorrect information. They will provide incorrect information if the are defective, there is an exhaust leak, there is a leaky injector, or there is a miss."

That brings me questions about the control system and what things I can do?

I'm curious what causes the MAP to be high at times? I wonder if I should replace the MAP sensor - can it read incorrectly if failing similar to the O2 sensors?

The coolant issue is also confusing, but my last run to emissions I had the car up to 210 degrees at test time based on the dash temp gauge. The thermostat is recently new and 180 degree. Could this be as simple as too high a coolant to water ratio or is the coolant temp sensor a possible culprit here?

Also, based on what I'm reading, double and triple-checking for a vacuum leak will be in the plan.

 

Update 7-22-11:

After the new O2 sensors and other work did not fix the high HCs at idle, I laid down the dough for an emissions waiver from a local shop (150.00). They did some testing to try and ID the problem. They did a cylinder kill-test - I don't know the formal name for it if there is one. They killed one cylinder at a time and recorded the difference in RPMs, etc. and found the two cylinders, #4 and #8 were 'weaker' than the others.

Figuring it would be either injectors, plugs/plug wire (which are newish), or an internal engine issue it was suggested to go over those things, including a compression test.

The compression test may not have been done exactly right, but I think we got the info we needed. We tested 3 cylinders total with only one plug removed at a time and did not block open the intake, which after some reading after the fact I learned should be done (ty shbox). As you probably know, 8 is especially a PITA to get to. Compression test results:

#4 read above 150psi.
#8 read approx 118-122psi.
#3 read 150-160psi.

These results lead me to think next is a 'Leak-Down' test. Again there are no codes, and vacuum and exhaust leaks have been all but eliminated. Occasional 'misses' (from 8, I suspect) and a low RPM/Idle 'slower than optimum get-off' are the current symptoms beside the high HC idle emissions. All other emissions passed just fine. Don't need a re-test until 2013, so my main concern is not that.

Do I spend money on a leakdown test or save my money knowing there will have to be some engine work done? Will I cause damage if I continue driving for awhile while I build up some funds? What types of things should I start concerning myself with?

Thoughts and feedback on what to do next appreciated.