That's what led me to replace the egr valve. It didn't help though.

This can be a frustrating experience if the computer doesn't have any codes to point you in a specific direction.

 

Injuneer:

I checked the fuel pressure regulator with a vacuum gage (it's fine) and ran the car tonight with the fuel pressure gage connected.

At all ranges of cruising the pressure stays up in the 38-40 psi range. When pressing the accelerator a bit the pressure goes up just a tic and then returns to 40 or so when you let off. When the motor starts to act-up the fuel pressure stays steady. So I think I can rule out fuel pressure.

I pulled a plug to see how they were burning. The insulators were bright white, no soot or other deposits. It looked to me like it was running lean. (But I'm an old drag racer and what do I know about these stupid computer cars)

The idle is still high and I can find no vacuum leaks anywhere.

With a Baro reading of 28.37 the MAP is 19.5 at idle. Long term fuel trims are now 121 and 123.

Your "Scanner Reading" page info says injector pulse widths should be 1.4 to 1.6 at idle. Mine are 0. They will go to 4 blipping the throttle slightly. Do you think this is significant?

IAC is at 44 with a 650 rpm requested but the actual idle is 1100.

MAF flow at idle is 10 gps and the O2 sensors are ranging bewteen 96-400 on the left and 89 to 720 right.

Someone said that this looked like the MAP sensor was bad. Does that make sense?

One other thing, when I got the new ignition module (from GM PartsDirect) it was in an already opened bag and the heat sink grease was missing. I complained about it and they assured me it was brand new and not damaged (this is a long story I won't get into right now). I got some heat sink grease from Radio Shack and installed the module. It has worked OK for 2 months now but the question is: if the ignition module is defective, when it gets hot would it cause my problem?

I appreciate any input you may have.

 

Sounds like your having the same symptoms as me, except mine runs fine for a while after closed loop. It will run for up to 2 hours and be fine. Then it goes crappy. Also, everything on the scanner checks out within spec... EVERYTHING! Well, the IAC count is 160, but that's only due to the fact that the computer tells it to open because it idles like crap. When the IAC is unplugged it just idles crappy, but doesn't race. Sounds to me like you have some sort of vacuum leak if the IAC is staying at 44 counts. But also raises another question... Why is the IAC staying open if the idle is 1100 with a requested 650 rpm? I don't get it and this just confuses me more on my issue. <-- That makes two of us!

 

You're right, it's confusing.

Give me a good old fashioned pre 1970 small block and I'll be happy.

 

Yeah, I'm only 20 and the only experiance I've had is with newer cars. Well, 1990 and newer... I guess that's new to some people, lol. I've only been in school for Automotive Technical Services for one year, but I have learned A LOT. The most of what I know is from school and it is mostly all based on newer vehicles (fuel injected anyway.) I have even stumped one of my professors with this problem. We scanned it and he was still stumped. Were gonna set the minimum idle air on wednessday as a lab. He said i should start there because the cover was missing from the screw and he said someone might have played with it before.

 

Agree.
Sounds like the PCM is effectively controlling A/F ratio.
Have you checked the TPS voltage at closed throttle? Is it under 0,90V?
That's a problem. You say the engine is "bone stock".... MAP at idle should be 9 to 10"Hg. In effect, you are only pulling 9" of vacuum with a stock cam. Are you sure the throttle blades are closed?
Within an acceptable range. But is this true for all/most of the cells?
Not sure what it means. My quote of "1.4-1.6 at idle" seems to be on the low side. I see a lot of people wrestling with why they see 3.0mSec pulse widths at idle. Pull the fuel rails up, pressure the fuel system, and watch for dripping injectors.
Definitely a problem, and one that is hard to explain. If the idle is above spec, the IAC motor should be closing down. Are you using the scanner to read RPM, rather than the tach?
MAF seems a bit high, but that's because of the excessive idle RPM.
See comments above. Your values are wrong. Either the throttle blades are open, the valves are too tight and not closing or the sensor is faulty.
Try spacing the IC module away from the head. Shoebox's Tech Pages have a suggested method. Are you sure its dielectric grease that is used? I though it had something to do with heat conduction?????

 

It's highly unlikely that there is a single misfire on the cylinder that is glowing. Even more unlikely that it's firing late. Shoe was closest by mentioning to swap that injector with a good cylinder. A valid test and I would like to know the results. BUT what I want to know is what are the results of doing a leak down test on all cylinders. I think you could have a burnt exhaust valve on that cylinder.

A lot of people do a compression or a leak down test last. When they should be doing it first. Compression is not near as good as a leak down. It will give false indications.

 

Yes, it's 0.4v

Yes, I've checked that at least three times. And, the hidden fixed adjustment screw has never been tampered with.

I can't check that with my scanner. It's not a real expensive one.

I'm going to do that today.

Yes.

I guess we're drifting towards the MAP sensor? It's seems like it's a pretty important part of the fuel management system.

Yeah, I had a brain fart there when I wrote that. I put on heat sink grease not dielectric.

I really appreciate your help in going over this stuff.

 

An update:

It's not open/closed loop related.

Did a check today and the system goes closed loop before the problem starts to occur.

What do you think?

 

ok if you replaced your opti, you most likely moved your wires a little bit, make sure they arent touching any of the pulleys... this happened to me and ive had to replace them several times... make sure all of your wires are getting power from the opti to the spark plugs and it isnt stopping along the way.

 

Just wanted to let you guys know that about 99% of you are azzhats and Injuneer is the only guy on this site that knows what he's talking about.

Goodbye.

 

If you've got a problem with us them don't ask us questions. What the heck is an "azzhat" anyways??? Just remember buddy... whos the one with the car that doesn't run right? And do you honestly expect anyone to make a right on diagnosis before asking any questions without actually seeing the car? Get real dude. I sure as heck don't want to see any more questions come from you.

 

your welcome for my imput, if you wanted Injuneer PM him or specify him in title...

Shoebox has been a great help for all my problems and all my problems have been fixed due to the Azzhats on this site, although my problems have constantly been elctrical thats what i suggest because thats what i know... thanks for the insult.

 

Among many is wisdom...shunning everyone else for trying to help is pretty pathetic. I for one appriciate every person that offers his/her assistance when I'm confused. Something makes me think no one here is offering their advice to point you in the wrong direction. Pretty crappy....

 

There's another "ignore" to add to the list.