SweetZRag

I have been having a problem with rough idle and hesitation and now I am getting a code 27 (using Freescan). I didn't get the code until I started troubleshooting the EGR circuit. I found a small vacuum leak between the manifold and the EGR solenoid which I am repairing.

I ran the electrical and vacuum tests called for in the service manuals and it is telling me the PCM is the problem. I don't believe it. I am looking for other ideas. Can anyone help?

Here is what I know... The battery voltage is present on the input to the solenoid. THe control line from the PCM (A9) is always low when I turn the key on. If I disconnect the A connector from the PCM, it goes high so I know that the activate signal (low) is coming from the PCM, not a short in the wiring.

Besides a faulty PCM, what else could cause the signal to stay low? Also, the code does not get set until the car is above idle. If the EGR solenoid is stuck on due to the signal from the PCM, shouldn;t the code get set at idle when the EGR is not supposed to be "ON"?

Any help would be appreciated as I am getting mixed signals.

Jeff Muller

SweetZRag

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SweetZRag

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SweetZRag

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Injuneer

PLEASE follow board rules.... "TTT" and "bump" are only permitted once per 24 hours.

You have been warned. Failure to abide by the rules can be grounds for removal from the board.

SweetZRag

Injuneer, Let me respond professionally.

First - take it down a notch. A friendly reminder would have been nice. Thank you for the "WARNING". I wasn't aware there were rules on tis kind of thing. I'll certainly read them if you'll be so kind as to help me find them. Not everyone is an expert on this board and and we may need your help, not your scolding. I'll do better next time.

Second - What does "TTT" mean?

Third- My apologies to anyone else who is reading this since this conversation has nothing to do with my original request for help. I would have preferred my scolding as a private message but I guess unprofessional public responses is not against the rules.

Fourth - I am still trying to resolve this problem and would greatly appreciate any help anyone can give.

Fifth - Can anyone recommend another method, that complies with the rules, where someone who is sitting at their computer looking for immediate feedback on an issue can keep there question current?

Thank you to all of the board members who have helped me in the past. I hope this board stays as friendly as it has been so it can continue to attract new members who are learning the ropes.

Jeff Muller

Injuneer

For your enlightenment:

http://web.camaross.com/forums/showt...&threadid=5485

SweetZRag

Injuneer,

Thanks for that article. I can better appreciate your position after reading it. Have a good weekend.

Jeff Muller

shoebox

If you put a test light across the EGR harness plug terminals, with key ON, engine not running, there should be no light. The EGR only operates during part throttle so that is probably why you get the code at the time you do.

SweetZRag

Shoebox,

Thanks for your help. When I turn the key on with the engine not running, the test light does turn on. The only way I can get it to go off is to disconnect the A connector from the PCM. It appears that the problem is with the PCM. Since the car has over 250,000 miles on it, I decided to replace the EGR solenoid and the vacuum harness to be safe.

I drove the car for about an hour today and the code 27 has not come back yet. I wouldn't have expected that what I did would have fixed the problem so I am still waiting to see what happens.

I am still having the original problem that led to all of this. The car runs rough until it has been running for a few minutes. I haven't been able to confim if the problem goes away at exactly the same time the car goes into closed loop, but that is what I suspect.

I have used the data logger in freescan and captured the data before and after the rough running condition. I have been analyzing the data but don't see a problem yet with any of the sensors.

Do you have any ideas?

Thanks,

Jeff Muller

shoebox

Will the freescan show when the EGR solenoid is activated?

Any possibility that some stray voltage is getting onto the control wire to the solenoid? Maybe a crossed wire?

To see if EGR activation is causing your rough cold idle, plug off the vacuum supply to it, so it cannot open.

SweetZRag

Freescan doesn't show the EGR activation status of the EGR system. I would consider buying a better program if it will work with my 94 Blazer(Tahoe) also. If you can recommend one, please let me know.

I might be able to rig a test light to monitor the status of the EGR circuit while driving. I will try it.

I checked the EGR circuit using a volt meter and the positive side is always hot as it should be. The control side (which connects to the PCM) was stuck low causing the EGR to activate when the key was on with the engine not running. It would go open when I disconnected the harness from the PCR so I think there is no stray voltage or ground in the wiring. I think I might have more than one problem and that is causing the confusion. I replaced the EGR solenoid and vacuum harness last night and the code 27 is not happening now but the car still runs rough.

I logged the data from Freescan last night while driving the car. The rough idle was occuring and then cleared up around the 100 second run time mark but I don't see anything wrong with the recorded data. The car did go into closed loop around the same time frame that the problem cleared up.

If I sent you the spreadsheet from Freescan, would you be able to recognize a problem?

I will try plugging the EGR vacuum feed tonight and let you know what happens.

By the way, about 1 week ago I got a code for a missing Hi Res signal. I replaced the OptiSPark. I am now not getting any codes at all but it still runs rough until the car reaches about 20 MPH. The roughness was happening before the OptiSpark problem so I think the roughness is a separate problem.

Even if the car is warm and turned off for 5 minutes at the convenience store, when I restart it, the roughness comes back until I drive down the road for a little ways and then the car runs fine until I shut it off again. It happens most times but not every time.

Thanks for your help. I'll try your suggestions tonight and let you know what happens.

Jeff Muller

SweetZRag

Some new information. I really appreciate your help.

Last night I noticed some flashing around the ignition coil so I replaced it. Even with the new coil I still see some corona but I think this is not an actual flash over.

I installed DataMaster and recorded some data. One thing I noticed is that the EGR duty cycle never changed from 0. Should it change when I rev the engine after it is in closed loop?

Even so, it doesn't explain the rough idle when the EGR is not supposed to be on. I capped the vacuum input to the EGR solenoid on the manifold side and it still ran rough.

I noticed that as the engine approaches closed loop mode, the IAC kicks way down and the the LTerm turns green and the STerm values turn red indicating an A/F mixture problem. When this happens is when the car starts to run smooth. It appears that the roughness occurrs while the car is in open loop and when the car goes into closed loop mode, the sensors kick in and the car is able to compensate for the problem by changing the A/F mixture.

I have posted a screen shot of DataMaster when the car just goes into closed loop and it goes lean. At the point this shot was taken, the car was idling smoothly. Can anybody tell what the problem is from this picture?

http://photo.starblvd.net/BigDaddy/6...w=*B5040576132

I have also noticed a ticking sound from the rear of the motor. It sounds like an exhaust leak. I can't identify the source with my hand (boy it gets hot back there!! ) It sounds like the driver's side. Could this cause the lean condition?

Jeff

shoebox

I don't think the EGR will energize unless you are actually driving. I might be wrong.

Datamaster. Much better. I can look at the file if you want to send it to me. I don't consider myself an expert, but I can look. I use it on my car.

Make sure that tick you are hearing is not from an arcing plug wire.

SweetZRag

ShoeBox,

I just emailed you the DataMaster file. It's a lot more useful than Freescan but I don't know how to read all of the data yet.

I will look for arcing from the plug wires tonight. I didn't see any last night but I only looked from the top.

Tonight I'll drive the car and see if the EGR activates.

Jeff