HELP! Master troubleshooter needed! Injuneer, Shoebox, anybody!
Registered User
Joined: Jul 2001
Posts: 1,009
From: so close I can taste it...
First I would try re-adjusting the minimum air gap screw on the throttle body to see if you can get the IAC counts down. Is the IAC a GM part or did you get it from a chain store?
In your service manual does it give a spec for how much fuel the fuel pump should be able to flow in a given time period? Have you verified it?
I would also check valve adjustment and try the test above to see if the cats could be plugged.
In your service manual does it give a spec for how much fuel the fuel pump should be able to flow in a given time period? Have you verified it?
I would also check valve adjustment and try the test above to see if the cats could be plugged.
Registered User
Joined: Oct 1998
Posts: 226
From: Raleigh, NC
Cherry red manifolds? I beleive that motor is running way too lean. Shoebox has the right idea with the MAP sensor. I'd crank the motor using controlled vacuum at the MAP sensor like he mentioned. You may want to check the output on the 3 wire connector to it with a DMM or use a scantool to see if varies between 0v and ~5v. GM used different colors inside the connector to tell what range they were good for.
Doug
Doug
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Joined: Dec 1969
Posts: 27,725
From: Little Rock, AR
Originally posted by multicar
Cherry red manifolds? I beleive that motor is running way too lean. Shoebox has the right idea with the MAP sensor. I'd crank the motor using controlled vacuum at the MAP sensor like he mentioned. You may want to check the output on the 3 wire connector to it with a DMM or use a scantool to see if varies between 0v and ~5v. GM used different colors inside the connector to tell what range they were good for.
Doug
Cherry red manifolds? I beleive that motor is running way too lean. Shoebox has the right idea with the MAP sensor. I'd crank the motor using controlled vacuum at the MAP sensor like he mentioned. You may want to check the output on the 3 wire connector to it with a DMM or use a scantool to see if varies between 0v and ~5v. GM used different colors inside the connector to tell what range they were good for.
Doug
Thread Starter
Registered User
Joined: Apr 2002
Posts: 124
From: Milwaukee, WI
Originally posted by Vader
My thoughts, for what they are worth, is that you need to ignore all that has been done, and diagnose with a clear head.
I may have missed it, but do you have any O2 sensor data?
Also, have you confirmed that the timing chain has not jumped a tooth?
Good luck, it can and will be fixed, because as they say, "its just metal...."
My thoughts, for what they are worth, is that you need to ignore all that has been done, and diagnose with a clear head.
I may have missed it, but do you have any O2 sensor data?
Also, have you confirmed that the timing chain has not jumped a tooth?
Good luck, it can and will be fixed, because as they say, "its just metal...."
The timing chain was replaced at the beginning of the troubleshooting...Gears were dot-to-dot..
Thread Starter
Registered User
Joined: Apr 2002
Posts: 124
From: Milwaukee, WI
Originally posted by shoebox
Red manifolds, IMO takes it back to too much fuel. The excess fuel is burning outside the head when it hits the manifolds. As I said before, the MAP is way high. The pcm would consider this a high load and likely add the fuel. Gotta figure out if the sensor is the problem or something is causing it to read like it is.
How about a test to fake out the sensor?
Do you have a Mityvac or similar? Remove the MAP sensor and plug the hole in the manifold. Apply about 20" of vacuum to the sensor with a hose and your Mityvac. Crank it up and see what happens. Can you monitor it with Datamaster when you do this?
Red manifolds, IMO takes it back to too much fuel. The excess fuel is burning outside the head when it hits the manifolds. As I said before, the MAP is way high. The pcm would consider this a high load and likely add the fuel. Gotta figure out if the sensor is the problem or something is causing it to read like it is.
How about a test to fake out the sensor?
Do you have a Mityvac or similar? Remove the MAP sensor and plug the hole in the manifold. Apply about 20" of vacuum to the sensor with a hose and your Mityvac. Crank it up and see what happens. Can you monitor it with Datamaster when you do this?
Thread Starter
Registered User
Joined: Apr 2002
Posts: 124
From: Milwaukee, WI
Originally posted by Dan K
First I would try re-adjusting the minimum air gap screw on the throttle body to see if you can get the IAC counts down. Is the IAC a GM part or did you get it from a chain store?
In your service manual does it give a spec for how much fuel the fuel pump should be able to flow in a given time period? Have you verified it?
I would also check valve adjustment and try the test above to see if the cats could be plugged.
First I would try re-adjusting the minimum air gap screw on the throttle body to see if you can get the IAC counts down. Is the IAC a GM part or did you get it from a chain store?
In your service manual does it give a spec for how much fuel the fuel pump should be able to flow in a given time period? Have you verified it?
I would also check valve adjustment and try the test above to see if the cats could be plugged.
I have not played with the air gap screw or measured fuel flow...Two excellent points...I'll try those tonight....This weekend I'll drop the cats down & see if the exhaust is an issue....
The IAC was a napa part...I really havent figured out any way to verify if it's actually working or not..I tried holding the old one off the car and started the car ....diddn't notice it moving, but when I cut the car off the spring and pintle flew over to the other side of the garage!
Thread Starter
Registered User
Joined: Apr 2002
Posts: 124
From: Milwaukee, WI
Originally posted by multicar
Cherry red manifolds? I beleive that motor is running way too lean. Shoebox has the right idea with the MAP sensor. I'd crank the motor using controlled vacuum at the MAP sensor like he mentioned. You may want to check the output on the 3 wire connector to it with a DMM or use a scantool to see if varies between 0v and ~5v. GM used different colors inside the connector to tell what range they were good for.
Doug
Cherry red manifolds? I beleive that motor is running way too lean. Shoebox has the right idea with the MAP sensor. I'd crank the motor using controlled vacuum at the MAP sensor like he mentioned. You may want to check the output on the 3 wire connector to it with a DMM or use a scantool to see if varies between 0v and ~5v. GM used different colors inside the connector to tell what range they were good for.
Doug
Thread Starter
Registered User
Joined: Apr 2002
Posts: 124
From: Milwaukee, WI
Did anyone see anything unusual on the datamaster files that I sent out?
P.S. I really appreciate all the input...
I was at the point where I ran out of ideas and was about to take [tow] it to the shop!
P.S. I really appreciate all the input...
I was at the point where I ran out of ideas and was about to take [tow] it to the shop!
Registered User
Joined: Feb 2001
Posts: 1,967
From: Bay Area, CA, USA
Check the coolant temp sensor in the water pump... I broke mine doing the supercharger install and my car would be okay but once you press the gas it bucked and wanted to die.
Also, I remember a while back somebody having major probs on a 93 LT1 because his chip was not plugged in correctly. It's worth a try, just make sure it's plugged in all the way.
If you want another opinion on the logs, send em my way. R4a2m0o@aol.com
Also, I remember a while back somebody having major probs on a 93 LT1 because his chip was not plugged in correctly. It's worth a try, just make sure it's plugged in all the way.
If you want another opinion on the logs, send em my way. R4a2m0o@aol.com
Registered User
Joined: Jul 1999
Posts: 3,647
From: Winnipeg, Manitoba, Canada
Are you sure your cats aren't clogged?
Disconnect an O2 sensor and see how it runs in open loop.
If it still stalls or has red manifolds then its not a sensor issue.
Run your car open headers to see if it helps.
Disconnect an O2 sensor and see how it runs in open loop.
If it still stalls or has red manifolds then its not a sensor issue.
Run your car open headers to see if it helps.
Registered User
Joined: Oct 1998
Posts: 226
From: Raleigh, NC
It's sounding more like plugged cats or a serious vacuum leak. If the scan data shows 120 long terms, yes, it's pulling out fuel. I've seen red manifolds on turbo systems just from the shear heat of the exhaust moving through it and they weren't running rich. Didn't see the O2 readings in the prior posts.....0.9 is rich. The 160 IAC counts suggest it's starving for air or it can't pump out what it has.
Registered User
Joined: Nov 2000
Posts: 676
From: Calgary
This is probably one of the most informative troubleshooting threads I've read on any forum I frequent in quite some time.
I wish you luck in finding your problem, the advice offered here in this thread is well beyond my knowledge. I'm going to track it though because I'm reading this like watching a cliffhanger movie.
I wish you luck in finding your problem, the advice offered here in this thread is well beyond my knowledge. I'm going to track it though because I'm reading this like watching a cliffhanger movie.