Extreme Rich problem causing missing 85 corvette advice?
Thread Starter
Instructor
Joined: May 2006
Posts: 128
Likes: 1
From: KY
Extreme Rich problem causing missing 85 corvette advice?
Last week I drove it home to change the oil. After changing the oil I took compressed air and blew the engine off because it's been quite dry around here. After doing that I started it up to check oil pressure which was fine. Yet soon as I started the extreme rich problem started. It blows a combination of blue/black/Gray smoke constantly and misses. What I have done is as follows;
Compression check on all the cylinders which was even 235 psi on all the motor is new with 1400 miles
I have a dmm and have ohms all the spark plug wires which were in range going by the spec of 1000 ohms per foot
I have checked fuel pressure which is 42 psi, exactly what I set it a month ago
I checked the timing which is 10*, hasn't changed, I checked it with esc unhooked
I also changed the spark plugs to eliminate the possibility
I have checked the resistance of the injectors which are stock 85s they all spec 16-16.5 ohm, admitable I forgot the scale on my meter I was using
I have a OTC scanner, my dad was a previous mechanic and the data looks normal, and have no trouble codes.
I have had the valve covers off to check for broken valvesprings and valvetrain which is all fine.
I have checked all vacuum lines, but will be checking them again
Any advice is appreciated thanks guys
Compression check on all the cylinders which was even 235 psi on all the motor is new with 1400 miles
I have a dmm and have ohms all the spark plug wires which were in range going by the spec of 1000 ohms per foot
I have checked fuel pressure which is 42 psi, exactly what I set it a month ago
I checked the timing which is 10*, hasn't changed, I checked it with esc unhooked
I also changed the spark plugs to eliminate the possibility
I have checked the resistance of the injectors which are stock 85s they all spec 16-16.5 ohm, admitable I forgot the scale on my meter I was using
I have a OTC scanner, my dad was a previous mechanic and the data looks normal, and have no trouble codes.
I have had the valve covers off to check for broken valvesprings and valvetrain which is all fine.
I have checked all vacuum lines, but will be checking them again
Any advice is appreciated thanks guys
Le Mans Master
Joined: May 2004
Posts: 5,866
Likes: 60
From: Hellinois
Finalist 2020 C4 of the Year - Modified
Check the connection at the mass air flow sensor, you may have knocked it loose. If it is okay then tap the sensor with a screwdriver handle & see if it straightens out. If tapping on the sensor fixes it then it's time for a new sensor but do some tests on it first to verify.
Le Mans Master
Joined: Sep 2006
Posts: 6,050
Likes: 147
From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
Wow, I wish I was so rich that it was a problem............................... 
The 85 has a MAF module. Sometimes when it goes bad, it tells the computer that there is a lot more air going in then there really is. the computer kicks in the fuel to match the airflow, and the fuel rate of enrichment outweighs the oxygen sensor.
You might try checking the oxygen sensor wire. and The MAF, and the vacuum hose on the regulator.......
Although, if you somehow disturbed the EGR solenoid, it might keep the EGR valve open, and cause it to run rough. On an 85, it is at the rear right hand of the plenum. And it's on top, easily blown with compressed air.
The 85 has a MAF module. Sometimes when it goes bad, it tells the computer that there is a lot more air going in then there really is. the computer kicks in the fuel to match the airflow, and the fuel rate of enrichment outweighs the oxygen sensor.
You might try checking the oxygen sensor wire. and The MAF, and the vacuum hose on the regulator.......
Although, if you somehow disturbed the EGR solenoid, it might keep the EGR valve open, and cause it to run rough. On an 85, it is at the rear right hand of the plenum. And it's on top, easily blown with compressed air.
Last edited by coupeguy2001; Nov 14, 2010 at 07:51 PM.
Thread Starter
Instructor
Joined: May 2006
Posts: 128
Likes: 1
From: KY
I'll try without the maf hooked up, I've already unplugged the oxygen sensor which made no difference, but I did not check if I was getting a signal from the harness. What is so annoying is it will not throw a service engine light, not even a rich code. When the problem first occurred it would go into closed loop rich, now the o2 voltage will vary (always rich), but will stay open loop. I'll keep trying, I appreciate the help
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Le Mans Master
Joined: May 2004
Posts: 5,866
Likes: 60
From: Hellinois
Finalist 2020 C4 of the Year - Modified
If you recheck my earlier post you will see I said to verify, I guess I should have spelled it out and said to test the circuit and see if the maf is getting the power it is supposed to. Did you try cleaning the maf connections?
