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Help! 1986 Trouble Codes 42 & 44

chris123

Well-known member
Joined
Jul 7, 2006
Messages
73
Location
Wilkes Barre, PA
I just purchased my 1986 Convertible 4+3 earlier this month, and am trying to get a bunch of stuff straightened out; the car never really had any power over 2,000 RPM's since I got it, so I was hoping that after my tune-up, it would be corrected, however it seems to be a little worse now; the check engine light will come on occasionally and I was able to pull codes 42 (Electronic Spark Timing (EST) & 44 (Lean Exhaust Condition); here is what I've replaced so far (all AC Delco parts)


Plugs
Wires
Distributor Cap
Rotor
Ignition Module
Oxygen Sensor
Coolant Temperature Sensor
Fuel & Air Filters
Even the sock filter attached to the in-tank fuel pump
Ignition timing set at 6 degrees
TPS set to .54 volts
Lightly tapped on the MAF sensor with no RPM change


I'm pretty decent with these L98's, however this has got me baffled; the car will sit there an idle perfectly, no missing or shaking; you can even rev it up and it sounds strong, however as soon as you get it over 2,000 rpm's when driving, it has no power and starts bucking and hesitating; it almost seems like the cats/exhaust is blocked; not sure if it could be fuel or ignition related; I did the diagnosis for code 42, and it led me to a possible bad ECM? Was going to try and replace the ECM and ESC Module to eliminate those 2 items; any additional suggestions before I take it to my mechanic? I went back over and double checked all my work, and everything looked fine, and as I said before, it still is showing the same symptoms (maybe even a little worse) than before I started my work; it's keeping me up an night trying to figure it out; wish I knew so I don't have to just throw parts at it...........
Thanks for any help or suggestions, Chris :)
 

jmhorn52

Well-known member
Joined
Feb 24, 2008
Messages
145
Location
Hampton VA
Corvette
2008 Yellow ZHZ
It sounds like the cats are blocked. I drove a car and it would run great to 35 then lose power and not go any faster. The cat was bad and was backing the exhaust up.
 

John Robinson

Gone but not forgotten
Joined
May 3, 2005
Messages
1,555
Location
Muncie, Indiana
Corvette
1993 Polo Green Coupe
The sensors are not the problem. The ECM is reacting to weak or lost signals from the sensors. Because the car is a plastic body the grounds are critical. Clean all the frame rail grounds and the collection of grounds on the bell houseing above the oil filter. Pull the connectors off the ECM and shoot some dialectric grease into the holes with pins and reassemble. Use the dialectric grease on all the connecotrs. Start the car and see if it improves or changes how it runs. If it is still not running well then start to follow the wires back along the wiring harness untill you find the ground bundles that are wraped in electrical tape. They will probable be corroded and need to be cut off and the wire stripped and resoldered to make a new common ground joint.

With all the work you have done replacing sensors you have pulled and tugged the wires and connectors to remove them. The wires for the sensors are very small and will brake easily now that they are old. Untill you have thoughly check all the wires and grounds don't buy and ECM. It took me a while and a new ECM before I learned that the wires were the problem on my car. I have replaced a lot of wire in the past year and finally have a car that runs like it should.
 
Last edited:

chris123

Well-known member
Joined
Jul 7, 2006
Messages
73
Location
Wilkes Barre, PA
It sounds like the cats are blocked. I drove a car and it would run great to 35 then lose power and not go any faster. The cat was bad and was backing the exhaust up.

That's what I am thinking as well; the fuel and ignition systems appear to be solid; before all the tune up work, it had a pretty crappy exhaust system from the cat on back; it was very rusty and had some holes in it; as part of getting the car ready for inspection, I installed a new rear y-pipe and mufflers, and now it seems to run a little worse, which would make sense since the exhaust is now more solid with no additional sources for exhaust to escape; I will see if I can take my mechanic for a ride and see what he thinks; hopefully that will solve my problem; will keep you posted; thanks for the reply :beer
 

chris123

Well-known member
Joined
Jul 7, 2006
Messages
73
Location
Wilkes Barre, PA
The sensors are not the problem. The ECM is reacting to weak or lost signals from the sensors. Because the car is a plastic body the grounds are critical. Clean all the frame rail grounds and the collection of grounds on the bell houseing above the oil filter. Pull the connectors off the ECM and shoot some dialectric grease into the holes with pins and reassemble. Use the dialectric grease on all the connecotrs. Start the car and see if it improves or changes how it runs. If it is still not running well then start to follow the wires back along the wiring harness untill you find the ground bundles that are wraped in electrical tape. They will probable be corroded and need to be cut off and the wire stripped and resoldered to make a new common ground joint.

John: I may try to take my mechanic for a ride to see what he thinks in regards to the exhaust; see my reply to the other post that just came through; hopefully I won't have to spend hours chasing down poor ground connections, however I will definately double check the ground bundle near the oil filter, as an oil change is the last thing I will need to do after I get it running correctly........
 

jmhorn52

Well-known member
Joined
Feb 24, 2008
Messages
145
Location
Hampton VA
Corvette
2008 Yellow ZHZ
IF you have time maybe disconnect the cats and drive it see what happens.
 

chris123

Well-known member
Joined
Jul 7, 2006
Messages
73
Location
Wilkes Barre, PA
IF you have time maybe disconnect the cats and drive it see what happens.

Update: Thanks to all that replied; I replaced the front pipe with the pre-cats and the main catalytic converter, and the car runs like it is new with full power; what a difference; as I come across the various grounds throughout the car, I will clean and double check each one to prevent any further possible issues relating to poor ground connections..........

Regards, Chris :)
 

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