Intermittent Lean running and Erratic TCC
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Intermittent Lean running and Erratic TCC
86 LB9 transplant. Everything was new at the time of the transplant with a few exceptions. The MAF was replaced at first fire up cause the one from the donor was bad.
Lean Symptoms.
Every so often the engine will go way lean on accelleration and cruising. Say fire it up and drive around the neighborhood. You can lay on the gas and all it will do is slow down and if pushed far enough it'll do a small lean pop through the intake. It will usually only do it for a minute or two or a mile or so if that. Then it goes away.
There are times where it will come back but for a very short time. Say at a stoplight it'll idle fine. Then you start to open the throttle and it's fine for a second then it goes way lean. It'll do that for a few seconds and then go away.
Lean testing.
Unfortunatly it will never do it while I have the scantool hooked up to it. Also in many cars I have found allot of problems like this to be difficult to diagnose bcause the system is running in diagnostic mode with the scantool hooked up and it changes too many things IE Idle speed etc and often covers up the problem you are trying to diagnose.
So I have back probed test leads installed so I can see if TPS voltage or MAF voltage do anything funny when the engine does it's lean thing. I have two voltmeters to watch at the same time.
With the scantool hooked up everything looks good. MAF is 12gps @1K idle (higher cause of the scantool hooked up) MAF reads high 100s at full throttle. MAF is a rebuilt unit as the good new ones are not available locally.
TCC symptoms.
Tcc is intermittent all the time. It will constantly go in and out.
TCC testing.
All variables look good while cruising, TPS steady etc...
Usually when I come across problems like this it's caused by a bad ECM. Was just wondering if anyone had any similar experiences. (have replaced lots of bad GM computers especially on 94-95 cars)
I have to check the yard again wendsday to see if I can find an ECM to try out. I would usually just buy a reman but I am going to be converting the system to a 7727 ecm once this issue is worked out and i put in a new engine.
Lean Symptoms.
Every so often the engine will go way lean on accelleration and cruising. Say fire it up and drive around the neighborhood. You can lay on the gas and all it will do is slow down and if pushed far enough it'll do a small lean pop through the intake. It will usually only do it for a minute or two or a mile or so if that. Then it goes away.
There are times where it will come back but for a very short time. Say at a stoplight it'll idle fine. Then you start to open the throttle and it's fine for a second then it goes way lean. It'll do that for a few seconds and then go away.
Lean testing.
Unfortunatly it will never do it while I have the scantool hooked up to it. Also in many cars I have found allot of problems like this to be difficult to diagnose bcause the system is running in diagnostic mode with the scantool hooked up and it changes too many things IE Idle speed etc and often covers up the problem you are trying to diagnose.
So I have back probed test leads installed so I can see if TPS voltage or MAF voltage do anything funny when the engine does it's lean thing. I have two voltmeters to watch at the same time.
With the scantool hooked up everything looks good. MAF is 12gps @1K idle (higher cause of the scantool hooked up) MAF reads high 100s at full throttle. MAF is a rebuilt unit as the good new ones are not available locally.
TCC symptoms.
Tcc is intermittent all the time. It will constantly go in and out.
TCC testing.
All variables look good while cruising, TPS steady etc...
Usually when I come across problems like this it's caused by a bad ECM. Was just wondering if anyone had any similar experiences. (have replaced lots of bad GM computers especially on 94-95 cars)
I have to check the yard again wendsday to see if I can find an ECM to try out. I would usually just buy a reman but I am going to be converting the system to a 7727 ecm once this issue is worked out and i put in a new engine.
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