Just purchased an 1989 Pontiac Trans Am. It has the F Code engine. 305 TPI. The car was involved in a minor wreck in 1996 on the right side behind the front wheel. It would not run after the accident so the computer was replaced with a NAPA direct replacement. The cars runs terrible. I sent the timing tonight but the distributor does not advance the timing until the engine hits 3000 RPMs. Then it breaks loose and comes to life. Why does the timing not advance util 3000 RPMs? I know how to properly set the timing so this is not the problem. Where should I look? What should I change to fix the problem? Any and all help would be appreciated. Thank you. Jim Armbrust

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Newbie 1989 Pontiac Trans Am w/305 TPI

 

Jeasen,

Welcome aboard!

You base timing is set similarly to any other engine, except you must disconnect the ESC bypass connector to eliminate any advance from the ECM/EST module. The connector is located in a tan/white wire at the rear of the engine compartment:



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Later,
Vader
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"Let the bodies hit the floor!"
Adobe Acrobat Reader

 

Maybe I unhooked the wrong connector when I set the timing. The one I unhooked was closer to the heater fan motor. I will try again tomorrow. Even if I did, why does the timing not advance until the engine hits 3000 RPMs? It seems like it just breaks loose at 3000. A real dog before that. What could this be? Vader, are you from the Turbo Buick list?

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Newbie 1989 Pontiac Trans Am w/305 TPI

 

Sorry, but I don't get on the Buick board much at all.

That's probably some other guy who saw my rear license plates from the pilot seat of his Buick.



Anyway, you timing should be ramping up well before you hit 3,000. Are you monitoring the advance with a light while running? As soon as the EST bypass connector is reconnected you should see a substantial advance in idle timing. This may retard slightly with the first "blip" of the throttle but should advance steadily after that with RPM. Maximum advance added by the EST and ECM is generally around 26° with a stock PROM in the ECM.

I'm not certain, but the advance may be a function of the TPS sensor as well as the engine RPM signal from the distributor reference pulses. What other symptoms are you experiencing? (Poor idle quality, wandering idle, stumbling on acceleration?)

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Later,
Vader
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"Let the bodies hit the floor!"
Adobe Acrobat Reader

 

No other symptoms. Just sluggish throttle response until 3000 RPMs. The timing does not advance until it reaches 3000. It stays at 6 degrees until 3000 RPMs then it advances. I am using a timing light to see this action. I know how it should work, but it does not work properly. Any idea what could be causing this? Should I change the distributor module? What else should I look for? Could the new computer be causing this? Thanks again.

 

Any ideas? Anyone?

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Newbie 1989 Pontiac Trans Am w/305 TPI

 

I had a similar prob.
How do you know that the timing is advancing?

How do you know that the timing only advances at 3K RPM?

I had the same prob.It turned to be a vacumme leak and a Idle air control valve(IAC). The stupid ECM was conpusating for the leak. Once I replaced the Gasket in the TBi the leak was fixed and I had to readjust the IAC for the stupid,dumb,stuburn,and No error code giving ECM. stupid computer!!

NEXT TIME I WILL PROGRAM THE DAM THING MYSELF!!

 

Well the problem is fixed. Along with the new computer there was an ignition module laying in the car. I changed the module back to the original GM one I found laying in the car. I reset the timing to specs and the car runs perfect. The timing advances like it should. The motor sounds strong. Now that the mechanicals work right, I will do the needed body work. Then I will have a very nice TA to drive around in. Thanks to everyone who tried to help.
Jeasen

 

Hey Jeasen, welcome to the group!
Later
Mike

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