I have a 1986 tpi with 21,000 miles. The motor starts fine, slight rough idle, If you rev it up it will back fire at the throttle body or runners. There is also a smell of gas. After 4-5 minutes the motor is perfect at all rpms. The scanner says there are no problems. I relpaced plugs, egr senser mas flow senser. I checked injectors for ohms looked good. Any ideas ?
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Re: 1986 tpi backfiring
Rick, I had an 87, but I am not really a diagnostician. Maybe I can give you some more shotgun ideas. If you don't have the Helm (factory) service manuals, they have excellent fault tree charts for diagnosing problems like these. Advanced engineering degrees are not enough to understand some of them.
You said you checked the injectors...did that include the start-up injector. (I think this car has a start injector.) The rough idle and back-firing may be caused by rich mixture from the start injector not shutting off completely for the first 4-5 minutes.
I'm surprised you have NO trouble codes. I would think any kind of abnormal mixture would set off some kind of code...you may not understand what it has to do with the problem, but it seems like you should get something.
If it has never been done before, now is probably a good time for the throttle body to be removed, disassembled, and given a good thorough cleaning. This would probably also be a good time to replace your idle air valve if it hasn't been done before.
The smell of gasoline can result from the vacuum controls on the emissions canister not working properly, but that symptom is usually only evident after shutdown of a hot engine.
Good luck.
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