Hallo to everybody,

I’ve got a problem with my ’87 TA 305 cui TPI which I could’nt solve yet and I’ve searched the forum for it but without success. The driveability of the car below 1500 rpm is really bad (jerking and stalling). So I connected a timing light to check the ignition timing while engine idling and tan bypass wire disconnected: it was exact 6 degrees btdc. Then I did the same with the bypass wire connected: the ignition timing went to the left out of table (much before 12 degrees btdc, I suppose about 20 degrees btdc). At first I thought the knock sensor could be the reason but that is illogically because the knock sensor only retards the ignition timing (that means it should go to the right hand side: late).
Can anybody tell me which part or electronical component can be responsible for this symptom? Any help is appreciated.

 

That's what it's supposed to do.

 

May not be a good idea to have your VIN as a name.

 

Supposed to do what? Please more actual.

 

Exactly what it's supposed to.

That tan wire you disconnect is for the timing control, you have to disconnect it to set the baseline timing with NO computer input. As soon as you plug it in the car is using readings from all sensors to adjust the timing on the fly. The timing jumping around when you plug it in is perfectly normal, just make sure it doesn't do it with the wire disconnected. If it runs good at high RPM I doubt you have timing issues (although it's possible). The knock sensor will make it feel gutless if it goes bad, but shouldn't cause you any stalling or hesitation issues.

I would look other places first though. Start with checking plugs and wires, and a coil test. Check for proper operation of your EGR. Check for bad vacuum leaks. Make sure fuel pressure is adequate. Those are all more likely.

Don't overlook that EGR (like everyone always does when I mention it) you'll kick yourself for it later if that turns out to be it (which it has for MANY people with problems like this) and they're easy as hell to check

 

Thank you Dizturbed One.
The EGR and the vacuum hoses hav'nt been checked yet. I'll do that next. I forgot to mention that I get no error codes. Please excuse if my english sounds strange, it's just because english isn't my native language.

James

 

also check your manifold absolute pressure sensor (map) my 91 camaro is doing similar things and i took it to my automotive tech class and i thought it was the timing too but when i timed it it was doing the same thing well we unplugged the vacuum line to the map and my car idled alot better but didnt quite run in gear so thats what im saving for but dont forget the egr it could be that too

 

I have had to break my works on this car for some month, but now I could continue it and I am happy that I can tell you: "The problem is remedied!". It was the EGR-Valve.
Thanks again to everybody who helped
James