I hope this is the correct place to ask this but I figured you guys would know the answer.

I have a 1989 GTA as my sig says that has been converted to 5 speed. It looks, drives, and feels like a factory 5 speed but it recently come to my attention that I may have missed something.

I have the computer (factory stock prom) tricked into thinking that it is always in neutral. I read in an online article that TPI cars don't advance timing properly when in neutral or park. Does anybody know if this is true? Can anyone think of a way I could remedy this situation if it is true?

It would seem that, if this is happening, that it is costing me power and prob hurting my mileage also. I'd like to get to the bottom of this if I can.

 

Does your mask show a Idle-spark advance value? Is that what you are refering to? My EBL does. I believe there may be a bit to check to utilize that SA value. My SA when not in idle at 800-900 35-40 map(where I idle manual trans) is much higher. I idle at 18d and found more SA was not as good. I may drop to 16 but have not yet.

 

I have not yet begun to burn my own. I'm still in school on that so to speak. But I figured you guys on here would be able to best answer this question. I have read that timing advance is limited to 20-22 degs in park and neutral with a TPI. Since I drive around with a 5 speed with a auto ECM that thinks I'm always in neutral, this may be a problem for me.

Does anyone know if it's actually true though?

 

I dont think the carb guys run that much timing. maybe 22 ded adv is for TPI and emishions? all i know is my car idles smother with less timing. I am TBI. I should check what stock timing is for a V8 TBI with emishions. I am non emishions. I suspect you too have a commanded idle SA. now the tables that I have have seperate drive/park RPM vs coolant. I set both tables to same RPM. Another variable.

 

walrus108, I don't know the answer to your question as I haven't looked at the MAF code in this regard.

However, the Park/Neutral input to the ECM should be left open. Not connected to anything. This has the ECM seeing 'in drive' all of the time. Which is the same as stock GM TPI stick vehicle set ups.

RBob.

 

What they I've been hearing, the 20-22degs would be the total max advance. Usually in my carb days with HEI and vacuum advance I'd have like 38degs total but that was with crappy 1970 BB Olds heads.

 

That would be what I want to do then. Even if it wouldn't matter, which I don't know, I'd be covered.

Do you know how I'd go about doing that? It may already be done if the wires were in the console. I tricked the neutral safety switch into thinking it was always in neutral so it would start. Maybe that's all I needed to do?

I really appreciate any info that can be offered.

 

On the auto shifter there should have been an orange/black wire. Smaller gauge then the safety switch. This is the input to the ECM. Just tape it off so it won't short to ground (which is park/neut).

This wire goes to pin B10 on the ECM. So can also pop that pin out of the ECM harness connector. Which may be easier then pulling the console.

RBob.

 

My comment was in regard to idle SA.