[Mike56]

My son just completed a carb to TPI change: matching computer, gas tank, outside rear electric fuel pump, trans accel cable change, etc. His car is an '86 Camaro 305 IROC. The TPI/manifold and computer is off an '89 Z28. His major problem is the fact that on cold start he has to crank over the engine for up to 15 seconds before it fires. Then, it idles at over 2000 rpm and he has to pop the hood and reset the idle(until the next time he starts the engine). The car has no smog and my son talked directly to a chip manufacturer that custom made a chip for him with no smog and maximum performance. He also mounted a high flow external electric fuel pump back by the tank.
My son repairs and custom builds PC's for a large electronic co. Thus, he plugged into the ecm via his laptop and, of course, verified all codes and wiring. Any help would be appreciated. Derek's very punctilious and is trying to figure it out on his own, and it's not working(if he knew I was writing this, he'd probably shoot me!).

[Eric Kammerer]

Hi Mike! Welcome to TC!

We are more of a 67-69 site, but I might be able to help.

First and foremost, I'm going to point you to a good Third Gen site:

http://www.thirdgen.org/newdesign/tech/

Second, I know that TPI units up to 1988 used a separate injector for cold start whch were a problem. 89 and up just used the other 8 injectors. If someone mixed and matched injectors, it could cause what you described.

http://thirdgen.org/techbb2/showthre...ght=cold+start

The throttle position sensor (TPS), Idle Air COntroller (IAC), and fuel pressre are also usual suspects.

Go to the above site, but keep checking back here. We do have some 3rd gen folks that may have answers.

[BonzoHansen]

I thought only 85 had cold start. Huh, learn something new. If this were a stock application, I’d say check fuel pump relay. I’d get fuel pressure measurements. Having to change the throttle setting, that is odd.

[Mike56]

Hi Eric,
Oops! Didn't know it was a 67-69 site, but for info, I'm 57-Bought a brand new 69 Corvette Stingray, 435 hp/Turbo 400 automatic(found out later that they only made 244 units of 435hp/auto.
However, thanks for your help, and I'll check it out. Have a GREAT DAY!!
Mike56

[Mike56]

Hi Bonzo,
Where I'm not the sharpest knife in the drawer, you lost me. The 85 has cold start? You mean that the fuel is kept pressurized? He was adjusting the throttle body idle.
Thanks for your help.

[Eric Kammerer]

Bonzo -

What I have read said 85-88 had cold start injector, 89 up did not. I never owned one, but did a fair amount of research when I was considering a TPI motor for the 68. I decided to stay old school though...

Mike, yes the rails that the injectors sit in are always under pressure, and if there's a problem in an injector (or more than one) the pressure bleeds off and causes problems.

[Mike56]

Thanks for the quick reply, Bonzo. We'll be pulling the injectors this weekend, checking on the fuel pump and fuel regulator. Since I asked you about cold start, I researched it on the net and came up with the same year. Wonder if it can be incorporated into the '89 system? GREAT INPUT! You get an 'Adda Boy'!

[dnult]

Many TPI systems have been converted to a later program that does away with the cold start injector. The ARAP bin file is one that comes to mind that is a popular upgrade. But it seems like it is written for a 700R4 application. In any event, it uses a rich injector pulse during crank instead of the cold start injector. Unless you feel like getting up to your neck in ECM acronyms you might want to just diagnose and repair the cold start circuit if that is what is wrong with it.

[Supertex]

***Moved***

[kustomwerker]

look into the fpr bleeding off pressure...could be the line is charging during the 15 second crank when it should already be charged...you said he was adjusting the throttle body idle...is it tbi or tpi...adjusting the butterfly for the tpi air intake will throw the tps sensor out of adjustment, so set the tps via the screw you are messing with, and then leave it alone...the idle is adjusted thru the computer via an iac(idle air control) motor...its a valve with a 4 wire plug on it...pass side right under the tps(throttle position sensor) sensor...my guess is it`s inop, and thats your idle problem...could be no power to it, or no ecm signal, or even just crapped up real bad...pull it, and inspect the pintle and seat for carbon build-up...hope this helps...post back if not, and we`ll keep picking at it...