I have been in the middle of a tpi swap on my 91 RS for quite sometime now, 2 kids and a divorce have stalled it but now I'm triing to get it finished. I have been away from the boards and from cars for a while now. I had a 90 speed density setup from a Firebirdbut the wiring harness and ECM were toast. My buddy is stripping his 89 IROC and said i could have his TPI which I know works bc i've seen the car run(it has a bad MAF).

My question is how much of the actual assembly is the same? Are the bases the same, the runners, teh throttle body, or the plenum? I already have the speed denisty stuff bolted on so if I don't have to change anything but wiring and some sensors that would be great.

 

If your TBI harness is still fine on the car with a few mod's it can run TPI as speed density. You just repin the ecm connectors with 730 ecm connectors. and add TPI injector plug harness and lengthen TPS and IAC harness.

Theres some tech articles on here how to do it.

 

Already stripped the TBI and got rid of it around 4 years ago thats how long this has been on hold for. So i don't have the harness for it anymore.The speed density unit I got was supposed to be 100% intact but the harness was mangled c100 bulkhead connector completely gone all undercar sensor wiring cut off and a bad ecm.
the unit i have now 89 maf setup was running 2 days ago before we started parting it out and since I'm helping strip it i know nothing will get mangled.
I just have the intake for the speed density unit on the car already and need to know if i can leave any of the existing setup in place or does it all have to be changed out.

 

I forsee one issue coming up

89 had cable driven speedo yours doesn't. Therefore 89 harness won't be able to drive your speedo. Others are 89 TPI plenum has no port for MAP vacuum or a boss to mount the MAP sensor bracket. If you haven't hacked the cars other wiring inside or the bulhead connector by the brake booster I think it would be alot less work just finding a 91 TBI harness and adapting it then making a 89 harness work in the car.

A 91 TBI harness probably cost you 50 bucks maybe ... I just see that as your easiest route and forsee a nightmare happening using that 89 harness I also know for instance 91's wiper harness is integrated into the headlight portion of the bulkhead connector by the brake booster. 89 will have it in the other side bulhead connector. So god only knows what will happen when you plug a 89 engine electrical harness into the other side ... but have a fire extinguisher handy.

sell the 89 harness to fund the correct TBI harness LOL this way everything works on your car with alot less hassles.

 

I know this is all true cause I tried using a 1989 ecm and main electrical engine harness with my 1990 dash harness and things wouldn't work. This was on a TBI car but I'm sure TPI is no different.

 

I used a 90-92 speed density TPI harness and ECM when I did my conversion last November. I was informed by several sources that this would be the easiest method as the engine harness would plug right into my '90 TBI car with no mods other than bypassing the VSS buffer in the TBI system. I also used an 89 TPI assembly and everything worked well after I drilled and tapped a third vacuum port in the plenum. The MAP sensor was kept in the stock TBI location on the lip of the firewall as well with no issues.

 

I can get anything i need from the doner car. All free which is why I would like to go this route. I can get the other wiring harness from the doner as well as any other things i need i just need to know what. Money is a very bug concern for me as i Have none to really work this project with that is why I figured I'd just grab everything from my friends car.
Still i would like to know about the TPI bases, are they the same or dufferent? I have pulled the plenim and runners today and pulled the wiring harness for the speed density out(except the connectors under the car)
Do I need anything off the tranny, The other harness for the engine bay(lights and accy.), do I need the bulkhead connector from inside the car or any dash wiring?