iroczen

Hello all im new to the site and have a question to see if anyone else has ever done this. I have a 1991 Camaro rs that is my project. It has a 305 TBI. I also have a 1985 Pontiac T/A that Im going to use for parts. I want to put the low mileage TPI motor from the poncho in the Camaro, but so far no one can tell me if the wiring harness where it plugs in on the drivers side firewall has the same layout and fuse set up between the two. I know Ill have to swap harness, fuel pump, lines, ecm, and of course motor. I also know that the 91 if it would have been tpi would have been map not maf. Then to further muddle things the camaro has vats on the key so i don't know if the 85 computer will allow it to start? Please I pray that someone out there has an answer for me I don't wanna have to keep looking for another donor car. Thanks all

John 89 Formula

The entire 85 system is completely different than your '91, your best bet is to find a complete harness and ecm from a '91 tpi car, or there are companies that will convert your existing tbi harness to tpi, but you will still need to find the correct ecm.
Also the tpi from your 85 will have to be modified slightly to fit the 91 longblock some of the bolt holes have different angles, there other differences but you should be able to work around those.
The fuel pump will also have to be changed, but I would get a new one rather than using the one from the 85.

samiam91RS

good luck, i just swapped my tbi 305 to a 350 tpi. lemme tell yea, you have to be on point with all the merchandice to make this go smooth. and yes there will be a big diffrence in the years, mostly because of MAP vs MAF. especially if there are laws you have to obide by. i did a swap in my 91 for an 89 engine.

iroczen

I don't have to worry about emissions where Im at so that is good, and I guess I was wondering since the harness and the computer and prom chip were all for a maf setup if things would be ok? The part im most worried about is the port on the drivers side firewall where the power for all the underhood stuff comes through. They are the same shape and both bolt on with one bolt in the middle. I am inclined to think that they would use the same setup (example a= fuel pump, b=headlights) for all the cars from 82-92 so as to not have to retool the assembly line every year. I just need to find some kind of schematic to show the layout I went on mitchell and printed a wiring diagram for both cars but it just shows the wires not where they are located on the plug. I might just have to spend several long hours out in the cold 14 degree weather tracing wires to their source to see if they lay out the same. I am inclined to think it will be plug and play, but I dunno. Thats y im asking for input from all Thanks

samiam91RS

that im not too sure about. like john said your comparing a 91 to an 85. when i did my swap i had the harness from my 91(tbi) and the 89(tpi). the harness was screwed up mostly on the bulkhead connector that plugs into the firewall so i was going to get it all fixed up at a place in texas, cant really remember the name...anyways, dyno don told me that the harnesses would not match up and instead he took my 91 tbi 305 harness and converted it to link up to the 89's 350 tpi. that way, everything matched up, and like john said if i recall, he told you that you'd be better off getting a harness from a 91 so it will all match up. good luck with it

a1raceworld

just sign up and I myself am looking to change from tbi to tpi system. What I have found that the harness will have to be change in order to work . have you check on a painless harness to do this swap?

John 89 Formula

I bought a painless harness 15 years ago when I did this swap, problem was that the harness was only for the engine, all the secondary stuff had to be stripped out of the stock harness and reused. I was a major pita that I wasn't prepared for. (I ended up buying a used one from a member here)
It's quite possible that since then they have updated thier harnesses to include the secondary stuff also, but I don't know. The painless harness is good if your dropping an
L98 into a '72 nova. your best bet is to find a good used harness from the same year vehicle or have your tbi harness converted.

mattfick

you cant just pull everything you need from the donor car?

fireburdluvr85

not much support for this swap unfortunately. i went 89 to 91 myself. took for ever to make it a plug and play harness. can be done tho.

mattfick

What exactly is not plug and play?

John 89 Formula

Your best bet is to find a harness and ecm from a 91 tpi car and use those.
the tpi itself should work but will need some modification to fit right

insomniac

iTrader: (3)

i did that swap last year. trust me get a 91 harness and ecm. will save urself alto of head aches


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mattfick

I dont mean to be rude but i keep hearing abt the headache yet no one elaborates, everything is in tactfrom the 88 i dont understand

insomniac

iTrader: (3)

well for starters the speedo can't work without the 91 harness.


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Rod Behring

The plug you are referring to is the c-100 bulkhead. Wires are routed differently through the years and you will need a service manual with wiring diagrams from both years and systems to see exactly what needs to change.

This is not a simple swap.

mattfick

would i be able to get away with a 90-92 ecm? or would i still need to switch wires? im putting an engine from an 88 in, would this be a problem because the ecm from 90-92 is speed density and 88 is maf?

John 89 Formula

You would need to repin the harness on both ends, at the bulkhead connector and the ecm.
You would need to eliminate the maf circuit and wire in a map sensor circuit
plus the 90-92 ecm has 3 plugs on it the 88 harness only has 2 you would need to find a third plug and switch the appropriate wires into it.

Find a harness from a 91 and use that.

mattfick

i think my problem is solved. a buddy of mine is selling me his 1991 tpi engine, harness ecm, everything, is it plug and play? or are there changes that need to be made first?

Blade09

I'm lost on where the major issue is? If you have a tpi a motor along with the harness and ecu, just remove the original harness and ecu and put the tpione in place. If that's all it took to run in whatever car it came out of, why wouldn't it run in your car?