Hey guys,

Im doing my engine swap soon which is the perfect oppourtunity to sort out my cars horrible wiring harness as its pretty chewed up, ive had a MAF burnoff problem for years which i suspect is due to this horrible mess of wires.

I bought a nice clean harness a few years ago off a guy on here actually, and it looks like its from a later year car as its got the rounder style relays and not the square ones.

Will this just plug in and work ok ?

 

Harness will PnP to the engine sensors
May want to compare the firewall connectors http://www.berlinetta.info/C100.htm
for any wiring differences at the plugs

 

ah right, thanks for that mate

 

There will probably be a number of changes from an 87 to an 88 harness.

In 87 engines were "V" belt and in 88 they had a serpentine system. IIRC most of the engine accessories will have a different plug. At a minimum the accessories are mounted in different locations.

In 88 the wiper motor/wiring changed.

The 87 engine bay used 3 harnesses, The headlight, ECM, and Engine. In 88 there was just 2; a headlight and a Engine/ECM harness ( the Engine & ECM were combined into 1 large harness.)

Your BEST BET is to be sure of the year that the replacement harness was pulled from. Then you can use the C100 diagrams to make a direct comparison between the original harness and it's replacement. It's possible that very little changed at the C100 side, but there is almost certainly going to be some needed modifications to a few wires/plugs on the engine side.

To figure out the year of the harness, see if it's got starter plugs and ECM plugs on the same harness. (85-87 ECM harnesses are independant of the Engine harness, 88 + used a huge harness for ECM and engine. ) Then check for the wiper plug,....(85-87, or 88-up) then check for a MAF plug (85-89), then check for a cold start connector (missing on 89). If there is a electric VSS plug to the tranny than the harness is from a Firebird/TA. If there's no MAF plug than it's a 90-92 Speed Density harness.

That should help narrow down the vintage of your replacement harness.

 

Thanks John ! very helpful info there, i will have to get the harness out and check it out

 

Well im still not sure what year this harness is from but im pretty damn sure its not going to work for my car

This afternoon i got my cars harness all disconnected and out completely, so i thought i would compare them starting from the ECU connectors and straight away there was a difference.



This is my cars harness, and this grey plug in the middle goes to a connector up under the dash, but on the other harness ive got thats not even on the harness itself ! not sure what it is but it obviously does something.

Then theres different shape and colour connectors and i also checked the big fuse box connector and the location of some pins is different too.

So back to the drawing board. Ive seen a few places on the net that make new harnesses for TPI motors, is there anywhere that makes factory replacement ones, not just for hot rods or kit cars ?

 

The Grey plug is essentially a "Power Plug", transferring 12v from the fuse box to the Injectors, Fan, Cold Start Switch (IIRC). Those same power connections are now coming through the C100 connector in your newer harness, so you just have to make sure the pins in the C100 are actually matching up internally.

 

the pins are quite different on that too, basically this harness is no good for me, i dont want to get involved with rewiring stuff, i just need it to plug in and work so i guess im on the lookout for another 87 harness

 

Ya', That grey plug is C221. Apparently 87' was the last year it was used; when I looked @ my 88' Dash connector I noticed that C221 wasn't there. My 88 has the injector power @ C207 Pins B & G.

If the replacement harness you've got has a MAF connection and cold start than it's 88'; If no Cold Start it's an 89. If there is an electric Speedo connector than it's from a Firebird/Trans Am; no speedo plug and it's from a Camaro.

Sorry to hear it wasn't a plug-&-play, with any luck it will not take long for Ya' to find the proper harness !

 

I will have to double check it than to see what year its from. I bought it from a guy on here a few years ago and i was assured it was from an 87, when obviously its not ! its sat in a box since i got it, as i thought i would get round to swapping them one day.

the most annoying part is, its in mint condition ! thats why i bought it, and now i cant use it

 

i checked out the harness i got with the 5.7 and its actually in pretty good condition now ive properly looked at it, the only downside is he cut the harness where it goes through the fender and into the car as he couldnt get the fender off from the crash, so i will have to cut my harness in the same place and solder all the wires back on, but apart from that it all looks alright

theres hope for this TPI yet !