Ok heres the story, ive swapped my 5.0 TPI engine for a 5.7 TPI, from the exact same year car (1987) I also got the wiring harness as its in much better condition than mine, apart from where the guy crashed the car it pushed the fender up against the door trapping the harness where you would unplug it from the ECU and pull it out through the engine bay.

So me and my friend who is good with electrics cut that part off my harness and began the task of soldering it together checking each wire one by one, and now there is one blue wire left over !! i traced it back to being the blue wire on the MAF sensor plug. on my 5.0 harness its sliced into the MAF power and MAF burnoff relays really badly for some reason, im not sure if its supposed to be like that.

on the other wiring harness im not so sure as all the black plastic cowling is still on. My friend seems to think its looped into another wire which returns to the ECU anyway but i dunno.

Im just annoyed there is a wire left over when i was assured the wiring harnesses would be exactly the same. especially for something like the MAF which is really important.

 

http://92b4crs.tripod.com/86wiring/dia-pics/22-5.jpg

 

thanks, we know where the wire goes but for some reason the 5.7 harness has one more wire than my 5.0 harness, and the only one left is the blue wire coming from the MAF sensor plug that goes straight to ECU plug

 

Had another look at the harness last night and everything is connected up from the harness to the ECU plugs and the remaining blue wire is spare coming from the ECU plug itself ?

both 87 TPI harnesses, wtf !

 

It certainly must be related to the splice in circuit 994 on diagram in post #2. This shouldn't be to hard to find. Right now, where does the blue wire on the MAF relay at pin D go? Old harness or new, that wire has to go somewhere.

 

Can you identify which ECM terminal ?

The only solid blue shown on a '165 ECM is to the TPS

http://www.chevythunder.com/198689_f...dy_1227165.htm

 

Blue wire off maf plug goes to both burnoff and maf relays. There is a splice to run to both. It ends there. It does not come back to ecm

There are no other dark blue wires goin to ecm. Just tps but that doesnt go to relays

 

I will have to check it again tonight when im working on the car.

There are two other dark blue wires going to the ECU though, you can see them in my picture

 

There should be a dark blue and two light blue wires

Google austin thirdgen wiring. There are great diagrams for the 87 tpi system on there.

 

Thanks man, ive actually got a factory service manual for my car with all the diagrams but i just havnt gone through it all yet incase its something obvious.

Right, thought i would open the harness up a little as i couldnt quite trace it to which plug it goes to on the harness. However it is connected to something because when i took all the tape off its actually spliced into another blue wire which does disappear into the wiring harness



This is what pin the wire goes to on the ECU plug, it doesnt have a number above it though as its near the centre,

 

Anyone ? havnt been able to get in the garage this weekend as i want to trace the blue wire to which ever sensor, plug or relay it goes too, i followed it and it split again halfway down the harness but thats as far as i opened it up

 

From what I see, its connector "D" pin # 11 which on the diagram show a grey wire (?) A/C pressure switch.

http://austinthirdgen.org/mkportal/m...ine_wiring.gif

http://austinthirdgen.org/mkportal/m..._continued.gif

 

:/ well thats not right then. definatley a blue wire which splits off a few times through through the harness

Im going to have to go through my shop manual and see if it says the same thing. If it is for my AC then thats fine as ive take it all off anyway !

 

Ok finally managed to trace this damn wire, so it is Pin 11 on the D side, on the grey ECU plug, it splits before the big connector through the fender so im wondering if that connects to something inside the car ?

then once through the harness i found a ring connector that had been taped up around the outside of the black plastic tubing ?? i found this rather strange as it looks like its been like that for years and years, surely not from the factory ? this should be connected to something ? its right next to the connector you unplug when setting the timing



So then i traced the wire further as it goes the other way and it ends at a two pin connector near to the TPS, IAC and temp sender plugs at the front of the engine



Any ideas if this sounds right ? and more importantly that bare wire near the ECU plug, should that be connected to something

 

My 87 Camaro L98 has the same blue wire+ring terminal hanging out near the blower. I haven't taken the time to trace it. I am interested to hear what you find.

 

So yours isnt connected to anything either ? weird. well i can just leave it then. and im sure i will find whatever that connector plugs into when i put it back in the car.

Its just the bare wire near the actual ECU plug then im concerned about now as it was obviously connected to something when i had the 5.0 in the engine.