Green89IROC305

Hi guys, Im having trouble with the burn-off function on my 87 Iroc TPI.

Ive done some digging into the car and this is whats happening.


Burn off is not occuring automatically upon shut off.

I have tried several burn-off relays. tried a different ecm.
I am using 4-pin relays.

If I manually activate the relay(I have one popped open and I can manually engage the contacts) Burn off occurs. This tells me that the wiring from power to the MAF is intact.

I have 12v at pins C and D both orange; both in run and not in run as it should be.
If I measure from pin B(black-ground) to either orange I get 12v.

with the run circuit off I get no voltage reading from pin B(black-ground) when I measure from that to ground.

When I measure the above with run ON I get a 12 volt reading from what should be ground to ground. This is confusing. It could be normal if its designed to prevent grounding of the relay by routing 12 volts through the relay's ground, much like battery lights work in cars without gauges.

With run off and a jumper wire from pin B(black-ground) to ground the relay activates and burn-off occurs.

Tl:dr I can manually activate the burn-off circuit but the ecm does not activate it upon shutdown of the car.

I have checked continuity from Pin B at the Burn-off relay to pin D12 at the ecm. Their is continuity. Reading .3 ohms(this is including a jumper wire)

It seems to me that the ecm is not getting the signal indicating that the engine has shut down.
This could be due to the auxilary oil switch giving a false reading to the ecm. My only thought to effectively test this is to unplug it and jumper it to the oil pressure sending unit that supplies the reading to the gauge. The ecm should still get a reading from that, although it could be a different signal coming from that switch than the computer would be looking for.
Any Ideas as to what could be happening?

RussC

sorry to dig up an old post but i'm having the same problem, exactly the same actually. did you ever figure out what the problem was?

Russ

Green89IROC305

no worries. glad I had sub service on. I did figure it out.

Simply put, the solution was to replace the relay.

Although the relay functions it would seem the computer is unable to ground it properly. Why I could not truly say. could be increases resistance in the relay or in the wiring. Bottem line is although the relay functions it did not function as intended.

the relay is 10 bucks at oreily auto in theory it should fix it for you.

gta_knight

Ive got this code on my car at the minute, MAF burnoff circuit failure.

im wondering if this is whats causing my car to feel like its misfiring a bit if the MAF is dirty inside ?

RussC

sorry i hav't been on in a while, i did finally figure out my code 36, it ended up being the ground wire from the ecm to the burn off relay. luckly i tightened up the connection and bam. no more code.

gta_knight

my wiring near the relays on the firewall looks horrible so i wouldnt be surprised if its bad wires to be honest, more stuff to check into.

sometimes i wonder why the hell ive got a 3rd gen as it just constantly needs something fixed

gta_knight

Hey guys, thought id chime in here again instead of making my own thread, i took the relays off the firewall to have a look and.....oh dear, i removed the black plastic tubing that hides all the wires and was surprised to find my MAF burnoff one has had all its wires cut and reattached for some reason !

There is also a blue wire on pin A of the connector thats been cut but there is no corresponding wire with the other wires ???

can anyone tell me if these wires are on the right way round and what should be connected to that cut blue wire on pin A ?

Tuned Performance

iTrader: (92)

gta_knight

so if im reading that right there should be a blue wire that goes all the way from the connector on the MAF sensor to that cut wire on the connector for the relay ? looks like i need to start with a blue wire on the MAF connector and see where it goes

thanks for posting that

gta_knight

ive just compared my pics to a new connector you can get on tpiparts.net and it appears i have the right number of wires, the blue one seems to be an extra one so im guessing its a different connector from something else.

looks like the dark green wire shouldnt actually be there ?!? it should be orange, orange, black, blue, and my factory wires before the blue connectors are orange, orange, green and black

and going off the original posters info about testing the voltage on the pins, my wires are on the wrong pins

im more confused now but its no wonder my burnoff isnt working if everything is hacked to hell and wires on the wrong way round etc

Tuned Performance

iTrader: (92)

I more fond of the newer style relays like acdelco 15-8240 pigtail PT1115, looks like yours is all jacked up.

here is another link that shows the inside circuit of the relays better. I would solder the connections and use shrink tubing those but connectors are only a problem waiting to happen.

http://www.chevythunder.com/maf_code_33.htm

gta_knight

yeah Jacked up is one way of putting it, i can sort of figure it out but this dark green wire is confusing the hell out of me, there should be a blue wire going to it.

the only dark green wire should go from the MAF to the ECM going off this diagram

looks like lots of things are messed up, urgh

Tuned Performance

iTrader: (92)

I think the wiring pigtail you have might be from another vehicle or maybe they changed the colors from 86-89

gta_knight

looks like the connector is indeed from another car that just happens to fit the relay. Just looking on tpiparts.net they do the new connectors and 86-87 should go blue, black, orange orange.

So im still confused as to why i have a dark green wire instead of blue

RussC

i waas looking at the pic again and i don't think that's the burn off relay. i think the relay should be a cube shape and not rectangular.

gta_knight

well theres only 3 relays at the firewall, one of them says MAF POWER in red lettering on the top, and the one right over nearest the fender is for the fuel pump so its gotta be the right one.

I tried my spare MAF tonight, i drove the car from the garage where i keep it home which is only 5 minutes along the road and it drove exactly the same, got home, went in the house for about 10 minutes to get something, came back out and set off and the ran awesome !!! i drove it around for about 15 minutes and couldnt get the smile off my face.

stopped at the petrol station as it was getting low and put some Shell V-power in, set off from the petrol station and it was running like crap again, argh ! but instead of just going straight home i went for a cruise along the coast and it slowly got better, it still doesnt feel 100% but its definatley better than it was, maybe it just doesnt like the V-power fuel ? i'll just stick regular unleaded in when i need fuel again

gta_knight

ok ive fitted my new coil, cap and rotor, the reset the timing back to 6 degrees as it had fallen to 4, took the car out and its driving great !

however i think it will start running crap in time again with the burnoff function not working,

could anyone else with an 87 post pictures of their wiring colours and which pins on the connector the wires go to ? i still dont know why mines got a green wire instead of a blue one