hey guys help
i'm about to pull out my hair.
my car won't run with the ESC plugged in
its an 87 2.8 mpi firebird
and i have replaced the
dist.
the ignition module
pickup coil
coil
cap rotor
wires
even the ECM
still no luck
it idles great with the tan/black timing wire disconnected.
but when you plug it in and try to start. it fires and then the timing goes beserk and it dies.
autozone says theres no knock sensor, cam sensor, or cranksensor. if thats true i have a ?
when i reworked the heads 2 years ago i didn't know about
the timing disconnect and i was turning the distributor and it wouldn't die. so how does that work without a cam or crank sensor????????
preemptive thanks

 

What's your base timing set at?

Sounds like for whatever reason, the ESC is pulling MAJOR timing, but see it shouldnt be able to pull it to less than your base I dont think? Unless it's just ADVANCING the **** out of it but.......I dunno Ive never heard this one before. If the ESC is causing it to shut down it must be making some pretty major changes at idle.

Okay just a shot in the dark that just occured to me, someone correct me if Im wrong.... When the ECM advances timing, what does it use to determine WOT to add it....TPS input? What if the TPS was faulty.....could it cause the computer to do crazy things to the timing?

 

Ok, disconnect the EST and set the timing to 10* BTDC, that's stock. You have no Knock sensor, crank sensor, or cam sensor, that's true and without knock sensor, there's no ESC system.

What it sounds like is that the timing is set too high, and when the computer tries to advance it with the EST plugged in, it's too far and it can't run right.

As to your question of no crank/cam sensor and how does it work...there's a pickup coil in the distributor, it doesn't tell the computer exactly where the crank is in the firing order, all it does is say that a cylinder somewhere is coming up on TDC on compression so it should fire the coil. Then the distributor takes care of where the spark should go.

 

i agree thats what it sounds like but thats not it.
with the timing set correctly.
it still will not run with the EST plugged in.
does this car use an spark control module other than the one in the dist.?? pontiac dealer said they couldn't find it.

 

Nope, it's just the ICM in the distributor. Are your plug wires right? We had a car into the shop recently that had a similar complaint and the customer had permformed his own tune-up, he got the plug wires onto the cap one set off so everything was advanced one notch. It would run with the EST disconnected, but wouldn't even hardly turn over with it connected.

 

yeah the plug wires are on right. TDC the rotor is pointing at #1
and the firing order is 123456.
that is right, isn't it??
i thought that 2.8s would have to use something in between the ecm and the distributor like the ESC module on a v8 car right??
I can't find it.
i replaced the ICM sevral years ago and last week when i took it to autozone to test it they had a updated part num. so i got the new one just to be sure. but it still won't run on the EST.
it appears to be retarding it way to far.
it may not matter but if i plug the EST in and ground the diagnostic on the ALDL. it will idle also but i understand that when in diag. mode the ECM does not control timing. thats why i thought it was my ecm.
?? when i replaced the ECM i had to use my old chips. could it be the chips?????

 

Had the same problem, turned out to be a broken spark plug wire.

 

i already put new wires on.

 

nobody has any ideas??

 

Mabe if you have checked everything else check if you have the right Prom chip in the ECM mabe its the wrong one or not complerely pluged in tho its socket.

 

well it is the original prom chip i checked to make sure its plugged in and it is but how can i tell if it is bad??? it seems odd to me that when i replaced the ECM i had to use it over.