hiofcrcobra

I have a '94 cobra body with a '93 motor, pcm & engine harness. None of the body harness was transferred over, I built the necessary circuits on my own. I'm pretty sure everything is wired properly, but I won't say I'm 100% sure.

The motor ran fine before it was moved from the donor.


Here are the symptoms:

~intermittent miss at all rpm ranges, under load and at idle... hot and cold.

~down on power, probably 10%-20% down

~high, surging idle (1k rpm)

~you can see the miss in the tach - http://www.youtube.com/watch?v=lUsDIXdW44E

~on start up it runs fine for about 5 seconds before the miss kicks in

~BIG ONE~ when the spout connector is pulled, the miss goes away and the idle drops to 800rpm

~no suprise codes during the koeo test... i cannot run a koer test for some reason.

~voltage across the battery drops about 2 volts when the miss hits. i'm not sure if the drop in voltage is causing the miss or the miss is slowing the alt and causing it.



So far I've replaced the coil, wires, plugs, distributer cap & rotor, TFI module, PCM, IAC, MAF, fuel pressure regulator, fuel rail, injectors & distributer.

I also pulled all my grounds, wire brushed and reinstalled em, then checked continuity from the grounds to the cage.


I have a running '89 5.0 / 5 speed for another project that can be canibalized for troubleshooting this car.




Please give me some ideas!!!

hiofcrcobra

can't believe no-one took a stab at this..!

Well, i found the problem!!! Somewhere in the harness the negative coil (signal) wire was compromised. I ran a jumper from the TFI to the coil and BHAM, miss gone... power back.

jkrum10238

haha glad u fixed it i was gunna say something about the coil wires a small miss wouldnt cause the tach to jump like that