: Northstar misfire and backfire

07-27-04, 01:57 PM
My 96 eldorado has been missing on #3 since my wife drove it high water 2 years ago. I assumed electrical at first, changed the coils no help. It started using water. I then assumed head gastket problems. I put bars leak in it and it got worse. It turned out to be top radiator hose. NO more water loss. It still wrecks #3 plug in a hurry. when it is firing most of the time it does not backfire. When it begens to miss as the plug fouls it will backfire through the induction system in a particular manifold pressure range. I don't know what the pressure is but it happens at moderate accelleration. I have not changed the plug wires and I think they are 117000 miles old. OBDII codes PC0300, PC 0603, IP1552, TC0073, TC0077, RS0061, PZ1558, PZ2473 all of them are history. Will someone offer some insight into this problem and advize.

Thanks JKP

07-28-04, 03:04 AM
Help please.

07-28-04, 10:18 AM
How does the #3 plug look?

Replace the plug wires.

Did you check the injectors from the other post? Have you done anything more than the original post? :hmm:

07-28-04, 03:48 PM
Interesting update. Today I navigated the diagnostic system completely. Much of what I saw I didn't know what it was, but much of it I did understand. When I cleared all the codes, the misfire stopped. I have only driven one cycle so far, but the engine runs smoother than it has in years. I think one of the codes was a check sum error history code. Could a historical checksum have put the one of more of the systems in override and caused the rough running.

The plug was simply wet and not carbonized. I was going to change the plug wires today but now that it seems to be fixed I am not going to break it. I will Know more after I drive it again. I still smell gas under the hood and am wondering about leaking fuel lines.


07-28-04, 09:07 PM
If you are smelling gas you may well have a leaking fuel rail. If you are not aware, they are in the process of starting to recall them. Be carefull. Find that leak and get it fixed. If you have to pay for it save the receipt for reembursment when you get the recall.

07-28-04, 11:16 PM
It was a leak. A pin hole in the line between 6 & 8. Dealer part $350 for nylon and $182 for stainless steel. I fixed it with glass cloth and epoxy.

08-03-04, 06:57 PM
I changed the plug wire and it runs very very good!!! Hot Dog!!!