: Chronic miss in 4.6L Northstar

01-14-05, 12:05 PM
I own a '93 4.6L Northstar with 74,000 miles on it.

This car has had a chronic missing problem. I had the valve seals replaced (because they were "allowing oil on to the spark plugs" which another Cadillac dealer said is wrong), repalced the plugs, replaced the ignition wiring TWICE, had it hooked up to the dealer's diagnostic machine,etc. I am averaging only 13 miles per gallon for combined street/highway driving. Does anyone have any thoughts on what to do next?

Could it be the injectors possibly fouled?

Thanks in advance!

01-14-05, 12:35 PM
do a search on fuel pressure regulators and read bbobinski's posts, I would also check you coil packs as they can also do this.

01-14-05, 04:51 PM
Thanks Jeff. I'll do that.

01-14-05, 10:44 PM
When I changed the plugs on mine I got a miss. I then changed the wires and applied a bit of dielectric grease to the inside of the wire plug. No help. I found that i had gotten a bad plug. Nbr 7 was dead. I changed it out and all was fine for about a week. A miss again developed and I found that Nbr 5 plug had died. I took them all back as the AC plugs do have a warrenty and replaced them all. I have had no other problems.

You can't allways get a complete set of plugs that are good. I found that out. That particular box may have been dropped thus cracking a porcelin insulator in a couple of plugs. Just can't tell. In the aircraft industry if a plug is dropped it is discarded.
Just another thing to think about while you are troubleshooting