3800Pro Forums banner

1 - 5 of 5 Posts

·
Registered
Joined
·
34 Posts
Discussion Starter · #1 ·
98 buick park ave ultra, 8th vin '1' 280k miles and still running strong (up to today)

Replaced head, intake, and supercharger gaskets 10k miles ago. Used throttle body cleaner to eat the carbon buildup in the cylinders. Changed Fuel, oil and air 400 miles ago.

Today I replaced plugs that came with car when I bought it used, mixture of champions and mighty plugs (wtf?!)

replaced plugs with NGK TR55's regapped to 58.

Car ran great for a few hours, now when in 3rd/4th only, car misfires badly on all cyls from 2500RPM+ , and I need to push the gas almost to the floor to get it to jump over 2500.

reseated wires, no change. (did not change, had belden wires still in good shape)

Car does not misfire under load in 1st and 2nd.

No current or pending DTCs.

Any ideas to what the problem may be?
 

·
Registered
Joined
·
660 Posts
How much is it misfireing? does it set the check engine light? Are you scanning ?
 

·
Registered
Joined
·
34 Posts
Discussion Starter · #3 ·
Its misfiring badly, tach jumps around from 2700 or so to 3200 when misfiring.

No DTC present, not even pending.

I will have to hook up my stepfather's matco scanner to it tomorrow for real time misfire data.
 

·
Registered
Joined
·
34 Posts
Discussion Starter · #4 ·
If I understand correctly, copper plugs, plus the now much shorter spark gap compared to the oh, 75+ on the old plugs, means for a cooler spark.

I'm wondering if in 3rd/4th gear, the EGR is dumping in enough return to cool the mixture enough that the new plugs are having trouble igniting, but the car sees the EGR acting as normal, is this worth looking into before replacing the plugs again? Or should I replace the coilpacks and wires before I replace plugs?
 
1 - 5 of 5 Posts
Top