Valve job on 2.8, now it misfires. (Page 1/2)
stinky817 FEB 27, 08:59 PM
So here's the story. A friend of mine has an 86 se with the 2.8 and he had someone do a valve job because he had a dead miss on cylinder 4. No compression. a little squirt of oil didn't help anything.

He had the car towed to my house after the guy had everything I installed and couldn't get it to run. I pulled the valve covers off and properly set the valve lash.(he had the valves about 2 turns too tight) I got it to run but I have a misfire on cylinder 4 and 5. Did a compression test on all the cylinders. 120 on all except cylinder 3, I have 100. If I pull the plugs out of 4 and 5 there's fuel on them. Connected a spark tester to wires and I have good spark. Changed the plugs just for peace of mind. Still no good.

Frankly I'm stuck. Anyone have any ideas?
La fiera FEB 27, 09:10 PM
Can you get a leak down tester and test the bad cylinders? You'll be able to find out what is the problem with a leak down tester fast and easy.
Patrick FEB 27, 09:21 PM

May seem obvious, but double-check that the spark plug wires are indeed going to the correct plugs.
stinky817 FEB 27, 10:06 PM
I'll borrow someone's leak down tester tomorrow.

As for the wires, I've made sure they're in the right order, about 5 times.... Assuming the firing order is indeed 1-2-3-4-5-6
cvxjet FEB 27, 10:28 PM
I had the heads on my 460 in my jet boat ported and the guy installed super-high-tech valve seals.....The exhaust valves got stuck open and I had to drive back 10 miles to the launch ramp on 4 cylinders (Hey, It proved that you could run a jet boat engine with DOD!)......The valves need a slight amount of oil seeping by to lubricate them.....Might be your problem; A leak-down will show you if it's that....(Actually, just a compression test should show that!)
stinky817 FEB 27, 10:42 PM
Yeah, did a static compression test. 120 on all except 3, which was 100. Did a dynamic (running) compression test, got between 40-50 at idle, and about 80 at a throttle snap.
Fastfiero1 FEB 28, 10:24 AM
You can never go wrong using a vacuum gauge. Usually that is a good way to tell what is going on inside the engine. Wanted to save myself some typing so here is a link to a good article on using a vacuum gauge to diagnose engine issues...

Fiero's Owned:

1987 Coupe 2.5 5spd May 99 - June 03
1987 GT V6 5spd July 30 2012 - Current

stinky817 MAR 01, 12:14 PM
Just checked vacuum. At about 1000 rpm idle the gauge is bouncing maybe 1" between 16 and 17".
Fastfiero1 MAR 01, 04:09 PM

Originally posted by stinky817:

Just checked vacuum. At about 1000 rpm idle the gauge is bouncing maybe 1" between 16 and 17".

What does it read at idle?
stinky817 MAR 01, 09:18 PM
that was the idle measurement. the car doesn't seem to want to idle lower then 1000.