89 S10 4.3 misfire

[SoCalSlaughter]

What do think of these readings??

Cyl 1 - 130 - Wet 140
Cyl 2 - 135 - Wet 155
Cyl 3 - 120 - Wet 130
Cyl 4 - 150 - Wet 160
Cyl 5 - 140 - Wet 150
Cyl 6 - 125 - Wet 130

[AussieinNC]

Originally Posted by SoCalSlaughter

What do think of these readings??

Cyl 1 - 130 - Wet 140
Cyl 2 - 135 - Wet 155
Cyl 3 - 120 - Wet 130
Cyl 4 - 150 - Wet 160
Cyl 5 - 140 - Wet 150
Cyl 6 - 125 - Wet 130

IMHO

These readings are indicative of a well used engine...

The variance between dry and wet are about standard, with the exception of cyl 2 which has some ring sealing issues.

Cyl 4 is the only one with a reasonable result....

[truckster]

They're probably not directly related to your misfire. While some of them are low, early gasoline engines ran with 5:1 compression ratios.

However, as Aussie said, #2 readings indicate you may have some blow-by, causing spark plug fouling. How does that plug look?

[SoCalSlaughter]

We have pulled the plugs and none of them stuck out from another. All looked fairly normal. No smoke from the tail pipe. We have changed the plugs and wires a few days ago. We did notice, after starting the truck a few minutes after running, the exhaust smells like raw fuel. The hard misfire is only present at idle, and moving from a stop. The truck can cruse on freeway going 70mph no problem. We have found a good used (Compression tested) engine a county over with 98k miles for $450. Might be way to go

[vince1]

I put quite a few hundred thousand kms on those. I think I changed at least three coils on the 90. One quit in the intersection and I had it changed before AMA arrived. They don't always quit outright. Keep a spare.

[SoCalSlaughter]

We tried the MSD coil out of my 90 Suburban and the mis is still present

[AussieinNC]

This sounds like a leaky fuel injector...dribbling fuel into throttle body causing over rich mix flooding a plug or 2....

Grab a couple of second hand injectors from a wrecking yard and try it,,,they are not that expensive to buy new.

[SoCalSlaughter]

Tried another set of injectors, problem remains. Time to get another engine.

[Wrenchbender Ret]

If it has a vacuum outlet on the back part of the intake manifold, a vacuum leak can cause a misfire like that. Check power brake booster & trans modulator & a/c vacuum resavoir.

George

[vince1]

Two of the three 4.3's I had leaked coolant into the rear left combustion chamber but you would have noticed that sooner it its life.