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Old 06-16-2020, 01:21 AM   #1
SoCalSlaughter
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89 S10 4.3 misfire

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
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Old 06-16-2020, 07:49 AM   #2
AussieinNC
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Re: 89 S10 4.3 misfire

Quote:
Originally Posted by SoCalSlaughter View Post
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....

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Old 06-16-2020, 11:08 AM   #3
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Re: 89 S10 4.3 misfire

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?
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Old 06-16-2020, 06:07 PM   #4
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Re: 89 S10 4.3 misfire

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
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Old 06-16-2020, 08:40 PM   #5
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Re: 89 S10 4.3 misfire

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.
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Old 06-16-2020, 08:47 PM   #6
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Re: 89 S10 4.3 misfire

We tried the MSD coil out of my 90 Suburban and the mis is still present
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Old 06-17-2020, 06:53 PM   #7
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Re: 89 S10 4.3 misfire

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.

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Old 06-18-2020, 09:13 PM   #8
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Re: 89 S10 4.3 misfire

Tried another set of injectors, problem remains. Time to get another engine.
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Old 06-27-2020, 04:02 PM   #9
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Re: 89 S10 4.3 misfire

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.

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Old 06-27-2020, 05:27 PM   #10
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Re: 89 S10 4.3 misfire

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.
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