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-   -   Need some help figuring out an engine miss (http://www.ifsja.org/forums/vb/showthread.php?t=116058)

bill32 01-27-2010 05:41 PM

Need some help figuring out an engine miss
 
1979 Wagoneer, 360 motor, holly 4 brl, motor has been rebuilt at some time recently and carb appears to be new (which the previous owner said he had bought. He converted it from 2 brl, installing Edlebrock intake and the carb. I Just purchased the vehicle.

The engine has a distinct miss at any speed, including idle. It appears that I am getting no or almost no power from #8 cylinder. I traced the miss to #8 by pulling the plug wires one at a time to check engine response when running. When I pull the plug were on # 8, it makes no change in engine idle or miss condition. Pulling plug wire on any other cylinder results in a noticeable decrease in idle speed and increased roughness.

OK, so I checked distributor cap and rotor, which appear to be brand new, and they look fine, no cracks I could see, not carbon tracks, etc. Checked the plug wiring to make sure all wires are to correct cylinder. Plug wires appear to be new. Pulled #8 spark plug, which looks normal for a firing plug. Reconnected plug wire, held plug against the block while engine running and can see plug sparking consistantly. Next ran compression test on #8 cylinder, shows 150 PSI, which is right on specs.

I am baffled. The cylinder has spark and compression, but appears not to be putting out any power.

Anyone have suggestions as to what to check next?

Thanks,
Bill

FSJ Guy 01-27-2010 07:08 PM

If the intake valve was not working AND stuck closed, it would show as having good compression, right? Maybe pull the valve cover and verify that the valvetrain is moving.

Just an idea. I've never run into this problem.

Ristow 01-27-2010 07:25 PM

or a busted exhaust valve spring. sucks the exhaust valve open on the intake stroke.

amcboy 01-27-2010 07:30 PM

This is a good place to start!

Assuming the mechanicals are good engines/cylinders don't fire for two reasons only:

1. No fuel
2. No spark

So If you have spark there must be no or not enough fuel...


Rag in the intake runner?

Ristow 01-27-2010 07:37 PM

i was working on pulling the head off when i found my problem. same thing, good compression,clean plug. no apparent reason for the miss.

http://www.ifsja.org/forums/vb/showthread.php?t=73220

Hankrod 01-27-2010 07:57 PM

Or a broken exhaust rocker arm. Hankrod


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