5.8 missing on 4 cylinders

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Apr 10, 2013 | 11:28 PM

sunk_boat

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5.8 missing on 4 cylinders

Hi, I am trying to help a friend troubleshoot a 5.8 in a boat. The engine is a 1996 with EFI SD. The boat was partially sunk and the PCM was toasted. We recently found a replacement PCM for a boat (not exact match but very close). Plugged in and the boat fired right up. We started to celebrate when we noticed it was running very rough. I can pull plug wires 2,3,6 and 7 with no change. So all cylinders on bank 2 seem to be not firing. Checked spark all is good. Pulled spark plugs and those 4 are wet with fuel so leads me to believe the injectors are working. Going to do a compression check, fuel pressure check and verify injector functionality tomorrow, but wanted to see if there were any ideas out there of what would cause 4 dead cylinders. I have scoured the web for any cases similar to this and have not found anything close.

Any help or ideas on what to check would be appreciated.

Apr 11, 2013 | 08:13 PM

baddad457

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Did you change the distributor cap and rotor ? Those 4 cylinders are one half of the rotation of the rotor in the firing order. The TFI module in the distributor may be toast as well. Based on those four dead cylinders, it sounds like an ignition issue

Apr 11, 2013 | 08:39 PM

Fordman96

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I'm having a similar issue on my 96' MAF 351 but its not 4 dead cylinders. I'm just having an occasional misfire while it idles and when I checked the MSD wires one of them was pretty charred but never hit the exhaust. I'm baffled but I might just go back to stock wires because they don't seem to be connecting properly at the plugs (had to custom cut/attach the ends to the wires).

Apr 11, 2013 | 09:29 PM

baddad457

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From: south louisiana

Get a set of Ford Racing 9mm wires. Those are the best wires at the best price anywhere. I used to use em in my 95 E150 van. They'd last a good 3-4 years in that hell hole of an engine compartment. (a box actually)

Apr 11, 2013 | 10:50 PM

sunk_boat

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Update

baddad457, thanks for the reply.

We have not changed the rotor or the dist cap yet. (I will pick one up tomorrow and try that) Next on the list, but now that you mention the TFI module is there a way to test it? I can see that I am getting spark on the 4 dead cylinders. If the TFI is toast will I still see spark at the plugs?

Using a noid light the injectors are firing.
Fuel pressure is at 32 PSI and holds nicely
Compression is around 110 for all cylinders

So I have fuel and compression for sure.

When I start up the miss isn't as noticeable. After about 15 seconds the idle drops and it is very noticeable.

Could a vacuum leak cause this? I am thinking not, but wanted to ask.

What other ignition test can I run to eliminate the possibilities?

Thanks for your help.

Apr 12, 2013 | 06:58 PM

baddad457

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From: south louisiana

I'm no expert on the EFI nor the TFI distributor, so I cannot answer that. Just seems odd that one half of the cylinders in the firing order aren't firing, and they're all in the same half of the rotation of the distrbutor. I'd change the cap and rotor and see what happens.