Cylinder 5 misfire - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 04-25-2007, 02:55 PM   #1
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Default Cylinder 5 misfire

The vehicle is 1995 SSEi.
Scanned with Actron and it shows cylinder #5 misfire. Misfire is noticeable at idle. No problems when running if not to mention some stuttering at low RPM (between 1500-1800).After 60-65 Mph no problem.
Wires are new and checked.Coil was swapped for three different working,sparkplugs were swapped too.Fuel filter was changed,PCV changed.Recently fixed boost finally(faulted BCS),but supercharger sounds like grinder at idle.
Is it possible that ignition module can be faulted and only one sylinder misfire? Another question is can it be catalytic converter involved in misfiring?(strange sound from under the vehicle).What about oxygen sensor? I didn't change it yet.

Any idea would be appreciated.
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Old 04-25-2007, 03:00 PM   #2
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Reach down and reroute the wire so that it'* not touching the O2 sensor..

This might not be the exact cause..but it'* typical of the #5 or #6 issues.
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Old 04-25-2007, 03:41 PM   #3
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A plug wire on #5 touching the O2? Wow. Neat trick. They're on different sides of the motor.

I've never seen a PLUG WIRE affected by the O2 unless it'* shorting against the body, but that'* not possible with the #5.

For the #5, make sure it'* not shorting out through the insulation against the front engine hoist bracket. I've seen 2 of these in the last 30 days. If this is happening, you'll see some faint evidence of carbon scoring on the insulation and the bracket.
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Old 04-25-2007, 04:50 PM   #4
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I'm afraid that'* not the case.
I tried another wires,few of them just to be sure and it was still same reading-#5 misfire.
Is it difficult to swap a fuel injectors to make sure it'* not the case?
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Old 04-25-2007, 04:53 PM   #5
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No. Should take you less than 30 minutes to pop the rail and swap the 3 and 5 injectors.
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Old 04-25-2007, 05:14 PM   #6
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Thanks for reply.
Is there anything I have to buy before swapping fuel injectors? O-rings ,some other parts?
And how to relieve gas line pressure safely without showering myself with a gas?
I 'm doing all of it on the street of big city ,just don't want to make any firework
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Old 04-25-2007, 06:50 PM   #7
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Uncap and carefully bleed off (into a rag) your pressure test fitting (valve on the fuel rail).

You may want to pre-spray each injector boss in the LIM with a light lubricant while you work. After the nuts/bolts/studs/vacuum lines are disconnected (take a pic first for reference), wiggle and lift the rail. You don't have to go far. Once it'* up enough, it'* very straightforward. Use vaseline or silicone grease in the injector bosses when you put it back. Your o-rings should be ok for now. If not, they're cheap.
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Old 04-25-2007, 07:14 PM   #8
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Ok.
Thank you for info.
That will be job for a next week.
Hope this is the case.

Regards
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Old 04-26-2007, 05:32 PM   #9
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I'd re-oring it while you've got it apart.good time to clean everything out too. GM sells
an oring kit for the fuel rail.

If it turns out not to be a faulty injector I would suspect the ignition module located under the coilpacks.
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Old 04-26-2007, 06:25 PM   #10
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I'm also inclined to think it'* ignition module.
The reason is sometime when engine is hot(especially after driving in heavy traffic) I experience a hard start after parking for 10-20 min.
It can be that internal cirquit resistance is changig under temperature.
I won't go into component level though.
Just saw it happened before with diff. electronic devices.
In addition to #5 on very rare occurence it shows #1 misfire too.
But 98% of the time it'* #5 only.

Thanks for info.

Regards
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