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1996 Pontiac Bonneville engine misfire

Tiny
BOB R 007
  • MEMBER
  • 1996 PONTIAC BONNEVILLE
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 200,000 MILES
Engine misfires when ever it wants to. Mostly when hot and idling or damp weather. I sprayed coil packs and wires with water mist and saw some very fine line arcing but the engine was running just fine at this time. What might be going on with this thing!
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Thursday, March 20th, 2008 AT 5:55 PM

13 Replies

Tiny
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Did you pull off the wires at the coil and check for any signs of corrosion?

Are these random misfires?

How old are the wires.

Even minor arcing isn't good.
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Thursday, March 20th, 2008 AT 6:00 PM
Tiny
BOB R 007
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No cor. Just a grease substance on coil end of wire misfires seem to be more random than a sure circumstance I was told at time of purchase (4 months ago)that plugs and wires were changed
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Thursday, March 20th, 2008 AT 6:11 PM
Tiny
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Any loss of coolant on this?

These are common for intake manifold problems that will cause misfires. Generally they don't tend to be moisture related, but could be consistent with the hot motor.

Are they decent wires or cheapies?

Pull a plug and check gap or condition at all?
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Thursday, March 20th, 2008 AT 6:19 PM
Tiny
BOB R 007
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Holds all coolant wires seem thinner than some that I've seen is this common for this type of car or a good indication of cheapness! Yes my next step was going to be to check plugs and wire ends at plugs boots etc
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+1
Thursday, March 20th, 2008 AT 6:38 PM
Tiny
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Usually there is a name brand on the wires. Have seen cheap ones fail.

Good news on the coolant!
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Thursday, March 20th, 2008 AT 6:47 PM
Tiny
BOB R 007
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What type intake manifold problems might exist on this engine to cause random misfire
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Thursday, March 20th, 2008 AT 6:55 PM
Tiny
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http://www.autoblog.com/2006/04/15/gm-to-handle-intake-manifold-gasket-problem-on-a-case-by-case-ba/

http://www.complaints.com/directory/2005/october/1/31.htm

A google search will give you more,

But in a nut shell, there is a coolant passage in the mainifold that gets eroded from heat and hydrolic pressure that corrodes an opening internally.

The plastic manifolds are a problem child, and have seen engines lock up because it can be that quick.

Happened to my Boss..twice LMAO!!!!!

(did I laugh out loud ?) :)
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Thursday, March 20th, 2008 AT 7:02 PM
Tiny
BOB R 007
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Wow sounds serious is there a test to verify such a problem
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Thursday, March 20th, 2008 AT 7:06 PM
Tiny
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Compression test.

Pull the manifold off and evaluate it.

Symptoms include:

Pull the plugs and look for coolant burning.
Loss of coolant.

PO300
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Thursday, March 20th, 2008 AT 7:13 PM
Tiny
BOB R 007
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Lets say that new plugs and new high quality wires are installed, compression is passable, coolant is full, and the same thing happens. What are some other alternatives
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Thursday, March 20th, 2008 AT 7:32 PM
Tiny
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Low fuel pressure, clogged injectors come to mind.
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Thursday, March 20th, 2008 AT 8:01 PM
Tiny
BOB R 007
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I guess im driving at a simple sensor malfunction is that possible
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Thursday, March 20th, 2008 AT 8:06 PM
Tiny
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Could be. See if there are any codes stored in the computer. If the wires are arcing, I'd eliminate that as a source to start with. I prefer Belden or Standard or AC Delco wires myself. Pull a plug too, the only two brands I would use are AC Delco or Autolite. The Bosch splitfire for example are usually for trouble than anything. But they are marketed to the public. I believe these should be double platinum. They are not meant to be re-gapped as the platinum can scratch off. They can be adjusted with care and common sense. If the gap is incorrect or there is an oddball brand in there, I'd change them.

Take a look in the throttle bore, is there a fair amount of carbon? If so there probably is on the intake valves as well as they should get cleaned.
Might not hurt to check you fuel pressure. Eliminating the basics can save a lot of time and hassle.
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Friday, March 21st, 2008 AT 5:04 AM

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