Misfires over 50? - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 06-07-2007, 10:36 AM   #1
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Default Misfires over 50?

Yea! A new problem.

At highway speed, the car 'feels' like it'* misfiring (I don't know for a fact that it is misfiring). I don't know how to describe it exactly, so I'll offer an analogy. Have you ever been walking down the sidewalk, and the next block of concrete is an inch higher than the last, and walking along normally your right foot hits it and half of you stops and the other half keeps going? That'* what it feels like.

I guess I'm saying I don't have the first clue whats happening, just feels like the motor is hiccuping.

Seems to only happen after it'* warmed up, at highway speed (between 50 and 70), and does it wether the AC is on or off. And it'* very rhythmic, about every 2 seconds, perhaps a bit less. But VERY noticeable.

I'm gonna run up to Autozone and have a scan run, but thought I'd throw this out in the meantime for consideration.

The only thing I've tried so far is to pour a bottle of fuel system cleaner in it.

Thanks -

Matt
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Old 06-07-2007, 11:24 AM   #2
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Well.. we might consider the wires and plugs.

I'm assuming when you did the motor, the old plugs and wires were reused from the two previous motors or .. the same wires that came with this motor were left on it.

That'll be a good starting point.
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Old 06-07-2007, 11:49 AM   #3
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Thanks Bill - I just got back from 3 places to have a diagnostic run, 2 didn't have the right kind of tester, the third said if the check engine light isn't on, there won't be anything to read anyway. (It'* not on).

So I'm with you, because he did use the old plugs and wires. Also I take back the bit about only at highway speed, it does it all the time, just much less noticeable at lower speeds.

Since it only seems to happen after it gets warm, I'm going to check the coil resistance values and see if they are in spec, then it'* probably off for a new set of wires.... event of that'* not the problem, needs 'em anyway.

Thanks again

Matt
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Old 06-07-2007, 12:15 PM   #4
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Toss some fresh plugs in while you are doing the wires. Most likely .. you'll find a bad looking plug(*) when you swap them.

Thinking back to your description of the issue is a chuggle which is usually igntion related and felt once TCC lockup occurs. Searching on chuggle..you will find many references to it and typically it is ignition/tune up related.
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Old 06-07-2007, 12:31 PM   #5
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Cool....

Here'* the reading from the coil packs:

CYL --- PRI --- SEC
3/6 --- .8 --- 6.24
2/5 --- .8 --- 6.01
1/4 --- .8 --- 6.00

These all seem to be well within tolerance, and they are still fairly warm from my trip, so I'm ruling out the coil packs for now. Up to get some plugs and wires, will let ya know what happens. If nothing changes, then I'll take it in for a tuneup.

Thanks
Matt
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Old 06-07-2007, 01:08 PM   #6
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Well, here'* more proof that I'm a complete moron:

Checked the back row of plugs..... went to pull on the boot, and.....it came right off. I don't mean it 'popped' off, I mean.... it wasn't even connected. I guess it was close enough for the spark to jump most of the time, or at least occasionally. Plugged it in, took her for a test drive. Problem still exists, but to a MUCH lesser extent. I'm guessing all that arcing burnt up the inside of the plug wire.

So here'* a tip for Matt: Hey idiot, physically check things out before you post.
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Old 06-07-2007, 01:15 PM   #7
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Matt...don't be so hard on yourself.

You didn't put the plugs on right? Asking/searching first..will give you others insight as to the usual causes so you don't waste time looking at the things that don't cause the issue.
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Old 06-07-2007, 01:33 PM   #8
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Thanks Bill !
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Old 06-07-2007, 04:04 PM   #9
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You want me to make you feel bad because you only tested 1/2 the coils? lol

When testing coils..build the confidence of your online buddy by not telling him..that to truely test..you must test the primaries also..that requires removing the coils. Always start with plugs and wires though.
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Old 06-07-2007, 08:53 PM   #10
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but... but..... I tested sec & pri.... It'* in the table I posted above
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