Engine Ever Act Like it's Running on 5 Cylinders??

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GSXMEN
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Engine Ever Act Like it's Running on 5 Cylinders??

Post by GSXMEN » Tue Aug 16, 2005 6:02 am

As soon as I get time, I need to pull my plugs and test my wires.

I installed new plugs earlier this year. Hasn't really run smooth this spring/summer.......not like it did when I bought it a few years ago. I had to install a new fuel pump & filter last year too.

Really gets to shaking the car/dash at slow speeds. Even the exh. tip looks like it's shaking. :-?

I'm wondering if I might have a cracked plug or bad wire? Wires are maybe 3 yrs. old too.

Other than plugs, wires & maybe a compression test (while the plugs are out) - what other things should I check out???
Scott

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luvgm
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Post by luvgm » Tue Aug 16, 2005 6:36 am

Mine did what you are talking and I found that it was the coil pack. They rarely go bad but it is something to check.
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GSXMEN
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Post by GSXMEN » Tue Aug 16, 2005 6:41 am

I had considered that, but haven't taken the coil pack off from the module yet. When I tested the secondary side (plug side) of the coils - I had readings in the 13k range.

Any idea if that sounds right? Know what the primary readings should be?

Thanks 8-)
Scott

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Post by luvgm » Tue Aug 16, 2005 6:49 am

How I tested mine (and got the **** shocked out of me because I did not use an insulated plug wire plyres) I pulled the plug wires off to each cylinder and sure enough the number one cylinder was not working. If you do it this way be very careful being shocked hurts. It is kind of an old school way of doing it but it works. I have a manual around for GM that I will look for if that does not help or you do not want to try that.
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buick1986grandnational
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Post by buick1986grandnational » Tue Aug 16, 2005 7:17 am

Timing light should also work to find a plug/wire that's not firing. Wouldn't get shocked that way either. Just hook the light up to the wire you're testing.
If not the coilpack (which it sounds like it's not since you have good readings of 13k ohms on all the towers) could be the module. A friend of mine with an '87 Grand National had that problem. We swapped coil packs first and the problem persisted. Swapped modules then and it went away.
Good luck.
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Post by calenatar » Tue Aug 16, 2005 8:31 am

check fuel injectors to make sure they are all working.
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BillyBoy
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Post by BillyBoy » Tue Aug 16, 2005 2:23 pm

luvgm wrote:How I tested mine (and got the **** shocked out of me because I did not use an insulated plug wire plyres) I pulled the plug wires off to each cylinder and sure enough the number one cylinder was not working. If you do it this way be very careful being shocked hurts. It is kind of an old school way of doing it but it works. I have a manual around for GM that I will look for if that does not help or you do not want to try that.
This actually does not work so well on our cars. Besides the getting shocked factor, the waste spark setup we have actually fires two spark plugs at a time. So if you pull the wire off of one plug, you actually disconnect both plugs on that circuit. One thing that might work is to pull one plug wire and short it to ground, but that is not very good for the coil.
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86 2dr.ltd steve
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Post by 86 2dr.ltd steve » Tue Aug 16, 2005 3:13 pm

Its most likely ignition but -

if anyone remembers I posted here once about how the inside of my fuel lines actually rusted and then broke loose and pluged up my pressure regulator, fuel rail and bottom of injectors. Under any load that car would buck like a bronc and smooth out some if just at steady cruise. I have never heard of it before or since and I could not believe my eyes but thats what happened. It was a 91 Regal Limited, origional owner car with 23_,000 miles on it in otherwise great condition.
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Post by GSXMEN » Wed Aug 17, 2005 7:06 am

Thanks guys!! That gives me some more solid ideas to check out.
Scott

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Post by GSXMEN » Sun Sep 04, 2005 6:59 am

Thought I'd update this a bit.

I haven't gotten the chance to check all the above suggestions yet.

Checked the coil pack & module......they both checked out OK. Primary side was on the high side of spec. at 1.1, but that was exactly the same as a new one. Secondary side was between 12.6 and 13.1.

Checked the resistance on the wires - all between 900-1500 ohms. Not bad for 3 yr. old wires.

After pulling the plugs, I found that plugs in #5& 6 were almost white.....the rest were between normal & slightly rich. Black, but not oily. I'm wondering if I have a couple of injectors partially plugged.....or possibly the rail as mentioned above.

Plan on running a compression test Sunday. We'll see what that says.
Scott

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GSXMEN
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Post by GSXMEN » Tue Sep 06, 2005 6:38 am

Ran the comp. test tonight and got some wierd results.

Front head had lower comp. and the back head had high comp.

1 - 115#
2 - 174#
3 - 125#
4 - 174#
5 - 130#
6 - 180#

Plugs on the other hand, were very similar condiiton from bank to bank.
Starting from the TB back:

5 & 6 were almost white.
3 & 4 were rather normal - slightly dark
1 & 2 were darker, but not oily

Can't say as I've ever seen a 50pt. spread between heads like this. :-? I'm wondering if the back cylinders might have excess carbon build up in the chambers?? That's about the only thing I can think of to account for the discrepancy.
Scott

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T
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Post by T » Tue Sep 06, 2005 10:56 am

That apears it might be the case. Buy some Chevron TECRON fuel system cleaner. It's the strongest safe cleaner you can buy nationally. This should do a decent job of cleaning things out.
-T

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