Rough idle, stuttering under load....and a big headache! - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 10-23-2005, 01:07 PM   #1
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Default Rough idle, stuttering under load....and a big headache!

I tried searching....found similar topics but they didn't help my situation.
Here'* my case -
About 3 months ago, my car started stuttering real bad. Mainly from a stop and going slow. Once it was out of low gear it smoothed out. Then the stuttering got worse, going up hills felt like the car was going off road....it stuttered that bad. So...I replaced the plugs, wires and fuel filter. Now mind you...my car sat for a while with a near empty tank of gas, so I thought maybe the crud from the bottom of the tank clogged things up. But I've filled the tank twice and drove on the highway to see if things claeard up but...nope....things got worse.
The plugs I used were the NGK'* recommended on here, and the Belden premuim wires.
The idle is still rough, still stuttering upon acceleration and under load is horrible. Shifting into overdrive is pretty bad too...the car shakes like crazy.
Is it still ignition related?? I have MSD coils probably 2 years old. Pretty sure I have the original o2 sensor in there. Oh, and the exhaust smells like gas...I mean strong!
Any help would be greatly appreciated!
Thanks guys!
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Old 10-23-2005, 06:40 PM   #2
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Default Re: Rough idle, stuttering under load....and a big headache!

Quote:
Originally Posted by SSEiGrl92
Oh, and the exhaust smells like gas...I mean strong!
That'* where I would start. How does gas get into the exhaust? Bad injector? Fuel pressure regulator diaphragm completely blown? One cylinder flooded out so badly that it fouls the plug? If so, you should be able to tell which by pulling the plugs and looking at them. Do this after a cold start, before things get hot enough for the fuel to evaporate. Then, you need to find where the gas is coming from. Pull the hose off of the fuel pressure regulator and see if it is dripping fuel. If so, change it. If the FPR is OK, check the fuel rail pressure a few minutes after shut down to see if one of your injectors is leaking and relieving the pressure.

May be others have some other ideas, but these cost nothing to check.

Hey...what happened with your brake lines?
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Old 10-24-2005, 05:59 PM   #3
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We attempted the brake lines ourself first....then decided to have my mechanic do it. I didn't trust my lack of knowledge...especially where brakes are concerned. So, had both rear brake lines replaced and she now stops!
In regards to the other issues, I'll check the FPR. This morning the SES light came on a few times too so, I'll run to Autozone and see what codes are stored.
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Old 10-24-2005, 07:03 PM   #4
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One or two cylinders misfiring can cause a foul gasoline smelling exhaust. The gas smell is a symptom of the misfire. I agree with pulling your plugs and reading them. Check your plug wire resistances as well, they should follow an even progression of resistance from shortest to longest. Also inspect the plug wires for carbon scoring where they may be arcing to chassis ground. If you suspect shorting wires, a good way to test it is to mist water on the engine at night while it runs. You'll see them that way.
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Old 10-24-2005, 09:47 PM   #5
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Default misfire

Check the individual coils. It sounds like one is not firing and the fuel from those two cylinders is going out the exhaust unburned. If you have the three separate coils pull the two wires from ONE coil and start the engine. The spark should easily jump the gap between the two terminals. Make sure none of the spark is going DOWN the side of the terminals to ground. If it is you will need a new coil. If the coil is bad you may not see any spark at all. If you are wondering what you are looking for try each individual coil one at a time and see what the spark is supposed to look like. Hope this helps.
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Old 10-24-2005, 11:55 PM   #6
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Default misfire

One other thing about testing the coils. If one out of the three coils tests bad swap it with one of your other two good ones. If the coil now fires on the two cylinders that were dead before you have a bad coil. IF the good coil does not fire on the cylinders that were dead the module is bad...no signal to the coil. Say coil 1/4 does not spark but 2/5 and 3/6 do, put the 2/5 coil on the module were the 1/4 coil was and tests it. If the coil fires at the 1/4 location the origonal coil was bad if it does not fire the module has no signal to the 1/4 position. Hope this helps.
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Old 10-25-2005, 05:02 PM   #7
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Default coil

you can accurately test your coils with a needle type ohmeter.
Check accross terminals on each coil. Resistance should be the same on all.
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Old 10-25-2005, 05:03 PM   #8
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Not ALWAYS true, as coils can be worse when hot. I had one fail that way. Resistance specs are in Techinfo.
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Old 10-28-2005, 10:24 AM   #9
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Thanks for the help!! I'll look at the coils this afternoon.
Oh...I had Advance Auto scan my car for codes, since the SES light came on twice. No codes were stored :( Hmm...wonder why the light came on then. Possibly b/c my car is running so rich right now?
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Old 10-28-2005, 01:18 PM   #10
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Alrighty...checked the coils. The middle coil was dead...no spark. When I had the 2 wires off that coil, the car ran the same as it has been. When the others were off...the car just about stalled.
There is a local speed shop that sells MSD coils, so I'm off to get a new one.
Can a bad coil really cause a car to stutter and hesitate that much? Thinking about it...without spark to those two cylinders...does that mean my car has been running like a 4 banger? Lol, please escuse my ignorance when it comes to these things....I'm tryin my best to learn here. Heck...I did tune up my car. those back 3 plugs weren't that bad
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