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View Full Version : Random rough idle and stall



ConnertheCat
07-19-2008, 10:32 AM
Hey guys, I have a 2000 LGT and an issue that started late april has continued to plague me... Every now and then (usually a week or so apart, but it can be sooner) the car will have a real rough time at idle. It's always fine the moment you turn the car on, but by the time I hit my first or second intersection (1/8th of a mile or so, around 2-3 minutes) the car will get a really rough idle to it when I'm stopped (the whole car will shake). As this happens, the car dips down below the usual 750 RPM into the 500 range. Sometimes it even sinks below that to 250 and then stalls (happened three times now I think). Sometimes I can recover by letting the car torque crawl, it helps the engine out a bit. Almost every time the car is fine once it's gotten about 10-15 minutes of driving in, but one time the issue did persist up to thirty minutes after I had started the car.

The thing is, it only happens when your stopped. When you're moving more then 5 MPH you'd never know there was a problem with the car. Also, my CEL came on for the third time now too - I'm not sure yet (haven't run the code THIS time) but the last two have been fuel trim issues. Both times I throw a thing of dry gas in the tank and the CEL goes away about an hour later. I'm pretty sure they are related, but not 100% sure.

I've spoken with a mechanically inclined friend of mine, he thinks it could be a leak in a vacuum hose - I have to get the timing belt replaced so I figured I'd just have the hoses done then. However, if anyone has any other possible ideas what could be causing this phantom problem that would be pretty cool.

Also, I did notice last weekend (during a 850 mile road trip in which the car never had the idling issue) that my temp gauge went up to 75%, then about 10 minutes later was back down to 50%. It was the first time I'd seen it that high, but the car was full of people and stuff, and we were going uphill and had the A/C on so I'm thinking that was just because the car had a lot of strain on it... I don't think it's related. Since then the temp has always been stuck at 50%.

Anyhow, any thoughts would be very welcome - thanks! :)

Reason
07-19-2008, 10:39 AM
First thing is first. Get the code ran again and let us know what it is. It could be a NUMBER of things.

ConnertheCat
07-19-2008, 10:47 AM
Well, I can but given it's the same issue for the third time in a row I'm putting all my money it's the same code I had a month ago (https://sl-i.net/FORUM/viewtopic.php?p=108883&highlight=#108883). And sadly, the bump up in gas didn't help.

J.McDonald Knives
07-19-2008, 05:39 PM
I was thinking that it was also a vacuum hose. You may have a crack in one and once it heats up it expands and once it drops down to idle speed it doesnt have enough suction to keep the crack closed. Basically when you are in the higher RPMs it has enough pressure to keep it closed but once it drops down it loses the pressure and allows it to suck in more air than is required so it idles rough. I would start with all your vacuum lines starting with the ones on your intake or at least start with the ones that feel the hardest and most brittle. Then start on the others. If that doesn't work let us know and we can come up with other solutions. Always start with the least expensive repairs.

ConnertheCat
07-20-2008, 03:20 PM
J - you had a much better explanation on why it would be the vacuum hose then my friend, thanks - it is incredibly logical. I really appreciate it.

And yeah, I was going to just have that done since it's cheap and if it doesn't work… well, then I'm out like $50.

jey
07-24-2008, 03:30 PM
It will still help for you to pull the CEL. You got a Cylinder #4 misfire the first time, but it would help to know if your misfire is consistently on the same cylinder, or only on #4.

If it's only on one cylinder you may have one plug that's going out or a bad wire or even coil pack. Could even be one injector. If it's all over the place, then you can look at more general sources of the problem, like vaccuum leaks, fuel filter, etc.

ConnertheCat
07-25-2008, 04:33 PM
I've never had a Misfire CEL - only Fuel Trim. It also went away last week end only to come back a few days later.

decke48
07-25-2008, 06:44 PM
fuel trim code would intend that you have a leak after the MAF/MAP or in the exhaust before the upsteam o2