Slightly Rough Idle

["C"]

Earlier today while at a stop light, I notice that every now and then my car would idle low with a hint a shakiness and almost feel like it wanted to die out. Not sure what it is, but I have no check engine light on, so I'm lost. It doesn't happen all the time, that's what's strange, my battery terminals are connected fine, and I have new plugs and wires.

I feel this shakiness near the floor pan, and like something is spinning or rotating when my foot is on the brake pedal. My power steering is whinning, I hear a noise while turnning the wheel from left to right, but my fluid is full and I'm not leaking anything.

[candycane]

I am having the exact same issue...what did u do to resolve the issue...???

[candycane]

or what can be done???

[ksurf_k]

i would say most likely IAC motor (idle air control)

[candycane]

i would say most likely IAC motor (idle air control)


would that be the culprit for the rough idle? what abt the other issues?? just had egr channels cleaned, egr valve/tube replaced...all new hoses and belt less than 3 months ago.

[dickwells]

When my coil was going bad it showed up first on damp days but I guess you do not have many of those in San Diego.

[93_97_07_TownCar]

Sorry to bring this back up, but was there ever a solution found to this problem? I have the same problem, and have even had the car stall at a light when idling for more than a minute. I am leary of it being caused by the IACV since when I power brake the car, I can still hear an occasional misfire, but cannot feel while driving.

[bryanhbre]

could the the IAC valve, but also could be a vacuum leak somewhere. My 93 tc had that problem 2 years ago. Couldn't figure it out, took it to a mechanic and it was the intake manifold gasket that was letting air in to the motor. replaced that and ever since has been working correctly. Also check the throttle position sensor, that may also give erratic idle if I remember correctly.

[dickwells]

Vacuum leaks can usually be pinpointed by getting some carb cleaner with a plastic spout and Judiciously spray around on the gasket areas and vacuum tubing. When you hit the bad spot the miss will disappear. (do this outside)

[Kielbasa]

My 1995 Executive started to act up like that aound late December until mid January 2009. I would be waiting at a light and when I went to give it gas, it would hesitate. After that first time about 1 1/2 miles down the road, it would not do it again. I had a friend come over with the computer. There were (2) codes, but I can not remember them. He cleared them. About 1 week later the car started to stall at lights, but I would not get the hesitation. A different code came up. (Something...... L bank) I brought it to the garage and it ended up being a cracked vacuum line.

Of course it was freezing cold outside around that time so I could not get outside and trouble shoot it.

["C"]

Yeah it was the IAC valve. I remove it, cleaned it up a bit, and put it back on. Everything has been fine since. No more rough idle or dips in the idle at a stop light. It also really helped smooth out the engine to near silence and giving me slightly better gas mileage.

I now know, when you first start up the car for the day, during a cold morning or whenever, if the car idles like crap, then it's the IAC valve. If it only does it every so often or when warmed up, it could be plugs, wires, Vac Leak and possible TPS.

For me though, my TC would idle like shit upon startup all the time ( IAC for sure), and the idle would get so low, I thought the engine was going to cut out. Even when sitting at a stop light, I would have to put the shifter to park in order for the car to stay running or give it some gas. This little device can cause all that mess, so if you have replaced everything else you can think of, and are still having rough idle issues, then the IAC is the problem.

This post was over a year ago! Wow it's been that long already? Crazy.