rough idle

[coffeecup2006]

I have a 98 malibu with a 3.1 the engine idles at 700rpm rough when it is put in drive. I can put it in park and it still idles at 700rpm but is not rough. I have changed the idle air control valve and cleaned out the port, cleaned the egr valve, and checked for vacuum leaks. I have no vacuum leaks that i can discover. Need help to find the problem. Any ideas would be appreciated.

[gentlemanjak]

Originally Posted by coffeecup2006

I have a 98 malibu with a 3.1 the engine idles at 700rpm rough when it is put in drive. I can put it in park and it still idles at 700rpm but is not rough. I have changed the idle air control valve and cleaned out the port, cleaned the egr valve, and checked for vacuum leaks. I have no vacuum leaks that i can discover. Need help to find the problem. Any ideas would be appreciated.

I would check spark plugs and H.T. Leads. If the full length of the leads are easy to see, try running the car at night in pitch black. Have someone sit inside the car and put it in drive, while you look at the leads and see if you can see any "tracking" spark jumping to engine block under slight load.
Does it run of under normal driving conditions?
I am not familiar with the Malibu but assume it is a V6 engine. If its a quad cam with the long tubes that go down into the head to the plug, then you can check the tubes for any blue spots which would be a sign of tracking also.
Also check engine mounts.

New plugs could be all it needs.
Good Luck

[bcopeland]

Same thing happened to us. We ran our 99 down until the gas light came on. Then it started to run rough in park at idle. However, in park it idles better.

[coffeecup2006]

I will try checking plug wires and plugs. I even cleaned the MAF and the throttle body. Still no change. If you have any more ideas pass them along please. thanks for the help.

[bcopeland]

I had a loose PCV hose.

[coffeecup2006]

Did that fix the rough idle in drive?

[coffeecup2006]

I changed wires and plugs and still no change. I'm stumped with this one. Someone help!!!!!

[bcopeland]

Yes it did and another thing - the last PCV valve was stuck up with some goo.

[coffeecup2006]

thanks, i will check it out

[gentlemanjak]

Originally Posted by coffeecup2006

thanks, i will check it out

You can try spraying fluid like intake manifold cleaner, or brake cleaner, or something similar, all over the vacuum hoses and manifold joints and bolts. If engine idle speed raises or starts to splutter, you will have found your leak. I am assuming you have replaced spark plugs or checked plug gaps? If nothing else works you will have to check engine compressions, or have tune scope connected to find which cylinder(s) is causing problem. The current draw across each plug will give good indication of where to look.

[kev23]

Hey Coffeecup

I have the same thing, I'm convinced it's not an engine problem but more of a transmission problem. I had done the plugs, wires, PCV valve etc. at the same time I did the Intake gasket, so all that stuff is fairly new.

I find, it feels more like the car is trying to start out in second gear instead of first gear. That shake isn't that noticeble when you're driving at higher speeds. Have you noticed a drop in your fuel mileage? I'm wondering if the car has a go home mode where if it senses a trani failure it locks it into 2nd gear.

Here's a link to the thread I started. Since my mother in law has the car now I cant get the car to work on it. But my plan of action is to do the PCS (Power control solenoids) when I can get to it. I'm interested to know if you have any luck with yours.

http://www.automotiveforums.com/vbul...d.php?t=461725

Kev.

[KidChaos]

Similar prob here with my 98. Mine happens to be a transmission mount. I'm replacing it this weekend. I'll post if it fixes the prob.

[coffeecup]

Originally Posted by KidChaos

Similar prob here with my 98. Mine happens to be a transmission mount. I'm replacing it this weekend. I'll post if it fixes the prob.

Did you get the mount changed? Did it fix your problem? How did you detect that the mount was bad....any signs i should look for? Sorry for all the questions but this problem has me stumped....Thanks for any input

[RahX]

checking a mount requires two people with common sense. i say common sense because one person has to be looking under the hood and the other has to be in the vehicle loading the car up in drive and reverse, dont need anyone getting ran over. anyway, load it up in drive/reverse and look at all the mounts. when i say load it up i mean full brake and enough gas to make the engine move against the mounts. DONT LET THE CAR MOVE!! the mounts will move a little bit but if they more more than a little bit i would be suspicious of the mount. how does the engine run when youre actually driving it?

[coffeecup]

Originally Posted by RahX

checking a mount requires two people with common sense. i say common sense because one person has to be looking under the hood and the other has to be in the vehicle loading the car up in drive and reverse, dont need anyone getting ran over. anyway, load it up in drive/reverse and look at all the mounts. when i say load it up i mean full brake and enough gas to make the engine move against the mounts. DONT LET THE CAR MOVE!! the mounts will move a little bit but if they more more than a little bit i would be suspicious of the mount. how does the engine run when youre actually driving it?

The engine runs fine going down the highway, only when you come to a stop you can feel the rough idle. It has no rough idle when it is in neutral or park. Just when you have it in drive or reverse then you can feel it.