Malibu idle problem

[rcorm]

2002 Malibu LS
Anyone have a problem with an unsteady idle ? The car runs fine at higher RPMs but runs unstable only at idle.(<600 RPM)
The "check engine " light comes on because I believe it is missfiring or fuel mixture is unstable.
Would any particular sensor be the problem?
Thanks for any help!

[burly]

The first couple of things I would do assuming you haven't already done these are:

1. Check that the air filter is both clean and seated properly.
2. Check that the spark plugs are foul-free.
3. Run some injector cleaner with some good 87octane gas in your next tank.
4. Make sure that you have both changed the oil within the last 5000k and that the proper amount is in the engine.

If neither of these retify your problem, it could be a vacuum leak, air bypassing the mass air sensor, a computer issue or something else that I am not thinking of .

-Zach

[rcorm]

Buly,
Thanks for the suggestions.
I replaced the air filter about 2 months ago and also replaced plugs with Bosch platinums and the car has run fine since then until now.
I ran a tank of fuel with Prestone Injector cleaner last week and I changed the oil about 2 weeks ago , to proper levels.
I did a quick look at all the sensors and vaccuum lines but didn't see anything suspect. I'm thinking i coould have a bad sensor (IAT,MAP,MAF,TPS) but i don't want to change them unless I know they are bad. If you or anyone could give a suggestion on testing them , that would help.
One other sympton is that the transmission takes a bit longer to shift to overdrive when cold. After about 5 miles, rpm drops to normal (~2000 @ 65 mph)
Other than this idling issue, the car runs great.

[Joe W]

Since the check engine light came on there is/are code/s in the comp. Autozone will usually read them for you,and it will point you in the right direction.

[rcorm]

Joe,
Thanks for you feedback.
I did check the IAT and TPS sensors. They seemed okay an wiring okay. No vacuum leaks (checked with carb spray all around intake,vacuum lines and connections) without changes to the rough idle and random skip.
Ironically, the check engine light has now gone off and the engine is now idling fine.No missfire or roughness!
Will the computer retain the error code even if the check engine light is now off?
Thanks for you help!

[Joe W]

The computer will retain the code and you need a scan tool to erase it.AutoZone will usually read these codes for you.

[dakotaquad4x4]

PROM - Cold Engine Idle Surge,Long Crank Time, No Start

File In Section: 06 - Engine/Propulsion System

Bulletin No.: 99-06-04-032

Date: September, 1999

TECHNICAL

Subject:
Cold Engine Idle Surge, Extended Crank Time, Crank No-Start
(Reprogram PCM)

Models:
1998 Chevrolet Malibu
1998 Oldsmobile Cutlass
with 3.1 L Engine (VIN M - RPO L82)

Condition
Some owners may comment on one of the following driveability conditions:

^ Cold engine idle surge/hunt
^ Extended cold engine crank time, followed by rough idle
^ Crank no-start concern after initial cold engine warm-up and shut down


Conditions may occur between ambient temperatures of 0 - 60°F (-18 - 16°C).

Cause
PCM calibration values for given ambient temperatures may cause the above conditions.

Correction
A revised calibration has been released to correct these conditions. Reprogramming the vehicle using the appropriate listed calibration should correct the concern.

Parts Information

Part Number Description

9369194 Federal/Canada - Malibu, Cutlass
9369204 Unleaded Export - Malibu, Cutlass
9369214 California - Malibu, Cutlass

The calibrations listed are electronic calibrations and are NOT available from GMSPO. Calibrations will be available from Techline starting June 1999, on the TIS 2000 Disc 12 CD ROM.

Warranty Information

For vehicles repaired under warranty, use:

Labor Operation Description Labor Time

J6355 PROM - REPROGRAMMING, Use Published
On Car Labor Time

[wpbharry]

Until the last 6 months, I've never had a starting or idling problem on my '98 LS, EXCEPT for 2 instances, one when the first battery died, of course (now on 3rd batt), and when the alternator was on its last legs 2 yrs. ago, which really threw the idle out of whack. Check Engine light came on with the alternator issue.

Lately it sometimes seems as if it really doesn't want to be alive. It starts, but not with any authority. My Chevron station recently became Sunoco, and after figuring out that the car just doesn't like Sunoco gas, I switched to Exxon, and everything seems fine again, for now.

Just some ideas. Here in FL, it's rarely below 60 degrees, so I don't know if the PCM issue would apply to me.....

[rcorm]

Thanks everyone for your comments.
The original problem I had seems to come and go randomly. The check engine light has remained off but I would expect it to come back on if the idle missfires too much.
The problem only occurs when the car is warmed up and at normal operating temperature.
I asked the people at Autozone to check the trouble codes but they said " they can only do it when the light is on". I mentioned that I thought the computer would retain the codes and they said no. They said the oxygen sensor fails quite often and that may be the cause. Is there any static test that can verify the O2 sensor such as an ohmic resistance test?
I bought the service manuals and I'll try to see if I can locate the problem myself with the hope of also getting the code(s) read at some point.
I have a feeling that the problem will show up again , especially when I have to get the state inspection which requires smog testing!
Appreciate any further comments, especially by any GM techs!
Thanks...RC

[rcohen_malibu99]

Hi,
I saw your post, and I had the smae or similar problem as you had.

My idle was dropping below comfortable for the car, and it would stall. So to get home one day, the last day, before the problem got fixed, I had to give a little gas to keep the car going. I thought, ok, what the h-ll is going on, I cringed, alternator, fuel pump, spark plugs...how knew!

But the garage hooked up a computer, tested fuel pressure, it was fine,
The sparks, electrical was fine. They were puzzled, BUT

what came up after computer diagnosis

.....was the idle control motor, (or something like that).

So they took it out, cleaned it up, lubed it, and put it back in.

77$ later, everything runs fine.

good luck

[Milamber_74]

I recently had this problem with my 97 LS (97k on it) and when I took it to the dealer, they said the computer was recording it as a fuel injector misfire. The car would run fine while you were driving, but if you came to a stop, or low speeds, it would start to sputter badly. The check engine light also flashed for awhile, then went solid, and then off.

I did a search on a site and they said the fuel injectors on Malibus are a common problem.

The dealer did a fuel service (over $400 to replace the injector which I wasn't willing to do) and that seems to have cleared up the problem for now.

Originally Posted by rcorm

Thanks everyone for your comments.
The original problem I had seems to come and go randomly. The check engine light has remained off but I would expect it to come back on if the idle missfires too much.
The problem only occurs when the car is warmed up and at normal operating temperature.
I asked the people at Autozone to check the trouble codes but they said " they can only do it when the light is on". I mentioned that I thought the computer would retain the codes and they said no. They said the oxygen sensor fails quite often and that may be the cause. Is there any static test that can verify the O2 sensor such as an ohmic resistance test?
I bought the service manuals and I'll try to see if I can locate the problem myself with the hope of also getting the code(s) read at some point.
I have a feeling that the problem will show up again , especially when I have to get the state inspection which requires smog testing!
Appreciate any further comments, especially by any GM techs!
Thanks...RC

[rcorm]

Thanks rcohen and milamber....
I appreciate your comments. My idle problem went away and came back briefly.
The check engine light stayed on less than a day.
I did get the service manuals and will be checking various sensors.
One item is the idle control motor you recommended.
That could be a relatively easy fix. I still need to have the codes read at Autozone, assuming the check engine light remains on.
Today the car ran perfectly withg no signs of stumble at idle and no light.
I am even thinking an intermittent connection somewhere in the harnesses.
When and if I find it , I'll let you all know.
Things were a lot easier when you changed and adjusted the points and adjusted the timing!
Thanks again, rcorm

[malibudrifter56]

this may or may not be your problem but here u go... if your idle seems to drop every couple of seconds try disconnecting your air injection pump on the passenger side of your vehicle, there will be a two prong connector. mine seems to do it only after its warmed up, i know the computer tells it to go on but i cant figue out why it is. i hope i was some help, let me know what happens.

[Patwin]

My Malibu races its engine when in park. Is this very serious?

[viperius]

1999 does it only when the A/C is on but no check engine light my mom freaks out and tuned the A/C off right away so i dont know what could have happend.

Anything I should look out for?