Wierd idling and surging

[INF3RN0666]

Hi

My mom's 98 Malibu 3.1L with 65000 miles makes strange sounds at the end of the exhaust. If you sit behind the car and listen while it idles, it sounds like the exhaust is intermitently sputtering and it's moving slightly up and down while it sputters. Also, when the car is warm and idling (or standing still at a red light while in drive), you feel a random pulse (hard hit from underneath) throughout the car ever once in a while.

Just a little background on the car. The engine makes the common malibu clicking noise when it's cold that fades when it's warm. Apparantly that's excessive bore clearange (faulty engine design). The other thing that might tie in is that the car seems low on power all the time. If you turn on the heat, everything dims. If you adjust the seat, everything stays dim as you're adjusting the seat and you can hear the difference in engine sound.

What could that be from? Poor fuel quality? Bad alternator?
Thx

[steve_o]

Your problem may be an IAC (idle air control) valve. Also, check for a faulty EGR (exhaust gas recycling) valve that may be sticking open.

Idle Air Control Valve (IAC) definition: An electrically-operated valve which allows air to bypass the throttle plate in a fuel injected engine to regulate engine idle speed.

The IAC valve is located on the throttle body. First, disconnect the battery's negative cable and unplug the IAC's electrical connection.

The IAC valve typically attaches to the throttle body with two screws, not sure on the Maliby but my Ford’s were Torx-headed or vice-versa.

With the IAC removed, clean any dirt and debris from its mounting hole the problems are often in their valve-spindle extension shafts get black and gunked up.

I used some throttle body cleaner and Q-tips and an old toothbrush. My Haynes manual made some reference to the proper length of the plunger but I didn’t have any problems with that. Make sure the O-ring is good, then reinstall the IAC.

I cleaned it because I didn’t want to pay the ~$50 to replace it.

[INF3RN0666]

Wow, awesome reply. I couldn't have asked for a more clear answer. I'll definately try that out after my exams are done this friday (YEAAAAH!!!). Like you, I'm not willing to pay $50 for something that costs $5 to make. haha. thx again!

[bcopeland]

Did you get a check engine code like "Cylinder 2 misfire"?

[INF3RN0666]

I don't have a code reader and it's my mom's car. Taking it to a mechanic before it starts acting up isn't going to make sense to her. You know how women are (my mom and my sister), they don't 'feel' the car or how it's performing. as long as it's still driving, they think it's fine, even though the breaks might be completely out, it's making mad chirping sounds.

[johnholl]

INF3RNO666:

I replaced my battery a few weeks ago just to be on the safe side. For some reason the battery performance in this car drops off sharply after about 3 winters \years. Perhaps it is the electrical load that is placed on them, or poor altenator choice.

That's my advice...get a fresh battery

[INF3RN0666]

Thanks John, i'll make sure to check the battery right after my exam tomorrow . I had a feeling there's some poor electrical work in this car, and I'm gonna try to isolate it. You've all been a great help.

Thanks for the time you took to reply.