rough idle until I spray Mass Air Flow Cleaner in the throttle control body


Asked by May 07, 2008 at 03:19 PM about the 1998 Pontiac Sunfire 2 Dr SE Coupe

Question type: Maintenance & Repair

My sunfire has 101,000 miles, idles rough like it has a bad MASS AIR FLOW SENSOR. Seems to run fine as soon as you get going. The check engine light (IS NOT ON. )When you spray Mass Air flow sensor cleaner in a nickel size hole on the front of the throttle control body left of the butterfly the car will run smooth for about 30 miles. Is there some sort of sensor in the trottle body next to the butterfly that can be going bad? Whatcan be causing the rough idle problem

22 Answers


rough idle from lack of air, did you check your air filter and make sure the throttle body and everything is functioning correctly.

3 people found this helpful.

Sounds like you are running lean (not enough fuel) there shouldn't be any sensors after the throttlebody because the Mass air flow does the work (some fuel injected car have a baro sensor instead of MAF after the TB I would check the vacuum ports on the intake to make sure they are nice and clean you spraying cleaner in there might be enough to open them up slightly to flow for a short time. If that doesn't work then you prpbably have a fuel injector that is dirty. Your local parts store should sell a 3 step intake and fuel injector (DECARB) kit made by 3M its reletivly inexpensive and should work only use the 3m kit tho all others don't work as well. I must say it is odd to spray it in there and it run well for 30 miles or so usually if you are haveing a lean issure that will only work for 30 seconds or so. Pual

2 people found this helpful.

check the injector o rings...sounds like one has failed...simple to pull them out..takes 15 minutes...look at o rings carefully...hopefully this helps...

4 people found this helpful.

It is you idle air control valve. it is located in the throttle body and reads air/fuel mixtures in the intake and adjusts the two to match. The valve is reading your car rich, that is why it is idling rough. the valve is telling the computer you are using to much fuel and the computer is in turn starving the engin for fuel. You are tricking the valve by spraying the cleaner into the intake, by making the reading so far out of sync that the computer goes into saftey mode until it thinks the sensor is reading correctly again.

16 people found this helpful.
Best Answer Mark helpful

They are right!!! I have the same thing going on with my 2002 Sunfire and thats what the mecahnic told me.. I also have a rough and low idle while the AC is running but fine when it is off.... and drives well, but when sitting at the light i have to cut the AC off or the "jump" of the idle will cut the car off.... It feels as if it is not getting enough gas... so yes my IAC is going, so replacing this weekend,... I hope you got yours going good by now :-)!!!

5 people found this helpful.

I am having the same problem. My sunfire has a rough idle. The battery is new. We have changed the mass air flow sensor, throttle position sensor, idle air control, spark plugs, fuel filter, had the fuel injector clean, new exhaust, new catalytic convertor. After over $1000 spent, we still have this problem. Dont' know what to do next.

11 people found this helpful.

If it is a 6 cyl, they tend to run rough as they age. But I would replace the pcv valve if you have not already. I would also take a look at the ignition control module, depending on which engine you have it may be located on either the firewall of under the coil packs if it is a v6. Honestly, may just be a bad coil pack. pcv=$10, icm=$30, coil=$50(v6 has 3 coils). Hope that helps

1 people found this helpful.

I have similar issues, Engine won't start on it's own, have to press accelerator a little. Once running, idles rough. Runs fine when accelerating, but stalls or wants to stall upon deceleration under 20mph or when coming to a stop. For anyone who doesn't know this, for the most part, on fuel injected vehicles, the PCM uses input from the following to control idle speed: Intake Air Temperature Sensor, Manifold Absolute Pressure Sensor, Throttle Position Sensor, Camshaft Position Sensor, Crank Shaft Position Sensor, Engine Coolant Temperature Sensor, Vehicle Speed Sensor, Air Conditioning Relay, and Idle Air Control Valve. I may have missed something, but as you can see there are a lot of factors involved. Unless you have the specs in each part to be able to check resistances and voltages, it's almost a hunt and peck situation. Code scanners are helpful, but as I have found, the PCM's don't always register a code for a defective part. One thing you can do is check for vacuum leakage. The easiest way to do this is to put the vehicle in gear and with the brake pedal pressed firmly rev the engine slightly. If it stalls out easily you probably have a leak somewhere. Another thing to do would be to remove the Idle Air Control valve, and clean the end with Gumout. Be careful not to move the valve stem in or out as it is a stepper motor and very sensitive. Also clean the port where the tip of this valve goes into. Also, if you disconnect the cable to it, the PCM will go through a re-learning stage in which vehicle may still experience idle issues for a while until the PCM re-learns this information. Hope this helps some..

5 people found this helpful.

vacuum leak- usually intake manifold is cracked, warped, or has EGR valve leaking/ opening at idle-( shouldnt open at idle)

1 people found this helpful.

I had rough idle on my 2000 Pontiac Sunfire and found out that the rubber line to the MAP(?) sensor, that sits to the right of the throttle body, was rotten. I replaced the rubber line (sells by the foot at any auto parts store, cost a few cents) and the idle has been locked at 500 rpm ever since.

4 people found this helpful.

I had a problem with my 1998 4.0L V6 EFI Ford Explorer XLT 2WD Idling Rough, and running rough at stops, and take off. After replacement of the Idle Air Control Valve, Air Filter, Throttle Position Sensor and PCV Valve, My Check Engine light came on. Had the code checked at a local auto zone. p0302. Misfire on Cylinder #2. Replaced spark plugs myself and no more rough idle. Engine purrs now and Idles like Brand New.

1 people found this helpful.

2004 Pontiac Sunfire, I have been waiting for a long time to say this, it is one dam thing making this misfire, & some dum GM, macanick is looking at this right now laughing, well MR such n such, we are paying 1000 bucks for the same dam sensers, it is 2014 now ! So will you fininly tell us yet! My car runs like crap, but I drive the chugging dame thing, around, so that stupid air trottle part ima, cut the dum as thing off end of it, & see when I put it back in will my car run right, no its more like why when is rains out does the car misfire, or when it is hot out side, Or I run threw a puddle, splash then the car runs adddhhh ahhh, wat senser it that mr micanik hhuuuahhh!

2 people found this helpful.

& dude by the way, I got 125,009, on it, it runs rough, but good I just got two custom fans & wired them the the wiper motors, fuse in the fuse box, so they are always on when the car is started, ok & it is going ok my car will not over heat, I will flush then engine next week, with the hose in resivore, & the bolt out of the ratiator, so it will drain out, start the car, Ima let it run for two hours, to clean that crap out!


I am going to also replace the throtle gasket. I was just joking about cutting the throttle senser!

2 people found this helpful.

I had the hiccups at idle and the skipping and missing and stuff. When I replaced the distributor, the car idled like new, ran like new and is still running like new today. that was about two years ago. Maybe its distributor if your car has one.


Your car misfires in the rain or wet conditions likely because you have a crack in the casing of the ignition control module, when it gets wet it shorts out. (I am a mechanic)

1 people found this helpful.

can you rinse the inside of your air intake..if not is there a way to clean it..01 cavalier 2.2...thanks

1 people found this helpful.

I have a 2000 Chevy cavalier and I have similar problems. At first in the morning it would start right up, but as I get to the store and do what I need to do and try to turn it on it only keeps cranking until I press the gas pedal! I changed the coil packs, spark plugs, boots, and housing but I still have the same problem! I don't know what else to do. Does anyone have any suggestions?

2 people found this helpful.

try replacing the crank shaft censor on it if it runs good in the winter & won't run in the hooter weather like summer. My mom had a 2000 pontiac grand am 2.4l & she had it for many year & it was a good car, but it got to where you couldn't depend on it starting back after you drove it a while it would cut off & not start back. After she got rid of it she found out it was the crank shaft censor & they replaced that & the car ran good again, & as far as I know its still driving around somewhere today. maybe this info. will help someone somewhere.

i have an 99 sunfire 2.3 with 244566 on i was driveing it and the theft system oil battery coolint and the rpm gage does not move do you know what is going on with my car if some one can help me out to know what it is

i have an 99 sunfire 2.3 with 244566 on i was driveing it and the theft system oil battery coolint and the rpm gage does not move do you know what is going on with my car

jluthye, I know it was 8 years ago, but was a new IAC to fix that worked?

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