1998 Pontiac Sunfire SE 2.4L Rough Idle

ericv1984

ericv1984

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I noticed about a week ago that the car has a rough idle so here's what I've done so far.....

New Air Filter
New Fuel Filter
Replaced the IAC Valve

None of those things fixed the idle. I also have a new set of spark plugs that I will be installing. If the spark plugs don't fix the idle, then what else could be causing it?

It idles at normal RPM, which is around 1k but has a stumble.
 
Do you have a check engine light? When you replaced the IAC did you look in the pasage way for any carbon build up?
 
melsg5 said:
Do you have a check engine light? When you replaced the IAC did you look in the pasage way for any carbon build up?
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No CEL. And I meant to look in the hole and clean it out but forgot, not sure if there is any carbon build up anyway since I cleaned it out a few days ago when I cleaned my old IAC. Might as well take off the IAC and clean the hole out again just to be sure.
 
ericv1984 said:
No CEL. And I meant to look in the hole and clean it out but forgot, not sure if there is any carbon build up anyway since I cleaned it out a few days ago when I cleaned my old IAC. Might as well take off the IAC and clean the hole out again just to be sure.
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Cleaned the hole out but there wasn't much carbon build up.
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be sure to clean the throttle body out,we have alot of customers come in with that problem and its just dirty throttle bodies.
 
Cleaned all the carbon build up on throttle body, which was a lot, didn't help at all. Also, when I was about to leave, I turned my car on and noticed a put put sound coming from the exhaust. More noticeable from the exhaust but I can hear it with the hood up too.

View My Video


View My Video

Sounds to me like a misfire, yet the car accelerates fine and has a good amount of power. Minor misfire???
 
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its possible...also might be good to pull the valve covers and check to see if you have any broken springs. that would cause your symptoms too.
 
your second video with the engine view,you have a lifter or rocker arm tapping.
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tomgp said:
your second video with the engine view,you have a lifter or rocker arm tapping.
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A guy on the dsmtuners website had a lifter tapping problem and he fixed it with an engine oil flush followed by an oil change. Any thoughts on that?
 
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never tried it before,i would still pull the covers and see if there is any play on your rocker arms...they should all be tight,if they are still tight then try the oil flush.
 
If they aren't tight, can they be tightened or would they need replacing?
 
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if your rocker arms are loose then you have a bent push,bad lifter or a broken spring... all will cause that tapping noise and a misfire.
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tomgp said:
if your rocker arms are loose then you have a bent push,bad lifter or a broken spring... all will cause that tapping noise and a misfire.
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I looked in my Chiltons and it doesn't show rocker arms for the 98 2.4L, only lifters. I bought some Rislone - Engine Oil Stabilizer (http://tinyurl.com/8jsqwum) and did a fresh oil change with that and Castrol GTX High Mileage. I haven't pulled the valve cover yet cause it was getting dark after the oil change. I'll be doing it soon since I have to replace the spark plugs anyway.
 
You have an overhead cam engine so there are no pushrods.
 
I replaced the spark plugs tonight. The ones that were in there didn't look burnt or anything but I replaced them anyway. After I replaced them I took a test drive and the car seemed to run good at first, but half way through the test drive, it started stumbling on idle again. The same as before, not any worse.
 
I know you have no check engine light but go to autozone or similar place that will do free code lookup and see if anything comes up.
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melsg5 said:
I know you have no check engine light but go to autozone or similar place that will do free code lookup and see if anything comes up.
Click to expand...

My friend told me that last night, I plan on going there in the next couple days.
 
I was reading up on symptoms of a bad camshaft position sensor and it says...

"Engine Hesitates
A bad camshaft position sensor will make the engine hesitate while idling or accelerating. As the gas pedal is pressed, the engine will begin to accelerate, but hesitate or stall during this process. This hesitation is a symptom of a bad camshaft position sensor because the cylinders are not being fired in the proper order and the computer is not registering the correct information in order for the cylinders to fire properly. The vehicle owner must take the automobile in to a mechanic and have vehicle placed on a diagnostic computer to determine if the camshaft position sensor is bad when this symptom occurs.

Engine Misfires
The engine begins to misfire when the camshaft position sensor is bad. The automobile engine cylinders are blowing combustion through the exhaust, causing a loud sound to be heard and the automobile to act as though it is going to die. This misfiring happens because the cylinders are out of time owing to the bad camshaft position sensor. Each cylinder must fire in the correct order for the engine to run efficiently and smoothly.

Read more: What Are the Symptoms of a Bad Camshaft Position Sensor? http://www.ehow.com/list_7517747_symptoms-bad-camshaft-position-sensor.html#ixzz2722hMJq6
Sounds pretty much like what the car is doing so I plan on cleaning the sensor first, and see if that helps then maybe buying a new one if the cleaning doesn't work or works a little bit. Any thoughts?

When I accelerate fast, around 40 mph I hear a popping sound from what I think is the exhaust, but not everytime. Is that the "causing a loud sound to be heard" that they are talking about?
 
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If thats the cause why no CEL. Did you ever test your fuel pressure?
 
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