Rough idle

[rwolfe]

i have a 99 grand am se with about 100000 miles and it just started idling rough and i have a brand new air filter and fuel filter. i dropped my stock exhaust and put a flowmaster on it could that be the reason i have this problem?

[andy05cars]

I have the problem man and it only happens at certain times. I have a custom air intake and have magnaflows on mine. I'm not sure what the deal is.

[mikekanzler]

ha i have a 2.4 and mine does that also

[Howlin' GA]

not completely sure but it could be fouled spark plugs, dirty injectors or anything but i would check those first.

[rixGAphx]

In all cases of erratic idle with no SES/CEL 'on', the first thing to check is a vacuum leak: Tube, device, or gasket allowing air to be sucked-in.

Anybody with 75k-100k on the spark plugs should change them (and the wires/boots), but they will only cause a poor idle if they are also causing an actual ‘misfire’, which the PCM will identify with a P03xx code and the SES/CEL ‘on’.

An easy DIY vacuum-leak test is to warm the engine and let it idle, with the ‘roughness’.
Using Winter Starting Fluid or other spray can o flammable stuff (most carb/FI cleaners), spray around each vac device, connection, tube, and gasket/seal.
The leak will suck-in the fluid, the rpm’s will rise, and the idle will smooth-out.

Hope this helps,
-Rick

[andy05cars]

Thank you Rick. I will do that soon.

[andy05cars]

I think I found out why it might be idling rough.

It's the EGR valve. I think this link will be helpful if you don't know what this is.

http://autorepair.about.com/od/glossary/gr/def_egr-valve.htm

so i'm going to buy this on-line b/c it is $100 cheaper than Autozone. This is a link to buy it. It's one website that I found at a good price:

The one you want if you have a 3.4L grand am is :

Delphi EGR Valve
1996-1999 Pontiac Grand Am
Price: $154.95

Link: http://www2.partstrain.com/store/?Ntt=egr%20valve&N=1697%204294967267+11519

I hope this helps everyone.


-Andy

[rixGAphx]

That article is quite old, and very misleading.

Yes, a faulty EGR valve CAN cause problems, especially at idle.
All early EGR's (we're talking 1970's when they were first introduced) were vac-operated, and failures in them often had to do with their little vac tube; so a 'faulty EGR valve' WAS a 'vacuum leak.'

BUT, that article speaks particularly about EGR's as a "vacuum-controlled valve".
On GA V6 engines since '96, and late-model GA 4-cyls (though I'm not sure of the year), the EGR valve is ELECTRONICALLY operated, and there is NO vacuum at all.
True, the EGR passage opens into the intake manifold like other vac ports, and if the valve is stuck, it can seem like a 'vac leak' since too much air is entering the intake manifold when it shouldn't.
So similar erratic performance can result.
BUT, there is a sensor on the electronic EGR valves, and it tells the 'puter when the EGR valve hasn't closed as it should; the 'puter then flashes the SES light.

Your EGR valve may indeed be faulty, but it is far from certain at this point.
Certainly not sure enough to throw $200+ at it, without doing the other troubleshooting mentioned above.
It's your money, we're just trying to save it.

Finally, about half of all 'faulty' EGR valves can be fixed just by removing them, cleaning them with toothbrush and spray FI cleaner, chasing the two ports that they serve, and reinstalling the original device.

Good luck,
-Rick