Odd idiling

My 99 Grand Am Se 3.4L has recently been idiling very wierd. When driving, there is no problems, but when sitting at a light, parking spot, or anything of the sort the RPMs jump up and down. Not much, about 100 RPMs. Also, when its does that, the car bucks back and forward, even in neutral its noticable. I replaced the MAF, MAP, Idle air valve.

Have you cleaned the TB and or upper intake ?

How old are your plugs & wires ?

I cleaned out the TB, the wires are kinda old, but the resistance on them are good. That also goes for the coils. The only thing that keeps running through my mind is the EGR going bad.

maybe the TPS?

That could be it too. I'll have to check it out later.

I doubt its the TPS, you can test it. Thiers a procedure in the Tips & maintenance section. :thumbsup:

AN EGR problem usualy throws a code and the SES light.

I would say replace your plugs & wires see how it does after that.
And check for vacum leaks!! Especialy the hard line(s) that runs from the air intake to the rear valve cover and the other one back there on the purge valve, and all the others. ;)

How many miles on your 99 ??

I'm starting to think there is a vacumn leak. I noticed there is a little bit of coolant leaking out from the LIM. I'm guessing the sealant didn't set properly or there wasn't enough applied. I have 111,111 miles on my GA.

BTW, the line from the purge valve to the back valve cover is fine. What's a good way to test for vacumn leaks in general?

A LI leak will cause some rough idling and running overall. :eek:

I use propane gas with a hose on the end , and follow the lines around,,, after a good visual inspection of coarse.
You can use carb cleaner, but its messy and can catch fire if sprayed in the wrong spot.
But either will make it idle up and smooth out if thiers a leak.

Also if you have a scan tool, look at the Short Term Fuel Trim (STFT) value while you are using carb cleaner or propane. :thumbsup:

The car itself runs fine when driving, its just when idling. Also, I noticed i'm getting a lean code bank 1.

Hold up, I think I may know what the problem is. I have a intake and I think I may of over-oiled it. I'll try that in the morning if the weather permits.

So was that a p0171 or what exactly ?

Sounds like an O2 sensor might be goin bad. They can be tested, check the Tips and Maintenance (http://www.automotiveforums.com/vbulletin/forumdisplay.php?f=2148)subforum for the procedure.

That was my first guess I had tested the O2 sensor it and it's fine.

Here is a clip of what I hear
http://boxstr.com/files/3348418_b921n/08-29-08_1638.3gp