Thread: Vacuum leak? 06 GXP

My car has been idling higher than usual. Around 750-ish. So I decided to look at the throttle body to see if there was any carbon build up. And there was, alot of it. So I went to Autozone and got me some throttle body cleaner and cleaned the throttle body.

After that I put everything back together and wanted to go for a drive. But as soon as I started her up I knew something was wrong. Now not only is it idling even higher, around 900, but when I'm driving about 60-65mph and let go of the gas to slowly slow down for a red light, the rpm's hover around 1500 and only slowly goes down to around 1300. From there I pretty much have to engine brake to stop.

I don't know what I did wrong. At first I thought maybe I damaged the MAP sensor beause I took a screwdriver with a rag wrapped around it to clean passed the throttle body. I took the MAP sensor out and saw that there was a little gunk in it. Not knowing if that was the problem I just got a new one. But it didn't change anything. I also changed the MAF sensor, also didn't change anything. Was going to change the throttle position sensor until the guy at autozone told me that the throttle body and throttle position sensor are one piece so I'd have to buy a new throttle body which would set me back around $226. I decided to pass on that one.

Anyways, I've been talking to a guy on here, Jeff, who thinks its a vacuum leak. I found this tube coming out of my throttle body that isn't hooked up to anything. I put my finger on it with the engine running, but didn't feel any pressure or vacuum. I don't know if that means anything or not. I took a picture of it. Kinda hard to see but I'm pointing at it with a screwdriver. Anyone know what it's for? Also, doesn anyone know where I can find like a vacuum line diagram for an 06 GXP?

Any help would be appreciated.

Did you check the Oring seal for the TB? I have R&R'd my TB several times and always find some gunk between the SC and the TB. You can also use an unlit propane torch to go around anywhere you think there may be a leak. Use a piece of hose to attach to the end of the torch get into areas you can't get the torch. Go around the composite manifold as well, I know there were issues with the composite manifolds on some of the LS series engines and the Vortec's as well. When the idle goes up you have found the area. Some people like to use carb cleaner or brake cleaner as well. I prefer propane, to each his own.

Jeff

Took tb off to check on seal. It's still there and in good condition. Will try propane to check for leaks when I can

Did you fire up the car before or after you replaced the MAP sensor?

Both before and after. Why you ask?

Btw, I had two codes before I disconnected the battery. P0420 and p0121. P0420 has come back.

I hope it's not the throttle position sensor. It and the throttle body are one piece. I'd have to buy a new throttle body and they're $226. I'd get it if I knew that was the problem but $226 is an expensive gamble.

Originally Posted by wikisi9

Both before and after. Why you ask?

Was just going to suggest to make sure you put any o-rings back in with the new MAP sensor

Originally Posted by wikisi9

I hope it's not the throttle position sensor. It and the throttle body are one piece. I'd have to buy a new throttle body and they're $226. I'd get it if I knew that was the problem but $226 is an expensive gamble.

You would probably find a cheaper one at your local pick-n-pull

Any idea if any of the other grand prix models have same throttle body and gas pedal as the gxp or would I have to look specifically for a gxp if I wanted to pull these parts at a local pick n pull?

Check Rock auto for a cross reference. To be honest your TB looks exactly like mine, so I am betting they would cross.

Jeff

Ok, i went to Rock auto and looked up throttle body for my car. When I clicked the part number, all it says for pontiac is "PONTIAC GRAND PRIX (2005 - 2007)". That's it.

Have you ever seen any GXP's at the LKQ, Jeff?

No, but there are several GTP's and I left an 04' ther when I pulled the SC. There are a couple of 06's coming out in the next week.

Jeff

You can try mine if you want.

Let's try it, Jeff. Thanks.