RPMs drop and almost dies....

[zwack88]

Ok my dads 03 GM is being a real bitch as of lately. It has stumbled since last summer at idle in any position on the shift indicator. I looked and the stumble was in sync with the belt tensioner flapping around. My dad let it slide since it was nothing big. I just replaced it the other day and it still had a slight stumble. Well saturday I replaced the front brakes because the rotors were warped and I put everything back together and go for a test drive (turns out the rears are warped also, fucking 03+'s). I back it out and the rpms die way down and the car gets quiet but didn't die. I notced the battery light blinked at me a couple of times. It did this many more times when you just put it in a new gear. I plugged my x cal 2 in it to check for codes but it was clean. The car has 35,900 miles on it and it shouldn't be doin this shit. My vic has 92,500 on it and runs smooth as silk. He does have 100 miles more before the warrenty is up so I hope he takes it in but most likely I will have to deal with this. So what could it be? I know it is a very broad question and it seems like a vaccum leak and all the hoses are plugged in. He hasn't washed the engine lately so it is nothing to do with moisture.

[Archangel]

Actually the tensioner flapping is a result of the stumble, not the cause of it - when the engine revvs up after it slowed down it pulls on the belt harder, causing ithe tensioner to move. The battery light you saw sounds like something worth investigating, maybe something wrong with the charging system? Like battery's about to die and the alternator is working like crazy to keep it up and the car running? Dunno man, better tale her to the dealership before the warranty expires, as it may turn out expensive to fix.

[gadget73]

I'd vote some vacuum line unhooked or the IAC bad. Take it back before that warranty is up.

[zwack88]

Ya I was thinking it was probably vacuum related. The new tensioner did solve the flapping. It just still has a stumble. Any ideas on how to do a scott smoke test on a maf car? I want to blow some smoke in the intake to see if I can find a cracked hose or something but the way the airbox is it will be hard.

[zwack88]

Well today she has been really good. So that means it is more or likely the IAC messing up right?

[Paul_]

From what I know of the 4.6, that's a good indicator of the IAC gone south.

[Freshmeat]

Warranty...

[zwack88]

Well fuck. I replaced the IAC about 5 minutes ago and cleaned the MAF at the same time. Still the same shit. I can actually hear a slight backfire on high idle in park with the resonators gone now. It does have the ever so slightest miss to it. I just don't get it as the car is a real runner and he gets 18 mpg in town and about 25 highway. I am confused as hell. The idle aways seems to be changing when idling like from about perfect to way low to about perfect again. I just don't get this shit.

[gadget73]

check it for codes? Should have taken it back to the dealer for a warranty fix.

[zwack88]

I know man, my dad drove it 150 miles the day after I originally posted it so it is sol. I did scan for codes and nothing came up. I am going to search cvn to see what I can find. I am really starting to lose respect for these cars.

[p71towny]

Is there any sort of vaccuum leak you can hear hissing???

[DarkKnight]

Zwack if you do dig anything up please let us know :-D case thats one of my prob's as well :-D


D.K.

[drock96marquis]

Check the condition of the supply tube for the IAC. It may be cracked, loose, etc.

[gadget73]

Thats a good point. Make sure any tubes connected to the air supply tube are connected tight. I knocked one off my truck and it ran like ass. MAF is really picky about that.