ibanez7

iTrader: (7)

2001 z28 m6 with 63,000 miles.

I have had this problem for awhile and no one can give me an answer on what the problem is, and the only answer GM dealer mechanics give me, "is you have to go to a performance shops\"

Before I go to my local shop, Speed Inc. Does anyone have any last thoughts or ideas so i can maybe fix this myself.

the problem is rpm surging, here is the problem which it doesnt do it all the time just way to often, this is very different then other rpm surging:

I can be driving down the road at 45mph in 6th gear, depress the clutch and my RPMs will rise to 2200, with the clutched still depressed, i rev the engine to 3000 rpms and then they drop back down to a 1000. Then the car runs fine for awhile.

Another instance is I'm going down the road at 45mph or faster, depress the clutch, and my rpms fall to 1000rpms like they should, but then i shift the car into the neutral gate, let off the clutch and coast and my rpms will surge to about 2600rpms and stay there as I coast down the road, as I slow down the rpm come down. If I maintain speed I depress the clutch, put the car in gear, rev the engine to 3000rpms and all is fine again.

at idle my car usually revs between 1000 and as high 1600. This problem has been going on for about 6months without an SES code until this last week. But the SES code comes and goes, when checked at autozone, the code came back as Throttle position sensor. Can that cause my idle to be like it is?
Also I have not lost performance either!

Its annoying cause my gas mileage has become worse.
much of the time when shifting between gears my rpms stay up, making for hard shifts.
and I miss having an idle at 800rpms.

the only intake mods done are, SLP lid, KN filter, fernco bellow, SLP z06 MAF, and ported intake. No cam or computer programming yet! These mods where done about 2months before the issue

Attempt to fix the problem was replacing the IAC which did nothing. check for vacuum leaks and nothing.
The GM dealers blame this problem on my computer not adjusting properly to my intake mods.
The intake mods that I have are very common, so I cant see them causeing this problem, which I believe is a very uncommon problem.

Any ideas will be greatly appreciated. thank you, thank you and thank you!

TNormZ28

iTrader: (9)

Try swaping out the MAF with a stock one and see if that corrects the problem.

ibanez7

iTrader: (7)

I problem actually started when I had the stock MAF. sorry for not writing that in

horist

ported Intake... as in a ported stock intake manifold? or do you mean ported Throttle Body ?

Sounds like a vacuum leak, can you have anyone w/a scanner get some logs? Specifically LTFTs (bank 1 and bank 2)

efizjb

iTrader: (1)

May be intermittant TPS sensor problem, that's easy enough to swap out. I've worked at many GM dealerships, and have seen TPS sensors fail in very erratic fashions as you describe. If it is reading higher voltage than what it truly is, it will richen up the fuel mixture, hence why the idle goes up. Being intermittant as it is I doubt you'll find that on a scanner. Be certain you have no vacuum leaks as someone stated in earlier post.

ibanez7

iTrader: (7)

its a ported throttle body not intake manifold.

I will be replacing the TPS this weekend, I hope that fixes the problem, I just cant believe it would take 6months to set my SES light off

ricekillman

Sounds like a vacume leak. (At idle? IAC?) Is there any hissing? Take a can of carb cleaner etc. and spray it around vacume areas like the back of the intake around the TB and so on. If you have a leak rpm will change. Have you checked to see if everything is plugged in all the way. MAF/IAC/TPS etc. Try unpluging the TPS also and taking the car for a short drive. See if the problmem dissapears possibly TPS sensor. But i'm leaning towards a vccume leak.

Another_User

Actually, I was thinking...it may be something far more simple...have you (and the retard GM techs) checked the PCV? If it is stuck open you would probably get those symptoms. Maybe gummed up with (cough cough) oil. Not that oil ever gets into our engines through there...LOL.

BJM

iTrader: (1)

It could very well fail and not throw a code. The failed portion of the sensor may simply be providing an incorrect but still plausible signal to the PCM and it will respond accordingly giving you screwy results. The PCM can really only notice things like the TPS going impossibly high or low, if its still in range but wrong there are very few ways to figure that out.

bullygoat

Simplest way to check if the TPS is hanging(which it sounds like is happening), is to check the voltage when you let off of the throttle. It should be around .5 volts when throttle is closed. If it's hanging it will be anywhere between .5 and ~4.8 volts. Like was stated earlier, if the voltage is an off idle voltage, the pcm will add fuel thinking you were getting into the throttle.

ibanez7

iTrader: (7)

Thank you to all of you!!!

I beleive my agenda for this weekend will be to check for vaccuum leaks around the TB/intake, replace the PCV(needs it anyways 63,000miles on it), and check volts on the TPS.

hopefully its get fixed, as I want to install a new clutch, cam and headers before spring. But not if I still have an RPM problem