BigZee71

iTrader: (5)

93 Z28 auto. LT4 hck pcmforless tune. stock stall.

When the engine is running in gear and I move from lets say drive to reverse,
the engine revs up to around 1300 RPM and hanges there for several seconds
before dropping back down to normal 800 rpm idle.

Problem is while it jumps to higher rpms, it makes shifting from reverse to drive or vise versa a pain in the *** and annoying as hell as it like to jerk or pop into gear. I could just hold it in neutral for a few seconds, wait for the RPMs to drop back down, then select the gear, but thats also annoying
and the problem still isnt fixed.

So whats causing this? Otherwise, the car runs excellent.

Could it be a slow Idle air control valve causeing the idle to jump and hang?

daniel6718

iTrader: (36)

ive been wondering the same kinda thing in my 6 speed and chcked everything...nothings outa speck...everything works fine...they told me its in the tune from the factory? mine a 6 seed and slowing to a stop when cold it idles about 1600

3rdgen92maro

iTrader: (20)

Mine does the exact same thing. As soon as it warms up it stops and idles normal. I would have to say its set in the tune from the factory to idle high until the engine is a normal operating temp.

BigZee71

iTrader: (5)

IT never goes away, and its a PCMforless tune. Should I contact them?

3rdgen92maro

iTrader: (20)

So the idle stays at 2k? if so i would deff contact PCMforless and see what they say.

Alvin

iTrader: (2)

Sounds like it may be a vacuum leak or a improperly setup aftermarket throttle body. Check this link. It will help you or anyone else with a LT1 setup proper idle with aftermarket throttle bodies (or big cam for that matter)

http://www.pcmforless.com/images/dat...m#Idle%20Setup

1badzee

iTrader: (12)

Eh, mine did similar stuff it was the TPS..

sdm1234

iTrader: (8)

Mine did that ever since I got a PCM4less tune. It idles high, around 1500-1600. When I'm coasting in neutral, the RPMs bounce down to 1000 then back up to 1500 until I go below 5mph. Brian told me to check my TPS voltage but that was spot-on. It has to be in the aftermarket tune (IAC tables/throttle follower).

Ihasfip

iTrader: (5)

My Trifecta tune is doing the same to an extent. If I hold in the clutch at highway speeds it stays at 1500 until I stop then aprox. 2 sec later it idles down to 850-875. It was way worse and Vince fixed it. But I didn't notice it doing it like this until after I sent the tuner back, so no biggie. He said it was in the IAC values IIRC.

D

Alvin

iTrader: (2)

Another thing to check is the throttle bellcrank where it is pressed onto the throttle shaft. they develop some slop there.. if the idle ever hangs high again don't touch the gas, get out and push the throttle closed with your thumb under the hood. I've had to spot weld a couple just to fix that issue.

BigZee71

iTrader: (5)

Ok Heres an update.

Checked and the Throttle body is closing all the way.


Now, when I move the gear select out of gear, be it to neutral or to park, the idle jumps up and hangs for a few seconds then COMES BACK DOWN to 850ish PRM.

Its just something hanging, If I move from reverse to drive, or vise versa, or just put it back into park, the RPMS raise then eventually fall to 850ish RPM.

Im not going to point to the tune, but It didnt have this problem before hand.

I may pull out the new PCMfl chip and reinstall the orginal and see what happens.

**something else- everyso often the car will not start unless I hold down the go pedal.
Related issue? Once it warms up though (I think) everything seems fine.

Thanks for yalls input.

ALVIN^^ from PCMforless? That you? If so, thanks for the tune, car runs like a raped ape.

1996camaross

my car kinda does the same thing. every so often it stays revved up to 2,000 when im coasting in nuetral, then as soon as my car comes to a complete stop it drops to 800. My car has been tuned by pcm4less. i sent it back to get retuned and now its better but everyonce in a while its still there. im also a 6-speed car and my buddies gto 6-speed does the same thing but alot worse...

IronOutlaw

iTrader: (4)

Do you have a stock cam? could be cam surge...

BigZee71

iTrader: (5)

LT4 hotcam kit, auto. I dont think its surge, Ive had this cam in a 94 formula and it didnt have this problem.

Im going to pull and replace the IAC today after work, Ill post up results. May just
try to clean it first.

blackz93

iTrader: (2)

My stock 6 speed car did this. Once you slowed down to a near stop, or stopped, it would idle back down.

brokenbird

iTrader: (5)

my six speed dose that untill i come to a stop then it goes away just like what every one is saying

riceburnerZ28

iTrader: (20)

It may be the tps or a vaccum leak. You should check for codes too !

hyperzone

I get the same thing with my 6 speed where I'm in neutral coasting to a stop and the idle is annoyingly high till I almost completely stop and goes back to 800. It doesn't do it all the time, just occasionally. Nothing else seems to be wrong. It just gets annoying to pull up to stop with dumped duals and people looking at me funny.. hehe...

I'm going to change the TPS soon and see if it helps mine. This seems like a pretty common problem seeing how many are chiming in. I'd like to know what you eventually find with yours. *that goes to anyone really...

daniel6718

iTrader: (36)

seems almost every 6 speed guy has that problem...and i understand them needing vacume for brakes...but it does it until after you stop which makes no sense...

ss.slp.ls1

iTrader: (36)

I doubt its a tuning issue. My money is on a vacuum leak, sticky IAC, or maladjusted TB.

I had a problem with my car idling high, turned out I had not one, but two vacuum leaks. Make sure all of your ports on the intake are either used or capped off. Also check ALL rubber/plastic lines that go to and from your intake & TB for holes or corrosion. Remove and clean the IAC. Make sure that the TB blades close all of the way and that it's not sticky at all.

Get your car hooked up a a scanner, if you have a vac leak, you should have a high long term fuel trim.