It has brutally cold here the past few days, and I fired up my Z to head back to school today and I noticed it was acting strange. The idel would go back and forth from like 1200-1800 or so constantly, even once it was warmed up, While driving it appears to perform fine but when you try to come to a stop, the rpm's are reluctant to come down and on two occasions overpowered my rear brakes "on snow packed roads" If anyone has any suggestions please let me know... Would this be ice in a vaccum line? or somethign odd like that? or could it my idle sensor going out? Thanks in advance for any help

 

It sounds like you may have a vacuum leak. Does your oil pressure needle fluctuate at idle too?

I just had one and replaced the small rubber hose at the bottom of my EGR valve and it fixed everything.

Check all your hoses and see where there's a hole.

 

Thanks, once it warms up outside I will take a closer look at my lines, I looked today but it was so cold out that I didn't even locate my lines I just wanted to get inside. Thanks for the advice though, last thing I want to do is take it to a shop for something simple

 

THere arent too many vacuum lines to check, luckily. Buy a can of brake clean, and start the car and let it idle. While its idling spray around the intake on the :

Engine side of the MAF where it connects to the baffels
Where the intake Baffels meet the TB
All around the machined edges of the TB
Where all the lines and hoses hook up to the intake manifold
Check the EGR, its not likely, but worth looking at
Spray all around the intake manifold where it meets the block & heads

If there is a vacuum leak, you will notice the car will sputter or rev up, it will definatly be noticable.

Also, are you sure your throttle blade isnt just sticking? Clean it up and lubricate the return spring if its dirty.

Also, try and get a diagnostic scanner and see what everything is reading. Check MAF, MAP, O2.

I could be crazy, and this may be totally off, but what if the fuel pressure regulator isnt working properly? Couldnt this cause it to lean out or get rich and idle high, but once in gear, would die down?

You'll have to check some stuff and post a reply. Hopefully someone on here can help you out better than me, I have a LT1 car so some things are different ... OBDI too

 

I had ice built up on my throttle blades, I guess when it gets to -30 anything can happen, it warmed up today, got most of the ice out before it melted, it she runs fine now. Thanks for all the help

 

-30 has to be absurdly cold. At least you didnt break down somewhere with it that chilly though...

 

i had a similar problem with my old TPI 305 once. only it wasn't ice build up it was the fact that i cleaned the TB with choke cleaner and dissolved all the lubrication off the blade axle.

the spring wasn't strong enough to pull it back closed. it would accelerate anytime i was over 50mph with out having me put my foot on the gas. and my brakes could barely stop me when i'd get to a slow speed.

lubbed up the tb blade axle and it was fine.

similar symptoms, semi-similar causes