IA counts go from 175 to 0.0 HELP

[jarredsoon]

Ok so I have a stock car with 42 inj and TT chip.
Scan numbers are all within normal limits, 128 INt and 126 Bl
af is 5 at idle
tps is .42

when I first start the car it ildes fine and the iac is 175
when the temp reaches 165 or higher the iac drops to 0.0 and rpm riase to 1500-1700.

I did a search and unscrewed the throttle blade screw and nothing changed, I shut the car off for ten seconds and checked again.

I do not see any vac leaks before or after the maf???

Also I looked inthe TB and no deposits and very clean.

Thanks,

Jarred

 

[mo86gn]

what is your tps voltage. key on engine off should be .42 to .46 full throttle 5.0

 

[jarredsoon]

Yup tps is within normal limits .42 at idle and 4.3 at wot. I am going to correct the tps to be >4.6 at wot after I finish setting the throttle blade position and iac valve

 

[TurboBuRick]

Whats the rpm as the car is warming up?

Does the motor get to temp then start to race?

You have checked all vacuum lines at each end?

Did the tps value drop when you adjusted the throttle plate?

 

[jarredsoon]

Rpm at idle while warming up is around 700
Motor does not begin to race until it reaches operating temp
The iac goes down steady to 0.0 and rpm increases at same time.
Checked vac lines can't find leak? Will recheck
Tps dropped from .44 to .42 as throttle blades closed

Could this be from a header leak?? I did not use a gasket but used orange high temp sealant.

 

[chopped39]

Are you running an EGR? If so disconnect it and see if that helps. If not I would block off pcv and seal off both breathers to valve covers and then take vacuum gauge and hook it to dipstick tube. If there is vacuum the intake gakets are probably leaking . Do it cold and hot to verify. Exhaust leak wont do it. Hope this helps.

 

[jarredsoon]

I thought that egr is turned off with a TT chip?? What do I have to do to disconnect it unhook the vac line to it or the wiring harness? Sorry not too familiar with egr valve

 

[Blazer406]

I'd start by setting the IAC correctly..... by adjusting the throttle screw... until the IAC values are around 20-30 in park idling with the car at operating temp.

I would then reset the TPS for .43-.46 at idle.

The fact that it goes to 0 means that it is trying to close the throttle farther and it can't.

Re-set correctly.... and see what it does aftwards at cold startup..... and after warmed up.

FWIW... the fact that your BLM's are 126 lead me to believe that there is no unmeterd air entering the system... i.e. vacuum leak somewhere. so I would re-set IAC as described above and go from there.

HTH

 

[jarredsoon]

Ok I can't back out the throttle blade screw any more and the idle air counts are still going to 0.0 when car is warm.

Is this a bad iac valve?? Or more likely sn egr thing??

 

[Blazer406]

Ok I can't back out the throttle blade screw any more and the idle air counts are still going to 0.0 when car is warm.

Is this a bad iac valve?? Or more likely sn egr thing??

Could be.

You haven't had a big backfire up the intake have you and bent the throttle blade? I have seen that happen on a carb'd car.

I don't have any experience with the EGR thing.....mine has a plate on it.... no EGR......

 

[whitehot1]

Ok so I have a stock car with 42 inj and TT chip.
Scan numbers are all within normal limits, 128 INt and 126 Bl
af is 5 at idle
tps is .42

when I first start the car it ildes fine and the iac is 175
when the temp reaches 165 or higher the iac drops to 0.0 and rpm riase to 1500-1700.

Did this just start happening all of a sudden on it's own or did it start after you did some work or adjustments to the engine? Were you running it hard then it happened?

I read somewhere a long time ago that if the IAC is out of adjustment to far it will have an opposite reaction to the normal adjustments,if i remember that correctly.

You may want to try this and get the adjustment screw back close to it's original position and set the TPS at .38 and go from there on adjustments. You don't have to turn the IAC adjustment screw very much for it to make big changes.

Often, on stock set ups, about 1-1 1/2 threads of the adjustment screw will emerge thru on the lever side of the throttle body. Restarting also rezeros the tps as stated in the prior section and removes any effect on idle speed that may have occurred due to tps movement. The IAC counts will probably be 30 counts, or more, higher on a cold engine than on a warmed up engine. The counts will also be much higher in gear as compared to Park, and, higher with the AC turned on.

Also you can go to this site for help with this and other problems.

Vortex Buicks