'82' Engine idol too fast

[Rmodeler]

'82' Engine idle too fast

Is the idle set electronically? Backed the idle screw all the way out but still idles 1000-1200rpm(suppose to be 500-600?). The linkage is back against the stop. I disconnected & blocked vaccum to headlights and it did drop 100rpm. I can't hear any other vaccum leaks. Is there a fast idle vaccum pull off switch?

 

[Jim Martley]

The idle speed is set by the Idle Speed Controller on the throttle bodys. The ISCs are controlled by the computer. You MAY have a massive vacuum leak between the top plate and the manifold, which is a common problem.

 

[Twin_Turbo]

ECM controls idle speed however you can set minimum air (IAC's closed, the air that passes by the closed throttle plates), high idle is usually a vac. leak as jim said.

 

[Rmodeler]

Thanks for the input, I'll check it out closer.

 

[John Ulrich]

OOPs....sorry I read your post and see you have a '82 not an '81!!!!!

**** For '81 and older
Do you have the factory air cleaner on it?

If so...Make sure the hose coming off the tube making a U turn on the drivers side around the "snorkel" is not hitting the throttle. Mine needs to be pulled forward whenever I have the aircleaner off or it pushes againest it.

Later,
JU

 

[wishuwerehere82]

If you backed off the idle screw all the way, you should see the throttle plates closed completely in the TB throats.
If the idle speed did not decrease when you did that, then the air is getting into the manifold someplace else, but the TPS voltage should have dropped well below .525Volts as well which should have decreased the idle speed.
Check to see that the throttle plates are all the way closed. and that the linkage is not hanging up.

Some possible air leak places are:
Manifold body gaskets.
TB body gaskets.
AIR pump valve Vac. lines.
EGR valve Vac. lines.
Purge canister Vac. line.
Brake booster Vac. line.
MAP Vac. line.
or
Stuck IAC motor(1 of 2). To find this one, you can put some some duct tape over the AIC ports on the two TB's.
NOTE*If the motors failed electrically, the ECM will show a code.

Once you find the leak or whatever problem, you will need to reset the idle speed, and adjust the TPS voltage.
http://corvettefever.com/techarticles/4688/

 

[jdp6000]

It definitley sounds like a vac leak. Try some simple things first. Tighten down all the bolts on the throttle plate and TBI's. Vac leaks commonly occur in those areas. Check all the hoses as well.

As for adjusting the idle with the screw. Not as simple as that. By doing this you throw off the TPS, and TBI balance. I would put it back to where it was.

Another possible is your Coolant Temp Sensor at the front of the engine. It kind of takes the place of a choke. Your computer may think the car is always cold.

We need more info to propery diagnose.Any engine codes?? Does it always idle high? How does it idle when warm? How does it drive? If its always high I would definitely say vac leak OR CTS or MAP sensor.

Jim

 

[82X-FireVette]

Check all vacuum hoses and connections. There may be one or more leaking. The heater-A/C control valve may be leaking. Look for missing plenum bolts. Check the IAC motors for correct operation. Check the timing. The plenum gaskets may be leaking due to hardening from old age. You can get the gaskets from www.partsdinosaur.com and maybe Autozone. The screw you adjusted is the base idle screw. The engine will have to be recalibrated to get the adjustment correct. The GM shop manual has the instructions. Good luck!

 

[jiangtao]

I spent over a year trying to track down my high idle!! I replaced both intake gaskets, both IACS, thermostat, and the EGR valve. What I didn't do is clean the place where the IAC's go into the TB. After I cleaned them my idle went back to normal. If I were you I would clean the TB's and replace the gaskets and then check the TPS. If that doesn't do it, then I would replace the IACs.

 

[wishuwerehere82]

Any Progress?

 

[Rmodeler]

I have a trouble shooting guy checking it out now. What seems strange is that it has idled down like it should on a couple of occassions. Of course the one time that it did it was when I took it to the guy to check it out. Pulled into the stall, put it in neutral and it was idling OK, he says it sounds great! The next time it was back to the fast idle. Let you know what he finds out. Thanks for all the help so far.