Crazy problem

[ekaisinger]

The car is a 1982 Corvette and has 63k miles. My problems are cold and hot
idle. When the engine is cold first start of the day it will idle around 1500 to
1800 RPMs out of gear until it gets a little temp built up and then drops down
to within normal range. Then when it is at running temp in gear it idles at
around 500 to 525 RPMs and is a little choppy, add a little gas to run it to
around 600 to 625 RPMs and it runs smooth at idle. There are no problems when
driving. I have changed the O2 sensor, the Temp sensor with the new type 2 wire
sending unit that is recommended. The vacuum holds strong at 22 and does not
jump around or fade. The TPS is set at .525 volts. The fuel pressure is at 12
PSI. Could this be an ECM problem that it is misreading the info it gets or
could the TPS be bad and sending wrong info? Any other suggestions to look for
would be greatly appreciated.<o></o>

 

[dougelam]

The car is a 1982 Corvette and has 63k miles. My problems are cold and hot
idle. When the engine is cold first start of the day it will idle around 1500 to
1800 RPMs out of gear until it gets a little temp built up and then drops down
to within normal range. Then when it is at running temp in gear it idles at
around 500 to 525 RPMs and is a little choppy, add a little gas to run it to
around 600 to 625 RPMs and it runs smooth at idle. There are no problems when
driving. I have changed the O2 sensor, the Temp sensor with the new type 2 wire
sending unit that is recommended. The vacuum holds strong at 22 and does not
jump around or fade. The TPS is set at .525 volts. The fuel pressure is at 12
PSI. Could this be an ECM problem that it is misreading the info it gets or
could the TPS be bad and sending wrong info? Any other suggestions to look for
would be greatly appreciated.<o></o>

The one thing that comes to mind is the PCV valve, if it is not an OEM AC Delco type it will cause drivability problems just like what you are talking about. Remember that a PCV Valve is a calibrated vacuum leak and when the wrong one is used the computer makes fuel delivery decisions thinking it has the correct one and idle quality is the first sign it has the wrong one in use.

Hope this helps

 

[bill81vette]

Welcome to CAC!!!! enjoy!!!!

 

[Peer81]

And the problem is?
I think high rpm's when cold isn't a problem. Look in your service manual to see what rpm the engine should see when idling cold.

Greetings Peter

 

[ekaisinger]

I changed the PVC not long ago and the box said it was AC Delco but who knows these day, But the problem was there before I changed it. And the RPMs supposed to be around 1000 RPMs