I have a 91' Z28 with a 95' LT1 & 4L60E in it. I been reading about setting the throttle to the minimum air position. Before I do anything though I wanted to make sure I could do this with an LT1?

Okay on to my problem.

When first start the car the idle is very high then after it warms up it will drop down to around 1500RPM. When I put the car in drive it either stays around 1500RPM or it might go up to 2000RPM. Sometimes even surging up and down. My initial thought was maybe a vacuum leak, but after testing it yesterday the vacuum tester showed a steady pressure between 20 & 22Hg. (17-22Hg is normal operating condition for an LT1).

In addition the the high idle in park and in drive the SES light is now coming on. Should I be able to read codes with a paper clip like regular thirdgens? If so how should I go about doing this?

Last Question:

Do you think these problems would keep my car from performing right at highway speeds?

Any help you can offer would be great.

Thanks in Advance,
Jay

 

There is a throttle stop screw on the throttle body. The IAC might also be dirty.

I don't know anything about using a vacuum tester so I don't know if you still have a vacuum leak. A couple other ways to test is to spray small amounts carb cleaner around the edges of the intake manifold(be very careful) and if there is a leak the engine will react to the carb cleaner. Also, sealing the intake off(while having the engine shutoff) then use a vacuum pump and see if it holds the air in.

You read codes by using an aldl cable and software from a computer/laptop.

 

I tried to spray alittle carb cleaner around the intake but the idle did not change. My only guess now is that one of the sensor is bad because the SES light comes on as soon as I start the engine, which in return makes the fan come.

Thanks,
Jay

 

Take the IAC off the engine, spray it CLEAN with throttle body cleaner, and then spray the IAC air passage and the throttle bores/blades as well. Do it untill its all clean - may take more than one can of cleaner to do this.