Lately my car has been dropping to a low idle at strange times, it doesnt always happen, but at times it does after I have been driving at normal speed for a while and come to a stop. The idle will sometimes drop around 500 and seem like it is about to die unless i give it gas.

So I finally got my hands on an old laptop and used my ALDL cable to read some sensors with freescan. I dont know what I really should be looking for, or what ranges are good to be at with these readings so I'm hoping someone can help me out.

These are what I wrote down from just watching it at idle, after driving and coming back home. The rpm did not drop low during this time though.

IAC Position- 74-76
TPS volts- .75
Idle- Jumped from 925-1000 and the desired is 950
MAP- Bar Scaled- .61-.65 Volts- 2.7x-2.8x
Spark Advance- 28-31
Knock Count- 2976
O2 Volts- both sides ranged from .2-.6

If anyone can decifer these readings that would be awesome.

Then I found that I had two trouble codes logged, no SES light was on at the time...

Code 33- MAP sensor High
Code 21- Throttle Position High

I dont know if these actually were logged from previously when I installed my 58mm TB and forgot to connect the vacuum line and started the car and had a crazy high idle...

Thanks for any help you can give me fellas!

 

The rpm did not drop low during this time though. -You need to get the data when its idling at the incorrect RPM.

IAC Position- 74-76 - A bit high, but probably normal with a decent cam. What are the specs on the cam?

TPS volts- .75 - Normal

Idle- Jumped from 925-1000 and the desired is 950 - Normal range of deviation with a cam of any size

MAP- Bar Scaled- .61-.65 Volts- 2.7x-2.8x - High, but probably normal for a decent cam.... specs??

Spark Advance- 28-31 - Hard to tell, since the tuner will alter the timing tables, and may try and use them to stabilize the idle RPM.

Knock Count- 2976 - Meaningless. The knock count field just continues increasing until it hits the max value that will fit in the field, then resets to "0" and starts all over again. Normal for this reading to increment up on startups, shutdown, etc.. The important number is "knock retard"

O2 Volts- both sides ranged from .2-.6 - [b]Somewhat limited range, but they are changing 9 times per second, faster than some scanners can scan. Normally, they should cover the full range from 0xx-9xx mV (.0xx-.9xxV)

Then I found that I had two trouble codes logged, no SES light was on at the time...

Code 33- MAP sensor High
Code 21- Throttle Position High

I dont know if these actually were logged from previously when I installed my 58mm TB and forgot to connect the vacuum line and started the car and had a crazy high idle...

Pull the "PCM BAT" fuse for 30-seconds (key in "off" position) to clear the trouble codes. See if they come back.

 

Thanks for the help fred, cam specs are...
Gross lift .540 intake and .562 exaust
duration... intake..242 and exhaust..248