High revving at start up

[antisphere]

i have a 96 disco that revs to 2000 rpm at start up and will not go down untill you put it in gear. after it warms up you can shut it off and start it up with no problem. but if you let it sit for 20min or more it will do it. i have replaced the stepper motor and tps. and suggestions

[Savannah Buzz]

Codes? Don't throw parts at it. If you have a scanner that reads data check coolant temp. If temp sender is bad or disconnected, ECM thinks it is -40 F and increases fuel mixture. Also, your ECM may not have recognized and re-learned a new IACV, check procedure on that, RAVE tech manual is a free download below.

[antisphere]

there were no codes when scanned and the temp sender was replaced 2 months ago.

[Disco Mike]

So clean your throttle body as well as your IAC. Might also check your throttle cable for sticking.

[antisphere]

that was all done the same time i replaced the iac

[Savannah Buzz]

So with a data reading scanner, do you get sensor "values" that make sense? Like IAT being somewhat close to what the under hood temp is, coolant temp being realistic, fuel temp being realistic? Just thinking that a bad sensor will make the metered reading it sends to ECU be off. Or just a loose plug on one of them.

Just thinking that it might be a sensor that warms up and changes value. If you have it warmed up, you could spray sensors with something like brake cleaner that will cool them off to see if problem returns. The Vehicle Speed Sensor might be at play if the truck thinks it is in motion, and is disabling the IACV. The VSS makes the mph signal on the scanner.

What you are doing is really hard on the transmission. When I bought my Disco it was doing the same thing, and I finally had to replace the ECU ($40 at junkyard), the original one would not adapt to a replacement IACV.

Here's some pages from the RAVE on these sensors.

[antisphere]

ok can you recommend a good cheep scanner