car wont coastdown
 

when i let of throtle rpms will hang around 1400 mph stays like its on gruise control sparkadvance stays solid at 30 degrees on scanner any ideas

What does the TPS read? The blade of the throttle body could be hanging up, the iac motor could be bad, in need of tune, etc, etc, .....have you recently modified something that could have caused it?

tps bounces between 0 and 1 was tuned blade is free .no new mods

Strange... My 08 Silverado does the same thing... AND, it's bone stock, 18K on the clock. Ran over a mile this am B4 it started to slow. About the same rpm, too.

I think I'll try some adjustment on decel fuel cutoff, and see what happens.

The IAC motor could be acting up. You could try adjusting the throttle cracker and throttle follower. Or, try unplugging the IAC motor and see what happens.

Talk to your tuner. Sounds like DFCO isn't working and too much idle airflow.

How long has it been tuned for? If it has been tuned for quite some time and just started acting up, I wouldn't adjust anything. Just replace the IAC. All of these tables we have been talking about all adjust the IAC motor, how much to open, how much to close, how quickly to do it.

its an auto right? likely IAC counts are too low, too much base running airflow, throttle cracker table is wrong, follower table is wrong, likely a combination of all those things.... also remember that polluter cam is big..... dont expect it to drive perfect either

dfco??really? lol

yes it is auto will mess around with tables put in new iac motor same problm thanks guys

adjusted air flow tables much better now thanks guys

:thumb: Excellent!