lujandj

Here is my issue. My car seems to startup fine in the morning and idles at @ 900 rpm. In the afternoons or after a while of driving the idle does not drop below 1300 rpms. After I pull in and turn off the car I can hear the coolant pouring into the overflow tank. The servicing apprears to be good, I did a pressure check on the cooling system and that is good. I also notice the engine temp climbs ever so gradually when this happens and oil pressure starts to drop from 55 psi to between 45-50 psi. I know that as oil heats up pressure will drop. So...what is causing my engine to remain at a high idle? My assumption is it has something to do with the cooling or the hi idle is causing the engine temp to rise faster than the system can cool it down. This had only happend once about 6 months ago and this week it has been a normal occurance. I plan on replacing the thermostat this weekend, may this be causing the problem? how can I tell if the thermostat is actually working. My fan is set to come on at 160 degrees and does so religiously. I have a 180 degree thermostat in there right now, the previous owner had a 160 in there but I thought that was too low. Any suggestions?

Car specs:

351W block
383 Stroker kit
Vortech V2 strim 10 lbs
50 lbs injectors
MSD 6AL ignition
AFR 185 heads with spring upgrade
1.6 roller rockers
Aeromotive A1000 fuel system with fuel pump speed controller
Aeromotive Stealth fuel tank
Aeromotive Adj fuel press reg
Aeromotive Billet fuel rails
Pro-M MAF
Fluidyne aluminum radiator
stock Ford water pump
180 degree thermostat
Mobile one 15W-50 oil
50/50 coolant

mjr46

what is the coolant temp when the idle is high??

lujandj

It appears the hi idle starts at around 190 degrees, which should be cool for this type of motor...that's what has me confused. In the mornings after 10 miles of driving it barely breaks 180 degrees but in the mornings right now the outside temp is mid to hi 60's. And when the hi idle starts the temp will gradually rise to 220 degrees. So long as the car is moving fast enough to draw cool air in, it seems ok. But when I stop...say at a red light the idle will hit between 1300-1500 and I can see my AFR being rich. What all controls my idle? MAF, engine temp...

mjr46

Iac DOES, but other things can influence a change in the IAC , have you run a koeo/koer test and checked for codes???