What causes idle to vary on 1989 Ford Ranger V6.?

Question

I have a 89 Ford Ranger that runs smooth 90% of the time. Every now and then the CHECK ENGINE light comes on and the idle drops so low the motor almost cuts off. The truck seems to have less power when driving... then it will smooth out and the CHECK ENGINE light goes off after a few miles and everything returns to normal. To throw another monkey wrench into the system... every now and then the opposite happens. The idle goes WAY high... when I push in the clutch the motor over-revs and I have to let the clutch out and stay in 4th or 5th gear to drag the rpm's down... when I get the rpm's below 1500 or so the idle kicks in like it should and stays at normal idle until I rev the motor back up above 1500 rpms. Any ideas

Answer 1

my f-150 did somethin similair to that. it might be the idle air control valve. it shouldn't cost you but a couple dollars. mine would idle high and sometimes low and shut off most of the time. now it runs smooth.

Answer 2

if it is fuel injected I'm be pretty sure it is the throttle position sensor. that's the only thing i can think of that would cause a fluctuation in rpms like that. you may have 2 separate problems though. good luck

Answer 3

whitetrash is right check the iac motor mine does the same thing but i don't have money to buy a new one all though its only a few dollars

Answer 4

an 89 v6? Awesome!!

if it was EFI, my gut says oil pressure sensor

(assuming you did all the other normal maintenance, oil filter, PVC valve, air filter, fuel filter,)

Answer 5

another problem might be the mass air flow sensor.. that happened on my celica but i replaced it it ran fine

Answer 6

well i hate to tell you but ur first problem is that you own a ford.....the second prob you got is that you own a four letter cuss word that starts with a "F"......lol

Answer 7

vacuum check it out.