86 F-150 302 EFI (4spd manual)

Every time I use the AC or Defrost my idle speed goes down to about 400 rpm and struggles. Most the time it cuts off, this almost always happens when I slow down to make a turn and push the clutch in. Also, when I turn my steering wheel sharp at slower speeds 5mph or less the motor cuts off?

I have messed with the timing several times (basically turning the distributor to the left or right) but it doesn't help.

One other thing; the motor wants to cut off when I let out the clutch as well (AC or No AC)?

Any ideas on how to fix this? I know the clutch may be going bad but that wouldn't explain the idle problem.

Thanks!

 

my first guess would be that the bearings in the AC compresser are out our going out. causing a huge load on the motor when you turn it on.

 

You said you experiance this problem with the a/c and when you turn the steering wheel. Both of these do put a big load on the engine, but both of them also have idle up switches that are supposed to raise the idle speed when you turn the steering wheel of turn on the a/c. My guess something is wrong with that idle up control.

I'm not sure exactly how it's done on your truck, some vehicle send a signal to the computer to open the IAC valve and add more fuel (check your IAC), other vehicles have an electric vacuum solenoid valve that opens and sucks more air into the engine basically creating a controlled vacuum leak, Toyota did it this way for years.

At least this gives you a starting point.

-Jon

 

Does it struggle or sound like its trying to idle up or does the idle steadily drop and it goes dead? I ask because on our trucks a fairly common problem is the throttle body getting gummed up and it can't respond to the change in load. I had a similar problem and that was it. Anyway, its easy to check and free

If this is the case you would probably also notice a little hesitating when you mash the gas with or without the a/c.

 

I am going to try to buy a new IAC this weekend and try that. I will probably try cleaning the throttle body also. Anybody have a good suggestion on how to clean up a throttle body? Also, how do I check to see if the solonoid is bad on the Idle air control?

Thanks again for all the good advice