Hi,
I need some help from all the Aerostar gurus out here.
I have a '92 shorty 3.0L van with high idle. The idle is also a bit rough. I have replaced all spark plugs & wires, dist cap, checked vaccum lines & cleaned MAF & IAC.
Just now I pulled out a code 4-1-1 which indicates that the EEC is not being able to control idle speed properly ?
Any pointers are highly appreciated.
Thanks.

 

Have you tried to manually adjust the idle? Also, you might try pulling the connector to the IAC to see if that has any effect on the idle speed.

This also sounds like a vacuum leak somewhere.

 

The idle adjust screw is turned totally out.
Also disconnected the IAC connector - it doesn't change the idle rate at all.
Tried disconnecting the vaccum hoses from the spider at the back of the engine one by one- it didn't help.
Thanks for your advice.

 

According to my Chilton's manual, for the 3.0L engine "curb idle speed is controlled by the EEC processor and the idle speed control air bypass valve assembly. The throttle plate stop screw is factory set and does not directly control idle speed. Adjustments to this setting should be performed only as part of a full EEC-IV diagnosis of irregular idle conditions or idle speed."

Since your throttle plate stop screw is apparently "totally out" it has been adjusted incorrectly. I recommend getting a manual and going through the procedures outlined to reset the throttle plate stop screw correctly.

Your original problem may have been a sticking throttle plate and cleaning of the throttle body is recommended.

Ron

 

The majority of the air required for idle is supplied by the IAC. Disconnecting it sould shut the motor down, because the air allowed through the throttle plate at closed throttle should not be sufficient to idle the motor alone.

I would look for a major vacuum leak (pinch the brake boster line with a pair of pliers), then at the IAC valve...its possible that the valve or soleniod is stuck wide open, or the valve has a bad return spring. first try tapping on the solenoid and valve housing lightly with a screwdriver....then maybe pull it off and shoot it with a little lube and check the action. (the gasket usually comes off nice and clean and in one piece. if not, you'll need a new one)

 

..I picked this up on the Forum (I was tipped off). It is from the Ranger pages. According to this, the idle stop screw should be adjusted so that the engine idles (warm) at 700 rpm with IAC disconnected.

.................
.... If this condition occurs, the base idle setting will need to be re-set according to the following procedure.

NOTE: Engine should be at normal operating temperature before performing this procedure!

1) Turn off all accessories & disconnect the battery for 5 minutes.

2) Reconnect battery. Disconnect the Idle Speed Control (ISC) solenoid located just behind the throttle body on the drivers side of the upper intake plenum.

3) With the truck in NEUTRAL, run the engine at 2500 rpm for 30 seconds.

4) Let the engine idle for 2 minutes.

5) Put the truck in PARK (or NEUTRAL if manual trans.) and adjust the idle speed stop screw until the idle is at 700rpm.

6) Turn engine off and let sit for 2 minutes then repeat steps 1-5 once.

7) Disconnect battery for 5 minutes then reconnect.

8) Reconnect the Idle Speed Control (ISC) solenoid.

9) Run the engine at idle for 2 minutes.

10) Quickly depress the accelerator pedal to the floor and release it immediately, allowing the engine to return to idle.

11) Lightly depress and release the accelerator allowing the engine to return to idle.

After carefully following the above steps, the engine should now have reset its base idle to factory specifications. The idle should now be smooth and at approximately 700rpm at operating temperature. If this procedure does not correct the fast idle condition, carefully check for vacuum leaks at the throttle body flange gasket and at the intake snorkel to throttle body interface. If no vacuum leaks are detected and the condition still exists, a condition that is unrelated to the mechanical throttle body assembly exists and must be diagnosed and repaired.

 

Hi,
Thanks to everybody looking into my little problem.
I tightened the intake manifold - and the idle is a bit smoother and better. I presume there was a little vaccum leak. Will also pay more attention to the vaccum lines.
I will look into the IAC in more details as well.
Any more suggestions/pointers are welcome. Thanks again.