Hello, first post. I replaced my EEC because of 3 burnt capacitors. Truck now starts, runs and shifts good. But idle is way low. Will stall if not feathered.

Been driving it that way for about a week. Warmed it to operating temp and took codes.

KOEO 111
CONT 111
KOER 411 412 Cannot control RPM during low/high RPM check.

Replaced the IAC with a Wells part. Same low idle, same codes.

A little background: Truck started running rough some months back. Trouble codes pointed to the EGR and KAM failure. Replaced the EGR, EVP and the EVR. Also replaced the ECT and the o2 sensor. TPS tested fine. Went over the vacuum system with a fine tooth comb, all good.

It ran and shifted just so-so and still threw a CONT code 512, KAM test failure. Got a heads up to look at the EEC and found the 3 smoked capacitors. That's when I replaced the EEC.

So now I have a good starting, running and shifting truck.....but with the low (stall) idle. Took codes again and got the same as above. Don't know where to go from here. Can anyone help?

 

If the idle was OK before you changed the PCM Computer I would say you either have a bad Computer or you pushed a pin out of the Computer plug when you plugged it back in.

 

I too thought that might be a possibility. But the old EEC had no idle problem so I plugged it back in to see what the idle would do. Even with the old EEC the idle remained low. Opened up the new EEC and saw nothing burnt or unusual in there. Also took a good look at the pins and did a continuity check to the IAC through the harness.

I have the correct voltage at the IAC with the key on. I first replaced the IAC a week ago with a BWD from Advance Auto after I cleaned the stock IAC, which didn't help. Thought the BWD was bad because it was out of ohm range (7-13 ohms). It read 30 ohms.

Then I got the Wells IAC and still low idle. Everything else is fine. Starts, runs and shifts good. And no CEL. Just the low idle and the 411, 412 running codes.

 

Double checked everything today to make sure I didn't miss anything, no change in the low idle. Although I did find the vent line that goes from the vapor canister, splits and enters both throats of the throttle body in bad shape. So bad that when I removed the pair from the throttle body nipples, the nipples were clogged with deteriorated pieces of the black vent line

Removed the throttle body, cleared those passages and replaced the vent line. Still no change in the low idle.

Question is: With KOEO and CONTINUOUS pass code (111) and running codes of 411/412 (Cannot control RPM during low/high RPM check), if everything else like proper voltage and a serviceable IAC and continuity in the harness from the EEC to the IAC,.....

Is there anything else to check? What else should I be looking at? HELP!

 

First off, good job on pulling your computer out of the truck and giving it a visual check.

Now...........have you done the FORD idle set screw procedure ???

There is, I believe, two different procedures depending on whether or not you have an automatic or stickshift.
I'm thinking you have an automatic though based upon ("So now I have a good starting, running and shifting truck")

It's not hard to do, but, you may need a tachometer or a DVM with the tach feature or a timing light with a tach feature and a feeler guage to get it "dialed in" just right.

Bob

 

Sounds like the computer can not provide the ground required to cycle the IAC due to a fault in the circuit.

Check the Wht-lt blu wire for continuity between the PCM harness connector and the IAC harness connector.

 

If it idled OK before all of the problems then the throttle stop screw is OK and should not be touched.
Besides if the Computer cannot raise the RPM during the EOER test it would have nothing to do with the throttle stop screw. It is not a idle set screw.

If you unplug the IAC valve during idle and the idle does not change you have a problem with the wiring to the computer from the IAC, and bad IAC valve or a bad computer.

 

I checked and have continuity in the harness between the white/blue wire at the IAC connection and pin position 21 at the EEC connection.

Don't really understand this but, I have battery voltage back-probing the IAC connection on both the red and white/blue wires with the key on engine off. With engine running I have full voltage at the red wire but less than a volt at the white/blue wire.

I think the white/blue wire is where the IAC gets the "open" command from the EEC. And if I'm not getting full voltage at the wh/bl wire at idle then maybe the EEC is bad.

Make sense to anybody?

 

When the white/blue wire voltage goes down the idle should go up.
Sounds like a shorted diode in the IAC valve, IAC valve wired backwards or a stuck IAC valve.
Either way it sounds like a bad IAC valve or wired backwards.

The PCM computer is working right.

 

Check the resistance of the new IAC.

The computer controls most things by grounding them. The white/blue wire going "low" means the computer is grounding it and trying to control it.

 

After double and triple checking everything I figured the new EEC had to be bad. Sent it back to Flagship 1 parts. They took it back and replaced it no problem.


Just got it this morning, installed it and test drove it. Around town, lots of stop & go and a fast Interstate ride. Started, idled, ran and shifted great. No CEL.

Mr. subford called it, bad EEC. Well done and thanks to all.