2.9L IAC questions

[Uncle Gump]

So I've done a little testing on my IAC. Key ON I could feel it "click" but it didn't appear to be doing its job. I pulled it and it wasn't plugged up solid but I spent a little time cleaning it and put it back on. Same thing... click but not working. So I pulled it back off and tried bench testing it. While it will activate with that audible click... the pintle really doesn't move. If it is moving it certainly isn't much (0.010-0.020 inch).

How much should the pintle move? My thoughts are that it should be more then it does.

I've looked up the Ford part number and got E3FZ-9F715-A... Which is no longer available. I didn't or couldn't find a superceded Ford number. But while searching for a Motorcrsft replacement... I'm having zero luck. I see that Motorcraft part number CX1823 is listed for the 2.9L from 88 through 91 but it says it doesn't fit my 86.

Am I missing something here? Will this CX1823 fit my 86? My gut says yes but just want to be sure. If anyone clean offer info... I sure would appreciate it.

 

[RonD]

It only moves 3/8" maybe
Its a true solenoid so it works by the computer varying the Ground wire(PWM) which, in effect, lowers the 12volts so it can adjust air flow thru the passage
With key on computer open IAC valve all the way, so should see 11-12volts, after startup 7 to 8 volts, maybe a bit higher on cold start for higher idle

The click would be full voltage noise for start up

 

[Uncle Gump]

It only moves 3/8" maybe
Its a true solenoid so it works by the computer varying the Ground wire(PWM) which, in effect, lowers the 12volts so it can adjust air flow thru the passage
With key on computer open IAC valve all the way, so should see 11-12volts, after startup 7 to 8 volts, maybe a bit higher on cold start for higher idle

The click would be full voltage noise for start up

Well I haven't got far enough to check the PWM ground signal. What I had found while running it around was that a vacuum port on the tree was missing its vacuum cap. So I capped it... and the IAC would not vary or save it from stalling. So unless it has that vacuum leak it will stall. I do have 12 volts at the IAC and it will click with a key ON cycle... so that's when I pulled it to have a look. I really don't think the pintle moves any where near 3/8 inch. But I'm going to pull it again and double check. I really think it's stuck.

I would really like to buy a replacement because it seems these are getting closer to unobtainium. Did they change something in 88 forward in the IAC that it wouldn't fit my 86?

 

[Uncle Gump]

Thanks to @Paulos and @RonD i think I now know the difference in the later model IAC.

 

[kodogtwh]

It should move about 1/4 of an inch. Even though it's PWM controlled, the solenoid inside is beefy enough for it to heatsink and wont overheat like an injector when you give it full power. In terms of electrical checking it should have key power, pulsed ground, and there is a diode between the two pins. I forget the polarity of said diode, but it should be present. If you have complete continuity between the two in both directions with a meter, it'll need a new injector harness (I think that's where it's located on your model truck, it could also be in a molded piece of wire labeled DIODE somewhere near the passenger fender liner). Also in that case it would burn out a fusible link, so if that hasn't happened than its likely fine/open.

 

[Uncle Gump]

Just circling back to this...

So I put a voltmeter across yhe IAC connector. Key ON and I get near enough to battery voltage to say the circuitry is functional. Back to the bench with the IAC and it opens about 0.020 inch. So according to the TSB... the revised IAC will work with its built in diode. If if doesn't function wired like the 86... reverse the wires in the connector and it should work. I'm good with that and have a CX 1823 IAC on the way.

But from what I'm seeing... MY 86 is a bit of a bastard child. Lots of changes to the fuel system and engine controls moving forward. I started looking for a motorcraft MAP... same thing as the IAC. MAP sensor that fits 87 up 2.9L engines... won't fit an 86.

So... I'm wondering if anyone would care to share an 87 or 88 EVTM that includes the IAC and MAP senor wiring. My 86 is posted below. For the life of me... unless there was a connector change... I just can't see why it wouldn't work.

 

[kodogtwh]

You shouldn't be getting solid battery voltage across the IAC pins. One is key power but the other is pulsed ground; if you have solid ground you either have a short somewhere or a bad ECM.

Honestly, not being funny at all, you should rewire that truck for a standalone ECU. I'd be glad to help, I've don't it multiple times on 2.9 trucks. Allows for tuneability, other calibration changes, full data readouts on a laptop and in the process of wiring it, you remove a lot of unnecessary electrical circuits, failure points, and emissions equipment/functionality, as well as repairing any issues with it.

 

[Uncle Gump]

You shouldn't be getting solid battery voltage across the IAC pins. One is key power but the other is pulsed ground; if you have solid ground you either have a short somewhere or a bad ECM.

Honestly, not being funny at all, you should rewire that truck for a standalone ECU. I'd be glad to help, I've don't it multiple times on 2.9 trucks. Allows for tuneability, other calibration changes, full data readouts on a laptop and in the process of wiring it, you remove a lot of unnecessary electrical circuits, failure points, and emissions equipment/functionality, as well as repairing any issues with it.

The truck was NOT running... just key ON.

With key ON... ecm set IAC wide open for start up. There is no PWM going on then.

 

[Uncle Gump]

I'm also not opposed to doing a stand alone... at some point.

I really just want to make it run right at this moment.

 

[kodogtwh]

The truck was NOT running... just key ON.

With key ON... ecm set IAC wide open for start up. There is no PWM going on then.

You've verified that it loses ground with the key off? I haven't had a stock truck to bench test in a minute, info in my mind is a bit old for stock ecu stuff.

 

[Uncle Gump]

Well I verified that I have 0 volts with key OFF.

The problem is the IAC pintle doesn't move with key ON.

 

[Uncle Gump]

I understand PWM circuits... but the damn thing doesn't work with power and ground applied. It certainly isn't going to work PWM'd.

 

[2 bronco 11s]

This gives you the part numbers on the plugs. It is showing an 86 number and 88. Hope this helps , this a ford factory book.

 

[Uncle Gump]

Having a hard time viewing that on my phone. But I see two photos that show the same MAP connector.

Is that correct?

 

[2 bronco 11s]

they used an 86 which they changed part numbers in 88. Can you see the part numbers? If you need a picture of the ECM to see where the wires go in I can send it or any picture you might need .