GT40: Hot Idle Loping

My GT40 has 340 hours. It runs like a Swiss watch from hole shot to full power and everything in between. Really runs great!

Except after it warms up, we stop for a bit and restart. At that point, the idle is all over the place! Over 1000, down to almost stalling, back up and repeat. Very, very frustrating. And it seems to smoke some at this point too. It still has no hesitation and runs great at speed even when the idle is doing this.

I have searched the forum, read the many threads about this. I found one promising thread that stated to replace the idle air control valve. Did that. No luck.

Is this just going to be the way it is? Even my (very respected) repair shop here couldn't get this right.

Any suggestions appreciated!

Failed Map sensor will cause the idle to oscillate and motor may stall according to the manual in the reference section
ECT, ACT or TP sensor fail will cause 800 instead of 600 RPM idle.

Yes it's mounted to the front of throttle body, it has the vacuum line going to it. Pretty much plug and play.
It would help you understand where things are and what they do if you look over the GT-40 service manual in the reference section. It's in the manual section at the bottom.
There's a picture that points to all the parts and if you read the section called Theory of operation it gives you a simple understanding of what does what even for the non-mechanical minded.

Ford or auto parts store
Here's a picture with part number you could probably call ford to cross reference to current part number
Called my local he said that part is NLA from Ford he gave me this number and said a Napa or other would be able to cross reference off E7DZ-9F479-A

@gun-driver When you get a chance, can you pull back a little in your photo so I can see where this is located on my GT-40? I'm at home, boat in the storage so I'd like to know where to look when I get over there. It seems all I need is a flat head screw driver.

@gun-driver: Maybe I'm looking at a different service manual for the GT-40. I don't see a reference section or anything that says "theory of operation". I have the pdf file that I downloaded from here. The diagram that has the arrows pointing out the different parts is at the front of my manual and shows the MAP to be on the driver's side, front next to the EEC System Relay and STO/STI Connectors. It is shown in section 2A.

Is this the same location you said to look? When the part arrives, I'm heading over to install.

Any feed back on if this was solved and or what was the fix????

No you don't have to do anything to the ECA.
You may want to check your Fuel Pressure Regulator. One of the similar posts found his regulator to be bad causing fuel to migrate up the vacuum line (which shares the same line as the map sensor) causing erratic idle ( loping )
$20 at autozone

Thanks for the follow up.
We try to figure out these problems and a lot of times the poster never gives a follow up so we don't know if the recommended fix worked or not.

From another thread:

gun-driver wrote: Yes but I don't think that is your problem is the idle oscillating then stalling? Autozone/car quest # BWD 21704 OR You can ask for a regulator from a '92 Ford 5.8L Bronco or F250 Make sure it has the triangle base three screw mount the newer ones are two screw mounts

Not sure on difficulty.

gun-driver wrote: Easy peezy lemon squeezey

I hate technical jargon. haha

@gun-driver I bought the part. Before I head over to install it, do I need to bleed the line? I don't have any special tools. The YouTube videos all show a vacuum bleed tool removing the pressure off the fuel line first.

Also, what regular tools do I need to pull this? Is it connected with allen screws to the the three holes on the backing plate or flat or phillips head?

Anything else I should know? Thanks for the help!

For future troubleshooting reference I want to mention that I also had an intermittent oscillating idle after the engine was warm. Thanks to gun-driver’s insights in the 3rd post up above, I replaced the MAP sensor and idle is now smooth.