Interesting idling when weather is >65 degrees/interchangeable ECU's?

[Manlavi95]

Title gives it away. Any time the outside temp is less than 65°F, if I let the truck idle after a cold start, after about a minute or two, the RPMs will drop dramatically and it'll start sounding like it's cammed. I look at the sticky, none of those seem to be my problem, but I'll triple check tomorrow. Don't get me wrong, it sounds awesome, but I know it's a problem. Which brings me to a second question, what ECU's are interchangeable with the 2000 Expedition 5.4? I'm assuming any other 5.4 Half-ton above 1999 and before 2004, including F-150's. I'm asking because I know there must be something wrong with my ECU, because I contacted PHP and we narrowed the reason for my programmer not being able to program to a bad PCM. Both communication wires work, and I know the 18v wire works because I actually volt tested it at both the OBD-II port and PCM bulkhead connector. Gonna go to a parts yard and find another PCM. I appreciate anyone taking the time to read all of this, and here is a video showing my idle.

Interesting idling problem in the cold - YouTube

 

[Bowesmobile]

Okay, so I think you're on track. The cold idle seems a little high. But get a new PCM from a similar year and try it out. Watch out for the security and make sure the key will work. But I dont know what else to warn you about. You seem on track.

 

[Manlavi95]

Okay, so I think you're on track. The cold idle seems a little high. But get a new PCM from a similar year and try it out. Watch out for the security and make sure the key will work. But I dont know what else to warn you about. You seem on track.

Thanks for the reply, I've been hearing about this security stuff lately, what exactly should I do and not do? I thought it would be as simple as swapping PCM's

 

[Manlavi95]

Hmmm.

 

[FordandPolaris]

Colder weather will bring out ignition issues. I can't watch the video yet but the computer in my truck has seen -20 temps and keeps the idle ok, spark plugs and COP's on the other hand didn't take the weather well.

Im not saying the programmer guy is necessarily wrong, but if your motor is not running like a piston fell out, and is idling ok at some temps and not others, it seems much more likely to be ignition/sensor related.

 

[Manlavi95]

Colder weather will bring out ignition issues. I can't watch the video yet but the computer in my truck has seen -20 temps and keeps the idle ok, spark plugs and COP's on the other hand didn't take the weather well.

Im not saying the programmer guy is necessarily wrong, but if your motor is not running like a piston fell out, and is idling ok at some temps and not others, it seems much more likely to be ignition/sensor related.

I wonder when the plugs were changed last. Scares me. Still have to try a new ECU, know which one's are interchangeable? Should be bolt-in/plug-n-play right?

 

[jdecker]

Have you checked to see if you have any pending codes? It is acting like it's trying to compensate for a fuel mixture problem. Just guessing I would think it might be a leaking intake gasket.
Also the pcm will not be plug and play, it will have to be flashed to your particular truck and the pats(security) will also have to be programmed for your keys.

 

[FordandPolaris]

I got a chance to watch the video now. That is definitely interesting. Have you checked the idle air control valve? Your engine is idling high, even when not missing

 

[american steel]

your ECU PCM or computer is one thing that will not cause winter issues it happens but that is extremely rare on these vehicles.
sounds like you're having misreading issues one or some of your sensors need to be replaced and or cleaned out. check with your MAF sensor. that cause's a lot of weather issues, it sends signals to the ECU if its of the computer will try compensate for the weather barometric pressure temps and all that stuff.
more than likely its a sensor problem.
don't change your ECU don't even think about it!
spark plugs work better in cold weather so do injectors.
also check all of your hoses they might be rotted in a place you cant see.

 

[Manlavi95]

your ECU PCM or computer is one thing that will not cause winter issues it happens but that is extremely rare on these vehicles.
sounds like you're having misreading issues one or some of your sensors need to be replaced and or cleaned out. check with your MAF sensor. that cause's a lot of weather issues, it sends signals to the ECU if its of the computer will try compensate for the weather barometric pressure temps and all that stuff.
more than likely its a sensor problem.
don't change your ECU don't even think about it!
spark plugs work better in cold weather so do injectors.
also check all of your hoses they might be rotted in a place you cant see.

It's not just the idling that I'm worried about when it comes to the PCM. It's because I bought an Edge Evolution CTS, and there are three wires that communicate with the PCM. Two work because those are the ones that send info to the gauges on the screen of the tuner. I tested the third and it's getting the 18 volts that it should. So the only next option is to replace the PCM, because I can't figure out what else it could be. I'll clean the MAF. What should my idle be at?