4.0 runs better when cold - sup-wit-dat?

[kolb]

Hello all. Second post. Glad I found the site!!!

Our 2002 4.0 SOHC Explorer with AWD and 107,x.. miles runs MUCH better when cold. Great throttle response and decent power. Once the vehicle reaches operating temp, it acts like it has lost 20 or 30 hp. It's a big difference. When warm, it acts like it is starving for fuel or the timing is cutting way back. You can floor it, the rpms climb up to red line (+/-) but there aint much happening. I have changed the fuel filter, added a MAC intake and filter, and added a cat back exhaust. Is there something I'm missing here or is this just part of Ford's warm up strategy? Also, no codes or "check engine" lights. Thanks in advance for any help!

 

[BrooklynBay]

You are losing power when the transmission over revs (flares). Another possiblity is that the engine coolant temperature sensor, and the air sensor in the MAF are telling the computer the wrong information in relation as to which mixture you should have at specific temperatures.

 

[kolb]

For clarification - I have another problem that just started with the tranny slipping that I sent a PM to BrooklynBay about. Thus the "flare" comment.

This "low power" has been around with this truck for quite some time so I didn't think the two were related. They still may/may not be related. I don't know. Since the trans is most important at this point, I'll look at that first. Any suggestions on checking the sensors you spoke of?

 

[BrooklynBay]

Try cleaning the MAF, and check this chart for the ECT:

 

[kolb]

DUDE! You are EVERYWHERE!! I have been here for about 2 hours now and you had answers to both problems. Thanks SO much!

 

[BrooklynBay]

Check the links in # 42 if my list of useful threads for information on MAF sensors. Your vehicle should feel smoother after you clean the MAF. Take care cleaning it since it's a very fragile part.

 

[kolb]

Thanks. That helped, idle is much smoother now.

 

[BrooklynBay]

Thanks for the update!