From my login name, you could guess that I have a 97 F150. This has the 5.4, with an automatic. I've been having a tough time with it, and with everything else in my life I work on it, then not for a while. Of course, now I'm working on it!
Anyway, some history - engine light came on, upstream drivers 02 sensor. engine light, downstream 02. light, upstream 02 on pass side. light, downstream pass 02. Of course, there were intervals between these. It ran for about 500 miles, then i get a check engine for low voltage on the MAF, which I replaced. ran good for a while, then I'm getting low voltage on MAF again.
Sigh, I'm very frustrated. I took it into Ford to hook it up to their diag tool, and he basically told me he needed to check all my wiring (which looks really good, my truck looks brand new!) and wanted me to let him check wires at $100+ an hour with an estimate of 8 hours! Well, i broke out the book and looked at the wiring diagram. the wiring from the MAF goes directly to the PCM, power control module. I took my ohmeter and got continuity on the wiring from the MAF into the pcm. I took a good look at my MAF and found the wiring to not be completely inserted into the intake shroud. the intake plastic shroud makes it hard to get the MAF wiring plugged into it but I made really sure this time they were connected. So, now I don't have an engine light but my truck just doesn't seem to know when to shift. During all these check engine light episodes the truck would start shifting really hard but I hope the transmission isn't failing. Everything I read says that the first thing that would make the transmission fail would be an engine that was not running optimally. The truck starts quickly, has power, never seems to have a problem but it won't shift when it should, even though the shifting is smooth, it just seems like it doesn't know when. I was going to look for a possible vacuum leak, but if i had a vacuum leak that bad i would think the engine would not run as good as it does.
Does anyone have any suggestions? I am going to look into a replacement PCM, but i would think that would trigger a check engine condition and give me such indication. The engine runs great but it hesitates to shift on the accelerate phase of driving.
Any suggestions, help is greatly appreciated.
D

 

First question is.... what transmission is in your truck? im not familiar with what transmissions are available in the 97 f150. Is it a E4OD or a AODW? Your right about the vacuum leak....if you had one, it would affect the way your engine works, but these transmissions are fully computerized and they dont use a vacuum signal. I dont know if your truck still has a tv cable on it, but it might be a good thing to check first, since it controls the line pressure and shift points in the older AOD transmissions. also, as for trouble codes from the transmission...if i remember correctly the computer only monitors the gear selector switch, the temp and the seleniods. anything that is physically wrong with the tranny, the computer wont pick it up. hope that this helps start you on your way to figuring out your problem.

 

No tv cable on any '97 truck.

The computer monitors much more than that.

It checks each shift to make sure the RPM drop was correct. It check that the torque converter locks and unlocks when it's commanded to. In most transmissions it check the gear ratios to make sure it's in the right gear. There are about 50 different trans codes, and each one is for a different problem.

 

Well, not sure what transmission I have. I'll have to dig out the book and find out. Without an engine/transmission code creating a "check engine" condition or light, is there any way a diagnostic tool will help? I may just take it to Ford, but the guy just seemed like he wanted to rip me off, just made me feel like I was about to be slimed.
That is good info about no vacuum lines to the transmission, i'm back to looking at this PCM or power control module. Has anyone had one fail? Any idea about cost, etc? I know the thing is HARD to get to, I know I can get it out but one of the screws holding it behind the glove box will be a dandy to get back on.... I just don't know what to do!

 

It is quite unlikely that your PCM is faulty. That is somewhat rare.

If you don't have any transmission-related codes, it's more likely you have a mechanical or hydraulic failure. However, if you have ANY engine management codes, you're jumping the gun... They need to be corrected first.

I'd suggest you take it to a transmission specialist who can actually diagnose the fault and I don't mean one of the chains. They can attatch a proper scan tool that will monitor what the computer is doing and should be able to pinpoint what is going on inside the system.

A 97 w/5.4 should have the E4OD tranny.

Steve

 

That is the mystery of it... after all the codes I've had, I have NONE now - it just doesn't seem to know when to shift. You can't say that I didn't try, but I think you are right Steve, it's above me now. You've convinced me to take it in. This may take me a week or so, starting back night school next week and will be pretty busy. I will try to repost on the findings, etc.
Dwayne

 

BTW, thanks to all!

 

I apologize for not getting back with the end solution, I am just getting back into the online forum thing. I know, use you then abuse you...
Anyway, I took it into the Ford dealership. The guy was playing Solitaire on his computer when we walked over to the stall in their garage. They hooked up my truck, told me that my number 5 COP (coil on plug) was fine at idle but misfiring at high rpms. They charged me almost 300 dollars just to hook it up, and about 75 to replace that faulty COP. It ran really good after that, it was expensive but sometimes you gotta let them have their $$$ I guess.
Thanks again for the replies, sorry it took so long to get back to everyone.
D

 

Its amazing what ignition problems will act like isn't it?

Glad that you got it taken care of.

Darrin