So here's the deal. I recently purchased a '94 F150 Single cab short box with the 300 I6 in her. I have had nothing but problems since I have owned it. It will run like a top one day and then just crap out on me a few days later. I was driving to work the other day and it took a crap on me. I got it back to the house and discovered that I had some faulty connections back to my fuel pump. I re-did the connections on it and the fuel pump kicks on and the truck runs perfectly fine. BUT now that I have replaced the connectors, I can barely get it over 40MPH. I did take the PCM out and try replacing it (thinking that was the problem vs the fuel pump connections) but I put the old one back in. It runs at a high RPM while going down the road and when I let out of the gas it'll shift. But it runs a a very high rpm while going down the road, just sitting there idling it is a the right rpms. I checked the tranny fluid added some to her. I'm absolutely lost because before it crapped out on me she was shifting absolutely flawlessly. Can y'all help me PLEASE?!

 

when do you start to notice the high RPMs? Is it not up shifting at some point? Does it upshift or downshift when you let off the throttle? Sounds like a transmission/kickdown issue. Maybe a vacuum hose.

 

Is it an E4OD? Have you tried manually cycling between neutral and drive or a lower gear and drive to get it to shift and drop RPMs?

 

My girlfriends car had an issue with her fuel pump and ignition after I fixed it it ran fine for about a week the the same thing happened it would not shift and felt like it didn't have much power it was because of the cat being partially plugged up try disconnecting the exhaust just before the cat and see if it runs better believe it or not the back pressure in the engine will make it shift funny and feel like a transmission problem after I disconnected the exhaust and it ran better I just took a hammer and a piece of some steel rod and smashed all the honey comb ceramic out of the cat so we could drive it till we could save up for a new cat but you need to make sure to disconnect before and after the cat and blow all the chuncks out so it doesn't plug your muffler

 

jpbecker....I start to notice the high RPMs about half way through 1st gear. It continues to stay at very high RPMs throughout 2nd and 3rd. I havent got it to 4th yet because I havent got her over 40MPH yet. When i let off of the throttle it shifts up. I have tried cycling through the gears manually after I put the tranny fluid in and nothing really changes. Nothing significant at least.

 

I believe 1994 still had the same mechanical kickdown and vacuum modulated up shift. Unless the modulator has failed, it sounds likely to be the torque converter. Your PCM should be shifting and adjusting air/fuel based on things like throttle position, vacuum, etc. Even if it was the cause of the high RPMs, you should still have the response from the tranny. That is why I'm leaning more towards the converter or modulator. Do the upshifts happen at approx the same vehicle speeds as before? How far off are the RPMs from normal at the shift points?

 

Did you verify if it is an E4OD (E for electronic) trans? 20 bolts in the pan. Not a perfect rectangle. If so, and you've tried two different PCMs, then your are probably looking at a torque converter or Vehicle Speed Sensor or MAP sensor. Those should be the sensors that would influence shift scheduling and RPM. Do you have overdrive on/off? Is it working

 

I did verify that the transmission is in fact the E40D. I ran it down the road with the overdrive off and switched it back on. It is in fact working. I got under her and started drilling holes in one of the cats and it was hollow. I drilled a few into the other one and it has a ton of crap in it. I decided to cut the second cat off and the pressure was much more significant. BUT it didn't fix the problem. I'm going to rig up an exhaust and then try those sensors and modulators like you're saying JP. I can only hope that the cheapest one works. haha. I appreciate you helping me out though, I will most definitely keep you posted as to what I'm doing. I'll be hitting up autozone tomorrow so stay posted my friend.

 

To start with, the FIRST thing you do with an EFI vehicle is pull codes. Period.

Do that and get back to us.

 

There are no check engine lights on or anything like that.