crazyfazy

Hello to all.. I've got a pretty long story here, so please bear with me because I'm in desperate need of some advice...

I have a 1995 F150, 302 EFI that use to be an auto, but the guy I bought it off of swapped out the AT for a 5 spd. w/OD tranny. Ever since I bought the truck, it's had a random misfire. There never seems to been any rhyme nor reason.. no pattern, just every once in a while..out of the blue.. it would misfire. I've replaced all the basics, like spark plugs..wires..dist. cap..ignition control module...ignition coil.. even ended up replacing the whole distributor.

After searching the internet and asking friends and mechanics, there was a thought that maybe because the previous owner swapped out the AT for an MT, that the ECM needs to be replaced for the MT programming, and that's what could possibly be causing the misfire.

So... I tracked down an ECM for my year, model and engine size for the MT and decided to give it a try. Yesterday, after disconnecting the battery terminals, I removed the old ECM and swapped in the USED ECM that I bought, hoping to reconnect the terminals, jump in, turn the key and drive off into a world of mis-fire-less utopia..... EHHHH!!! WRONG!!!!

When I turned the key, the engine turned over, but there seemed to be absolutely no fire at all. After double checking everything, I thought maybe there had to be some "reprogramming" or some kind of key sequencing code to get the ECM to talk to my truck, so I called a buddy at the ford garage and explained to him what I just done. He said there wasn't any reprogramming that needed done and it sounded like I got a bad ECM.

SOOO... I disconnected the terminals again, removed that ECM and put the old ECM back in that the truck has been running on (randomly misfiring, but running). When I tried to start the truck after this..NOTHING!!! It turns over, but will not start at all. I had my wife try to start it while I pulled the coil wire to see if there was fire, but there is none.

In retrospect, I do remember seeing a slight arc when reattaching the battery terminals after installing/re-installing each of the ECM's. Could something have shorted and fried both ECM's???

After dealing with this misfire for about a year now, replacing this and that, and finally the ECM.. I don't even know where to start now. I'm completely disgusted! Can I just tear all the damn EFI stuff off of the truck and everything that's associated with it and go back to a carb with a duraspark ignition? I've gotta do something! PLEASE HELP!!!!!

Sorry for such a long story for my first post, but I have no idea what to do now.. Thanks for any and all info!

Just call me Sean

iTrader: (1)

Check for codes.

crazyfazy

pulled codes: 116, 637, 539, 654, 621, 622, 652, 624. Most of these codes seem to address the fact that the truck had an automatic transmission and is no longer in the truck. The only code that I see that may be a clue to a problem is the 539 which says that the system shows voltage at PCM pin 10 - is AC on? I'm still clueless...

ps. forgot to mention that these codes are from the ECM that was originally in the truck that was running until I swapped out for the MT ECM.

RLXXI

The 539 is exactly what it states, when you ran the test to pull codes the a/c was turned on, means nothing else.

If you don't have emissions testing in your state, yes you can yank all the computer controls, EFI etc drop an Edelbrock intake with a 4 bbl carb, and I wouldn't go with a Duraspark distributor, I would go ahead and get something more performance wise like Mallory adapt a performance coil to the ignition switch and end your misery.

You will also need to adapt the fuel system, after market pump of some sort.

Just call me Sean

iTrader: (1)

While you're dumping the EFI be sure to get rid of that pesky CD player and put in an 8-track.

If you're sure there is no spark have the ICM tested.

crazyfazy

well.. after pulling the codes today, I decided to start swapping out some ignition parts that I had on hand from before. I started with the coil with no success. Then, I had an extra ICM on hand an decided to swap it out to try that...and you ain't gonna believe this! When I pulled the old ECM, I must've caught the tab on the ICM and just barely pulled it out so it wasn't making a connection! I plugged it in, got in the truck and it started right up! I know, I'm a bonehead, but at least I fessed up to it! Anyway.. I'm not outta the woods yet. After recognizing the problem, I decided to give the MT ECM I bought another try. When I put it in, the engine will start, but I've gotta pump the gas to keep it running and it's sluggish as hell, almost as if it's out of time or something??? I checked the part # for the ECM I bought and it checks out ok. The part # is F4TF-12A650-AVA, which is suppose to be for a 5.0, EFI, MT. I do think I'm eventually gonna get rid of all the EFI and computer junk and switch to an aluminum intake and 4 barrel, but are there any suggestions as to why this new (actually used) ECM won't work right? Thanks..

Just call me Sean

iTrader: (1)

You have to pull codes on the new computer now.

crazyfazy

I know a lotta guys are against the "old school" way..and that's fine. When the "computer generated" engines and components are working fine, I'll admit they're hard to beat, but when something goes wrong, it's definitely a bigger PITA, and much more money...IMO.

Just call me Sean

iTrader: (1)

Not really. So far the only money you spent was from improper diagnosis.

RLXXI

Put the original pcm back in, that is NOT causing what you call a misfire. Go back to the basics, check the cylinder compression on all cylinders, they should be within 15% of each other and none lower than 100 psi.

Pull the spark plugs out and check for cracked ceramic, it's very easy to crack them while installing. Check for torn plug wire boots.

Could also be a lean misfire, check ALL your vacuum lines especially the ones that route around the throttle body, they have a tendency to suck air.