4.0L with OHV and random misfires on all cylinders

[Trader007]

http://www.therangerstation.com/forums/showthread.php?t=155690

 

[bobflood]

... problem is i have that stupid PATS system that wont allow me to change computers without a key-reflash. Problem is you need two chip keys to do that, and I only have one. Ford wants $300 for new keys and programming... screw that.

You can buy chipped keys off the internet, and some locksmiths have the equipment to program the keys. Will still cost something - but should be much less than the dealer. Good luck.

 

[Trader007]

You can buy chipped keys off the internet, and some locksmiths have the equipment to program the keys. Will still cost something - but should be much less than the dealer. Good luck.

called all around already... nobody has the equipment to do it. the programmer box itself costs like $1500, and ford forces everyone to license the software by year to the tune of about $1k/year... so no small shop will have it.

i already have the chipped keys, i just need to buy a used computer and have ford reprogram everything.

OR, if i could find the damn service manual for the PCM i could rebuilt it. I just need the datasheet for that engine computer. I know it exists, but there is little doubt it is saved on some corporate harddrive and they are not going to let it out in the public.

now, i can read the numbers on some of the power fet's in the computer, but if its anything like the other components i looked up i doubt ill find exact replacements. a datasheet would tell me the values and type of components they are, which i would then be able to find suitable replacements.

but today i replaced that main filter cap again. in 6 months it is already showing signs of wear (using my capacitance meter). this tells me i have VERY dirty power coming in (likely not the problem), or whatever the computer is trying to push is failing (the output transistors that fire the iginition coil specifically. if these are failing it could easily cause the power source components to be stressed).

replacing that capacitor again DID help. today i had decent acceleration again. if all i had to do was replace one capacitor every 6 months it would be fine, but i fear whatever is causing this capacitor to go bad will only get worse.

at the end of the day, i believe the problem is essentially the igniton module. problem is this truck doesnt have one, its built into the PCM. so if i had a datasheet i could isolate the components that make up the 'ignition module' and i could replace them.

 

[Trader007]

Update!

Pretty unbelievable, but I found the problem. This time the computer was in fact still OK. It was the spark plugs! They were last on my mind since I replaced them 8k miles ago

Autolites, never again. One had two cracks in the ceramic insulator! The others were severely worn. There is no reason for this, the truck was running fine with them until they failed.

I popped in NGK 4177's and instantly, for the first time in over a month, truck runs without miss, hesitation, backfire, bucking... its all gone. It runs absolutely perfect. Just turned 259,000 too.

I had so many problems with the computer in the past I kept thinking it must have finally gave out... but I checked as many components and points as I could and I simply couldn't find anything suspicious... now I know why, because the computer is working fine.

 

[gogetter22]

Hi!
I have a 1998 ford explorer sport (manual)
and here over a little while now its started a random backfire.

What happens is it cranks up and drives fine and ill just be cruising along and just randomly it will get a almost loss of power(morely my rpm will stay at the same spot but my mpg will go from lets say 60 to 50) and chuggish acting and if I let go of the gas it back fires and it will stay this way for a few mins and then just jolts right back to normal as if nothing ever happened and my check engine light is on and I had it checked and it read a few things and ive checked for a vacuum leak and its not that nor is it bad spark plugs because those have been replaced not to long ago. I thought maybe a Egr valve since the bolt is seized on? But I dont know!
Someone help