1995 4.0 missfire

[chiri]

Hi, Looking from some input from the experts.

Have a 97 ranger 2wd with a recently swapped Explorer 4.0, complete engine and wiring. Only pending issue is I am running a MT with a AT computer.

Its running quite well but at wot and around 3.000rpm, it starts missing on some cylinders. If I return to Idle it runs ok and can accelerate VERY careful but any more than feathering the throttle, return the missfire at all rpms.
This stays as permanent until I cut the engine and start it again and everything is normal until it comes again. Can drive all day if I am careful, this happens always when near WOT and always over 2.000rpm.

Changed the ignition coil but no change.
Tach keeps working during the missfire so this discard CKP failure(?)
Fuel pressure a little lower than specs but ok, no change during the missfire.

Any idea what to look for?

 

[franklin2]

Pull any codes yet? Some will not give you a check engine light. Since this is a swap, was the check engine light hooked up?

 

[gaz]

@chiri
Hello,
The fuel pressure should not be a little low. How did you check/measure the pressure?

 

[chiri]

@chiri
Hello,
The fuel pressure should not be a little low. How did you check/measure the pressure?

I am using a pressure gage on the pressure hose, have 28/40 psi.

 

[chiri]

Pull any codes yet? Some will not give you a check engine light. Since this is a swap, was the check engine light hooked up?

have tried but cannot connect my scanner, "cannot establish connection" or something, a friendo will try with a more capable one.

 

[gaz]

@chiri
I recommend determining why your fuel pressure is dropping. It should be constant while running and should not bleed off after shutdown; because I have seen the pressure solid after months of sitting, I know that it requires a failure to perform different.

 

[2011Supercab]

Only pending issue is I am running a MT with a AT computer.

And there's your problem.

Your computer thinks the engine is in park or neutral and is limiting the engine to 3,000 rpm

You need a computer for a manual trans or find someone that can reflash your current one to remove the auto trans..

 

[SenorNoob]

I'm surprised it took this long for someone to say that. Fairly well known issue. Ford tried to stop people overrevving their automatic trucks in neutral/park.

 

[chiri]

thank for the answers, I am changing the fuel pump, seems to be leaking back, also the regulator.

Regarding the computer, somewhere I read there is a hack you can do as a temporal fix, puting a resistance to mimic the transmission in gear, does anyone know about that?

I am looking for a MT ECU but they are not easy to find here, nor someone capable of reflash the one I have.

 

[franklin2]

I took a wild guess that you had a 1999 explorer swap with the 4R70W transmission. Here are some diagrams. One of them shows a transmission switch. Another shows the digital range switch and it does have a resistor in it.

 

[franklin2]

This one here is 270 ohms.

 

[gaz]

@chiri
I have only had a 2 stock Ford hi pressure fuel pumps go bad but when the 1st one died, I bought an off brand replacement...it did not carry the torch well.

All of the stock Ford fuel pumps turned out to be made by Bosch. Since learning this I will only buy a Bosch replacement. In my experience, it is worth the couple extra dollars.

 

[chiri]

I took a wild guess that you had a 1999 explorer swap with the 4R70W transmission. Here are some diagrams. One of them shows a transmission switch. Another shows the digital range switch and it does have a resistor in it.

Thanks, I am using a 95 Explorer but this is useful info, where can I get diagrams like that? the EVTM?

 

[chiri]

@chiri
I have only had a 2 stock Ford hi pressure fuel pumps go bad but when the 1st one died, I bought an off brand replacement...it did not carry the torch well.

All of the stock Ford fuel pumps turned out to be made by Bosch. Since learning this I will only buy a Bosch replacement. In my experience, it is worth the couple extra dollars.

I am using the Ranger 2.3 pump(no visible brand replacement), I am changing to the 4.0 pump that was working well and see if it corrects and maintains the pressure.

 

[franklin2]

Thanks, I am using a 95 Explorer but this is useful info, where can I get diagrams like that? the EVTM?

I got them from my local library. Most libraries have this service. Just go in and get a library card, it's free. The card has a long number on it. Then get online on your libraries website, and click on chiltons online or whatever they have. They will ask you for that long number off your card, and then you are in.