Hi! I have a '94 Ranger I did an engine swap on because of rod knock among other issues, it had a consistent misfire on 1 or 2 cylinders and its doing the same thing on the new engine that didn't have that issue to begin with. I put new plugs, plug wires and waste spark system in it and she's still misfiring pretty hard in the same way under hard acceleration. The old engine was doing the same thing, over more than 20% throttle she'd start bucking real hard and now the new engines doing it too.

I noticed on the bracket for the waste spark box theres what looks like a capacitor, should I try replacing it or should I disconnect it and see what happens? What is that for? Also my fuel pump is dying, I already have a replacement just need time to stick it in. Overall, she's running better than she did but she's still running very rich, so I'm sure I need to replace my o2 sensors. I also have backfire burbling in my exhaust after I rev it a bit. New issue is that she's burbling at all RPM now with that backfire like you'd hear on an old carburated engine out the exhaust. I also feel like there's a lack of power too, even on the old engine running on 4-5 cylinders I could take off at 1,000rpm but she won't do it now


As far as I could tell there were no chewed wires on the wiring harness, any ideas as how to fix this at all would be very very much appreciated. My only other thought is that she's out of gas and on a bad fuel pump, but lack of fuel shouldn't cause backfire like that. Could I need a crankshaft position sensor? New fuel injectors? Something with my timing? Help! This is the one time I wish I had an OBD2 vehicle!

 

That's just a noise suppressor, it helps cut static in the radio, safe to unplug.

Before spending anymore money on things that may or may not fix it, replace the fuel pump.
Low fuel pressure/flow will cause all kinds of issues.

 

+1 ^^^^

Also pull out the computer and have a look at the circuit board, especially the 3 Blue Capacitors, after 20 years they can leak and cause different engine issues, and its FREE to have a look
Under $5 to replace capacitors, which I would recommend in any case, and not hard to do

When you see an ad for "rebuilt" computer, it means those 3 capacitors were replaced, and that's about it, lol

 

Where is my computer located? On the donor truck I think it was on the passenger side in that footwell by the door, but that was a late production '93. Is it different between the 2 years? When I replace those capacitors do I need a soldering iron or are they clipped in?

 

It was a 1992 or older if it was in passenger side of cab

1993/4 4.0l would have it in engine bay, drivers side, below brake booster in the corner next to inner fender, just follow the main wiring harness down to the 60 wire connector

Google: 1994 ranger 4.0l computer removal

Yes, need a soldering iron to remove and replace Caps, also correct caps, they have a value and a voltage on the sides
There is also a positive and negative side, so take pictures before removal
Electronic repair place can do it, takes about 10min and they probably have the correct Caps on hand

 

Alright, I've put 89 octane in it and a new fuel pump and she's still backfiring like a **** and lack of power, I fixed the vacuum leaks I had and while she's happier to rev theres still lack of power and backfire on 2 cylinders. Give me possible reasons why this would be, my buddy says timing or a spark plug swapped around. What do y'all think?

 

I disconnected that noise suppressor and it actually made it run better XD

Not fuel supply issue anymore, I've gone through 1/4 tank of gas in 43 miles. Somethings making it dump fuel into the combustion chambers. My best guess now is fuel injectors, they're probably the original ones. Probably not a bad idea to replace them anyway. Whats your input?

 

Yes, if MPG is in the toilet then injectors would be a good guess

Not spark timing issue on a 4.0l
Spark plug wiring maybe

Coil pack wires
3 4
2 6
1 5
front

The 5 6 4 side always gets mis-wired
Trace #5 wire to center cylinder on drivers side
Trace #6 wire to rear cylinder driver side

Then do it AGAIN, lol

 

Thank you so much for mentioning what wires go where, shes running how she should be now. Still gotta see fuel milage not be garbage but its a great first step.
Ford seriously needs to go back to elementary school

*edit* Drove 75 miles doing 65 at 2500rpm, only ate 1/4 tank of gas. Not great, but not having a 5th gear to lower my rpms sucks. I'll be dropping it at a tranny shop in the next few weeks, theres a plethora of issues with the replacement