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4.0 running like crap


Tiph92

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I bought a 1992 ranger with the 4.0 back that I owned a few years ago. In that time it had another 4.0 installed right before I got it. It runs like crap. Idles fine, but and soon as you start driving, its popping and stuff real bad. Figured firing order. In the process of checking it, I found the the cam synchronizer on the back of the engine unplugged. Looked all over and couldn't find a connector to plug back into it. Figured it got ripped out or something. Went to the junkyard today and found a 1992 explorer that I went to pull the harness on and found that it doesn't have the cam sync on the engine. My guess is they installed the wrong year 4.0 and now I need to now whats my best option to make it run? Harness and ecu from a engine that has the cam sync or what?
 


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Dirtman

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The cam syncro is not needed if the current ecu doesn't have the hookup for it. The cam sync was originally a California emissions option. The engine is perfectly capable of running soley off the crank trigger provided your current computer is setup that way. You probably just got a later model (94+) engine or a California engine which again, doesn't matter if your ECU is not setup for a cam sensor.

The problem would be if you did the opposite and installed an engine with no cam sensor into a truck with an ECU setup for a cam sensor.
 

Tiph92

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Thank you for the reply.

Best I can tell, they left the factory 1992 harness and ecu in the truck. Doesnt appear any of that has been changed.
Only difference I could find is it having the cam sync now.
So, I take it the teeth on the crank trigger are the same and didn't change between the cam sync engine and non cam sync engine?
Just trying to get this problem narrowed now, its a nice truck and I'm excited to have it back, but now I want to drive it lol
 

Dirtman

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Crank trigger and gear is the same for both engines. All the cam sensor did was give the computer a bit more data to add a marginal amount of extra control over the ignition timing and fuel trims. With your symptoms I'd be more inclined to start by checking fuel pressure, look for vacuum leaks, and check the plugs, wires, coil packs.
 

RonD

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Yes, they swapped in a later model 4.0l and didn't swap oil pump drive in to replace cam synchro, which is fine

If cam synchro starts to squeal you will need to replace it with just the oil pump drive, no timing needed

Because its a pre-1995 and has the 60-wire OBD1 computer, I would pull out the computer and check the 3 blue capacitors inside it, these leak/fail after 20years and cause all sorts of engine issues, there is no "aha, thats the problem" when caps start to fail
$5 fix to replace them
And ALOT of chasing your tail if IT IS the caps and you don't look first, lol

Coil pack wiring is
3 4
2 6
1 5
front

the 5 6 4 side gets me most times, either at the coil or at the cylinders
So trace each spark plug wire, one at a time, to its cylinder

And on any 4.0l.............Clean the MAF sensor, once a year, easy to do
 

Tiph92

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Thank you everyone for the quick replies. Now that I know the cam sync is a non player in this, I can start looking elsewhere for problems.
 

PanteraGT5S

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Yes, they swapped in a later model 4.0l and didn't swap oil pump drive in to replace cam synchro, which is fine

If cam synchro starts to squeal you will need to replace it with just the oil pump drive, no timing needed

Because its a pre-1995 and has the 60-wire OBD1 computer, I would pull out the computer and check the 3 blue capacitors inside it, these leak/fail after 20years and cause all sorts of engine issues, there is no "aha, thats the problem" when caps start to fail
$5 fix to replace them
And ALOT of chasing your tail if IT IS the caps and you don't look first, lol

Coil pack wiring is
3 4
2 6
1 5
front

the 5 6 4 side gets me most times, either at the coil or at the cylinders
So trace each spark plug wire, one at a time, to its cylinder

And on any 4.0l.............Clean the MAF sensor, once a year, easy to do
One word - Yes.
 

rusty ol ranger

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If it idles good but goes to popping and sputtering when you try to take off id be checking fuel pressure first.
 


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