Hi Everyone.

For three weeks I've been chasing a very strange issue with my neighbors '96 XLT. Some days it drives perfectly fine, some days it's totally possessed. On the days that its possessed, the engine will randomly start cutting out very violently, like its hitting an extremely hard rev limiter. You'd be taking off from a stop sign, or on to a highway and suddenly it'll start shaking violently back and forth like someone is turning the engine on and off when it's in motion. Usually when this happens I pull over and shut the engine off. Sometimes it starts right back up, and when it does there's a 50/50 chance it will start bucking again, and on the other hand, it wont start at all. You'll get sputtering, but it wont completely fire up, and couple times I think I heard a pop from the intake. Once you let the truck sit for a couple hours or so, it'll fire up again like nothing happened, and eventually the problem will start again at some point.

Details on diagnosis: Every time the engine cuts, CEL will come on, and then immediately turn off when it gets power again, like its in perfect rhythm with each lurch the engine makes. There's no change in the gauges when this happens either, so I don't think its cutting battery power. Hopefully im making sense. This seems to only happen on acceleration, without influence from throttle position. I could floor it and it wouldn't make a difference. On a couple occasions when the bucking starts, I've been able to push the clutch in and rev it up a bunch, which seems to make it stop for the time being. There are no OBD codes whatsoever, nor even a pending code. I spent a few hours looking over the engine, cleaned the MAF sensor, IACV, throttle body, and replaced a split PCV hose that could have been causing vacuum leaks. Also replaced the fuel filter.

Something tells me perhaps one of the ignition modules is fritzing out(dual spark plug ignition), but I figure I should consult the pros here before I throw parts at it.

Thanks!

 

Any fault codes?

 

Welcome to the forum

No on the coil packs, both spark plugs in one cylinder fire at the same time, this dual spark adds more power but not enough to "feel" a difference if one wasn't firing
You can test coil packs and spark plugs fairly easily
Engine off(warmed up engine is better for test but not required)
Unplug the 3 wire connector on 1 coil pack
Start engine
If there is a steady misfire then one spark plug on that side is not working
Repeat test for other coil pack

[This test would be done differently on 1989-1994 2.3l Rangers]

It is possible that you have 2 spark plugs in the same cylinder that are BOTH misfiring, long odds, but possible
Spark system is monitored, so if this was happening then most likely a code would be set

The CEL comes on because 1 or more cylinders are not adding power to the crank speed at that moment, misfires, this can set a code but only if its consistent, yours is not
And having NO CODES set is also a clue, the computer monitors most systems, so looking at what it can NOT monitor is the clue

Best guess is that your fuel pump is cutting out
There is no "fuel pressure" sensor, so no codes would be set
Fuel pumps can become intermittent, could even be the connector on the top of the gas tank is corroded
If computer was cutting voltage to fuel pump that would set a code, so not a fuse or relay issue

It is possible the fuel filter is clogging up but I would expect that to get steadily worse not intermittent(you already replaced this)

People have installed a fuel pressure gauge on the engines test port and run its hose up, so gauge is visible when driving
1996 Ranger should run 30psi fuel pressure engine running


Just as an example of what it feels like when fuel pressure drops
If you are below 1/8 tank on fuel gauge, and turn right onto an uphill grade the fuel pump's pick up in the tank will suck AIR as all the fuel goes to the left rear of the tank
Engine cuts out HARD until fuel sloshes back so pump can suck it in again, then back to normal like nothing happened

 

That's a very good point regarding the codes. In that case, I'd say that definitely narrows down the possibilities. I've suspected the fuel pump as well, however I've driven it with fuel levels near empty, and completely topped off and as far as those levels go, the first time I personally noticed the bucking for myself was on a full tank. And for more clarity, when it bucks, its not like a sputter and cut, its a hard cut like someone's flipping a switch that's turning the engine completely off and on with nothing in between. I would only assume that if the fuel pump was cutting on and off, that there would be a second or two of sputtering before power is lost, but I'm used to working on Japanese and Euro cars, perhaps Fords react differently to fuel loss. I've also seen others mention on various forums that corrosion on the ECU plug (which they claim is a common issue on these trucks) can cause things like this too, but I'd assume if that were the case it'd be having a lot more trouble running.

 

When fuel pressure is cut engine just stops no sputter, just off, carburetor engines would sputter when you were running out of gas

About the CEL, the computer turns on the CEL when it boots up
When there is a hard misfire CEL will flash until you back off the throttle
If CEL is not flashing but just comes on and then goes off..................................maybe power to the PCM(computer) is being cut, this would turn off injectors instantly, then back on WITH CEL when power is restored
PCM relay in engine fuse box powers up the PCM with key on, and no codes because PCM was off, it just thinks you turned off the key and turned it back on

 

Check my post here https://www.ranger-forums.com/2-3l-2...60-mph-160439/
I had very similar issues with my 98 2.5L and it was a head gasket intermittently letting water into cylinder #1.

 

I've unplugged the fuel pump on my EFI Nissan when doing a compression check and it'll start and run for about 1 1/2 seconds, then sputter and die as pressure bleeds off. Same thing with my E46 BMW, but perhaps Fords act differently. It does indeed seem like the PCM is cutting power, but its hard to tell as theres no Tachometer in the vehicle, to which I assume would drop to zero every time the engine cuts. All the gauges stay operating when this happens so I know its not battery power thats cutting.

 

Look at this video. If you skip to 6:15, this shows exactly what the engine does, except in my case its at higher rpm going down the road. In the uploaders case it was something called a SPOUT plug that was bad, or something related to it.

 

SPOUT(SPark OUT) was on 1983-1994 Rangers, part of the TFI spark system

1995 and up spark system is in the computer, so no SPOUT or even similar