Flushed heater core now truck won’t run, misfire on all 6 cyclinders.

[fastpakr]

My 1994 4.0l 4x4 manual has all its original sensors and controls, except for O2's which are the only sensors that do wear out, 12 years or 100k miles

I did change the 3 capacitors in the computer a few years ago

I've had to swap a few DPFE's, but other than that I can't remember replacing any sensors.

 

[RonD]

Yes, DPFE sensors are effected/ruined by the moisture in the exhaust so I will agree that O2s AND DPFE sensors both wear out over time

DPFE sensor reads pressure in exhaust system to see if EGR valve is opening and closing like it should
If you don't have an EGR system then you don't have a DPFE sensor

Exhaust has water vapor in it, that's why tail pipe drips water out and why exhaust systems rust
So the hoses to the DPFE sensor have water vapor in them
The 2 pressure chambers in the DPFE sensor have that water vapor condensing inside them every time engine cools down
Over time that will cause a fault

 

[smythcounty]

Welcome to tonight’s episode of ‘What It‘s Not!’
1) I replaced the fuel filter, no change.
2) Seafoamed the engine, no change. (But engine ran great with MAF unplugged and shooting seafoam into intake.
3) Replaced IAC, no change.
4) Replaced Air temp sensor, no change.
5) Replaced MAF sensor, no change.
6) Fuel pressure - 6 psi at key on, 22-24 psi while started.
7) Replaced Ignition Coil, no change.
8) Throttle position sensor wasn’t in stock so couldn’t swap it.

I’m leaning towards swapping plugs and wires, I changed them about a year ago, unless someone else has some suggestions. When it does idle, it idles crazy rough, almost like a cammed up muscle car and I hear a backfire sound from the engine when you try to give it fuel.

 

[fastpakr]

Fuel pressure is a huge red flag.

 

[RonD]

YUP
1999 Ranger should be 60psi fuel pressure
So 24psi is way bad

1997 and earlier were 30-35psi but yours ain't that system, in case you saw those numbers applied to Rangers

 

[smythcounty]

So fuel pump? Is it possible my gauge isn’t reading correctly? What else could be causing low fuel pressure. I changed the pump four years ago. I still go back to the water in the engine compartment and it started immediately after.

 

[alwaysFlOoReD]

Fuel.pressure is too low. Pump or filters. Filters are cheap.

 

[smythcounty]

Can I change the cam shaft position sensor without messing with the synchronizer?

 

[fastpakr]

Can I change the cam shaft position sensor without messing with the synchronizer?

Why?

Replace nothing at all until you've resolved your fuel pressure issue.

 

[bobbywalter]

If I had a nickle for each time I said "firing order IS CORRECT" when it wasn't I could have retired at 25, lol

But that's really all there is in a 1999 4.0l

Long shots would be:
Shorted out condensor on coil pack, just unplug it, its for radio noise suppression
water/coolant inside Cam sensor
water/coolant inside 104 pin computer connector on firewall

After 1995 Rangers just are not that complicated

There is a reason I wanted you to unplug the maf . Shorting the pcm causes a few issues...


The fuel pressure regulator is in the tank on a 99 iirc...the screen could be plugged up or something got by and is janking up the regulator, or there is a power issue.


What codes with maf unplugged?

Cmp unplugged

 

[smythcounty]

There is a reason I wanted you to unplug the maf . Shorting the pcm causes a few issues...


The fuel pressure regulator is in the tank on a 99 iirc...the screen could be plugged up or something got by and is janking up the regulator, or there is a power issue.


What codes with maf unplugged?

Cmp unplugged

With the MAF unplugged I get a low circuit code from MAF sensor. I haven’t unplugged the Camshaft sensor.

 

[RonD]

You are "out of gas"...................with pressure at 24psi

You can change the spark plugs, change the computer, change the cam sensor, even check the air pressure in the tires, but you will still be OUT OF GAS

If you have a flat tire you don't change the oil to see if that fixes the flat tire, trust me it won't

 

[bobbywalter]

Ok ... Your pcm seems to be working.

Now. How long does it take to bleed down fuel psi after engine is turned off?


Might just need to re clamp or replace hoses on sending unit

I put good clamps on the one in my Jeep that the hoses were leaking by..then the hose broke at the crease above the clamp... right off...leaving my daughter stranded ...then I got to do it again....except that time with new hose and clamps. Like I should have the first time...


Problem solved....both times...just lasted longer with new hose. That idled good....just had low power and backfired with low fuel psi.


Or your grounds corroded at the pump ....or the pump is crap


Need to have a gawk in there

 

[Eddo Rogue]

I do it all the time -- even when I know what I'm doing - which is rare...

View attachment 70729

My parts cannon seems to result in the storage of surplus ammo.

 

[smythcounty]

Ok ... Your pcm seems to be working.

Now. How long does it take to bleed down fuel psi after engine is turned off?


Might just need to re clamp or replace hoses on sending unit

I put good clamps on the one in my Jeep that the hoses were leaking by..then the hose broke at the crease above the clamp... right off...leaving my daughter stranded ...then I got to do it again....except that time with new hose and clamps. Like I should have the first time...


Problem solved....both times...just lasted longer with new hose. That idled good....just had low power and backfired with low fuel psi.


Or your grounds corroded at the pump ....or the pump is crap


Need to have a gawk in there

The fuel bleeds down almost instantly. I’m at the fuel pump now. Have the left hose off the pump but cannot get the right hose loose. I tried the plastic and metal disconnect tools. Not sure what’s keeping it from being released. Maybe I have the wrong size. Does anyone know what size disconnect tool I need?