2.5L ('98-'01) 00' 2.5 - Low Miles - Engine Stumbles/Dies

[Bdbrown502]

2000 Ford Ranger 2WD - 2.5 automatic - 94k original miles

Engine is surging up and down intermittently at idle once warm. While driving I get a major loss of power. At freeway speed the engine stutters and seems to jump out of gear, revs freely then rolls or slams back into gear. As of last night, it now dies when this happens. I was able to restart after a few attempts.

With each stumble or surge of the idle, the fuel pump relay clicks. Relay tested and good.

Parts replaced:
IACV (aftermarket and OEM)
new plugs. coils and wires (tested)
new MAF (aftermarket - I suspect this to be an issue. Should I buy Delphi)
injector 1 and 2 (had previous cylinder 1 misfire intermittently - code would come up the truck would idle poorly then it would clear itself automatically) NOTE: this all started after replacing the fuel injector 1. However, I have confirmed everything is put back together.
Battery is strong.
Alternator replaced.
Fuel pump (pressure reads 65psi at idle - stumbles down to 60 with each stutter or surge and kicks back to 65psi.)
Fuel pump relay
Fuel tank pressure sensor
TPS
EGR sensor

No CEL. CEL does flash occasionally when idle stumbles.

I am completely lost here. I am starting to think this is either the result of a Duralast MAF or a bad PCM. However, I have a hard time believing that it is the PCM. No visible damage and the truck starts every time no issues, unless of course it just died on the freeway. I have had constant issue with idle and drivability with this truck since purchasing 30k miles ago.

Any advice helps!

 

[SenorNoob]

When the check engine light flashes, it's recording a misfire. Even if the light goes off, it should still have recorded code or 2.

 

[Bdbrown502]

Appreciate the response!

I drove the truck about 7 miles yesterday to the store and back with absolutely zero issues, aside from some hesitation rolling into first gear from a stop. However, I drove around the neighborhood a few times before then, it stumbled and stalled on one of the 3 trips taken. In total, since replacing the fuel pump (again) and the fuel pressure sensor, I have driven about 50 miles. No CEL or recorded CEL found on the scan tool. Almost like the issue does not "stick around" long enough to register a fault code. Even though it completely stalls the motor and restricts re-start occasionally. Very strange...

also, I have tried to test the MAF sensor. Unplugging the sensor will kill the motor. If I unplug and hold RPM at roughly 2000 manually, the truck still hiccups. So, I am fairly certain the MAF is not the issue.

Leaning more towards PCM. Finding one locally to test is another issue all together.

 

[scotts90ranger]

A dirty MAF is more suspect than anything or a ground issue somewhere...

Going the parts cannon route is NOT recommended, especially over the last couple years, new does ABSOLUTELY NOT mean "good"

For a reference it's almost never the engine computer... my '90 is running a '85 ECM and at times there's water running over the stupid thing and it just works... corrosion in the connector sure you'll get that

If you have something that will read live data I've heard the MAF output should be roughly the displacement at idle so like 2.5 g/s at idle...

 

[Bdbrown502]

A dirty MAF is more suspect than anything or a ground issue somewhere...

Going the parts cannon route is NOT recommended, especially over the last couple years, new does ABSOLUTELY NOT mean "good"

For a reference it's almost never the engine computer... my '90 is running a '85 ECM and at times there's water running over the stupid thing and it just works... corrosion in the connector sure you'll get that

If you have something that will read live data I've heard the MAF output should be roughly the displacement at idle so like 2.5 g/s at idle...

Appreciate the response, Scott.

To give a little context, after replacing fuel injector 1 (twice) to chase a "Cylinder 1 - misfire", I started getting these issues. I then replaced the MAF under suspicion that this was going bad. Granted, with a new Duralast unit (not recommended, I get that). While my misfire code went away, all these other issues started after then injector install but, before the MAF install.

I can pull the MAF off and the motor will instantly die. If I hold RPM's I still get stumble and the relay triggering. While all external factors point to a MAF issue when its removed, I still have issues. I have considered forking out for a DELPHI unit. However, I am fairly confident that the MAF is not my issue.

Going to test for vacuums leaks around the intake manifold again this evening. No leaks were present previously. The PCM is the last thing on my list, aside from some phantom intermittent ground issue. My thought process is, if it were ground issues, they would be present constantly not, intermittently.

Thoughts?

 

[scotts90ranger]

Have you watched live data? What is the fuel trim value showing at various operating conditions if it will stay running? Say at idle, 25mph, 35mph 45mph and 55mph just to cover the spectrum of some operating conditions. That should give an idea of how far off it thinks it is on fueling at least. I wouldn't be too surprised if the oxygen sensor could be bad too (that I'd think is safe to change, they're a wear item unlike most sensors)

I know low miles the compression should be good but have you checked it? doesn't mean something dumb isn't going on, I know someone that got a 2.5L Ranger for cheap because a valve spring broke, replaced it and it's been fine...

I'll keep thinking about things and will try to post back...

 

[Bdbrown502]

Have you watched live data? What is the fuel trim value showing at various operating conditions if it will stay running? Say at idle, 25mph, 35mph 45mph and 55mph just to cover the spectrum of some operating conditions. That should give an idea of how far off it thinks it is on fueling at least. I wouldn't be too surprised if the oxygen sensor could be bad too (that I'd think is safe to change, they're a wear item unlike most sensors)

I know low miles the compression should be good but have you checked it? doesn't mean something dumb isn't going on, I know someone that got a 2.5L Ranger for cheap because a valve spring broke, replaced it and it's been fine...

I'll keep thinking about things and will try to post back...

Funny you mention that, I am now starting to track these conditions. I should mention that both o2 sensors are roughly 2 years old. Right now, I've only been able to drive it around the neighborhood a few times and have not experienced any issues at all. I did notice however that "O2 Sensor 2 Bank 1 Short Term Fuel Trim" is not registering any % (see image). It seems to have voltage. It has also showed as "n/a%" Additionally, I am getting approx a 10% swing from -5% to +5% on "O2 Sensor 1 Bank 1 Short Term Fuel Trim". Is that normal?

Granted these are all on normal operating conditions. I have not been able to replicate the poor driving and stalling conditions since Monday night. But I have not taken it on the freeway.

Appreciate your help with this!

 

[scotts90ranger]

Other than the MAF flow rate being higher than I've heard it should be (I have very little experience looking at this so yeah...) nothing looks out of wack there... Usually there's not a fuel trim for the post cat O2 sensor, it's just a monitor for the catalyst to make sure it is working.

Intermittent problems suck and they're usually something stupid like a chafed wire or a rusty ground...

 

[Bdbrown502]

Appreciate the feedback.

It is very troubling as I have all the confidence in the world, until it stutters/stalls and all that confidence goes out the door.

I will be sure to record the readings when I am having issues. That should be more telling. Tomorrow is my WFH day so, I will be consumed with resolving this. Thanks again!

 

[Bdbrown502]

So... I believe I have finally settled on some sort of PCM issue.

After replacing just about every part on this motor and having no CEL codes, I went ahead and started to hyper focus on the PCM. Before finding a replacement, I went ahead and started with the PCM relay. While the relay bench tested "ok", I figured maybe, just maybe, there was an intermittent fault within the circuit causing the PCM to lose power randomly.

Replaced it and immediately could feel the difference. Three days later, driving around town, absolutely zero issues. It did not stutter, stall or misfire. Then boom. All the sudden I start it up last night leaving a comedy show back to square one. The idle bounced around for minutes, eventually stalling twice at idle. Thankfully, after getting it to settle, I was able to limp it home with only minor freeway hiccups (10min drive).

This morning, absolutely no issues until about 10min into my drive, hiccups on the freeway, the engine stutters, pops out of gear, free revs and then rolls back into gear. Sometimes slamming.

At this point, I have nothing else to conclude besides faulty PCM. While the relay improved my issues, it did not eliminate them. Certainly, open to any opinions here. I've checked for wiring issues and vacuum leaks, with no luck.

 

[Bdbrown502]

I was able to drive it to work with a few minor hiccups on the freeway. No stalls.

Went to start the truck again and it would not hold the idle. Fuel pump relay keeps clicking randomly causing rough idle and ultimately, stalling the motor.

I have pulled the wiring diagrams and have confirmed that the relay is getting power (both constant and key on). I do however notice a slight voltage drop with "key on" from 12.4 to 12.1-12.2 that mimics the "surges" I get at idle. Would that cause the relay to trigger and the fuel pump to cycle on/off? I am assuming not...

When I pull the fuel pump relay, I hear another relay located near my transmission that is also clicking or cycling on/off mimicking the surges I get while the motor is running.

Lastly, with Key On/Engine off the CEL flashes on and off at the same time the fuel pump relay clicks. I read that means the PCM is losing power and/or there's an issue with the PCM itself.

Has anyone had a similar experience?

 

[DeeRanger]

Sorry if I missed it earlier, but did you replace the fuel filter ?

 

[Bdbrown502]

Its about 1.5 years old.

I am 95% certain that the issues are electrical at this point. I am getting power at both the PCM and Fuel Pump relay (constant and ignition). I confirmed that power is getting to the PCM with a probe. I also confirmed that inertia switch is working.

Today, the truck hard a very hard time idling and after removing the PCM, checking for power and ground, it won't even trigger the fuel pump relay. I am assuming that the PCM is crapping out on me.

Ordered a new one on the way. Finger crossed this gets it done.

 

[Blmpkn]

If you have something that will read live data I've heard the MAF output should be roughly the displacement at idle so like 2.5 g/s at idle...

Neat. Logging this away in the ol brain.

 

[Bdbrown502]

Update: Replaced the PCM and of course, same issues persist.

My next solution was to "rig" a switch into the fuel pump relay location. This allows me to flip the fuel pump on and off. Since making that switch I have had zero issues with stalling and surging. Something is clearly triggering/cycling the fuel pump to turn on/off. The truck gets me from A->B now. However, I have very little power and intermittent rough idle.

Since installing the fuel pump switch, the CEL now flags a P0453 CEL (EVAP Pressure Sensor - high input). I read on another forum that the new PCM (from the same supplier) caused the CEL and issue. Hoping my CEL goes away however, this is clearly just a temporary solution to get me from work and back. I've read through, tried and replaced every component associated with the fuel pump relay. I am completely at a loss and at this point tired of dumping money and most importantly my time into it.

Planning to drive it into the ground and swap in a 5.0 in the next year or so.