New engine, new headaches

[SportTracMoneyPit]

2007 Ford Explorer Sport Trac Limited 4x4 194,000 with a freshly replaced 4.0 remanufactured engine. (Factory engine jumped time at 157,000. Replacement engine also jumped timing under 40,000 miles and luckily was replaced for free under warranty due to a defective parts).

I also replaced the catalytic converters and Y pipe after the engine swap as they were plugged. Fresh upstream o2 sensors. I have not replaced the downstream sensors yet.

The engine idles decent. It has gone through a full drive cycle and there are no check engine light and no codes. Fuel pressure reads steadily around 40 psi on my scan tool at idle and maintains around the same during parked rpm pulls. The truck drives fine under light load. The issues start to crop up under acceleration. Overall loss of power and the engine begins to break up and you can hear backfiring in the Y pipe area which leads me to think it’s an air / fuel issue. The air filter is new. Plugs are new. Plug wires are new. Fuel filter is new.

I lean towards it being a fading fuel pump under load causing bad air / fuel mixtures, but I’m just burned out with chasing things. The fuel pump and injectors are one of the few original parts left on the truck at this point. With no CEL or codes to steer me, it has gotten frustrating. I’m blessed to have a lift in my garage, but not a formally trained mechanic, so maybe someone else has some insight before I start my next round of replacing parts.

Thanks in advance.

 

[Blown09]

Need to check fuel pressure while driving also(loaded engine will put higher load on the fuel system). If pressure stays constant, that would rule out pump, and filter, but not injectors.

If you can watch airflow rate, via maf pid, that would also help.

Was it a complete reman, or did you have to swap your intake manifold?

Did you clear the ecm completely?

 

[SportTracMoneyPit]

It was a fully remanufactured long block with some reused parts including accessories and intake. ECM was cleared and codes removed from when the motor timing jumped. It’s gone through a full drive cycle and all systems seem to check out, but no CEL and no codes.

 

[SportTracMoneyPit]

The heads were trash as a valve broke completely off when it jumped. Block, heads and rotating assemblies are remanufactured.

 

[SportTracMoneyPit]

Need to check fuel pressure while driving also(loaded engine will put higher load on the fuel system). If pressure stays constant, that would rule out pump, and filter, but not injectors.

If you can watch airflow rate, via maf pid, that would also help.

Was it a complete reman, or did you have to swap your intake manifold?

Did you clear the ecm completely?

I took it for a run today with the scanner hooked up and watched the live data. Under heavy load fuel pressure dropped to 25-26psi vs the steady 38-40 at idle through the scanner. It was breaking up prior to the low fuel pressure flashed up and went back to normal. I would imagine it’s pretty safe to say the fuel pump is fading… but could it be the fuel pressure regulator? I’m more of an old school carb guy. I get a bit lost in the FI / TB stuff.

 

[Blown09]

I know you said the fuel filter is new… but how new is the fuel filter?

Doesn’t take but one tank of bad gas to clogged a filter up. Could pull the filter and give it a drain(backwards of flow) and see how nasty it is-or isn’t. At that point, I would suggest a fuel pump.

Unless the Fuel Pump module is acting up, but I don’t recall them failing in this way.

 

[SportTracMoneyPit]

The filter is literally miles old. Old one wasn’t that old, but I had a fresh filter in a box so I swapped, but the problem is still there.

 

[SportTracMoneyPit]

one of my neighbors had access to Forscsn and we scanned it. No stored codes. Took some shots of the live data and did a full ecm reset. Going to run it through a few drive cycles, but the problem is still there. Nothing stands out besides some differences in bank 1 and 2 LTFT. Scratching my head on this one unless there’s a vacuum or intake leak letting unmetered air in and throwing the air fuel mixture off.

 

[Todd Z]

Replace the fuel pump driver module.... Above frame under back of truck, Drop spare to find.... Its aluminum bolted to steel. It corrodes and causes all sorts of hell.

 

[SportTracMoneyPit]

So, after a month plus of this, I finally got 2 codes. P2135 and P0122. All throttle position sensor related. Makes sense with the terrible acceleration and power loss. The readings from the tps did not match what was really there. After some quick googling and forum searching I have the culprit. The terrible workmanship of the mechanic that swapped the motor.

He had damaged the wiring harness to the tps and taped it up and attempted to make it look stock. Started cutting back the harness and found more dry rotted wires from the years of baking under the hood. Going to replace the destroyed wiring and will update in the near future.

Without codes to point you in the right direction, you can end up on some wild goose chases.

Glad I finally caught it.

 

[SportTracMoneyPit]

I still have the issue after splicing and reinstalling the original connector back on. There was enough slack to cut out the damaged sections and still reach the sensor. There’s a possibility the sensor was fried with the bare wires crossing. If the new sensor doesn’t correct it I’ll have to dig deeper.

 

[SportTracMoneyPit]

I need to also to do a full reset to clear out the bad fuel trims from the previous issue. I will update when I get to working on this again.

 

[JohnPenny Peluso]

I need to also to do a full reset to clear out the bad fuel trims from the previous issue. I will update when I get to working on this again.

 

[carl beasley]

Whew.... I'm thinking of doing a Reman long block my self. Now me thinks, perhaps not...... Good Luck chasing this one down.
Carl

 

[Todd Z]

Fords wiring always has SUCKED !!!!

 

[Blown09]

Maybe I missed it…. Have you rectified the low fuel pressure issue?

 

[SportTracMoneyPit]

Maybe I missed it…. Have you rectified the low fuel pressure issue?

I haven’t had a chance to dig in deeper. This is a spare vehicle, so it hasn’t been a huge rush.

Finally getting a code on the tps sensor has me running that one down before I go back to the fuel pressure dip I was receiving. With the fuel trims compensating for false tps readings and not matching true air / fuel readings, I’m not convinced yet that it’s not all related to the tps… but this is like herding cats. Trying to tackle the tps first.

Hoping to get the new tps in tonight. Clear the ecm and see where everything stands.

 

[SportTracMoneyPit]

Whew.... I'm thinking of doing a Reman long block my self. Now me thinks, perhaps not...... Good Luck chasing this one down.
Carl

Factory motor lasted to 157k
1st reman motor lasted to 194k.
I only have a couple hundred miles on this one… hasn’t run right yet.

 

[SportTracMoneyPit]

Swapped in a new tps. Factory harness was spliced, soldered and heat shrunk before being wrapped in electric tape. Cleaned the throttle body. Inspected gaskets, harnesses and vacuum lines while it was partially disassembled.

Put it back together and it’s still running like garbage with no codes. Haven’t had access to my neighbor’s forscan yet to fully reset the ecm, but it seems like nothing has changed as far as the way it runs. Maybe with the fuel trims cleared it will be a different story.

I’m just amazed with all the sensors that something is still able to fly under the radar and not throw codes.

 

[SportTracMoneyPit]

Found a second damaged harness with crossed wires. Cut, soldered and fixed, still no change, except the electric fan seems to be working better now.

Finished the drive cycle from ecm reset and drove it (running terrible) to the state inspection station and it passed. No codes still.

On the way home it finally threw a random misfire in cylinder 3 code. I had taken the mechanic’s word that he put all new plugs in. When I pulled the plugs I found 5 were motorcraft and the last was an autolite. Interesting. Cylinder 3 was fouled badly. I cleaned the MAF and I replaced all 6 with fresh plugs and took it for a test drive.

Runs like a top with no hesitation or stumble up through 80mph. Before the plug swap it wouldn’t go above 50 without stumbling and backfiring.

I think this was a combination of electrical gremlins from the crossed wires and me not doing my due diligence and taking the mechanic’s word on the plugs. I’ve always been told to start with the basics and this time I overthought it.