Hi folks - This is a hail-Mary before doing the unthinkable ... taking my rig to the Dealer! Please help ... And thanks in advance for reading this long description and for your attention. And there's a beer in it for the first person that provides the fix!

This is a long sorted story and I hate to put it all here, but I also know if I don't I'll be called out for not giving enough information. I'm sure I'll be criticized for too much with this post, so I apologize, but I think more is better than less.

My rig: 2003 Ford E-350 Super Duty Cutaway (with a Turtle Top shuttle bus) with the 5.4L gas engine and Quigly 4wd conversion. I've built this up into my adventure vehicle, spending countless hours and money. I'm trying to keep this thing running, she's highly customized including an extended roof so I can stand up in it at 6'4". I really, really don't want to build-out another one nor do I want to get a mortgage to buy something new.

A year ago, at around 225,000 miles, I decided to swap the stock engine with a long-block, in an effort to ensure reliability and power since I frequently take this rig deep into the deserts and forests. I did not do the swap, I had it done at a garage and it came with a 3yr warranty. The engine swap went fine and she ran well after.

About 8,000 miles later, I started to notice a significant problem with acceleration and climbing hills. For example, hills that I can normally go up at around 50 MPH she'd bog down to 35 MPH. And she can barely get up to speed when merging on a highway if there's a slightest incline, she'll just run in 1st or 2nd at high RPM. Shifting seems rough and unexpected and she downshifts way too easily.

Nothing physical changed: same tires/tire pressures, similar weather conditions and similar vehicle weight

I've worked a lot with ChatGPT and other AI tools to help with troubleshooting as well as my own knowledge and an friend who's an engineer.

Since the engine swap was just a long-block, over the following month or two, I did the following in an effort to resolve the problem:

• Replaced air filter
• Replaced all plugs/coil packs with Motorcraft
• Tested and cleaned all fuel injectors
• Replaced fuel filter
• Replace Fan Clutch
• Visually inspected the engine for disconnected/loose wires, vacuum hoses, vacuum leaks, intake passages. Nothing awry was found

I took it to a muffler shop to have the exhaust tested. They found nothing wrong with exhaust flow

I took it to a Transmission shop, he agreed it was having some problem even with shifting but didn't feel it was related to the transmission or torque converter

Based on that, I replaced TPS & MAF sensors, but to no avail.

I got an OBD scanner and checked all the sensors it was capable of while driving, all sensors seem to be reporting expected and smooth values.

No codes, nadda

I took it to Davey Coach (where they build-up these Turtle Tops) and paid for a diagnostics. They found nothing with the engine but they were suspicious of the transmission, despite my report from the tranny shop.

I took it to a different tranny shop, they said the tranny seem bad. I had them replace it, with an OEM re-built, which included the torque converter. THIS MADE ZERO DIFFERENCE IN THE PERFORMACE

WTF?!

I tried to do a fuel pressure check at the rail but the shrader valve seems damaged, so I'd have to fix that for this test, but I replaced the fuel pump/sending unit about 3 years ago so this seems unlikely the problem

I haven't done a compression test yet, again given the new block, but I'm at a point I'll have to take it to a garage to get both that and fuel pressure test done.

One suggestion that keeps coming up is to check the EGR, I did not do this nor can I determine for sure that it even has one? Besides it sounds like the EGR impacts primarily idle.

Does anyone out there have suggestions? Are there other sensors that I missed? Can this be an ECU problem??

Thanks again!

 

Engine off key out then unplug the electrical connector of your MAF (not MAP which your van doesn't have), then start it up and get a CEL (ignore it) and get rough idling (ignore it) and drive uphill again. If this helps then you either have a bad MAF or bad wiring that needs cleaning or repairing. It's fine to drive without MAF for diagnostic purposes since the factory default air-fuel ratio will be used when your ECU can't locate the present of your sensor. When the test is done just plug the connector back in then the CEL will go away. This test takes just a few minutes to complete.
Another easy test is to remove the ECT (Engine Coolant Temperature) sensor (for ECU, not for cluster), remove just the electrical connector, then clean using electrical contact cleaner or 91% isopropyl alcohol. And of course you can also use a scanner to verify for proper temperature.

 

Thanks for the suggestion heiko, it will be a few days before I can give this a try. And thanks for the clarification, I always mix up MAF & MAP!

 

We do not know why the engine required replacement,,,,,,,,,,,but,,,,,,,,,,,,,if there was a misfire condition, the catalytic converter could be suspect.

Can you fill us in regarding that, thanks.

 

Like I said, I swapped the engine only to ensure future reliability. It was running fine, no backfires. And wouldn't the muffler shop caught the cat if that was the problem?

Weather has been extremely cold lately so I haven't gotten around to try Heiko's steps.

 

Did you ever get any print out of the data stream info when the "diagnostic " was done?

How was anybody able to do a fuel pressure test if the schrader valve was not available to use ?

 

No I did not get the data stream. The shrader valve will of course need to be fixed in order to get a fuel pressure test.

 

Heiko - I haven't gotten around to the drive test without the MAF, just been too snowy and cold to be motivated. I did confirm however the Engine Coolant data looks good on my scanner, it starts low when cold and seems to max out at 170 degF and is steady. I'll watch this on the road test to confirm it stays that way.

 

170 degree is way too low. Check below. You ever replaced your tstat and how long ago? A stuck open tstat can definitely cause lack of power.

 

Oh really! Ok good to know. I've owned the rig for nearly 10 years and I have not ever replaced the tstat. Is there value in un-plugging the coolant temp sensor for test drive too or just replace the tstat and then check it/drive it?