1994 E350 with 460 wont run when engine is warm. (motorhome)
 

Hello everyone. I have been lurking around this site for knowledge but I have run out of things to try.

The situation is as such.

The vehicle starts fine in all situations. Always. When it's cold (engine not ambient) it starts up and runs fine. But if I drive it from anywhere from 1 mile to 5 miles it runs poor. It will not rev up past idle much if at all. It back fires if I stay in the throttle. And I'm basically stranded and it won't move. When I turn it off anywhere from 2 mins to 5 mins it will start and run Above idle so i I can drive it home. Even when it's aflicted and not running past idle it will always start it I shut it down.
But once it's warmed up it will only run ok ( rev above idle) for a very short time
Usually less then a min

Things I've done and checked.

Fuel pressure........it's above 40lbs. I plumbed an in line pump in case it was a flow issue and even with all pumps it behaves exactly the same

Sparks changed out

Replaced pcm with used one. All same number. No change.

Distributor. No change

Throttle position sensor changed ..no change

Ignition control module. Changed no difference

MAP sensor. Changed no difference.

Coil. Changed no difference.

Fuel pressure regulator. Changed no dif.

The check engine light is not on and when checked all I get is 1-1-1

So I'm running out of things to throw at this thing.

I am hopping my set it issues can ring a bell to someone that might shed some light into what in the world is going on.

Thank you all

All the best.

Sounds almost like an old-fashioned vapor lock to me, but that isn't supposed to happen with fuel injection. I don't have a specific answer for you, but I'd be looking at the fuel system.

Sounds like it might be a bad Engine Coolant Temperature sensor (ECT) (the two wire sensor) or Intake Air Temperature sensor (IAT).
But back firing when the throttle is pushed down sounds like a lean fuel condition.
You need to have a fuel pressure gauge on the fuel rail when this happens to see if it is fuel or one of the two sensor I noted above.

Drive it with the fuel pressure gauge connected and see if it drops when the problem is happening. My guess is a clogged pick-up screen or maybe a bad pump. An inline can help a weak in tank pump, but if the flow to the inline is being restricted in the tank the inline can't do much.

Hi to all, by coincidence I just purchased a 1996 motorhome (Coachman Mirada) and have zero experience with the motor as Ive always been a 7.3 idi deisel user (F250,F350). Upon driving this newly owned rig to the house about 45 miles, It had issues of poor power and a little backfiring if you pressed the accelerator down and kinda tried to check the acceleration. After getting it home I was removing and looking to replace the broken air filter housing it had. The top part of the filter housing was busted and missing leaving a small diameter ( @ 1/4 inch black hose with no connection. I was suspicious of this causing my trouble and Subfords post on a Air Intake sensor really is interesting. I was going to start a thread of my own and probably will but just thought I would mention this broken Air filter box because of the similarity of backfiring and poor power. The rig had had an in tank fuel pump recently installed and It also causes me concern. My apoligies as Im not trying to hijack Soyomakates thread but because of the similarities described I thought this may help solve his and mine problem. Again thank all for their understanding as Im not very computer experienced.

So once you fixed the box with the hose connection did it fix the backfiring and poor power issue Remote95? Soyomakate how are your vacuum lines? I third the putting a gauge on the fuel rail and check while driving. Revving an engine doesn't demand much fuel compared to actual driving.

Remote95,
I am thinking a 1996 Coachman Mirada motorhome is a class "A" on a F53 chassis.
I am also thinking it has a fuel problem. You need to put a fuel pressure gauge on it and have someone watch it while you drive it.

Spaznaut, I aquired this motorhome 4 days ago and have only driven it 40 miles to my house. As yet I have not found a filter box replacement as ford says is obsolete. I wish I could answer you question but until I find a box I simply wont know.

Thank you subford for the advice. The Vin is 3FCLF53GOVJA00989 . I have posted on another site and curiously enough someone mentioned that because of backfiring it is possible that this caused damage to the air filter housing box, which would explain its condition. I wondered how anyone would have been negligent enough to rip this box apart ? The bottom is cracked lengthwise on one side and the top cover is busted apart with 70 per cent missing?

So following the fuel pressure gauge advice. I had previously just checked fuel pressure at idle while cold and it running well and I had 43psi. I left it connected and went for a drive. As usual it stalled. It would start right back up and idle but not rev up. And under these conditions I only have low 20s psi of fuel pressure. So I've ordered the pfs48 fuel pump. Will replace and report back.

Thank you.

Ps. I really don't see how damaged air boxes could have any detrimental effects. This engine does not have anything electronic to measure air from the air filter all the way to the throttle body is just pipping. So short of just sucking on hot air I don't even think the engine know if the air box is attached nor the piping

With that VIN you do have a 1997 F53 chassis and not an E-series chassis as the OP has.
The lean mix backfiring is out the exhaust and not the intake so no the backfiring would not hurt the air box.
You can get another air box form Colaw RV Parts & Salvage, 10389 Cimarron Rd. Carthage, MO 64836.
(417)548-2125 Email: www.colawrvsalvage.com
Actively dismantling hundreds of damaged RVs for the purpose of reselling used RV parts.

Where did you post the other Thread at?

I have a 1997 Damon Day breaker with 7.5 ford . Found the problem ! It would start and within a short distance would stable and loss power. Pressure dropped to 5 lbs. Had a shop put a new fuel pump 800.00 -- Drove for 100 miles and bang new pump did it again. nursed it home and took it to a different shop Rock River Trucks - they tested all the ignition and exhuast. Dropped the tank and found dirt around the fuel sock. Sent the tank out to have cleaned and new pump because they would not put the new pump in because of strain on pump. Well, $$$$ dollars later -- fixed..

This is a long shot but here it goes (this happened to me). Check your water pump. If it is in really bad shape, your engine block will get hot (very quickly) and boil your fuel.

I looked at a cherry Ford van on Craigslist. The guy was beyond frustrated after a tune up, changing both in-tank pumps, filter, etc. He was asking $600...said he would take $500. So I started it and it ran great for a few minutes, then sputtered out. I gave him his asking price because I felt like I was ripping him off. Once I realized it was getting hot, I changed out the water pump and drove it for 40k miles trouble free.

I would replace the Engine Temperature Sensor.

Mine went bad - I just replaced it a couple of months ago on my 1990 E350 with 460 engine. In my case, it would idle poorly when cold, but work fine when hot. My guess is depending on how the thing has failed, it could send the wrong temp to the computer - either hot or cold.

It is an inexpensive part, and is easy to get at from the front of the engine once you have removed the air cleaner box assembly. It's right on top of the engine, near the distributor, on the driver's side of the engine.

Steve

Any updates on your situation?

My RV is doing something similar. It is stumbling under load after it warms up.

Steve