Final troubleshooting for Ford 460 motorhome, advise?

[TheWanderer]

Hello again everyone!
Been a while since I got a post up concerning the major work I have been doing on my 1988 gulfstream motorhome with the ford 460 7.5L V8.
I was very successful finally in getting the reman crankshaft and new bearings installed, as well as oil pump, oil pan, and other parts listed below over the last 2 months.
I am now to where the engine will start well, idles fairly well (maybe not perfect) and revs well returning to idle rpm correctly. It has been an insane battle to get to this point every step of the way. Haha
Almost all of the issues are resolved now. The new oil pump fixed the oil pressure issue, the new crank and bearings are running smoothly, and the issue starting when the engine is hot seems like it was the fuel pressure regulator I replaced.
Seemingly the final issue I am facing is a lack of accelleration and power when starting from a stop. Not that the engine isnt trying, it sounds like it is trying to climb a hill. Understandably this is an 11,000 lb motorhome fully loaded, but I am talking craaaawling from a stop until I hit at least 15 or 20 mph and then it seems to level out and stop working so hard for so little and run better. There seems to be a strong rich exhaust smell afterwards as well which leads me to assume incorrect air/fuel mix for one reason or another. The fuel pressure regulator fixed the issue not turning over when hot, but the lack of power from a stop remains. Doesnt sound like misfires or any lurching in speed, just lack of. The issue does seem more prevalent once the engine has warmed up, but I feel even from cold start it isnt quite what it should be.
I just patched a small leak in the EGR system just prior to the EGR valve, as well as cleaning the valve itself (it wasnt that dirty) but havent had a chance to run it since.
Through researching it sounds to me most likely to be either EGR, fuel pump or filter, fuel injectors, or possibly an ignition coil issue (though the engine starts just fine now) maybe I am missing something but what do y'all think would be tbe next best step?
I will list all the parts replaced in the last 2 months below:
Crankshaft
Main bearings
Rod bearings
Oil pump
MAP sensor
PCV valve
Purge valve solonoid
Checked and replaced any problem vacuum hoses
Starter
Battery
Fuel pressure regulator
All spark plugs
All plug wires checked
Timing checked
All new seals for pans and covers
Full fluids change with Lucas additives

[enblethen]

Thanks for the update!

[TheWanderer]

Hey everyone just a happy update.
Got the catalytic converterfor the RV squared away and my lack of power improved! At this point all planned repairs are completed. She starts, idles, and runs well, and is ready to hit the road again!
It has been such a huge battle between replacing oil pump, pan, crank and bearings, exhaust components, battery, and so so much more. Really feels good to see her running (nearly) perfect.
Thank you all for the advice and help! I really appreciate it.
I am sure I will check in now n then and when more inevitable repairs ensue! Happy Trails. 🙂

[enblethen]

PIP
Profile ignition pickup
This is what previous poster is talking about, I think!

[TheWanderer]

maillemaker wrote:
I just had to replace the cat on my 1990 E350-RV with 460 engine. I had an overheat last year and I believe this cooked the PIP, Engine temp sensor, and the cat.

You might find an old-school shop that will straight-pipe your cat (cat delete), or you can do it yourself. With that old an RV as was pointed out you won't have an O2 sensor downstream of the CAT so no check engine lights to worry about. If you live in a state that doesn't do emissions you can get away with it.

I could not get my cat off by myself so had to have a shop to it, so I had to have a cat put in.

Thanks for the heads up! Were you also experiencing issues with lack of power under load?
Also what is the PIP?
I had to wire in my own dash sensor and gauge for temp (as well as replacing engine temp sensor) but thankfully thermostat and water pump and all that still work as they should.

[jkwilson]

maillemaker wrote:
I just had to replace the cat on my 1990 E350-RV with 460 engine. I had an overheat last year and I believe this cooked the PIP, Engine temp sensor, and the cat.

You might find an old-school shop that will straight-pipe your cat (cat delete), or you can do it yourself. With that old an RV as was pointed out you won't have an O2 sensor downstream of the CAT so no check engine lights to worry about. If you live in a state that doesn't do emissions you can get away with it.

I could not get my cat off by myself so had to have a shop to it, so I had to have a cat put in.

It would be rare to find a shop. Fines are pretty bad if they get caught.

OP, look around on the web for a “test pipe”. They are made so you can take the cat out and put the test pipe in to see if the cat is the problem. Wink wink. Nod nod. Say no more!

[maillemaker]

I just had to replace the cat on my 1990 E350-RV with 460 engine. I had an overheat last year and I believe this cooked the PIP, Engine temp sensor, and the cat.

You might find an old-school shop that will straight-pipe your cat (cat delete), or you can do it yourself. With that old an RV as was pointed out you won't have an O2 sensor downstream of the CAT so no check engine lights to worry about. If you live in a state that doesn't do emissions you can get away with it.

I could not get my cat off by myself so had to have a shop to it, so I had to have a cat put in.

[jrloucks]

I have a Class C with a '84 Ford e350 XL chassis, 460ci engine. Holley Carb, LIST-50005-1. At one point she would stumble from a standing start. The problem was caused by a faulty (leaking) accelerator pump on the carb. This little pump squirts more fuel into the carb when the accelerator pedal is pressed (standing start). I replaced the pump diaphragm (required removing the carb from the intake manifold), and this fixed the leak and standing-start stumble. I have pictures I can share if that'll help.

[TheWanderer]

Yeah they can do that, but thankfully due to the age of this vehicle there isn't even a downstream oxygen sensor after the cat or on the cat itself. Just a single sensor prior to the cat.
Exhaust Manifolds --> Header Pipes --> Inline 02 Sensor --> Converter --> Muffler --> Tailpipe.
EGR system feeds from header pipe as well as the top of the cat.
Sweet and simple. Haha

[opnspaces]

Sounding promising, thanks for the update. Definitely look over your whole exhaust system as sometimes the manufacturers put in a pre-cat upstream of the actual converter.

[TheWanderer]

Ok well i am definitely leaning towards the catalytic converter being plugged now. Havent actually removed it to inspect visually yet but I loosened the bolts in front of the cat to create a 1/4 inch gap or so between the flanges, then took it for a test drive all the way to having the engine hot about 15 minutes or so.
While the issue isn't 100% eliminated by doing this, it is NOTICABLY improved. Particularly accelerating from a stop even when hot, and perhaps a smoother idle. Even the higher range speed acceleration is seemingly improved a bit.
Not a concrete proof with only one test drive so far, but definitely something.
Going to look into cat work this weekend I think.

[opnspaces]

I think they melt down from the front to the back. So you might be in luck as far as inspecting it.

[TheWanderer]

Thankfully I have some experience in cutting exhaust components and reconnecting with a good strong steel sleeve and U-bolts. Always seemed to do the job well if everything is sized right.
Definitely will have to take a peak inside before if possible, the front is bolts and gasket style, back is welded.

[opnspaces]

If the cat is bolted on see if you can unbolt it and look through it. That vintage might be the old pellet type that you can't see through. But if it's the new honeycomb style it will be obvious if it's plugged or not.

While I would never recommend defeating emission components long term. If the cat is plugged you can probably knock the center out for a test.

If it's welded on you're going to have to go to an exhaust shop to have it cut out and inspected/replaced.

[TheWanderer]

Ok so right off the bat, temperature test for the cat does not look good.
The area after the cat stays about 1/2 the temp compared to before entering the cat. (Eg: last scan was 547 degrees before cat, 283 after, scanning the first and last 6 inches of piping with IR gun and reading max temp. Scan before that was 419 vs 218.)
I am taking this as to mean my cat is likely plugged up either due to build-up or melting from overheating? Would explain the engine struggling more under heavier loads when more exhaust needs to be pushed through, as well as why the problem worsened so noticably after it overheated.
Real bummer if so as it is about a $400 part, but at least I have some indication to what might be causing the issue.
Thoughts and opinions?