Hot weather problem

I have a 1992 Class C motor home with a 460 Ford Motor. It runs great until the temperature outside gets near 100, then it misses, backfires then quits. It acts like an old Pontiac we had in the 60’s that vapor locked. No one can find anything wrong and it always runs when the temp cools. It does not register hot nor does it overheat. I recently drove from Oklahoma to Florida with no problem but going around Jacksonville on a hot day it died. I made it home fine but last week in the Oklahoma panhandle it died again. I had a great-grandaughter with me and we played cards until the sun went down and it ran. (I am really thankful for generators and air conditioners.) I am frustrated as I travel alone most of the time. One mechanic, after checking everything, suggested I watch the weather channel and just park it if the temperature got over 95.

As a guess I would suspect the fuel pump first or the power connection to it. My second guess would be the crank sensor.

Check the ignition module. You describe a classic symptom of Ford ignition module failure for the early 90’s.

Cougar, thanks for the suggestion. Is this something that should show up when they check it on the computer?

tardis, thanks to you also. I will have a mechanic check it out.

We have what sounds like the exact same problem. We are travelers too with a 1992 Airstream class B motorhome 460 engine. Ours started in AZ climing moutains in the Tonto Basin and repeated a few times in the moutains of Or, Wa,. Seems to be getting worse; happened last week in Odessa TX in 80 deg. temps. in traffic.Ran ok after getting out of town. Noticed the smell of raw gas a few time during these events. Also noticed the fuel consumption is getting poor. Help, let us know if you solved the riddle.

I haven’t solved it yet. Should know by July when the weather gets hot.

I removed the ignition mod. and had it checked, no problem even after gitting it warmed up and trying it continuously fpr at least ten times. I talked to a guy with a 95 motorhome who said he had similar problems. He added a external fuel pump to boost the pressure; said that did the trick.

Thanks for the information. I am not having much luck finding a mechanic that wants to mess with it. I will keep trying.

Where are you located? I try to do most of my own auto work. I have not been all that happy with outside work I have had done and It is expensive. I have not had the problem lately but I noticed a lot of pinging even under a moderately heavy load so it might be running lean. I plan to check the fuel pressure next. The problem is I have never had the problem except when hot out. I guess the only time testing might do any good is when the problem happens.

I live in north central Oklahoma. Actually 20 miles from Kansas.

It did it again in Hobbs NM. I am spending the night by a Autozone. Planning to test the fuel pressure in the morning.

I tested the fuel pressure today while running the rig hard and after about a hour the pressure started going down. Pressure is supposed to be between 28-45. When I first tested it was at 39 snd it stayed there for a long time until I started running it hard in the heat of the afternoon. When I ran it for about an hour under a load in the heat the pressure started going down and finally after it went down to 20 and lower and the engine stalled. I started installing a new pump this afternoon. I will let you know what happens in the future.