Thread: 96 Ford F53 460cu in runs rough at operating temperature only.

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Normally I would be talking about my 71 GTO 455HO 4sp but this time I need help with my Ford 460 in my 34' Motorhome...........just think of it as a big hot rod!!

Last spring I installed a Gale Banks Power exhaust System/ram air. The increase in power was unbelievable. When I parked the Motorhome for the winter last fall it was running good. I started it at least once a month during the winter as usual. I have 44.000 mi on the motorhome. 8700 mi ago I installed a new rotor/distributor cap, spark plugs (Bosh Plat 4) and Accel hi performance ignition cables. The coil was not touched.

This spring I found it was still running as good as ever until the engine reaches normal operating temperature. Then even under light acceleration the engine runs very rough, shudders and lacks power. If it is stopped and cools down for about 10-15 min it will almost burn rubber when compared to when it is hot.

I have been a “back yard mechanic” all my life but I gave up and brought it to my local garage mostly due to the lack of the needed analyzers etc. I will summarize:

1. On their portable analyzer there were no codes to read but the EGR voltage was not according to spec so it was changed along with its sensor and then gave the right readings but did nothing for the problem.
2. Again on the analyzer the oxygen sensor kept switching in and out of a closed loop which could cause the motor to run lean – that was changed – still same problem.
3. I greed to try a “Motorvac CarbonClean Fuel System Service” (www.snapon.com) to cleanout the Injectors and any carbon deposits from the valves and piston rings. Still the same problem.
4. Since I have recently changed the fuel pump, I suggested to check it and its pressure checked out good and we tried it with their external fuel pump (RV pump bypassed) and the problem was still there so it is not in my installation of the new pump. Running the engine both ways the 460’s regulator provided 30 lbs pressure and the specs say 30-40 lbs is normal. I am a little bothered that the reg is at the lower end of the scale.

The next thing on the list this week is to do a complete engine analysis to check out the electrical system and see if the spark is breaking down, bad coil / sensor when hot etc etc. This takes about 2 1/2 hours. The garage lets me stay right with them as they troubleshoot so I know exactly what is being done. What has us baffled is that on their portable analyzer a lean condition shows up when acceleration lightly under load………..but why. Both a bad EGR and oxygen sensor could have caused this – since they are now new, we know that it has to be something else. The one thing they mentioned as they were not familiar with the Gale Banks exhaust is that the oxygen sensor is moved from the exhaust manifold (extension cable provided by Gale Banks) to much further down the exhaust pipe.. They were wondering if the oxygen sensor gets hot enough in this new location to give the correct readings to the computer – I think that Gale Banks would have thought of that. (I have called the Gale Banks Corp. and they said they have hundreds and hundreds of the system sold for 460's and this has never reported to cause a problem)

Has anyone ever had this problem with a hot engine? Please remember that it has unbelievable power until it gets to operating temperature. To be exact the problem happens precisely when the temp gauge gets to the letter “r” on “normal”!! (does not read out the exact temp but their analyzer showed the water temp to be 193f) Any suggestions would be appreciated before I have to re-mortgage the house to pay for the bill when I get it!

i'd check that thermostat closer. if its opens to soon it will make the computer run to rich.

The continuing story..................

Today we road tested with a fuel pressure tester hooked up to the rail and under load when the shudder/lack of power was happening the fuel presure stayed at 38-40lbs thus eliminating the new fuel pump, filter and the existing regulator.

I tried to cool things down with a gardon hose (wetting sensors one at a time to see if the problem would go away while in my driveway put although last week it did it easily when loading it down with the foot on the brake, now it seems to need highway driving and it took about 3 miles at 50 mph before it reeked its ugly little head again.

Tomorrow morning we are going to scope out the entire ignition system. Has anyone ever heard of a fuel injector breaking down when hot? The thing is that when driving it with the dog house off it seems to be more of a miss at times when it happens.............but still could be air fuel ratio.

I don't count sheep to go to sleep anymore - I count plugs and ejectors!!

Denny- that is a no to the airflow sensor.

One othger thing - yesterday morning I drove for 60 miles in unusually cold conditions for this time of year (about 45 f) and it the problem was gone! Today it is about 65 and the problem is there after a shrot time at highway speeds.

Originally Posted by fallowfield

One othger thing - yesterday morning I drove for 60 miles in unusually cold conditions for this time of year (about 45 f) and it the problem was gone! Today it is about 65 and the problem is there after a shrot time at highway speeds.

i'd scan the motor, and if nothing showed up i'd move on to the IGN. , things that dont show up on a scan, plugs, wires, etc.

Possibly coil or ignition module,common place thing if the ignition module is still on the distributor,they make a kit to relocate it to the firewall ,this was a call back on many ford 460 motors ,ignition module heats up, truck,van or motorhome, runs like poop. Coil does the same thing heats up ,runs like poop.I think ,unless it was relocated from the banks install,it is mounted on the drivers valve cover and gets very hot!!also when a computer fails they get weird too

another thing that i've seen this in the shop on cars with built up motors, is air intake tempature.... if you're taking air in right from the engine compartment, it can get hot enough to make the computer give a lean condition... if this is the case, you can pipe your intake to suck from a cooler spot such as from under the motorhome or someplace else with moving air, if you do run it under the vehicle make sure it wont suck up water when it rains.... a cold air intake is one thing the rice boys have right.... but even then we had it before they did... its called a hoodscoop

thesals,
The air intake is a Gale Banks ram air with a low restiction lifetime filter specialy designed for motorhomes. It goes all the way out to the grill (about 5' from the engine center). When running the throtle body intake is actually cool to the touch. Mybe not as good as the ram air through the scoops on my goat but it is still pretty good.

I would pull your Accell wires and check the resistance of each wire.

I will run through today's advrenture.............still have the problem:
1. Replaced the coil- no change.
2. Scoped out the ignition system - all looked normal even when the engine was doing it's shuddering thing.
3. Scoped each injector seperately and each had a norman trace.
4. Samplesd the exhaust with the analyser and it never showed any characteristics of an engine which is missing.
I was wrong when I told Denny- "that is a no to the airflow sensor" - I must have been blind! There is and when checking out the specs it says that it does not come into play until the intake air temp is above 10c (50f). Last Monday when I drove in the unusually cold 4c (35f) for 1 1/2 hrs the engine worked great. When the temp rose to about 11c (52f) the problem reappeared. Coincidence??
Today it is in the upper 70s and it is there mostly all the time although it sometimes dissapears for a few seconds when accelerating. For this reason one is on order for tomorrow as well as a coolant temp sensor just in case.

continues.............

The TPS was checked - ok with no flat spots. I will take the picture you requested and get back to you.

The picture of the motor/sensors.

Thanks, I will check.

Denny,

What bothers me with all of this is that it runs perfect with lots of power when the outside temp is cold! Keep in mind that it ran perfectly when the outside air temperature was below 50f. I don't see this would not be a charcteristic of plugs, wires, cap/rotor etc. On monday I did 65mph for an hour and a half and it only started near the end of my trip when the outside temp rose to about 51 (I have an outside temp readout on my electronic compass) When it starts its thing is perfectly predictable looking at the temp guage as long as it is over 50f.

Later this morning I will be getting the intake air and coolant sensors. I will let you know what develops. By the way I realy appreciate you input! (that goes for everbody) Looking at you website I see we are the same age!

Denny,

What bothers me is that it runs perfect with tlots of power when the outside temp is cold. Keep in mind that it ran perfectly when the outside air temperature was below 50f last Monday. This would not be a charcteristic of plugs, wires, cap/rotor etc. I did 65mph for an hour and a half and it only started near the end of my trip when the outside temp rose to about 51 (I have an outside temp readout on my electronic compass) When it starts its thing is perfectly predictable looking at the temp guage as long as it is over 50f. I will be getting the Air intake and coolant sensore later this morning and will let you know the results. I realy appreciate your input (that goes for everyone else also). I see by your website that we are the same age!