1991 F53 Chassis
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1991 F53 Chassis
Have a 91 F53 chassis with a 460 fuel injected engine. The engine became hard to start and once on the road could not exceed 50 MPH. Problem with the speed is worse. RV won't go over 25 MPH. Changed the plugs, wires, cap, rotor, air filter and fuel filter. No change. Thought the catalytic converter was clogged so it was cut off and engine ran with it off with no change. Had the EGR valve checked by a mechanic who said it was ok and would not cause this problem. I sprayed out the throttle body and idle air bypass and problem remains. Checked the fuel pump and its putting out around 40 PSI when idling. Once engine is started it idles fine. But when you look to give it gas to accelerate it bogs down and sputters. Check engine light goes on and off from time to time. I was told to change the distributor itself that the electronics in that could be bad. Was also told to change the throttle positioning sensor. Any help or advice would be appreciated.
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Joined: Aug 2005
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From: Cleveland, TN
You said the check engine goes on and off,, well what codes are you getting..
You have checked the codes haven't you?
You can throw parts at it all day, and you might hit the right one sooner or later.. or you might not...
You have checked the codes haven't you?
You can throw parts at it all day, and you might hit the right one sooner or later.. or you might not...
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Unfortunately I don't have an OBD1 right now. Do plan on borrowing one in the near future. Was kind of hoping someone had a similar problem. I'm going to wait til I get the scanner before I go sinking anymore time and money in it.
Postmaster
Joined: Aug 2005
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From: Cleveland, TN
Well a code reader is nice,, although a luxury...
Go here to read up on how to do it VERY simple... Ford Fuel Injection How To Run a Self-Test
Go here to read up on how to do it VERY simple... Ford Fuel Injection How To Run a Self-Test
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Joined: Nov 2009
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What GVW is your F-53. By 94, the 15,200# chassis had no converters; I'm surprised you had one.
As you can measure fuel pressure, do it while you accelerate and see if the pressure keeps up. Apparently pumps can easily fail on these (or filters clog). The Pressure should be 39psi above the pressure in the intake manifold. Most gauges measure relative to atmosphere. So 40 at idle may be too high. It should be maybe 10 psi higher under load than at idle relative to atmospheric.
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Finally got around to getting the codes on the RV. Codes 55, 56 and 65 flashed up. 55 is key power input to processor open circuit. No idea what that means. 56 is mass air flow circuit above maximum volts of 4.5. Also TOT sensor output is greater than self test Max value or 4.8 volts. Problem here is I don't think there is a MAF sensor on the RV. I checked along the snorkel where I usually see them and nothing. I have no idea what a TOT sensor is. Last code 65 has to do with cycling the overdrive off switch during testing. If someone can shed some light on that TOT sensor, I'd appreciate it. Thanks for the help so far White 97 and MJP
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Joined: Aug 2010
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From: Abingdon, Va
Finally got around to getting the codes on the RV. Codes 55, 56 and 65 flashed up. 55 is key power input to processor open circuit. No idea what that means. 56 is mass air flow circuit above maximum volts of 4.5. Also TOT sensor output is greater than self test Max value or 4.8 volts. Problem here is I don't think there is a MAF sensor on the RV. I checked along the snorkel where I usually see them and nothing. I have no idea what a TOT sensor is. Last code 65 has to do with cycling the overdrive off switch during testing. If someone can shed some light on that TOT sensor, I'd appreciate it. Thanks for the help so far White 97 and MJP
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Mass Air Flow sensor is along the intake snorkel between the throttle body and air cleaner, correct? I checked and there is nothing there. I have a class A 34 foot coachmen RV. I don't know if they did something different or it dosen't have one.
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I'll check again tommorow. I think my throttle position sensor is on the driver's side of my throttle body. I checked on that alldatapro.com and they didn't even list a MAF for my year and engine. All I know this is pissing me off and my tailgating season is starting this Monday night and it don't look like the Rv is making the show..
Fleet Owner
Joined: Aug 2005
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From: Easton,Ks
You do not have a MAF sensor on your unit, you have a MAP sensor.
Make sure the vacuum line is plugged into the MAP sensor as they like to fall out and it is hard to see on your unit.
The TOT is the transmission temp sensor in the E4OD transmission, it is just saying the transmission was cold, its OK and not your problem.
55 = For your unit Ford does not list a 55, better recheck or something is wrong with the Computer.
56 = We will say you had a cold transmission and call it OK.
65 = Says you did not push the button on the end of the shift lever when you should have.
Make sure the vacuum line is plugged into the MAP sensor as they like to fall out and it is hard to see on your unit.
The TOT is the transmission temp sensor in the E4OD transmission, it is just saying the transmission was cold, its OK and not your problem.
55 = For your unit Ford does not list a 55, better recheck or something is wrong with the Computer.
56 = We will say you had a cold transmission and call it OK.
65 = Says you did not push the button on the end of the shift lever when you should have.
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Hey guys, ran another diagnostic check and I appeared to get 3 digit codes after it gave me my 2 digit. It gave me 56, 55, and 65 first, I left the key in the on position and it flashed 112 and 212. If someone could shed some light, would be appreciated. Going out now to check for the map sensor and vacuum line.