FI 460 leanout under power
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New User
Joined: Jul 2002
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From: Meridian
FI 460 leanout under power
I have a 1990 Flair RV with a F/I 460.
When the engine get warm like on a long hill the engine sputters back through the intake and looses power. Let off the power and it stops. When cold it runs great. The computer has NO stored codes. He is what I have done:
Fuel filter and pump (recomended by RV mechanic at dealership)
coolent temp sensor
new plugs, wires etc.
New TPS, fuel pump relay
Does not loose fuel pressure
A jug of your choice to whoever can solve my problem
Baffled in Boise
When the engine get warm like on a long hill the engine sputters back through the intake and looses power. Let off the power and it stops. When cold it runs great. The computer has NO stored codes. He is what I have done:
Fuel filter and pump (recomended by RV mechanic at dealership)
coolent temp sensor
new plugs, wires etc.
New TPS, fuel pump relay
Does not loose fuel pressure
A jug of your choice to whoever can solve my problem
Baffled in Boise
Thread Starter
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New User
Joined: Jul 2002
Posts: 3
Likes: 0
From: Meridian
FI 460 leanout under power
Baffled in Boise
I think I found my problem. I climbed under the rig to check the o2 sensor and started following the wiring harness. Well.... I discovered that one of the fram clips had broken and and a connector had come in contact with the exhaust manifold and fried it and the wiring. So I was not getting any input from the O2 sensor. Two trips to "mechanics" and 1 trip to the dealer and about $2000.00 in bills and they missed it. Apparently it was not sending a O2 sensor code to the computer any I did not have a "check engine" light.
I'm repairing the wiring and will give it a smoke test. I'll let you know if it works. If it does....I'm going to by myself a jug of Jack.
Not so....
I think I found my problem. I climbed under the rig to check the o2 sensor and started following the wiring harness. Well.... I discovered that one of the fram clips had broken and and a connector had come in contact with the exhaust manifold and fried it and the wiring. So I was not getting any input from the O2 sensor. Two trips to "mechanics" and 1 trip to the dealer and about $2000.00 in bills and they missed it. Apparently it was not sending a O2 sensor code to the computer any I did not have a "check engine" light.
I'm repairing the wiring and will give it a smoke test. I'll let you know if it works. If it does....I'm going to by myself a jug of Jack.
Not so....
New User
Joined: Jul 2002
Posts: 10
Likes: 0
From: Colorad Springs USA
FI 460 leanout under power
You might take a look at the MAF (mass air flow sensor) I'm not certain if your model has one but it most likely does. It will be located on the air intake after the air filter. You may have some problems geting the retaining screws out as many will have the tamper resistant heads. When you have it removed visually inspect the wire element in the sensor. If you have an ohm meter check it for continuity if not just be sure it is very clean by carefully cleaning the element with a q-tip and a mild cleaning solvent... mineral spirits, alcohol etc...use nothing that dust will adhere to. It might help. Some of the computers will give an OK condition even when the sensor is not responding correctly. The MAF does what the vacuum advance did in days gone by.
Good Luck
John
Good Luck
John
Senior User
Joined: Jun 2002
Posts: 263
Likes: 1
From: British Columbia
FI 460 leanout under power
You should check for backpressure caused by a plugged cat, it is a slim chance but it might be the problem. If that doesent pan out, and you are not going lean under load the only other thing that I have seen is the valves sticking in the guides. I have seen this a lot on Fords.
The engine has to be hot and under a load of a hill of a brake stand stall etc.. You will feel the engine missfire (not bog) and eventually backfire through the intake as the valve hangs open.
Backfires through the intake are caused by running lean or by a mechanicle problem as described. Just a tip.. you can determine if you are going lean by simply hooking up to the O2 sensor signal with a digital VOM. If the voltage takes a dive under load (.200-.000) you know that you are running lean.
Nick from the frozen north
1974 F-250 4X4
soon to be 429
dana 60 front and rear
The engine has to be hot and under a load of a hill of a brake stand stall etc.. You will feel the engine missfire (not bog) and eventually backfire through the intake as the valve hangs open.
Backfires through the intake are caused by running lean or by a mechanicle problem as described. Just a tip.. you can determine if you are going lean by simply hooking up to the O2 sensor signal with a digital VOM. If the voltage takes a dive under load (.200-.000) you know that you are running lean.
Nick from the frozen north
1974 F-250 4X4
soon to be 429
dana 60 front and rear
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