Engine Mis-firing?
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Engine Mis-firing?
Took my truck this weekend on a hunting trip and during the 3 hour drive there I noticed a small mis-fire when at low rpm's, mainly when I am cruising and encounter a small hill and need to give it enough gas to climb and keep speed but not shift to the passing gear.
On the way back it got progressively worse. Truck idles fine and doesn't have issues when you get down on it, just when I'm cruising at low rpms. No codes, no check engine light. Truck is a 97 F250HD with the 5.8 in it. It's been running rich and barely and I mean barely passed inspection and the mechanic told me I needed a tune up and that would help so get that done before the next inspection. I'm guessing either 7 or 8 is misfiring. In the spring I was planning on a tune up so guess it will have to be done earlier. Can you think of any other reason for this?
On the way back it got progressively worse. Truck idles fine and doesn't have issues when you get down on it, just when I'm cruising at low rpms. No codes, no check engine light. Truck is a 97 F250HD with the 5.8 in it. It's been running rich and barely and I mean barely passed inspection and the mechanic told me I needed a tune up and that would help so get that done before the next inspection. I'm guessing either 7 or 8 is misfiring. In the spring I was planning on a tune up so guess it will have to be done earlier. Can you think of any other reason for this?
Cargo Master
Joined: Jul 2009
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From: Des Moines
Why do you think it's 7 or 8 that's misfiring?
Also, if you haven't done a tune up in a while then yes, I'd say go for it. But as for running rich, the computer controls the fuel/air ratio, so if there is a misfire then that could be off setting what the computer sees in the exhaust via the oxygen sensor(s) and it's adding fuel to compensate.
I don't know if it applies to your 97, but some trucks have a cross fire issue depending on how the spark plug wires are routed. Check your firing order and plug wire routing against this and see what it looks like: Fuel Injection Technical Library » TroubleShooting EFI Problems NOTE: This only applies if your firing order is the same as what's pictured. I cannot confirm if this applies to your engine or not b/c I don't know if this only applies to certain years.
Also, if you haven't done a tune up in a while then yes, I'd say go for it. But as for running rich, the computer controls the fuel/air ratio, so if there is a misfire then that could be off setting what the computer sees in the exhaust via the oxygen sensor(s) and it's adding fuel to compensate.
I don't know if it applies to your 97, but some trucks have a cross fire issue depending on how the spark plug wires are routed. Check your firing order and plug wire routing against this and see what it looks like: Fuel Injection Technical Library » TroubleShooting EFI Problems NOTE: This only applies if your firing order is the same as what's pictured. I cannot confirm if this applies to your engine or not b/c I don't know if this only applies to certain years.
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