motor noise question
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Mountain Pass
Joined: Jan 2003
Posts: 203
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From: Central Florida
motor noise question
I have a 97 F250 with the 5.8 and have a noise very much like spark knock or preignition. No matter what I do though I can't get rid of it. I have run super unleaded and octane boost and changed plugs, wires ,cap and rotor and still it remains. I checked the timing which is dead on. Any ideas on what next or what could be causing it? It mimicks spark knock on that you only hear it on acceleration.
Postmaster
Joined: Feb 2002
Posts: 3,496
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From: Calgary Canada
motor noise question
Originally posted by WIKD
I have a 97 F250 with the 5.8 and have a noise very much like spark knock or preignition. No matter what I do though I can't get rid of it. I have run super unleaded and octane boost and changed plugs, wires ,cap and rotor and still it remains. I checked the timing which is dead on. Any ideas on what next or what could be causing it? It mimicks spark knock on that you only hear it on acceleration.
I have a 97 F250 with the 5.8 and have a noise very much like spark knock or preignition. No matter what I do though I can't get rid of it. I have run super unleaded and octane boost and changed plugs, wires ,cap and rotor and still it remains. I checked the timing which is dead on. Any ideas on what next or what could be causing it? It mimicks spark knock on that you only hear it on acceleration.
I'd try the O2 sensor first, it's cheap, around $20. Then try the anti-knock sensor (AKS).
O2 sensor controls fuel mixture, and can cause a lean condition.
However, your AKS should be detecting the detonation and retarding the timing. The AKS is capable of adjusting the timing within ~ a 5 degree range based on the detection of vibration in the block caused by pre-detonation. If the engine runs well under normal conditions, only detonating under load, then most likely it is your AKS.
Waxy
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Mountain Pass
Joined: Jan 2003
Posts: 203
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From: Central Florida
motor noise question
Unfortunately no codes, that would make it too easy. I thought if the O2 sensor went bad it would throw a code? I'll try it and see. As for running well it runs fine but makes the rattle on acceleration regardless of whether it is just pulling away from the stoplight or accelerating hard.
Postmaster
Joined: Feb 2002
Posts: 3,496
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From: Calgary Canada
motor noise question
You're right, the O2 sensor will almost always throw a code.
I'd suggest this, manual retard the timing. Retard it by 2 degrees and see if the knocking goes away or is lessened. If it is, then go after the AKS, it should retard timing by at least 2 degrees if knock is detected. If after you retard the timing ~2 degrees you don't see any decrease in performance, there's no problem in leaving it there.
If 2 degrees doesn't eliminate the problem, retard the timing until it is eliminated and see how many degrees are required.
Are you running a "winter blend" fuel, aka a methanol or ethanol blend? These can wreak havoc with the engines fuel/ignition system.
Waxy
I'd suggest this, manual retard the timing. Retard it by 2 degrees and see if the knocking goes away or is lessened. If it is, then go after the AKS, it should retard timing by at least 2 degrees if knock is detected. If after you retard the timing ~2 degrees you don't see any decrease in performance, there's no problem in leaving it there.
If 2 degrees doesn't eliminate the problem, retard the timing until it is eliminated and see how many degrees are required.
Are you running a "winter blend" fuel, aka a methanol or ethanol blend? These can wreak havoc with the engines fuel/ignition system.
Waxy
