running rough
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Joined: Oct 2023
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running rough
Good afternoon i have a 95 f150 with the 302 engine a few months ago my truck started having a rough idle and started to spark knock on the passenger side of the engine and is idling rough i have replaced distributor, plugs and wires, alternator (battery light was on) and the idle air control valve and the ignition coil oh and the mass air flow sensor
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Joined: Jul 2007
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From: Cape Girardeau MO
Welcome to the site!
May try pulling one plug wire at a time, if the idle or running doesn't change, have narrowed the problem to that cylinder, be it plug, wire, injector, etc. A misfiring cylinder with freak out the O2 sensor with too much remaining oxygen, causing the other cylinders to lean out and suffer as the fuel mixture is adjusted out.
Has the timing been checked?
May try fuel from another station on the thought of bad gas. Hope you've been sticking with 87 - long term use of 91 or higher can result in carbon buildup leading to knocking, detonation, etc. While arguable, I prefer to stick with top-tier (e.g. name-brand) fuels for the extra detergents and stuff claimed to keep things cleaner. Perhaps extreme, but an old-school trick was to slowly introduce a can of SeaFoam through the brake booster hose, slow enough that the engine didn't die until near the end of the can, then dumping the remainder to gag the engine to die on the last bit. Let it sit for a half-hour, then light it off. Not something to do in a neighborhood, as the expected black tailpipe exhaust is quite a nuisance - but it does help to clean any carbon out of the cylinders causing potential higher compression ratios and related knocking / detonations.
May try pulling one plug wire at a time, if the idle or running doesn't change, have narrowed the problem to that cylinder, be it plug, wire, injector, etc. A misfiring cylinder with freak out the O2 sensor with too much remaining oxygen, causing the other cylinders to lean out and suffer as the fuel mixture is adjusted out.
Has the timing been checked?
May try fuel from another station on the thought of bad gas. Hope you've been sticking with 87 - long term use of 91 or higher can result in carbon buildup leading to knocking, detonation, etc. While arguable, I prefer to stick with top-tier (e.g. name-brand) fuels for the extra detergents and stuff claimed to keep things cleaner. Perhaps extreme, but an old-school trick was to slowly introduce a can of SeaFoam through the brake booster hose, slow enough that the engine didn't die until near the end of the can, then dumping the remainder to gag the engine to die on the last bit. Let it sit for a half-hour, then light it off. Not something to do in a neighborhood, as the expected black tailpipe exhaust is quite a nuisance - but it does help to clean any carbon out of the cylinders causing potential higher compression ratios and related knocking / detonations.
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Joined: Oct 2016
Posts: 3,695
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From: Parts Unknown
I would check for any codes and connect a vacuum gauge just to make sure you have a steady 18-22 inches of vacuum. Any misfires will show on the gauge. If this condition suddenly appeared, I would not dwell on areas that would affect the engine's performance gradually. That would include timing( which won't change on its own unless the timing chain jumped) , carbon, gasoline octane etc. You have gone overhill on many of the parts you changed, now is the time to diagnose and stop with the parts changing.