PCM causing misfire ?
Thread Starter
|
New User
Joined: Nov 2019
Posts: 5
Likes: 0
PCM causing misfire ?
I have a 93' f350 4x4 with a 460 and I had a misfire on cylinder #1 now it is misfiring on cylinder #4 and not #1 anymore. I put in new plugs,wires,distributor cap and rotor.I have good compression on all cylinders. I swapped injectors and plugs and plug wires with other cylinders and #4 still misfires. I had a bad PCM 10 years ago which caused rough idling and went into limp mode, replaced it and it ran fine until two days before the warranty on the PCM expired. I was lucky and got a replacement PCM free. I am totally stumped and the only thing I can think causing the misfire is a bad PCM especially since it seems to change cylinders. Anyone have the same problem ?
Fleet Mechanic
Joined: Mar 2014
Posts: 1,926
Likes: 116
From: Saskatchewan Canada
I would like to know how you determined cylinder misfire. Your truck will be EECIV and the code list is pretty limited.
https://www.blueovaltech.com/tech/eecivcodes.php
https://www.blueovaltech.com/tech/eecivcodes.php
Thread Starter
|
New User
Joined: Nov 2019
Posts: 5
Likes: 0
I used an inferred temp gun and also pulled spark plug wire when it was running. Strange thing is it was # 1 cylinder and now it is # 4. Obd 1 scan showed bad throttle position sensor which I replaced.
Cargo Master
Joined: Jul 2009
Posts: 2,541
Likes: 54
From: Des Moines
Have you checked whether or not the #4 injector is pulsing? Swapping the injectors only rules out the injector, not the wiring.
Don’t get hung up on the misfire changing cylinders just yet - unless it’s constantly jumping around, treat it as though it’s isolated to #4.
Don’t get hung up on the misfire changing cylinders just yet - unless it’s constantly jumping around, treat it as though it’s isolated to #4.
Fleet Mechanic
Joined: Mar 2014
Posts: 1,926
Likes: 116
From: Saskatchewan Canada
Thread
Thread Starter
Forum
Replies
Last Post
Pikachu
1999 - 2003 7.3L Power Stroke Diesel
36
Mar 29, 2019 02:44 PM
Bunggo
1997 - 2003 F150
27
Mar 25, 2010 10:55 PM
