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Ron, ASE Certified Technician
Category: Ford
Satisfied Customers: 23821
Experience:  23 years with Ford specializing in drivability and electrical and AC. Ford certs and ASE Certs
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Random cylinder misfire, only when I,m cruising, I have

Customer Question

random cylinder misfire, only when I,m cruising, I have changed both cam sensors, and alternator,cleared that code, now random misfire and misfire on # 5 and 6 cylinders replaced coil packs and plugs ,still misfire
JA: Have you seen the misfire code before? Has the car been stalling?
Customer: just since I changed cam sensors
JA: What is the model/year of your Ford?
Customer: 2006 mustang gt 4.6 liter
JA: Are you fixing your Mustang GT yourself? What have you tried so far?
Customer: yes, new cam sensors ,alternator ,coil packs,spark plugs
JA: Anything else you want the mechanic to know before I connect you?
Customer: no
Submitted: 9 months ago.
Category: Ford
Expert:  david craig replied 9 months ago.

Hi Im David, what was the reason for replacing the cam sensors?

Customer: replied 9 months ago.
p 340 code is what the first code was cam sensor
Expert:  david craig replied 9 months ago.

ok....before you replaced that was that the only code?

Customer: replied 9 months ago.
even after I replaced both ,still threw up 340 code , checked alternator, diode bad so changed alternator with new one,now I get misfire code random,and misfire on cylinder #5 and # 6,ready to buy a chevy lol
Customer: replied 9 months ago.
I changed out coil packs and plugs ,still misfires when cruising, I stomp it and it doesn't misfire
Expert:  david craig replied 9 months ago.

ok. you're throwing parts at you car not knowing if they are bad. when you have a situation like this. you back track. if you still have all the old parts. take an old coil pack and a new coil pack, put a meter on the pins of one coil pack and compare the resistance of to the other. if they are close in resistance then that coil pack didnt need replaced. do you have a noid light to check injector pulse?

Customer: replied 9 months ago.
Expert:  david craig replied 9 months ago.

check injector pulse on #5 and #6

Customer: replied 9 months ago.
well ,at work right now,can't do at moment
Customer: replied 9 months ago.
why does it surge and misfire only when I'm not on throttle,
Expert:  david craig replied 9 months ago.

surging as in idle going up and down?

Customer: replied 9 months ago.
only when I'm going down the highway ,when I'm not in to it or off of the throttle
Expert:  david craig replied 9 months ago.

if it was surging at idle only i would say iac. if its siurging while cruising AND youre getting misfires, you need to check the timing. it doesnt do it when you're "on it" as you say because the timing is all the way advanced..........

Customer: replied 9 months ago.
That doesn't sound good
Expert:  david craig replied 9 months ago.

dont totally freak out yet. what you need to do is put the #1 cylinder at tdc and check your timing marks

Expert:  david craig replied 9 months ago.

when was the last time you changed the oil?