2004 V6 3.9

Ok so I just purchased a Mach 1 . I'm picking it up tomorrow afternoon but there is a slight problem with it.. The check engine light is on (i brought it to ford to have them check it out) and it says 7/8 are missfiring but the car runs great and the ford tech couldnt find one problem.. So far from checking out the car it has been slightly lowered and has a CAI.. any ideas what are causing it? One thing I thought was maybe the dealer has been putting in 87 gas or maybe the CAI...

Shaun351

I would bank on the use of 87 octane or even check the gas cap.

REDFIRE_GT_BEAST

i think it might be a leak in the CAI my dad had same problem they couldnt find anything and when he checked his CAI one day is was worped from heat of engine. I just put side exhaust on my car and my check engine was on for a day before it went back to normal and i guess the computer got use to it so if CAI is new that might be reason.

cwf340

It is possible that it has burned exhaust valves, did the ford tech perform a IDS relative compression test? or a cylinder leakage test? Ford has a tech bulletin #06-5-13 covering missfire codes caused by burned exhaust valves. the tsb states they are most commonly burned in the left bank.. hope this helps..

cwf340

oh and 87octane, CAI, and loose fuel caps will not set missfire codes.

rygi23

Codes ordinarily don't show up out of thin air. Take the info cwf340 has kindly given you to the dealer. DO NOT buy the car w/o something IN WRITING stating the problem will be fixed. Actually, don't even buy the car until the problem is fixed. We're in the internet age where you can find another one no problem. Good luck with it and pics in the "Pics of your Machs" sticky if all works out.

2004 V6 3.9

I dont think they have.. They said they could take out each individual coil and stree test it but the dealer said he would take care of it, said he checked and everything was fine.. He ended up bringing it back to Ford although and they still couldnt figture out whats causing it.. My service engine light was blinking for about 5 mins earlier today then just went back to being solid/on. If you turn the service light off it stays off sometimes for about an hour then back on

watman02

I would not buy this car until it is fixed!!!!!!!
that tsb is a good one and i would take that number into the dealer that you buying it from and say i will not buy this car until it is reparied.
and it pry does have burnt valves and thats why its on and comes back soo soon.

cwf340

A flashing cel means you have a catalyst damaging misfire happening, basicly it means the engine isnt burning the fuel in the cylinder and its dumping raw fuel into the cat that can and will damage it. I would keep look for another mach 1. Im a ford mechanic and I dont see that valve problem that often but the last time I did it was on a cobra. I replaced the head and the car ran great for about 6k miles then it broke a piston. I dont know if the owner was running 87 octane in it but I suspect he was to cause piston damage.

REDFIRE_GT_BEAST

Um cwf340 yea the CAI does i seen it with my own eyes the CAI was worped from heat of engine so we took it out put new one in and the check engine light went off so yea i think CAI can unless you have some other reasoning.