PugDawgRacin

I have a 03 Mach1 (4.6 liter, DOHC, 32valve engine) w/manual trans and 108k miles. Under full throttle acceleration the engine stumbles/hesitates in the high rpm range (approx. 5,000 rpm & above) .

I have replaced the spark plugs, air filter and fuel filter to no avail. I purchased the car in Aug of 2013 and it passed CA. smog at that time. I don't know if it's relevant but I've also replaced the front brakes, rotors and wheel bearing "hub assemblies".

I followed the owners manuals instructions but is it possible that I messed something up when I washed the engine two months ago?

I appreciate any assistance you can provide.

MustangVixenGT

Throttle body might need cleaned, or maybe injectors need cleaned or replaced. Congrats on the Mach1 though! Those little beauties are collector items there hold onto that one and keep her in good shape!

I doubt you messed something up in the engine, unless your just drenched it in water. I lightly mist my engine and clean it out every time I was my car.

TXMach

Check the coils.

PugDawgRacin

Thank you both for your responses.

TX Mach,
Would (should) Autozone be able to identify a coil problem with a OBD "trouble code read" ? I'm hoping that Chilton's OHM meter testing procedure isn't my only/best option here.

Thanks again !

TXMach

In my particular case when my engine was misfiring, I didn't have to wait for an SES light. I ran a scan and the codes showed up anyway. It's free for Autozone to try, so I say give it a shot.

PugDawgRacin

TXMach,
I'm gonna try and hit Autozone today, I'll let you know how that part of the story turns out. Since it seems likely that I'll wind up buying replacement coils, could you tell me which brand etc. you used in your Mach1 ?
Thanks again for your help !

TXMach

I use MSD Blaster COPs. About $400

PugDawgRacin

TXMach,
The saga continues, with a twist. Turns out that AutoZone's [I]in California[I][I] no longer do free code scans due to legislation passed 2 yr.s ago. So, I'm off to find one of a few local repair shops that's supposed to do free code scans.
I'm almost to the point of saying the "H" with it and just replacing them but a glance at my checking account sobers me on that idea.
To be continued......................................... ..........................