yesterday i drove almost 300 miles to a track in NC to shoot the Battle of the Belts race in Fayetteville, NC... had the cruise on pretty much the whole way there. on the way back i did the same thing. well when i was coming back thru some of the hills it would go into boost to keep the speed and it started breaking up or something around 2-3psi... so i switched my RPD over to spark/KR, it showed ZERO KR so i then swapped it over to the wideband, it was perfect for the stock tune, showing mid 14's then itd nail 14.0 when it was breaking up, then i checked the cam phaser, everything looked normal, the more i was checking stuff the higher the limit seemed to be that it would start breaking up...

i cruised for a while longer since it was 4:30 in the morning on I20 and it was fine cruising for the most part. checked it every 30 min or so and the limit seemed to have made its way up to 8lbs or so before it would stutter. then back in greenville it would take 15psi no problem untill ike 2500rpm... I dropped my friend off then hit it in 1st and 2nd... car would free rev fine and it seemed fine at WOT in 1st but now it had moved up to 4000 before it would break up... all the while im checking wideband to see if anything goes nuts. the limit keeps going up and then it makes a full pull thru 2nd and makes some audible exhuast note changes thru the pull.

the car was making 2050psi of fuel pressure and it was 69* outside and about 768% humidity and like 13-14psi at this point.. then the car just pulled fine... checked the stupid little hp gauge, it showed a spike of like 275tq and it would settle down and it supposedly made 260...

*Cliffsnotes*
car ran like crap then started slowly running better, eventually ran fine. Do these things have a tendency to gunk up spark plugs or something?

 

mine did the same thing after a similar trip, hasnt done it since

 

Dude, you're not supposed to run it underwater...

 

My car did the same thing on a recent road trip to Houston.. I was about to blame it on bad fuel, but that was from a Chevron station in a populated area.

Anyways, I found it would start misfiring at WOT in 3rd at about 4k RPM. Got the result to repeat several times. Since I've come home and have been doing more stop and go driving the problem has gone away.

I'm going to go out on a limb and say that deposits form on the injector tips when high fuel pressure isn't reached for a long period of time. Either that or they don't burn off because of lower combustion chamber temps.

 

mines been fine ever since now... these cars seem like there was a lot of loose ends left to tie up... my "piece of crap mustang" never had any of these weird issues.