so last week my tribute started to hesitate, stutter, and lose power when i gave it gas. the CEL started to flash which means i'm misfiring. the CEL doesn't stay on though.

i order 6 new coils, manifold gaskets, pcv valve, egr gasket, and such. i figure if i'm gonna change out 1 or 2 bad one, might as well change them all out and do a maintenance overhaul. when pulling out the rear coils, i notice some oil on them and in the spark plug hole when i pulled the plugs out. crap, valve cover gasket or spark plug hole gasket. i order the valve cover gasket set.

i replace the valve cover gaskets, put in new plugs, put in new coils, put in all gaskets (upper and lower manifold, tb, egr, iac, and pcv), she starts right up!

i can feel random misfires and hesitations still. she drives for about 10 yards hesitating and chugging, then goes fine as long as i stay under 50mph or don't punch it too hard. as soon as i hit 50 and try to give it more gas, i feel hesitation and a loss of power. stay under 50 and she seems to be driving okay. no CEL at all?!

i cleaned the maf, iac, and tb thoroughly. still she drives like crap. i'm not sure what to check next. my instinct is to replace injectors.

any ideas? i'm stumped. she starts up, drives, stutters, then goes up to 50, stutters and loses power. even weirder, when i'm at 50, if i turn off the O/D gear, she goes, but if i leave it on, then she hesitates? what gives, this can't be a tranny issue. she idles fine other than the hiccups when it misfires.

so i took her for a quick drive around the block hoping a code would pop up and low and behold, the CEL flashed indicating a misfire. i pulled over, shut her down, waited a minute, started her back up, and got a solid CEL. got back, pulled the code, P0303: misfire cylinder #3.

i just changed all the coils? all the plugs? i guess i'm gonna have to pull it again and visually check for sparks, test the injector, etc.

also, i noticed that the exhaust was giving out puffs of fumes versus a steady stream all the while idling and randomly misfiring. possibly the cat is plugged? i just might yank out the cat and start her up without one!

any more help would be appreciated!

 

I'm guessing fuel pump.

 

i would like to think so but it just doesn't add up. if it was the fuel pump, i would be getting codes for misfire on all cylinders, not to mention the car would run like crap in its entirety. in my case, the car runs well and then just hesitates every so often and under load. almost like it can't breathe or a clogged something. thanks for the input.

i won't rule out the fp but it's just not as likely.

 

Mileage? Year? Catalytic Converter?
I got the following list from a big shot on another forum. I added a few things and had to convince him that catalytic converter/poor exhaust flow can cause a misfire.

Missfires Can Be Caused By a Million and One Things,

Vac Leaks
Wiring Issues
Spark Plugs(Even Fresh Spark Plugs That Are Crappy Quality.... E3 And Such)
Ignition Coils
Alternators (Search EMI)
MAFS
Injectors
Injector O-Rings
Intake Gaskets
TB Gaskets
PCV Hoses
PCV’s
Malfunctioning EGR
Malfunctioning CAS
O2 Sensors
Aftermarket Intakes
Intake Hoses
Vac Lines
Timing Chains
Timing Chain Tensioner
Broken Cam Gears
Malfunctioning Cam Sensors
Incorrect Crank Gears(The I4 Has Like 40 Different Configurations For Whatever Reason)
Incorrect PCM Flash
Issues Within The PCM
PCM Wiring
Bad Diaphram Within The FPR
Issues Within The Fuel Pump
Dirty Fuel Filter
Dirty Fuel Lines
Pre-Cats/Poor Exhaust Flow

If the above gaskets/seals have not been changed, change them. Clean your MAF sensor, throttle body.
Change your PCV valve and probably that short hose as well.
Inspect the intake accordian tube for cracks. Inspect for vaccuum leaks.
Put in a good Fuel system cleaner: Red Line Synthetic Oil - Gasoline Fuel Additives - SI-1 Complete Fuel System Cleaner
Inspect wires. Re-set ECU after doing above.
READ: How can I tell if my catalytic converter is... — Yahoo! Autos

 

thanks for the input! i realize that misfire can have a guantlet of causes. i was trying to figure out the more common ones. the car is a 2002 ES with 104k miles. she ran perfect until we broke the 100k mark. all maintenance on schedule throughout. it's funny that i always joke about the gremlins coming out after 100k miles, haha.

i will work my way through the process of elimination.