postmastrr

I've been noticing this problem getting worse over time. After starting my '03 Mach 1, and letting it warm up, if I rev it up to about 1700 RPM, it misses something awful, and the RPM fluctuates. But on heavy revs, all is well. Now if i drive in first gear, and just go at about 3000 rpm, it sputters a bit. Cruising on the interstate at about 60 presents no problems either. I've tried turning off my EGR with my tuner but that that hasnt seemed to help. I'm thinking I might just need a good dyno tune because of my mods that can be read below. Any ideas? it's driving me nuts.

devongarver

Aside from the tune, have you checked the basic ignition/fuel related causes first? Read the COP Sticky in my sig, it should fill you in on some things to try first.

postmastrr

Well, the fuel filter is brand new, spark plugs done about a year ago. Car itself only has about 70K miles on it. I have no trouble codes, which makes it extremely odd. Thats why i dont think it could be something as complicated as a COP.

PaintballFreak

I have the same ****ing issue. Just replaced all my plugs with no luck. Now about to do the COPs. Engine diagnosis reports misfiring on at least 4 cylinders. I really can't imagine that many COPs went bad at the same time since there is no oil in the wells and the plugs are sealed from up top. Wtffff

Bmitchell373

Mine as well, Its not horrible, but noticeable. I have no check engine light coming on either. Ive put new plugs, bought the fuel filter today, but haven't installed it yet. I'm wondering if it could be a lazy sensor. My Ranger did it all the time, but it threw the Crank Position Sensor and I swapped it, and it fixed it. Without having someone read live sensor data, it could be, cam/crank/MAP sensors that could cause it I believe.

dwtjr3

this is going to sound rlly stupid but my cousin had the same exact problem only with a gt not a mach one and he replaced plugs coils everything you guys are talking about and the problem continued he finally changed the oil and the problem stopped

Bmitchell373

Odd, Maybe if there was fuel in the oil somehow. I duno. lol Mine has a fresh oil change so that couldn't be it. Just put more expensive oil in your car it'll fix everything lol

cliffyk

There is a table in the tune named O2 Transport Delay defining the amount of time in which the PCM (in closed loop mode) expects to see the O2 sensors react to a change in injector pulse width.

When LTs are installed the O2 sensors are moved downstream and the transport delay needs to be increased to accommodate this--not doing so can create the symptoms you describe.

evanjp

cliffyk...

i'm running a bassani catted x pipe off a 98 or 97 cobra (i have a 2002 GT). the upstream o2 sensors are located in a different position than the factory GT h-pipe sensor locations. every time i disconnect the neg battery hub for a few minutes and start the car (when the guages go to the other side and back) the car runs GREAT. after a week or so, the car becomes sluggish when gaining speed at light throttle and feels like there is no torque in 3rd gear from 30-40 mph. the clutch doesn't engage a gear very easily either. it shutters the clutch kind of bad sometimes when taking off in 1st, and doesn't feel like it's a consistent grab into gear. the exhaust note from 30-40 is loud, but the car doesn't seem to be responding/running up to par... it feelslike the car has more torque and more overall power after a 5 minute period witht he neg battery hub off the battery.

could the o2 sensor differences cause this problem? does this sound like a familiar problem to you cliffyk? any idea? running lean? rich?

btw. only mods are adjustable cable/quadrant/adjuster, bassani catted x pipe (off the cobra), weld-in flow 40's, 75mm bbk throttle body, c&l plenum, and k&n air filter.

i drag race the car sometimes and it had 47000 miles on it.

evanjp

*has

and i don't mean to hijack the thread. it's been an ongoing annoyance