jayken302

Ok, I really need some help on this one...
I got a 04 with 70k miles. It started just after I bought it, and very very slowly (like over the next 2,000 miles,) got worse. It has a very light miss while driving 35 to 55 mph and you can feel it in neutral or park while slight reving of the engine. About the same RPM to drive 35 to 55
mph. To describe it in detail it feels alot like a drive shaft out of balance.
I replaced all the coil packs, went with the Granatelli OEM replacement for 10% to 15% more spark. This did nothing, except for give me better response of the throttle.
I replaced the spark plugs twice first with NGK Plat, then with Autolites Plat.
I blocked the EGR with a plate to check if that was it.
Then I cleaned the MAS.
Lastly I found TSB 16941 which had me remove unplug the fuel pressure switch to check for a faulty fuel pump.
All did nothing and there are no fault codes.
A buddy of mine has a $2,000 Snapon scanner and we couldn't find anything wrong in there.
Oh yea, all the plugs are exactly the same looking showing a nearly perfect air/fuel mixture. Grey with a touch of black.
I ohmed out the injectors and they are all within .7 ohms of eachother.

Any thoughts??? I need all the help I can get!!!

Stick462

check the front crank balancer and the flex plate (were convertor bolts to the engine)

jayken302

Dude, I didn't think of that...
Thanks!!

jayken302

Ok,
I put a can of Sea Foam in the tank and half another can in the intake. I drove it about 5 miles so far and it felt like the miss is less. This makes me believe it is an injector problem more than anything else.

Thanks!

jayken302

I still have the miss/roughness while driving...

I got a programmer that gives me read outs while driving. When the engine is cold, my long term fuel trim is 26%. Then when it warms up and I am driving between 45 and 55 mph (during the roughness/miss,) the ltft bounces between +6% to +16%. Both banks are always within 2% of each other while they are ranging up and down. So it looks like I am getting more air than what the mass is expecting right? I sprayed the hell out of the engine with starter fluid with no change in RPM. Should keep looking for a vacuum leak, or look into replaceing the MASS? If it is the mass, do I have the same mass as the CVPI since mine is the sport?

jayken302

Well after a 3 day crash course of searching on the internet I got it troubleshot down to either a fuel pump, fuel pressure sending unit, or the fuel tank evap controller. My fuel trims are 0 at idle and high vacuum instances, but over 10% at light and medium loads. This means that it is impossible to be a vacuum leak. The mas tested good, and the MAP reading are right on with my gauge. I am going to install the Ford GT fuel pump kit ($140 from RPM Outlet in Texas,) soon and I post if it works.

mojo46

Have you checked each and every ground connection?

jayken302

Damn!!! I am an idiot!!
Well after buying a supercar fuel pump (that I havn't even installed yet!) I almost lost between $650 and $1800 for a tranny rebuild that I didn't need. A few people got me looking at possible torque converter shutter so I took it Atomic in Elmhurst and they were going to clean out my pocket book!!! I then took it to a Ford dealer who charged me $110 and checked everything! They felt it was a vibration from somewhere, but couldn't put their finger on it. He verbally told me to change my Mustang rims back to Crown Vic rims. So to shorten this long boreing story up, I found both my middle exhaust hangers broken. Took it to Quick Service (used to be a Vasquez and Sons,) they put a new exhaust from the first cat back for $380 and the Vibration is gone!!!!
Oh and buy the way... These guys did an AWESOME job. It looks like something store bought, well except for they are not mandral bent.
Damn!!! I am an idiot!!

rtg143

Thanks for letting us know the outcome. That will probably help someone else in the future.