WOT 3rd gear shudder 4R70W
 

Hey guys, I have a 03 GT with the 4R70W automatic. I went for aircare today and was running my Diablosport 93 Octane tune and went for a drive on the highway. Once I got on I pulled a WOT from 2 to the end of 3 and it was fine and pulled easily to 160.

On the way back I repeated a WOT 2-3 shift merging and when I hit 3rd gear right around 4000rpms my car started shuddering hard and would not accelerate further like it had lost all power (I also let off rather quickly after feeling it). Did it a couple more times and same thing! What gives?! Only third gear from around 4k on. I don't know if it is a transmission problem? I thought maybe fuel but I installed a brand new fuel filter, new fuel pump a while ago and cleaned my injectors and gears 1-2 WOT blow through like nothings wrong with fuel whatsoever. Tranny fluid is at a good level as well and I have a cooler and its not running hot! :banghead:

That's weird, it sounds a lot like a fuel problem but if it's only in 3rd it wouldn't make sense. I wonder if the torque converter is locking up prematurely?

Yea that's what was confusing me, plus my fuel pressure gauge didn't do any drastic drops or else I would have noticed. Funny I did it again just a couple hours ago to show my Pops and it didn't happen car wound up all the way. Weird...I wonder if your right with the torque converter. Ill have my mechanic check into it. Lucky for me I got another one waiting to go in soon lol! :tup:

Interesting, it happened again today but this time I really took note of the fuel pressure gauge and I noticed it dropped to 2PSI!! I was trying to pass someone three quarter throttle in third and it completely didn't want to go. My fuel gauge was a little before E and the day was hot out. Any ideas!?! Fuel filter is brand new.

Sounds like either fuel pump or a crack on the intake plenum to me. Especially since it was so close to Empty, that's usually when a weak pump will fail.

I'd start with a new pump and make sure to clean the fuel tank out completely to make sure there isn't something periodically blocking the pickup.

Don't think its got anything to do with intake, but I bet its the stupid pump again. Already got my mechanic to replace it once, I bet he put a return style pump in and it the bed early. Or could be full of crap in the tank. I notice when I have about half to 3/4 of a tank it doesn't crap out like when it does near E! Im going to get a new 255LPH fuel pump I guess..

Also my fuel pressure is around 27-28PSI idling. Does that seem too low? Shouldn't it be in the 30's idle and more like high 35-40 something at WOT? Bad Fuel Rail Pressure sensor? Drove it again today, and it chucked from third the 2nd gear drop and dropped fuel pressure again. Filled the tank to 3/4, did the same run and it did the whole RPM range fine.

Yeah if it's not doing it at 3/4 of a tank, but does near empty, I'll stick with my first answer....fuel pump!

Agh! :banghead: What I pain in my arse! I check the fuel rail pressure sensor and it was fine. Your probably right. What do you think about these Pumps? Look pretty nice and flows 255-265 LPH which would be a step up!

HFP 255LPH Returnless Fuel Pump Ford Mustang 1998 - 2011

http://treperformance.com/i-6290880-...1998-2010.html

http://www.summitracing.com/int/part...view/make/ford

http://www.summitracing.com/int/part...view/make/ford

http://www.summitracing.com/int/part...view/make/ford

Do I need the whole module or just the pump like these?