PRmustang

It's been a month now that my car has this weird hesitation going on. When I start it up in the morning and the car is cold it runs perfectly, once it starts warming up to operating temperature it'll start bucking and hesitating under 2,000 rpms, once over that 2,000 it runs more or less normally, but it doesn't feel as strong as it's supposed to be. And the car seems completely normal when idling. There is no MIL and when scanning for codes there are none. Three different mechanics have seen it, and none of them know ****!!! This is the list of things I've done to the car with no effect:
1. Replaced fuel filter
2. replaced spark plugs
3. cleaned maf
4. compression test, normal (done by mechanic)
5. cleaned fuel tank, cleaned fuel injectors
6. replaced fuel injectors
7. replaced 3 coil on plugs (3,4, and 8, under another mechanic's advice)
8. replaced clogged stock cats with magnaflow high flow cats...
9. like a million fuel injector cleaners..


I swear it's driving me crazy!!!! Please help me if any of you have any advice or know what's going on, any help is appreciated.

By the way, it's a 99 mustang gt 5 speed with 42k miles on the odo.

callmecobra

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jdaniel

If the Mass Airflow Sensor is wet ot has a tendency to buck pretty hard down low. I just went through that. Also a stopped up cat makes bottom end drag prety hard.

timtimmehh

my old 90 celica did something similar like that and it was just the throttle position sensor. but im pretty sure that would be throwin a code.

Jugador

me and black mage are also having this problem. i figured it was some stupid turbo only bull****, but apparently its a general issue.

RJM02GTDrag

OK this is a really stupid thought but did you disconnect everything and just reboot? Its my rule for the computer seems to fix everything.

Dan04COBRA

Look into upgrading your MAF & replacing your O2 sensors.

PRmustang

Wouldn't bad O2 sensors throw a code?? And yes, I have done the resetting the computer thing a couple of times...

PRmustang

After looking for more information, I read that a way to test the maf, it could be disconnected to see if the lean symptoms went away. Well I did just that on my way from work, and the car did improve! Although not completely, there is still a little hesitation mainly in fifth gear, but not as bad as before. Just to let you guys know, if you have any suggestions please let me know. Thanks!!

Redline03GT

I have come to conclude that our cars have loads of problems in the heat and in the humidity...and these could be contributing to your problems. Gonna have to get it dynoed