# 98 mustang gt with major engine hesitation/loss of power **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** hesitation, mustang, engines, ford\ **Created:** [December 28, 2009, 10:19pm UTC](https://community.cartalk.com/t/98-mustang-gt-with-major-engine-hesitation-loss-of-power/41432 "2009-12-28T22:19:07Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![BrianEvanoffHI](https://avatars.discourse-cdn.com/v4/letter/b/e68b1a/32.png) [@BrianEvanoffHI](https://community.cartalk.com/u/BrianEvanoffHI)\ **Post date:** [December 28, 2009, 10:19pm UTC](https://community.cartalk.com/t/98-mustang-gt-with-major-engine-hesitation-loss-of-power/41432/1 "2009-12-28T22:19:07Z")
I have a 98 mustang gt 4.6l v8 all stock parts, besides the exhaust, which is a straight x pipe. My engine seems to be loosing alot of power, if i accelerate past 3500rpm my engine will start to hesitate and stumble, and if i go to wide open throttle while the engine is stumbling i will loose all power and my engine will drop to about 1500rpm and will begin jumping…almost as if i am pulsing the throttle. but the wierd part is if it starts to hesitate and i turn my engine one and off it will regain power, until i go wide open throttle and go past 3500rpm. my first thought was my fuel delivery, so i installed a inline fuel pump right after my inline fuel filer by the gas tank. i put the second fuel pump on a toggle switch so i can turn it off and on. when my car begins to hesistate i flip the switch to turn on the second fuel pump and its like a shot of NOS and i get 100% power back for a few miles then it begins to hesitate and stumble HEAVILY. I do get one engine code P1443 “EVAC Purge valve fault”. The engine will only hesitate under load, if i put in my clutch and rev it will seem fine, until i put load on engine, it will begin to stumble. it seems to be getting progressively worse everyday…please help. and cheap ideas would be good because I’m a broke college student hah, but i need to get my pony fixed. thank you for your time, feel free to email me at Bevanoff@hawaii.edu ---
**Author:** ![realbinky](https://avatars.discourse-cdn.com/v4/letter/r/a87d85/32.png) [@realbinky](https://community.cartalk.com/u/realbinky)\ **Post date:** [December 28, 2009, 10:29pm UTC](https://community.cartalk.com/t/98-mustang-gt-with-major-engine-hesitation-loss-of-power/41432/2 "2009-12-28T22:29:54Z")
Throttle body/MAF sensor? ---
**Author:** ![DiAngelo-South](https://avatars.discourse-cdn.com/v4/letter/d/51bf81/32.png) [@DiAngelo-South](https://community.cartalk.com/u/DiAngelo-South)\ **Post date:** [January 12, 2010, 6:21pm UTC](https://community.cartalk.com/t/98-mustang-gt-with-major-engine-hesitation-loss-of-power/41432/3 "2010-01-12T18:21:49Z")
I have an '01 GT model that was hesitating / jumping rpms when the weather got colder. If I stomped the gas when it hesitated (thinking it was lack of fuel) it got worse and sometimes stalled. A friend suggested a new mass air meter. I replaced mine with one from Pro-M and haven’t had any further trouble. I’d give it a shot. ---
**Author:** ![Beadsandbeads](https://avatars.discourse-cdn.com/v4/letter/b/c57346/32.png) [@Beadsandbeads](https://community.cartalk.com/u/Beadsandbeads)\ **Post date:** [January 13, 2010, 2:01am UTC](https://community.cartalk.com/t/98-mustang-gt-with-major-engine-hesitation-loss-of-power/41432/4 "2010-01-13T02:01:11Z")
Could be the MAF. YOu can clean the wire with spray electronics cleaner. I would consider the TPS as well. BTW, since when is NOS “stock” on GTs? ---
**Author:** ![paiger](https://avatars.discourse-cdn.com/v4/letter/p/a698b9/32.png) [@paiger](https://community.cartalk.com/u/paiger)\ **Post date:** [February 6, 2010, 9:00pm UTC](https://community.cartalk.com/t/98-mustang-gt-with-major-engine-hesitation-loss-of-power/41432/5 "2010-02-06T21:00:33Z")
I sometimes have the same issue. I have pinpointed it to being ETHANOL. The cheaper the gas and the more ethanol it has in it the worse my 99 mustang runs.