Berkin Parlakay

Hello everybody, I am a newcomer and I have a problem that I have been suffering from for a while, and that is sudden power loss. I own a 2005 Limited 4.7L Jeep Wk. I'll get to the chase.

Personally, I like to push things. Wether it is going faster than the speed limit in a parking garage to hear the engine, to flooring it on empty roads.

So one day, I am on the highway with friends. When the coast was clear, I floor the car, and suddenly there is a drop in performance. The acceleration slowed down, the gears wouldn't switch in time, and the car would be stuck at high rpms for a while then slowly drop back down. The sound of the car went from a growl to the sound of a Mack truck.

But just last week on my way to the airport, all of the problems went back to normal till I hit the highway, and it happened again. If you'd like, I can send a video of the sound of the car. i have a feeling that the fan might be making a lot of noise (spinning when it's not supposed to), and the exhaust might have either come off or have created rust holes. Keep in mind that this is a 12 year old DD Jeep. Any ideas?

dave1123

Welcome to CF!

I'm sorry, but there are just too much electronics involved to diagnose this via a keyboard without doing some checking of systems. Having said that, there are knock sensors that will retard the spark if they detect detonation during acceleration. At least it's something to check. Good luck.

Berkin Parlakay

Thanks for replying and the welcome, Dave.

So what do you think I should do? Should i use an OBD censor and check what's hurting the car? Considering that the car gains back its performance from time to time until it goes bad again, I don't think it's impossible to fix.

dave1123

I'd use a scanner and see if there are any trouble codes either set or pending. If you can find someone with a DRB scan tool, that can find stuff that a normal scanner won't. I had an ABS light on in my WJ and my mechanic buddy used his DRB and it told me my left front wheel sensor was bad. It pinpointed which one!

The problem is, a fault has to occur long enough to set a trouble code or CEL, so sometimes it's difficult to find it. A DRB scan tool takes the guesswork out of the equation. These units cost about $1000, so most backyard mechanics can't afford to buy one just for an occasional use. Repair shops can't do business without one. Of course, the dealers have the DRBIII tool, but charge around $100 just for the diagnosis.

Berkin Parlakay

Okay thank you very much! Your knowledge has been a lot of help and with a DRB I might be able to get my baby up to speed and growling again. If you'd like I'll keep you updated because I might need more advice in the future

dave1123

I'm usually here at least once a day. No particular times either.

Berkin Parlakay

Do you have ANY idea what it might be? I'm thinking that it's because of my radiator fan, but the fan draws battery life, not engine power. Would an exhaust leak cause it? Blown head gasket?

dave1123

Look, not to be mean, but your WK is 5 years ahead of my experience AND a 4.7 which is highly complicated. The 4.7 doesn't take kindly to bashing like hemi would. ANYTHING I tell you would be purely speculation. I'm a 72 year-old hotrod freak, but from before computer engine controls. At present I'm just trying to get along with my 2000 4.0! My basic engine design is from the 50's and yours is a second generation OHC with aluminum heads.

I told you what I know about it and I'm not going to speculate on what it COULD be. If I was there, hands on, it might be different.