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BAD POWER LOSS! Ideas?

J

jeepercreeperXJ

NAXJA Forum User
Location
Glendale, AZ
I was driving home from work and notice that the jeep was lagging big time when I press the throttle a good amount.. One time it kicked in like it should, but dropped down again. I'm sure it could be a bunch of different things, but I want to see what you all think it could be.

--Chris--

89XJ; 4.0; K&N intake; Pacesetter Header; Flowmaster 40; Aw4; 5.5 Long Arm; 33x10.5 BFG MT's
 
Fuel Filter? TPS?

Clogged fuel filter tends to show its face when you really give it gas...not so much at idle...
 
might be crap in the bottum of you tank stirring up even if you havent run it completely dry..
 
Fuel filter is cheap insurance, change it, if still the same gut the cat. my 2 cents. good luck
 
Mine did the same thing when the cat was clogged....
 
Alrighty folks,
So I've changed the filter and cat, but still have the problem. I stick my head out the window when I push the gas down and hear like a backfire sound or a pop/clunk from the front. It's actually getting worse. It seems like each time I drive it, I lose more usable pedal before it starts "chuggin".
 
have you changed plugs, wires, cap, and rotor. maybe air filter? check all the simple stuff first.
 
The motor just had the head replaced, valve job and head gasket replaced. As well as new plugs. Cap & rotor and wires are fairly new. Hopefully it's not something to do with the motor work. I'm not sure how I can use the labor warranty if the shop is all the way back in Cali.
 
Can you give us all the recent history, in sequence, and what is already fairly new, etc.

Could definately be a fuel problem, a ground problem, a transmission cable setting problem, bad TPS, bad Air intake sensor (but that usually causes hard starting unless it is cold), Coolant temperature sensor, Definately could be an O2 sensor acting up, could be in the igntion including the new cap androtor parts (they can be bad or go bad fairly quikly, due to quality issues), bad igntion coil, and so on. Could be a mechanical problem in the engine, but more likely it is not.

Best thing to do is a get a renix FSM, Mulit meter and start testing each one of these guys. It is fast and simple to do, and lot cheaper that buying parts at the craps table.

From the sound of it I would check the TPS first!

Why was the head replaced, upgrade or damage? I take it, it ran OK for a while after the head job, so again I would target the TPS first, then O2 sensor, then the fuel pressure (test it with a gauge), then look at that ignition wiring and the HV coil - electronic igntion modual, etc., again.
 
I decided to start with the basics. I just changed the cap and rotor, as well as the O2 sensor. Also "recharged" the K&N. Cleaned up some aged & ugly wiring.

This greatly improved my throttle response when reving at a stand-still, but the issue isn't resolved. Someone told me it may be the computer and to disconnect the battery for a good ammount of time, and maybe the computer will reset. We'll see...

Oh and also to add: Now it seems to accelerate almost normal right after I start the motor, but then it chugs 5 seconds later.
 
Not sure of the injectors. How can I check? All the vacuum lines are brand new, and they look fine.

I let it idle for a while and after about 30 seconds the RPM started to fall and rise. One time when it went down on its own, I pressed the gas and it sputtered and died. HMMMMM.
 
jeepercreeperXJ said:
Not sure of the injectors. How can I check? All the vacuum lines are brand new, and they look fine.

I let it idle for a while and after about 30 seconds the RPM started to fall and rise. One time when it went down on its own, I pressed the gas and it sputtered and died. HMMMMM.
Click to expand...

Did you ever test the two temperature sensors ( coolant and air intake) with an ohm meter? If they are off they can cause your problem.

Also check the wiring connector on the O2 sensor and the TPS and make sure they are not connected backwards. I had both mine connector backwards once and I had the same problems you are having.

You can use a stethoscope to listen to each injector as a partial test.
 
So I took it to the dealer last week and they said its probably the fuel pump and it would cost $450 to fix. NOOOO WAY! I pulled it outta there right away! I bought a pump from the parts store, but didnt want to do it, 'cause I thought it was a real hard process and I'd need to drop the tank and all that. But since its lifted, I was able to sit straight up under the Jeep and change the pump in 25 minutes! Only costed me $120 (I got the whole kit with the new floater and wiring harness and everything).
PROBLEM SOLVED! :cheers:

And it runs great now since I changed to cap/rotor and fuel filter before this.

XJ is back in business! thanks everyone!
 
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