Random stutter/loss of power...
 

Picked up a '96 4.0 xj last week and have a few issues. First off it will not start on the first crank when its cold... get in and try to start it won't, but if you let off the key and try again it starts right up?! also have a random speed stutter/loss of power... if you let off the gas or give it more it'll come out of it pretty quick and then it wont do it for awhile. Lets say i take off from a stop sign sometimes it'll get to 25 then stutter/lose power and i have to get out of the gas or give it more and it'll eventually come out of it. Runs great other than those 2 issues, i replaced plugs/wires and still have same problems. Any ideas? 02 sensors?

The first item sounds like the fuel pressure may be bleeding off while the engine is off. Try this: turn the key on for 5-10 seconds before trying to turn the engine over and then try to start it. It may be a check valve in the fuel system (fuel pump) going south.

I've experience the 2nd, although when just pulling out. I replaced the TPS and it seems to have diminished.

tps was my first thought on the 2nd issue also...

You might check your engine ground to the firewall. Mine was shorting and causing a misfire.

Try this.

Note, when you turn it to run, listen. You should hear the fuel pump priming the fuel system.

Turn the key to run, then off. Then run, off, and run. On the third 'run' crank it all the way. If it cranks right up you have a worn check valve in the fuel pump. The check valve is what keeps the pressure in the fuel system while allowing the pump to put more fuel in... so that it doesn't bleed back into the tank. It's a one way ticket for fuel to move from the tank to the engine, and when it wears out it lets it bleed back into the tank (aka doesn't maintain proper pressure in the fuel system causing sputtering)

I replaced the whole assembly in mine, but the check valve was the only thing bad. If I could go back I would have spent every extra damn penny and just bought the Bosch. I'm doing it now.. only I had to spend 211 on the airtex and 85 dollars on a tow to find out Autozone ONLY carries airtex and that's what I get after I bring them the other failure. Not a process I want to repeat every 2 months for the rest of my life.

What EVER you do.. DO NOT BUY AIRTEX. Mine died yesterday, others have bought them and they die or are dead right out of the box. Yes, they have a warranty. And I'll be glad to explain to you how that works.

You see, when it finally dies (and it will) you have to pull it back out, take it to the place (advance and autozone sell strictly airtex) and they're going to hand you another airtex. A few months down the road, you're going to repeat that process. They don't give you an in-store credit for jack. Once you buy that pump you're stuck with it for life if you want your money out of it. You actually lose money, and get very pissed off, when you find yourself on the highway needing an $85 tow back to your house. In the end it actually costs you money. Then you have to drive your happy *** back to the parts store for another one. And hopefully that isn't far. For me it's 38 miles. Also, you obviously won't be driving your jeep. Hope you have two vehicles or a ride out there.

Go ahead and google Airtex and jeep. I am one of many happily pissed off customers that learned the hard way. Every damn parts store is going to tell you "well we never have any problems with them." Jeeps also go offroad and bounce like a mother. Airtex can't handle it. It's a soccer mom's fuel pump. Has the ruggedness of a cotton ball.

If I was you I wouldn't get worked up about anything outside of the fuel pump. I bet after you replace the fuel pump your problems will go away. Faulty fuel pumps cause intermitten, or solid, stuttering.

Also, the reason it starts better when it's warm is because when the engine, and therefore fuel rail/injectors, are hot the fuel is vaporized. When it's cold, there's no gas fumigating inside the engine to help the starting process. A tell tale sign your pump is bad. I actually used the poor man's prime for a few weeks before I replaced my pump. Only needed to do it in the mornings. The rest of the day it was fine.

I recommend you go on Amazon and order a Bosch from there. You can get them $100 cheaper than you can find in a parts store. Only about 30 bucks more than a Failtex right off the shelf. For an extra 5 bucks they'll have it to you next day. I just bought one for 235 plus taxes and 5 dollars extra shipping for next day (which will actually be Monday). Came out to 260 something.

sounds like a fuel pump to me... checked amazon and the bosch is only $93? you must have a newer xj? Gonna check everything underhood anyways but will probably order a fuel pump asap.

Keep us posted if you change the fuel pump. If that solves your problem, I'll change mine.

There's no way you found one for that price unless it's used/bad. I would check the rating on that seller, and make sure it's bosch. There are a bunch of no name pumps on there (TKO Auto) that are selling for that price. Even Airtex still costs at least 160 on that site, so I wouldn't trust anything that sells for less than that.

Even if the seller checks out... if it sounds too good to be true, it probably is.

You don't want to be out that money when you have to replace it, or it just doesn't work to begin with.

I even checked napa's website and they have it priced for under $100.... napaonline.com look up a pump for a '96 4.0L....

https://www.napaonline.com/Catalog/C...+50038+2038004

thats the one i want right?!

You have a different pump. I have the 97 newer style of Pump. I forgot yours was easier to fix.

Superclyde: How was the engine ground shorting out? What did you do to fix yours replace the ground completely?

You can't short a ground. A ground is a ground. It IS the end of the road for electricity. Once electricity makes it to the ground, it has reached its final destination. You can't shorten the path (therefore bypassing something) for a ground.

You CAN have it misgrounded, and have a bad ground for something else. For example.. having multiple things grounded to the same spot.

What can happen there is the ground from one... instead of going into the intended ground area (engine block, frame) flows through the OTHER ground. That's only if the other ground is more conductive than the ground you are using. Electricity always takes the path of least resistance. I like to separate my grounds so it's not something I have to worry about. Unless I'm installing something that specifically says to ground it otherwise (Innovate Wideband 02 sensor is like that).

My question to you is if the noise you're hearing like a loud knocking noise, with momentary loss of power and then starts running fine.

The noise that you're hearing is it like a momentary knocking noise and then everything is okay for a bit?