So to start this off my Xj is an 88 4door, 4x4, automatic. so I was on my wayto sedona and all of a sudden the Jeep wouldgo way down on power then pop out tail pipe. Then it would come back up on power and then down again
I'm baffled as to what would cause this. This was about two weeks ago. Since that time I have replaced distributor cap, Rotor, Wires, Flugs, and fuel filter. It runs good until it hits running them and the poop hits the fan. It falls on its face pops out the intake and runs like crud. It looses all power and just runs terrible. I dont know where to go with this. One of my buddies recommended replacing the tps, I not sure that this would fix it or not. Any halp would be greatly appreciated

Could be TPS. Its not happening all the time? Are you under load when it happens? Is it at the same speed each time?

Are you getting good exhaust flow? Could it be a plugged cat? I saw that happen once on the way back from Table Mesa. When up to speed the back pressure would build up and kill power. He drilled holes in the cat on the side of I-17 and that was good enough to get it home and fix.

I vote fuel pump. grab a $14 fuel pressure guage from harbor freight and check it. IIRC it should be around 40 psi

K7VZ wrote:Are you getting good exhaust flow? Could it be a plugged cat? I saw that happen once on the way back from Table Mesa. When up to speed the back pressure would build up and kill power. He drilled holes in the cat on the side of I-17 and that was good enough to get it home and fix.

That was the other thing i was thinking.

Fuel pressure would make sense too. If it looses pressure and then gets a shot of gas, that could cause the backfire.

obdII codes? take it to autozone and have them scan the computer

offroadaz wrote:obdII codes? take it to autozone and have them scan the computer

X2

It's an 88. I didn't think OBDII showed up until the mid-90's.

K7VZ wrote:It's an 88. I didn't think OBDII showed up until the mid-90's.

January 1, 1996

defibvt wrote:January 1, 1996

My 93 xj had it.

Yeah so last night a buddy stopped by and we checked fuel pressure. It was 23psi vacuum on and 25psi vacuum off at idle..... Fuel pressure is way too low which I am figuring is causing it to go super lean and which is inturn causing it to fall on its face.

that's easy enough to fix. It can pretty much only be the fuel filter, fuel pump or fuel pressure regulator. (but the regulator is unlikely to fail)

I recommend doing both the pump and the filter, but If you're looking to save money start with the filter (or check the pressure at the pump with your gauge before the inline filter).

... and don't use the "bomba gasolina" from autozone. no fun doing the replacement twice.

could be the fuel hose that runs from the pump to the actual hard line in the tank...if its never been changed its probally rotted...the comanche had similar problems...would idle fine and sputter terribly upon acceleration...pulled the pump and the hose was completely rotted away. Changed it and been great ever since..$2 dollar fix

sweathog wrote:that's easy enough to fix. It can pretty much only be the fuel filter, fuel pump or fuel pressure regulator. (but the regulator is unlikely to fail)

I recommend doing both the pump and the filter, but If you're looking to save money start with the filter (or check the pressure at the pump with your gauge before the inline filter).

... and don't use the "bomba gasolina" from autozone. no fun doing the replacement twice.

It's all one unit. Cherokees have a single unit, pump/filter that all has to be replaced at once. IF that is the problem which sounds like it to me, one from the dealer is about $350. I wouldn't recommend buying one from anywhere else.

Bill, got it all fixed. New fuel pump and it is working great.

Yeah, and then had more issues, had to replace two leaky fuel injectors and the crank sensor wiring had been burned by the manifold so I had to repair some wiring.