Hi my 1995 xj started popping going up upgrades throttleing but didn't run bad when backing off on level ground until gassing it harder...it's misfiring bad now..I put new plugs wires n cap and fuel filter on and it's still bad..fires right up just runs very rough... haven't checked coil or fuel pressure any guesses w what I described? Thanks

 

Just offhand, I would check the Throttle Valve cable adjustment if you are not familiar with it already. It's a quick fix if it's the problem. I just had an issue yesterday (again) with this, it can cause a hesitation or apparent missing on startup from a light or whatever. There are probably explanations on this forum and YouTube has a number of videos on the adjustment. It's the cable that's the first one to the throttle linkage (from the front of the engine) and has a black button on the top of the bracket. You push that, the cable will pop out to it's full extension. Then you let off the button, push the black plastic thing back all the way. Then go in the Jeep and press the gas pedal down until you feel it click and reset. It should be readjusted, and the black plastic thing can be extended maybe a half inch or more, and fine tuning may be needed to get the actual correct position where the vehicle runs correctly. You should have the cable tighter than it may have been initially, this removes the slack but should not be too tight. Driving it will tell you the difference. Check out videos to actually see it done and you will understand better than my explanation. It may be something you've done already, but in my experience, it only works best within a fairly narrow range of adjustment and the gas pedal method may not nail it exactly. It's my belief that mine is particularly sensitive due to the lift on my Jeep and/or the position and length of the cable. I intend to check that in better weather to find out if the cable is affected by the flexing of the suspension or other movement relative to the trans and engine that would put stress on the cable. I only have a 3" lift but any alterations can have consequences that need to be considered.

 

You described two things that need to be "tested" (not replaced on a hunch) to start the process of elimination. Any check engine light? If so, use Key-on Key off technique to pull OBDI codes.

1. For a 95, you should have 31 psi of fuel pressure at idle. Then disconnect the vacuum line leading to the fuel pressure regulator and the pressure should jump to approximately 39 psi. If any raw fuel is in that vacuum line, replace the fuel pressure regulator as it has a ruptured diaphragm. If you don't have access to a fuel pressure gauge, call around to your local parts stores as many will rent you one inexpensively.

2. The ignition coil can be easily tested for both primary and secondary resistances with a manual and a meter.

3. Did you replace your rotor too on your tuneup? If not, do so.

4. A compression test is always a good "snapshot in time" of the internal condition of the engine. Spec is 120-150 with no more than a 30 psi variation between cylinders.

Start there and fuel pressure is #1. Plenty of time to move on after the basics are addressed. Good luck and keep us updated!