moglide

96 idles rough at start,little missing at start,pump pedal lightly and engine will catch up and run tight.Take off down road will run nice as long as you baby it.Put your foot in it and it just lulls won't die but doesn't accelerate either.It also seams like when its acting up the 5 speed trans isnt synced up and doesnt want to shift smooth some slight grind.When its running right it shifts smooth.when its doing it bad you can hear sucking sound from intake box,have to pump pedal over and over and it may even stall,start it back up keep pumping and it will catch up and run good again.Have changed plugs,plug wires,,removed cat,new battery,fuel filter totally lost where does process of elimination start.Anybody had this same problem before,thanks in advance,help please

Khyren

I'd start with checking the fuel pressure.

Bustedback

Funny how people will do a lot of work replacing unneeded parts rather that do a little diagnostic work.

moglide

thanks,thats what i'm going tomorrow,had advance auto parts check codes yesterday came up o2 sensor but since previous owner took out cat I would assume that code would come up anyway maybe im wrong,just dont want to start changing every sensor not to be the one at fault

Turbo X_J

Compression & fuel pressure test to start off. Without O2 sensor it will never run right btw.

Khyren

Yeah, it needs the O2 to get the mix right. The OBD 2 systems are a stickler about having the downstream one as well.

moglide

is there a way to check o2 sensor without replacing if sensor is not bad

Bustedback

A scan tool is the easiest way. Read the live data stream and make sure the upstream O2 voltage fluctuates up and down and the down stream O2 stays steady.

jamurrin

I think I've read here from others that the XJ does not generally run well without the Catalytic Converter. (It is illegal, BTW, to drive without it...but that is your choice.) I think I've also heard NTK O2 sensors are the OE, and off brands can be finicky. What brand O2 sensor did you use?

tjwalker

I agree with verifying fuel pressure first. Backfiring in the intake is often caused by a "lean" mixture.

Other possibilities include the MAP sensor and even the O2 sensor. Having a scan tool hooked up is a great idea; look at all engine management data real time.

moglide

Took to shop today had truck hooked up for codes came up lean fuel mixture,they didnt have time to test for fuel pressure but will do it tomorrow since they are doing it for free.Would lean fuel mean fuel pump or could it be sensors or other problems.

skife

Lean means it's not getting enough fuel for the amount of air it's taking in.

Check fuel pressure, if it's low, probably a pump.

If it's fine, check vacuum, if it's low you could have a big leak.