bigRyan1127

I got a 90 xj on a trade and I love it but when I'm barely on the gas it will sputter and misfire I put new plugs in it did better for a little while but now back to rough but if I get on it it will go plenty of power the egr valve is caped off and a couple other lines are looped it idles fine also

RTorrez1

When you changed the plugs did you do anything else such as change the cap, rotor and wires? Also what plugs did you put in. Doing half a tune up hardly is worth the time. Just a suggestion, you should run Champion copper plugs gaped at .035. Our 4.0's seem to run better with OEM type of plugs, which are Champion for 1999 and older and NGK for 2000-2001.

PocketsEmpty

Also part of every tune up should be a new air filter, and check and clean your throttle body

bigRyan1127

I've cleaned the tb and new wires plugs are the champion but it runs great if I get on it it's only when you try and cruise on the highway and hold speed it really does it could it be bad egr since its caped off

bigRyan1127

Also when I removed the first plug to change it it had no gap like it had been hit

bigRyan1127

Update it was the iac gettin new one tomorrow

cruiser54

I can't see that causing the problem, but keep us in the loop.

bigRyan1127

Yeah I replaced the tps plugs coil wires caped off the egr still ran I little rough with sputter and backfire I'm assuming its the iac cuz there is no difference when I disconnect it

bigRyan1127

I'm really new to the jeep thing so any input from you guys is very helpful

cruiser54

IAC won't cause sputter. Low fuel pressure?

highmileage

MAP sensor.. it can idle fine but get funny at speed when it's going out. Have you done the fuel filter. IAC shouldn't affect at speed driving?

bigRyan1127

Didn't work anyone have any ideas as to why my xj idles fine runs good when I get on it but if I try to cruse and hold speed it sputters and jerks like a misfire only really does it at mid acceleration or holding speed above 55 any thing under it will hold speed fine but still will miss and sputter at about half throttle

bigRyan1127

I unplugged the map sensor it died so does that mean its good

DFlintstone

Mine dies when I unplug the MAP.

In ether in my, or Cruisers signature you will find info on adjusting that new TPS. You might start by getting that handled...You will need a digital meter. Even the cheap $4 Harbor Freight ones work, at least for a while.

It only takes a couple minutes to check the CPS, rule that out....that darn trickster thing can do about anything! (like a condensers use to)

Do go ahead and check the wiring off the injector harness to your lower sensors. Sometimes they "get in trouble". Melt on something hot, rub on things. I did have roughly similar problems with some of mine grounding. SOOO just some things to check/rule out!

67 GMC

I'd check the fuel pump pressure on the rail too. Just before my pump went, it would idle fine but the pressure would drop / become erratic when I gave it some constant throttle. Look at Cruiser's book of wisdom of course. Can't do anything until you go through the tried and true advice found there.

Good luck and be systematic (try one thing at a time).

Also, punctuation helps us old guys read your posts.

wehatehavingtoreadallyourpostslikethiswithoutanyco mmasperiodshyphenscapitalsetc.