Ejboyce1313

i have a 98 XJ sport. I've been having an annoying loss of power when i press the gas pedal followed by a sudden surge of power sometimes....if i punch it it respondes better but... from a stop boggs alot doesn't stall but really boggy and i can here what sounds like a pop or loud tap from up front almost like a backfire...someone told me that it may have been my cat converter since it was already rattlin it may have been clogged. changed it and exhaust from there back ...same problem occuring...ne incite from u xj guys would be appriciated.....i love both my XJs.. b ut im new to workin around em bought both mine this year...thanks for the help

milliontom

I'm having the exact same problem with my 98 cherokee. Mine will fall to 100-200 rpms when I stop at lights and sometimes stall, soymetimes surge back up to normal idle. To get it to move after stopping, I basically have to floor it until I get to around 40mph or it will jerk and surge me all over the place! I know exactly what you mean with the popping sound but sometimes mine will slam and start moving normally after as if I revved it up and dropped it into gear. I've replaced the crank shaft sensor, map sensor and idle air control valve and none have helped. I also had the fuel pressure checked which was normal. Did you find a solution to your problem? I've read something about backing screws out on the ECM and will try that tonight to see if that works.

Jeepability

let me know what happens when you back the screws out. i have a 98 sport with 170 on the dash. mine hasnt done this yet but i wanna be prepared

Topjimmyk

my 98 does the same thing but only after start up. But after it runs normal. I had a fuse blown for the o2 sensors that i just replaced so, ill see if that helps but you guys problem seems worse.

milliontom

Well no luck on the screw backing trick. It ran fantastic for about ten minutes right after I did it, got my hopes up them crushed them just as fast. I'm at a loss...

black_police_xj

guy's this is not helping me at all! sounds like I have the same problem. ran fine yesterday, replaced the Holy muffler with a glass-pack. wasn't till after i had it installed that i noticed the rattle from the cat. mines also sucking air like a super vacuum, spits and sputters idles like crap, but then it will rev up all by itself for a few seconds and then run fine for a while! What the *&^%????

tjwalker

1. Ensure tuneup hardware is fresh. That includes fresh spark plugs (gapped to .035) new plug wires, distributor cap and rotor.

2. Any check engine light EVER? Pull stored codes for clues.

3. Checking fuel pressure for your symptoms is easy and something that should be ruled in or out early in the troubleshooting process. If this were in my garage, I would have a gauge on it pronto. For a 98, you should have 49 psi at idle, plus or minus 5 psi.

4. The throttle position sensor is responsible for a smooth "tip-in" of throttle. It can be tested with a manual with the procedure and a meter (analog best).

Good luck!

black_police_xj

it stopped! I'm thinking that the catalytic converter is breaking up(probably cause I was smacking it with a hammer trying to get the old muffler off) and clogging the exhaust creating tons of back pressure???

tjwalker

You can test for exhaust restriction (clogged cat) quite easily with a vacuum gauge and the ability to use it. SEARCH for the specifics.

milliontom

@tjwalker

1. Tune-up hardware looked fairly new when I got jeep 5 months ago.

2. Check engine light IS on...but there is no power going to the plug that reads codes therefore no code clues.

3. Fuel pressure was 50 psi

4. New TPS

@black_police_xj

Mine sucks air like a jet engine too, sometimes, but I have no catalytic converter installed (just straight pipe where it once was)

badger7182

I just post a new thread, but mine seems like it is just like this - I have done all the things you guys have done, and no luck - I actually kjust replaced both exhaust O2 sensors and got rid of the code, and that is when my issues started.

aaron99xj

My precious xj started doing this too, I have no cat w/ recent new flowmaster ex., plugs wires cap and coil are all new Accel, new BBK throttle body, cold air intake, deleted O2 sensors (the only code I'm getting btw), 4 hole injectors, I have put about 4,000 miles on her after the mods before I started having trouble and it has only done it a few times, the last time I took her out of the toy barn she ran fine (made a nice white cloud w/o brake torqueing) oh yeah fuel pressure was good too, if any1 figures this out please contact me and vice versa, just check out the picks and you can tell this rig is my baby most of the time I'm
but sometimes she makes me