96XJ-Mountaineer

i bought my wife a laredo last year. it's great, lifted it a few inches, nothing fancy really, just a good year-round mud and snow devouring champ. but it has a couple odd issues.

when it first starts up, it runs fine. it has an odd noise coming from somewhere in the motor-bay when put into any gear. like a dry tranny sounding noise. i dunno what it could be, but it's got a brand new tranny, and of course, it leaks like most vehicles do. especially jeeps with higher miles. but it never gets "low" i always keep it topped off, never over-full, never let it get to the point where it needs any, just keep it at an acceptable level. any idea what could or would make that noise?? it isn't the t-case or tranny (which is auto) but it sounds like it's coming from the high-rise cold air intake....

second issues. the one i worry about every time i drive it. it "chugs" for lack of a better term. it seems to misfire or pop out of rythm when at idle, but it gets really bad once you give it any kind of throttle -in gear-.... it never does it out of gear. it's done it for the last 2.5 years. never gets better or worse. but it bugs the heck out of me. i never know when it' going to fry the motor or worse, cause an accident. it drives fine once it get's going but starting off is a little hairy. safe to say i'd never take it crawling with my 96 XJ just for the fact i'm afraid of causing damage to it. has anyone encountered any similar problems with their 4.0's? i've had QUITE a few over the last 5 years, and not a one has given me any amount of grief. anyone have any ideas???


Thanks!

KF2M

That noise could be just the air going into the throttle body. The stock air filter/intake allows alot of noise. Disconnect the part of the air intake that goes into the top of the throttle body. If you get the same noise but much louder you just found the source. If not listen closely (but not close to moving objects), and pay particular attention near the timing chain at the front of the engine.

When was the last time you changed the plugs? Could have a plug or two going south. Do you get any pre-ignition (knocking)? Better yet is your MIL tripped, or getting any codes?

96XJ-Mountaineer

all circuits are good, all plugs are new, all wires are new. gapped properly, just seeming to miss. i have a feeling it is just slightly out of time. and the intake was the source of the mystery noise, did exactly as you said, the noise got louder, and it wasn't anything hinky. just the air making one hell of a "sucking" noise. and i don't have any pre-ignition knocking. it starts like any other 4.0 would. quick and easy, just idles a little odd,and acts funny for the first 5mph when in gear, but once it gets moving it runs great. it's just ione of those things that really trips out all the local mechanics, and really drives me nuts. every mechanic in town (home/shop guys) all have no idea what the problem is. we hooked up a timing lights, it's really close to perfection..... any other ideas??? all relays are new, all computer components are new, everything is in good shape! I R STUMPEDED.....

KF2M

I'm stumped as well. Could be a multitude of things. Did your mechanic check both ignition, and valve timing or just ignition? The timing chain could have jumped a tooth (or two), and the PO just adjusted the ignition timing (yours has a distributor, right?) to compensate. Just a hunch... I could very likely be wrong. BTW you still didn't say whether your check engine light is on or not, or if you got any codes.

96XJ-Mountaineer

definitely no codes or lights, nothing out of the ordinary as far as the computer is concerned, i tweaked the timing just a hair, it idles much better, but still does the strange chugging when put in gear and moved forward on reverse. all gears do it, even low range 4x4. really really strange. i drove it about 4 hours straight today to try a few different things: adjust timing, replace plugs and wires... again, replace distributor cap again, even went through the fuel lines, disassembled the line and removed the filter, it was clean as a whistle (well as clean as it should be after 50k miles). i cannot put a finger in the problem. i even went with high end wires and plugs, and the best carquest had to offer for caps. nothing fancy, just real expensive OEM parts. but yeah, no lights, no warnings, no codes. i had both local shops run the computer today and the o'rielly's in Showlow (45 minute drive at 65, and it did great, starting off and standing in gear at the lights were a different story, it almost died a couple times) so 3 computers all agreed there isn't anything wrong. oh and i changed the fuel cap. just as a precaution, and i wanted a locking one so the local hooligans (my brother in law) wouldn't siphon it again cuz it sits 4-5 days a week for more than 12 hours... any other ideas??? or am i just gonna need to put up with it til the motor takes it's last chugging breath? haha cuz i could let it do that, i'm going to stroke it if it dies anyways.