Evan Asklar

1998 4WD 4.0L Automatic Cherokee 170k miles. I have always had bad gas mileage (10mi /gal) but the car never had any problems running. Now when I turn it on it will stumble for about 20-30 seconds and then die unless I give it gas. Two-foot driving is req'd when pulling up to a stop. WIll also die if I slow down too much in DRIVE. Drives fine on the highway and otherwise. If I reset the battery it will idle well for about 10 seconds upon restart and then go back to eating ****. I have an intermittent CEL that seems to be related to the cruise control (P0121, P0700, P1595, P1682, P1683, P1694, P1698). So far I have replaced plugs, wires, cap, rotor, CrankPS, IACV (used), TPS. Throttle body and IAC have been cleaned. I am planning to check fuel pressure however the fact that it will idle fine on PCM memory makes me think its something electrical. I plan on replacing upstream o2 sensor next. Not sure what else could be the problem....Any help would be appreciated

00t444e

When the battery is going out they won't idle very well. I had the same problem and when I replaced the battery that fixed it.

Jeepwalker

Did you check vacuum? What's it giving you? Yeah, check fuel pressure. Grounds, all electrical. Did you clean behind the IAC and under the butterfly valve really well? Check/clean the EGR too. Ensure all EGR related piping, including any return plastic piping isn't cracked. Any sensors in the manifold? Those get gummed up. Ohm out temp sensors ...a bad sensor can throw off the temp the vehicle 'things' it is outside (and when running).

Good luck

downs

Sounds like a vacuum leak to me this could also be causing your horrible fuel mileage. Vacuum gauges are cheap and one of those things that eveyone should have in their tool box. I think I got mine on Amazon for sub 20 dollars. FWIW my 95 with 185000 miles pulls 20 to 22 inches of vacuum at idle.

Edit I'd still check your vacuum due to the crap fuel mileage BUT every single one of those codes you posted have to do with sensors, the ECU and voltages. Like a previous poster said get that charging system and battery checked and remove, clean and reinstall ALL OF YOUR GROUNDS. The XJ is very sensitive to bad grounds and charging systems in poor health causing the ECU to see erratic or incorrect voltage from various sensors which will cause everything to go haywire.

Jeepwalker

Yeah, low vacuum will prevent atomized fuel from properly evaporating in the air-stream. Therefore it won't idle well. Any leaks like bad or cracked vacuum hoses or other 'air leaks' which prevent the intake system from 'sealing' properly could lower vacuum and cause idle issues. Now, my 87 only produces 15" on idle ...but rises quickly to 18-19 at 1100-1200 rpm. Also, check the front/back bolts on the intake manifold. They're known for vibrating loose. I would ohm out the TPS to make sure you didn't by chance get a dud. Change the PCV if you haven't. Ensure it's working properly (if it has one), or clean the orifaces if it has constant ventilation.

Check that you didn't get a cracked or faulty spark plug when new (I've had it happen), no hairline cracks in the dist cap, and inside the distributor itself looks ok (not corroded). Coil wire?

Evan Asklar

All,
Thanks for the quick responses. I will be sure to check all grounds today after work, I also have a spare battery I can connect. I can also test the TPS and clean out the PCV. I was getting a vacuum leak code a few months ago and thought I went through the whole system then, but I can double-check for more. Does anyone have recommendations on buying a gauge? And am I correct in assuming I will use the evap test port?

downs

This is the one I bought. Not fancy or expensive but it works. I'm in a 95 but pulled my Evap connection at the intake manifold and tested there, but the evap system on the older Jeeps is a lot simpler overall than the newer ones.

Evan Asklar

All, turns out it was a faulty "new" TPS after all. Bought a MOPAR one, no issues since.

PatHenry

Thanks for the response!! Very important to get solutions when found so others can find answers when similar symptoms strike them. Glad to hear that you got it sorted out.

Lots of TPS failures in the past couple of weeks it seems.