jeep is running weird 1998

    Mine is doing the exact same thing. But seems to go away for weeks or even a month at a time. But it did set a code for the crank position sensor only one time, so I think that's what it is. I just have not replaced it yet. But since I swaped transmitions I cleaned up the sensor and made sure all the connections are tight it hasn't done the, massive misfire leaving the gas station that you described. Note it has nothing to do with the gas station it could do it any where I stop.

    Back to the top, it seems to constantly stumble, especially when warming up. Sometimes it drops to 200 rpms, then kicks itself up over 1k repeatedly, sometimes it has a high idle at 1500rpm. Does anyone have a computer they will let me swap into mine quickly? (Stafford).



    To recap:
    Replaced spark plugs and wires and used dielectric grease.
    Replaced TPS
    Replaced IAC
    Replaced MAP sensor
    Checked fuel pressure and it's fine while the engine sputters.



    Would taking video and throwing it on youtube help?

    The pin outs are no diffrrent for a auto or manuel. I just went through this with erics jeep. I way work would only take 5 mn to test. I still think we need to get it to someone with a full blown scanner so se can read all the sensor outputs.


    Aaron

    Crack open the butterfly on the throttle body and look for the little tiny hole in the drivers side. stick the nozzle of the throttle body spray in the hole and try and clean it out. To repeat what Keith said. Check all your vacuum hoses, on the intake, brake booster, ps side firewall etc.. There is also a small vac hose underneath the map sensor that I always seem to destroy when removing.

    2000 Sahara, All custom...
    2000 Cherokee Police package, Beater....


    I may be slowest and the stupidest

    Well, Aaron and Gavan came over tonight and helped troubleshoot. Plugged in a different computer and we got no difference. Tried different vacuum lines, and leaking propane/mapp gas around the throttle body and various vacuum lines and found no difference. Removed the TPS and it idled correctly .... :hmm:



    So, next step is to try a new tps/connector.



    To recap:



    NOT throwing any codes
    Replaced spark plugs and wires and used dielectric grease.
    Replaced TPS
    Replaced IAC
    Replaced MAP sensor
    Checked fuel pressure and it's fine while the engine sputters.
    Swapped in another computer.
    Tried leaking mapp gas through the throttle body and other various lines.
    Removed the TPS and it idles correctly (at least for the short while we had it removed for).

    I know this sounds stupid...but did you replace the TPS with a Mopar one or a parts store one?



    I have read online (which is always right) that the non-Mopar ones have cause issues.



    -Chris

    It was pep boys. I am gonna pull the known good one from erics jeep that is still in my drivway and see if that fixes it.


    Aaron

    Quote from astape


    It was pep boys. I am gonna pull the known good one from erics jeep that is still in my drivway and see if that fixes it.


    Aaron



    I'm pretty sure the TPS was from NAPA but either way ... kinda annoyed I threw $80 away ... I was trying to look at it as preventative maintenance ... :)

    Well, my TPS was missing a seal, so I found my old TPS, grabbed its seal, and reinstalled. Pretty much confirmed that that little thing was exacerbating my issue. I let it warm up in the driveway, only saw a slight high idle briefly, then limped it around the block in first gear. Brought it back, aired up the tires, decided to try my luck and had no issues until I got it into second gear ... found a very tame stumble which lasted for about 10 seconds. Drove around the block and parked it in the driveway (kept it in 2nd as my steering and track bar is very iffy). When coming to a stop it idled high for a few seconds also. So, looks like the root cause isn't found yet.

    hopefully we can get it to through a code. next step maybe to pull the tb for a good cleaning.


    aaron

    Not sure if you have checked your catalytic converter yet? I had an intermittent problem very similar to this were it would lose rpms and then I would have to pull over, restart jeep, and it would then run ok. Not try to throw more things for you to check but it would be easy enough to run with out the cat connected.

    98 TJ 5.9L, RE 4.5 SF, 35s, 4XDoctor Rocker Guards, AA SYE, Tom Woods DS
    2012 JKU 3" lift 35s

    [size=1em]jbates: not yet, but I am slowly going through everything I can think of, thanks![/size]


    [size=1em]Well, tonight Mr. Stapen and I went through it again. Secured the exhaust manifold bolts ... one was a tiny bit loose and torqued it to spec but the problem still persists. When playing with the TPS it still hesitates and raises RPMs when trying to move it in place even with the seal installed. Made sure that the TPS is on tight. Made sure that the air filter is clean. Removed the throttle body completely again, the gasket looks great, each sensor looks fine, when I had removed the original IAC it looked like burnt toast but this one looks brand new. [/size]


    [size=1em]EDIT: I should add that the hose underneath the map sensor is perfect.[/size]

    Stafford brought up those blue tooth ODBII sensors that he and I have in another post and it got me thinking.....


    I diagnosed (actually) confirmed a fuel problem I was having with my Jeep when I over fill the fuel cell by looking at the graphs on my scanner. I saw the fuel drop suddenly and then recover. I blame it on a venting since the fuel comes all the way up into the tubes when I fill it.


    Anyway, I was thinking you could use the same scanner and when the Jeep hesitates, you will have a log of what every sensor saw happen at that moment. This is a snapshot I took on my way home tonight to give you an idea of what I'm talking about. You can convert this data into other formats such as CSV and such. I'm just thinking out loud but it's worth a shot. You might see something that stands out. :shrug:


    Not sure if i'm late to the party or not, but that vintage of 4.0 has signal it searches for during ignition known as cam and crank sync. The distributor'd 4.0 had an issue with the cam signal pick up plate loosening in the distributor, it's fairly easy to check. Some of the plates were riveted, others were screwed. there is a small hole you can open a paper clip up and use to align the plate when retightening if indeed this is your problem. Also, if you have access to scan tool you can watch the sync signal in the data screen. If all this fails, I can borrow the DRB3 from work (the factory scan tool for that era) which can look at a lot more than standard scan tools.

    If you need wrenching advice feel free to ask! Others experience can be a good way to save time and money!

    Karvor, I really appreciate it, I may have to come down to Dover some time. Truth is after wheeling the past couple of weekends I haven't had any major issues with the mopar TPS in it. I think there were two original issues, one of which is gone (which had exacerbated the first). I can wheel all day without issue, although I noticed once or twice this past weekend that for a few seconds it seemed like it was missing as it had no power, but then it was running on all 6 but a few seconds later.

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