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View Full Version : Stumbling/dying on start up.


Demonoid369
April 19th, 2015, 11:41
Please read entire post.

97' 4.0l

Slight run down of what I've had going on the last couple weeks. So hopefully get a full detailed picture.
Got a check engine light 1.5 weeks ago that when it was scanned it showed for a O2 sensors. Been driving like that till I get my new exhaust. Earlier this week I had my battery volt meter go from about 14v to 19v as I was driving to work one afternoon. It lasted about 10 minutes then dropped back down to 14. Yesterday out driving and geocaching I turned my jeep off for a few minutes and when I turned the key, my jeep turned over weakly and bogged and died. I turned it off and then on again and this time I pushed on the gas and I kept the rpm up at 1k and after I let off the gas it went back to normal, Oddly though the check engine light disappeared?!?! So I put in reverse and backed out and as I let go of the gas to shift it just died on me. Just stopped running. Started it again and it was bogging again till I pushed on the gas then it settled itself. Took it to O'reillys and had it scanned and no codes were shown?!? Even my O2 sensor code was gone. Did a load test on the battery and it was great, did a test on the starter and alternator and both showed to be just fine. Now later in the evening, driving home my check engine light came back on.

My thoughts were the idle air control sensor as I've known idle issues from that before but the voltage spiking and check engine light disappearing and reappearing has me worried it might be more than just that. Is this just a case of coincidence with the other symptoms and a failing iac or does all this add up to something bigger?

Johnnie Walker
April 19th, 2015, 11:50
I know that the ECU controls the alt output on the later models, so that is a possibility. Are your battery cables and such in good shape? Good grounds? Did you confirm what the actual voltage was when it spiked or just assume that is what it was? Not sure of any tests to do with the ECU, maybe find someone local to you that you can swap ECU to possibly rule it out?
Get some quick dry electronics cleaner and clean your IAC.

8Mud
April 19th, 2015, 11:59
Could be a lot of things, but when my alternator was failing my IAC acted up, twice now when my batteries were on their last legs my IAC acted up. Leads me to believe any sort of major charging issue and the IAC is likely to act up.

The cause if your charging system issues is the question (maybe). The first thing I'd do is ohm check all my major ground straps, paying special attention to the battery itself, the battery to block ground and the engine head to firewall ground. And then hope it isn't my PCM acting up.

Just yesterday I unhooked my battery ground to rebuild my starter and when I reconnected it, half my gauges changed there normal positions. Oil pressure was higher and voltmeter was higher than normal. I honestly don't know if it was from the computer reboot or I had an issue with the connection? All I did was clean the ground terminal on the battery, the clamp and wipe down the top of my battery with Windex. When I clean the terminals and clamps, I clean them shiny clean with a 3M pad or sandpaper and then wipe them down with brake cleaner or another solvent. I did notice what appeared to be slight film of acid near my poles, whether this was a factor or not I have no idea, I wiped the top and side of my battery down with Windex. What I'm getting at is you almost have to make sure the basics are in order, before you start troubleshooting more exotic and complex issues.