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2001 XJ intermittenly won't Idle sometimes won't run

mchulse

NAXJA Forum User
Location
Austin, TX
Hello All,
I searched the forums for some time and tried most all suggestions but nothing has worked. I've gotten to the point where I almost want to sell the damn thing.

Vehicle Info:
2001 XJ Sport 2WD 4.0L AW4 217,000 miles
OEM CPS is only 10k miles old
NAPA TPS and IAC Sensors Brand New
Battery is New
Alternator Tested Fine
Cables and Connections tight and clean
Fuses look fine

Symptoms:
Initially wouldn't idle without pressing on gas, now doesn't even crank just one click.


Long Story:
So back in the summer it started not wanting to idle all the time. It would start just fine but without holding the gas it would just die. It was far and few between but I did do my best to fix it. Initally I changed my battery out, as it was pretty old and came back not holding a great charge. This fixed the problem for some time.

Then two months later it did it again but with even more symptoms. First it would start and run just fine then on the highway the "check gauges" light came on and the Voltmeter spiked to the highest it could go. Then all the guages died. It ran fine and has never happened sense then.

A week later it started just fine then would die if I didn't hold on the gas. So I figured, "check the alternator". I pulled the alternator and got it checked by 3 different places multiple times. Everyone said it was fine and not the issue. I hooked everything up, cleaned all the connectors and insured the cables looked good; It started right up and idled fine.... now I was thinking, "sensor or bad ground somewhere".

I went ahead and pulled the gauges, and my aftermarket radio to insure nothing was grounding out. Again, everything seemed fine. I checked all the ground straps under the hood and insured they were clean and tight. This fixed it for a week (I assume because I had the battery disconnected and for no other reason) then it started doing the same thing.

I did a lot of research on the forums and found that a bad IAC and TPS could cause similar symptoms. I went ahead and bough both and threw them on. It worked... for a week.

Then last weekend I went to drive it and the same thing happened. Started but wouldn't idle.:flamemad: I was pissed so I just held the gas with one foot and braked with the other. That worked fine. I got home later that day and packed for the airport, as I was leaving town. A few hours later I hopped in and tried to start it. Initially it made some clicking noises from the relay box under the hood but didn't start. Then it did nothing, no clicking, no nothing. Still had power in the ON position but other than that it didn't even think about starting. A few days later my wife called me and said she tried to start it and it started right up!

Today I hopped in and it wouldn't start again. I checked the fuses and relays. The fuses seem fine but not sure how to check the relays. Maybe it's the starter? I'm frankly tired of throwing money and time at this issue. Has anyone heard of something similar? Anything I'm missing here that could be the cause. I'm about at the end of my rope. Thanks for reading and sorry for the book.
-Mike
 
The symptoms you describe are usually a low voltage issue from:

• a failing battery
• a failing alternator
• a parasitic drain
• dirty, corroded, or loose wire connections
• internally corroded battery wires

For 1996+ Jeeps, the OBD-II engine computer (ECU/PCM) re-boots, and the idle settings are deleted, when you: (1) let the battery run down by leaving the lights or radio on, (2) disconnect the battery for an extended period of time, (3) when the battery goes bad and needs replacing, (4) when the alternator is not properly charging the battery, (5) or when poor battery connections result in a voltage drop at the PCM or poor battery charging.

Loose, corroded, or damaged battery cables or ground wires may also cause or contribute to the problem.

Your symptoms are: (1) having difficulties starting the engine without depressing the gas pedal, and (2) the engine will have a low idle and probably stall unless you keep your foot on the gas pedal. (3) The ECU will relearn the idle settings after a short period of driving and the engine sometimes will start and idle normally.

Begin with basic trouble shooting of the start and charge systems. Remove, clean, and firmly reconnect all the wires and cables to the battery, starter, and alternator. Look for corroded or damaged cables or connectors and replace as needed. Copper wires should be copper color, not black or green. Do the same for the grounding wires from the starter to engine block, the ground wires at the coil, and the ground wires from the battery and engine to the Jeep's frame/body. You must remove, scrape, and clean until shiny, the cable/wire ends, and whatever they bolt to.

Jeeps do not tolerate low voltage, bad connections, or poor grounds.

Place your DVOM (Digital Volt Ohm Multi-Meter) on the 20 volt scale. First check battery voltage by placing your multi-meter's positive lead on the battery's positive post ( the actual post, not the clamp ) and the negative lead on the negative post. You need a minimum of 12 volts to continue testing. Next, leave your meter connected and take a reading while the engine is cranking. Record this voltage reading. Now connect your positive lead to the battery terminal stud on the starter and the negative lead to the starter housing. Again, crank the engine and record the voltage reading. If the voltage reading at the starter is not within 1 volt of battery voltage then you have excessive voltage drop in the starter circuit.

Typical voltage drop maximums:
• starter circuit (including starter solenoid) = 0.60 volt
• battery post to battery terminal end = zero volts
• battery main cable (measured end to end) 0.20 volt
• starter solenoid = 0.20 volt
• battery negative post to alternator metal frame = 0.20 volt
• negative main cable to engine block = 0.20 volt
• negative battery post to starter metal frame = 0.30
• battery positive post to alternator b+stud = 0.5 volt with maximum charging load applied (all accessories turned on)

Test the output at the alternator with your volts/ohms multi-meter. You should be measuring 13.8-14.4 volts.

Have your helper turn the ignition key to START while you tap on the starter with a hammer. If the engine starts, you probably need a new starter.

Have the battery, starter, and the alternator Load Tested for proper function in a test machine that applies a simulated work load. Handheld testers are inaccurate and will often pass faulty parts.
 
Last edited:
Thanks Tim! I'll probably have to grab a buddy with a little more electrical experience than myself to help troubleshoot with the multimeter.

I just tried to start it and it clicked once then there was no juice to anything after that. I took the terminals off and waited 30 minutes. Reconnected and it started up find and idled like a rock. Sounds like you're probably right, I'll need to go through all the wires and grounds a little more meticulously if I'm going to solve this problem. The battery and alternator have tested fine so I'm running out of options on what could be causing it (hopefully).

Thanks Again.
 
PROBLEM SOLVED (years ago).

Wanted to follow up on the thread in hopes it might help someone with a similar issue.

Problem: I discovered that the previous owner had installed a CB and did such a great job of wiring it looked completely stock under the hood. It had a aftermarket switch I had checked but wasn't connected. What I didn't' realized is that the aftermarket wire running from the battery through the firewall was just cut when he removed the CB. This wire eventually started grounding out and causing all this havok.

Solution: I fully removed the entire wire from the battery through the firewall and any connections. These issues never happened again.

Lesson learned: Double check any aftermarket additions to make sure someone didn't half-ass it before throwing money at a problem.
 
Awesome. You deserve an award for updating this thread. So many threads here and elsewhere are never updated. Makes me think half the XJs out there just get junked or parked in a backyard and never fixed.

I learned much in this thread, and especially appreciate Tim's tutorial. What I'll remember is what Tim said: "Jeeps do not tolerate low voltage, bad connections, or poor grounds."
 
I will second the thank you because I've been having the same starting issues. Now I have yet another step to take before throwing money at it.
 
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