New plugs, sudden death after acceleration - JeepForum.com
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  • 1 Post By Wabatuckian
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  • 1 Post By Purcell69
 
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post #1 of 5 Old 04-08-2020, 04:05 PM Thread Starter
Purcell69
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2001 WJ 
 
Join Date: Apr 2010
Location: Oklahoma
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New plugs, sudden death after acceleration

Last week, I broke the kickdown cable for the transmission and replaced it, along with the broken Throttle Position Sensor. I had all of the Check Engine codes clear and the Jeep was running great, at least as well as a 2001 WJ Laredo 4.0L should.

Today, at lunch, I ended up sitting in queue at the drive-thru for 15 minutes or so, idling with the A/C on. Everything working as it should, Jeep in Park until it was my turn.

I pulled away, drove about a mile at 40-45 MPH until I got behind a semi that pulled on to the highway in front of me. He was rolling along at 25 MPH and as he cleared off at the next intersection, I rolled on to full throttle to check the kickdown cable. The transmission downshifted and I accelerated up to 65 mph and leveled my speed. Moments later, the engine cut out. I shifted in to neutral and coasted about a mile before stopping.

The engine would not restart, so I checked for codes and got P0353, P0352, P0351. A quick internet search led me to move around the wire harness at the rear of the motor a bit. The engine restarted, but had an obvious miss and flashing Check Engine Light. I was able to drive home and once there, I pulled codes P0300, P0302 and P0305 (Engine miss, cylinders 2 and 5). The P0351-0353 suggest a failing coil.

When I was working out my issues the other day, I had misfire codes for cylinders 4 and 6 and suspected they were related to the spark plugs a previous owner had installed (Bosch Platinum +4), since the engine was still running smoothly. I installed the factory Champion Copper plugs gapped to 0.035".

Am I looking at a failing coil pack? In the driveway, it is idling smoothly again now that it has cooled off, unlike the obvious miss that it had earlier in the day.

https://www.jeepforum.com/forum/f310...ssion-4392669/

-Joe

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post #2 of 5 Old 04-08-2020, 04:43 PM Thread Starter
Purcell69
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Ok, so I cleared the codes after letting the Jeep sit for four hours and then took it for a test drive. On start up, the idle is smooth. The engine ran well even with the A/C on. I let the Jeep warm up to operating temperature and ambient air temperature is 90*.

Driving down the street, everything works as it should. I made a couple of hard acceleration runs, including making the transmission downshift via the kickdown cable. On the highway, it accelerated as it should and cruise control functioned normally. After turning back off the highway and while coasting down to our mailbox, I got a Check Engine light again, but no other signs of trouble. I pulled back in to the driveway and checked the codes again. P0306, cylinder 6 misfire. I'm starting to think the coil pack is going bad.

-Joe
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post #3 of 5 Old 04-08-2020, 05:39 PM
Wabatuckian
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Quote:
Originally Posted by Purcell69 View Post
Ok, so I cleared the codes after letting the Jeep sit for four hours and then took it for a test drive. On start up, the idle is smooth. The engine ran well even with the A/C on. I let the Jeep warm up to operating temperature and ambient air temperature is 90*.

Driving down the street, everything works as it should. I made a couple of hard acceleration runs, including making the transmission downshift via the kickdown cable. On the highway, it accelerated as it should and cruise control functioned normally. After turning back off the highway and while coasting down to our mailbox, I got a Check Engine light again, but no other signs of trouble. I pulled back in to the driveway and checked the codes again. P0306, cylinder 6 misfire. I'm starting to think the coil pack is going bad.

-Joe
Joe, I would check the coil pack with a multimeter first. Procedure can be found in the manual.

Josh
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post #4 of 5 Old 04-08-2020, 10:28 PM
jtec
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DETAILS- it is not a kickdown cable but a TV cable.

Might start by checking the engine harness, they would chaff and rub thru causing a intermittent grounding issue that would throw the codes you mention. the rear head bolt on the left manifold side was the area to check. Sometimes tugging shaking harness would cause the issue to appear confirming the wiring has rubbed thru
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When I see the price of OEM I think aftermarket.
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post #5 of 5 Old 04-09-2020, 04:52 PM Thread Starter
Purcell69
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Quote:
Originally Posted by jtec View Post
DETAILS- it is not a kickdown cable but a TV cable.

Might start by checking the engine harness, they would chaff and rub thru causing a intermittent grounding issue that would throw the codes you mention. the rear head bolt on the left manifold side was the area to check. Sometimes tugging shaking harness would cause the issue to appear confirming the wiring has rubbed thru
I wasn't able to find anything obvious, but with 219k miles, anything is possible.

The new coil pack arrived today. I installed it and went for a 100 mile test drive with no check engine light and no problems, so hopefully it was the coil pack failing, but I will continue to look at the main harness at the back of the motor, since moving it was what it took to get me off the side of the road and back home.

I agree that it is a TV cable, however, some parts suppliers tend to consider the throttle cable to be a TV cable, since it opens the butterfly in the throttle body. Twice I almost ordered the incorrect part as a result. I referred to the TV cable as the kickdown cable as a means of clarifying only. Old school vs. new school I guess.

-Joe
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