NEED DIAGNOSTIC HELP: Dead Miss, No Codes, 2007 Liberty Limited - JeepForum.com
 
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post #1 of 9 Old 01-17-2017, 01:56 PM Thread Starter
RedJeepster45
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NEED DIAGNOSTIC HELP: Dead Miss, No Codes, 2007 Liberty Limited

At 245,000+ miles and a weekend wash job that included spraying under the hood (I know, I know), Monday morning's startup was normal, but a half mile into a 55-mile one-way commute to work, I noticed a slight miss, and just figured it was a little dampness. Three miles later it starts knocking so hard I thought it would quit before I could find a place to pull over -- but before I did, most of the knocking and missing subsided, so I decided to keep driving a see what happened. At open-road speeds (55-70), I felt almost nothing after a while, again attributing the trouble to leftover dampness under the hood. Made the 110-mile round trip OK, but the miss was still there, and was more pronounced during rapid acceleration (particularly from low speeds), and especially under a load, like going up a relative steep hill at anything less that 50 or so mph. The next day, I let my regular shop check it out. All they found was moisture in the distributor and a some other places. They dried it with compressed air and by hand as best they could, and sent me on my merry way. Made the 110-mile commute again, and felt an OCCASIONAL miss, but nothing like the previous day, so I assumed that there was just a little residual dampness somewhere, and that it would clear up within a couple of days.

About six months and 10,000 miles later, I still get the miss -- always most pronounced during rapid acceleration (particularly starting from a lower speed), and especially under a load, like when climbing a hill at reduced speed in overdrive (fourth gear -- and it's a 2-wheel drive, by the way). If i hit the traction button, it eliminates the miss almost completely -- at least enough that I don't notice a buck, or hesitation, or feel a misfire -- but then in the lower gear, I've got better torque so that makes sense.

The problem has NEVER set a (visible) code and the shop found no code when they checked it originally. There's basically no difference in the gas mileage, which ranges from about 22-23 mpg on highway driving at 65-72 mph up to about 26 mph if I'm driving long distances on two-lane roads at around 50-55 mph. And driving on level ground a 55 or faster, I never notice a thing.

Sorry for the long post, but I wanted to describe the problem fully. I still suspect something electrical (distributor, plugs, wires, coil), but I'm also wondering about vacuum leaks, or fuel/fuel filter issues, injectors, and even the catalytic converter.

I would appreciate any feedback -- guesses, similar personal experiences, whatever -- that will help me get a better diagnosis before I start dropping $$$ into this little jewel. At 255,000 miles today, I think i can get that many more out of it, if I can solve this (what I hope is a LITTLE and NOT SERIOUS) problem.

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post #2 of 9 Old 01-17-2017, 02:51 PM
joey671
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That sounds like an electrical nightmare. First off, before you bring it anywhere start inspecting your plugs for oil, gap or spark. If its surging from low rpm, sounds like a weak spark. Do you overheat? Look inside you coolant if and see if it has sludge. Could also be loss of compression due to a head gasket leak.


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post #3 of 9 Old 01-17-2017, 02:59 PM
cranbiz
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Is the 07 that much different from the 06? As your profile is not filed out, I'm going to assume you have a 3.7L. My 06 doesn't have a distributer, it's coil packs controlled by the PCM and I would suspect a coil pack/wiring that has an issue.

Can you plug into the OBDC port with a scanner and look at live data? Something like Torque with a BT OBDC reader and a smartphone should be able to capture that data and pinpoint which cylinder or cylinders to start looking at.

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post #4 of 9 Old 01-17-2017, 03:04 PM
joey671
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I just looked in my 05, i have packs as well, try removing your distributor and spray it down with wd40(water displacement). Although, the water shouldve dried up by now unless the damage has already been done. Look for any abnormalities.


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post #5 of 9 Old 01-17-2017, 03:12 PM
cranbiz
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You don't have a distributor, that's what's throwing me for a loop. The coil packs are fired by the PCM and the PCM decides when to fire the coil pack based on inputs from the crank and cam sensors.

I would start with pulling the plugs and replace them with OEM plugs. Don't buy cheap autolites or expensive double platinum plugs. Gap them and install.

Another thing for the OP to check right now would be the plugs into the PCM. Pull each one, look for signs of corrosion. reseat those connections and make sure the locks latch and the pins are not pushed in.

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post #6 of 9 Old 01-17-2017, 03:41 PM
Robert2005jk
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You have water in the cam position sensor plug. If you sprayed the engine off like you said. The water has settled in the plug. As the engine warms up the water starts to steam up and is causing a miss reading of the cam. Pull the plug off the cam sensor and inspect for condition. If you sprayed up under the engine on the passenger side the same thing should be happening with the crank position sensor. The electrical connection are almost 10 years old and the seals don't seal like they did when they were new.

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post #7 of 9 Old 01-21-2017, 02:59 PM
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Id question the quality of a shop that says you have a distributor on a 3.7L. Also, if it's an active misfire, there are several ways to find out where it's coming from. Sounds like water initially, but a lot of miles and time has passed. Should be long gone now. Could have a weak coil, or bad spark plug, or even a weak fuel pump. Decent shop with a real scan tool with a real level A tech should find the problem within an hour easily.
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post #8 of 9 Old 01-22-2018, 04:44 PM Thread Starter
RedJeepster45
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Help Me Diagnose This

2007 Jeep Liberty KK, 3.7L 2-wheel drive 4-door vehicle, approaching 270,000 miles. Never a significant problem, although I do presently have an intermittent miss, almost always noticed immediately after startup and at acceleration speeds. I'm convinced that's one or more failing coil packs, but that's what I DO know.

What I DON'T know is the source or a buzzing sound, noticed also mostly right after startup and at acceleration speeds. I first noticed it 6 months or so back, and I thought maybe it was a broken or leaking exhaust manifold heat shield. It has never appeared to affect the way the Jeep runs or handles, but the noise is getting noticeably louder. I've checked for braces and other parts with loose bolts that could be vibrating and found nothing. From the driver's seat, the sound seems to be coming from the front right (passenger) side of the engine, but when I raise the hood and check from outside, it sounds as if the noise is coming from the alternator or maybe the AC compressor. The serpentine belt is good, and appropriately tight, and I've checked the alternator output. It's at 14.2 to 14.4 consistently, and I've had no battery problem at all.

But what was at first a buzzing sound seems to be developing into a louder noise, with more of a rattling sound. But note that the noise IS NOT AUDIBLE at all when the engine is just idling. As soon as you give it gas and the RPM's start to run up, the racket kicks in. While driving, the noise seems either to stop or get much quieter (it's hard to tell which) if I release the accelerator, and it is not very loud at highway speeds (or I can't hear it because the vehicle speed and wind noise are making it less noticeable).

I'm wondering if maybe a bearing is going bad in the alternator pulley, or the AC pulley, or somewhere else.

Again, there seems to be NO DIRECT IMPACT on how the engine runs -- except that it's noisy and soon will be embarrassing to drive down the street at 25-35 with all that racket under the hood.

The only other think that MIGHT be important is that the AC hasn't worked in two years due to a body control module failure, but the AC was the only component affected, and I almost never drive the Jeep in hot weather with the windows up, so I've never bothered to replace the module.

Can somebody out there please point me toward the most likely place(s) to start checking. I can't be the only one who has ever experienced this irritating problem, and IT IS DRIVING ME CRAZY!!
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post #9 of 9 Old 01-27-2018, 02:50 AM Thread Starter
RedJeepster45
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Can Somebody Please Help Me Diagnose This?

2007 Jeep Liberty KK, 3.7L 2-wheel drive 4-door vehicle, approaching 270,000 miles. Never a significant problem, although I do presently have an intermittent miss, almost always noticed immediately after startup and at acceleration speeds. I'm convinced that's one or more failing coil packs, but that's what I DO know.

What I DON'T know is the source or a buzzing sound, noticed also mostly right after startup and at acceleration speeds. I first noticed it 6 months or so back, and I thought maybe it was a broken or leaking exhaust manifold heat shield. It has never appeared to affect the way the Jeep runs or handles, but the noise is getting noticeably louder. I've checked for braces and other parts with loose bolts that could be vibrating and found nothing. From the driver's seat, the sound seems to be coming from the front right (passenger) side of the engine, but when I raise the hood and check from outside, it sounds as if the noise is coming from the alternator or maybe the AC compressor. The serpentine belt is good, and appropriately tight, and I've checked the alternator output. It's at 14.2 to 14.4 consistently, and I've had no battery problem at all.

But what was at first a buzzing sound seems to be developing into a louder noise, with more of a rattling sound. But note that the noise IS NOT AUDIBLE at all when the engine is just idling. As soon as you give it gas and the RPM's start to run up, the racket kicks in. While driving, the noise seems either to stop or get much quieter (it's hard to tell which) if I release the accelerator, and it is not very loud at highway speeds (or I can't hear it because the vehicle speed and wind noise are making it less noticeable).

I'm wondering if maybe a bearing is going bad in the alternator pulley, or the AC pulley, or somewhere else.

Again, there seems to be NO DIRECT IMPACT on how the engine runs -- except that it's noisy and soon will be embarrassing to drive down the street at 25-35 with all that racket under the hood.

The only other think that MIGHT be important is that the AC hasn't worked in two years due to a body control module failure, but the AC was the only component affected, and I almost never drive the Jeep in hot weather with the windows up, so I've never bothered to replace the module.

Can somebody out there please point me toward the most likely place(s) to start checking. I can't be the only one who has ever experienced this irritating problem, and IT IS DRIVING ME CRAZY!!
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alternator , bearing , buzzing , catalytic converter , coil , distributor , injector , miss , pulley , rattling

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