Cannot resolve cel and occasional misfires - JeepForum.com

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post #1 of 23 Old 06-01-2016, 02:05 AM Thread Starter
AdamRice
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Cannot resolve cel and occasional misfires

I have an ongoing issue with my 98 XJ. Anytime I am driving I will feel a quick and sudden misfire at random. It is like the engine loses power for half a second and then immediately rebounds to normal. This occurs more frequently when cruising on the highway - or perhaps it is simply more noticeable at constant rpm. I also have a perpetual CEL with codes

p1391: loss of camshaft crank - confirmed
p0340: camshaft position sensor circuit - confirmed

I have already replaced
camshaft position sensor: napa part
crankshaft position sensor: mopar dealer part
tune up: rotor, cap, wires, and plugs: napa parts

With the cap and rotor off the distributor the shaft has slight side to side play in all directions. I wasn't able to measure it accurately, but it seems to be about 1/16 to 1/8 of an inch. Is this excessive?

I'm not sure if I'm looking at a bad "new" cam position sensor or if my distributor is worn out enough that the half moon plate isn't always triggering the sensor.

Any ideas of what I should replace to resolve this issue?

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post #2 of 23 Old 06-01-2016, 07:18 AM
CCKen
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Quote:
Originally Posted by AdamRice View Post
I have an ongoing issue with my 98 XJ. Anytime I am driving I will feel a quick and sudden misfire at random. It is like the engine loses power for half a second and then immediately rebounds to normal. This occurs more frequently when cruising on the highway - or perhaps it is simply more noticeable at constant rpm. I also have a perpetual CEL with codes

p1391: loss of camshaft crank - confirmed
p0340: camshaft position sensor circuit - confirmed

I have already replaced
camshaft position sensor: napa part
crankshaft position sensor: mopar dealer part
tune up: rotor, cap, wires, and plugs: napa parts

With the cap and rotor off the distributor the shaft has slight side to side play in all directions. I wasn't able to measure it accurately, but it seems to be about 1/16 to 1/8 of an inch. Is this excessive?


Yes, that's excessive. You should have no side to side play. Some rotational play is expected with an in-service distributor.

I'm not sure if I'm looking at a bad "new" cam position sensor or if my distributor is worn out enough that the half moon plate isn't always triggering the sensor.

Any ideas of what I should replace to resolve this issue?
Consider a replacement distributor.
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post #3 of 23 Old 06-16-2016, 01:38 PM Thread Starter
AdamRice
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I replaced my distributor with one manufactured by WPS and it included a new cam position sensor. There is no more side to side play.

Unfortunately nothing has changed. I am still getting a CEL and p0340. I am still getting random stumbling and loss of power while cruising. Essentially the jeep runs and drives exactly as it did with my old distributor.

I have
+ unhooked the battery for 15 minutes to clear codes
+ cleared codes with a scan tool
+ swapped out the cam sensor that came with the distributor with my previous unit
+ Sprayed the contacts in the cam and crank sensor plugs with CRC electronics cleaner.

Regardless the CEL and stumbling return in under 5 minutes of normal driving.


This is becoming very frustrating. What should I look into next?
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post #4 of 23 Old 06-16-2016, 02:24 PM
jordan96xj
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The next thing I would want to do would be to meter the input voltage to the sensors in question while jiggling the harness around to see if anything disrupts their input voltage. I would also want to do this with things hot to help determine if this condition is perhaps more likely as things get good an hot in the engine compartment. If nothing could be determined from those steps, I would probably want to find a shop that could put a scope on it so that they could visual observe that the sensors are producing the signals they should, with no weirdness.

Things I keep around that help fix Jeeps:
AeroKroil and Fluid Film
BAFX Products 34t5 Bluetooth OBDII Scan Tool and Torque Pro OBD2 App for Android
Etekcity MSR-P600 Digital Multimeter
Bernzomatic TS4000 Trigger Start Torch + MAP Gas
1/2 inch sockets, Breaker, Cheater Pipe, and BFH
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post #5 of 23 Old 06-16-2016, 11:47 PM Thread Starter
AdamRice
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How do I meter the voltage between the sensor and harness? ie: What pins or wire colors and what voltage is correct?
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post #6 of 23 Old 06-17-2016, 08:27 AM
Chrispigg
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I have a 95 country an I have replaced everything I can think of. My problem is getting worse. It runs fine then falls on its face with no power an backfires through the intake ifi try an give it gas the picks right back up. I have replaced cps, tps, IAC, distributor an pick upcoil, intake temp sensor an some more stuff please any ideas?
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post #7 of 23 Old 06-17-2016, 08:33 AM
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These types of sensors are often called 3-wire connectors, and they generally follow the same pattern. Which is that they have one wire that is a ground (usually black, but not necessarily). They have another wire that provides the sensor with constant voltage (for our jeeps typically 5v) this is sometimes called the voltage feed, or "input" wire. Then the sensor does its job (measuring something or another) and it uses its measuring to manipulate that 5v and return it on the 3rd wire which is called the "signal" wire. This signal is typically going to the computer, where the signal voltage (which is often between 0-5v) is letting the computer know that things are changing and how they are changing.

So what I was recommending was that you go to the harness where the connector for the particular sensor is, you can even disconnect the sensor if you want to, and check the harness-side connector to ensure that 5v is at least getting to the harness-side connector. Then one can reconnect the sensor itself and carefully back-probe the sensor-side connector and that will show that the voltage is getting through the connection and to the sensor itself. Wiggling the harness while this is being measured will help to show if anything is causing this voltage to be disrupted while the vehicle is bouncing around or moving down the road.

If you don't own a multimeter, or measuring voltage doesn't make any sense to you right now. That's ok, but it means you probably won't be comfortable doing these tests. They are not hard, and from scratch they can be learned with just a few evenings of watching youtube videos. I encourage you to learn more about it, but if that is not in the cards at the moment, then simple take it to a shop and ask them to diagnose the problem. At which point, they will start with the basics, such as measuring voltages just as described in this thread. (they may move on to more complicated tests, but they will start with the basics).

Things I keep around that help fix Jeeps:
AeroKroil and Fluid Film
BAFX Products 34t5 Bluetooth OBDII Scan Tool and Torque Pro OBD2 App for Android
Etekcity MSR-P600 Digital Multimeter
Bernzomatic TS4000 Trigger Start Torch + MAP Gas
1/2 inch sockets, Breaker, Cheater Pipe, and BFH
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post #8 of 23 Old 06-17-2016, 01:06 PM Thread Starter
AdamRice
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Quote:
Originally Posted by jordan96xj View Post
These types of sensors are often called 3-wire connectors, and they generally follow the same pattern. Which is that they have one wire that is a ground (usually black, but not necessarily). They have another wire that provides the sensor with constant voltage (for our jeeps typically 5v) this is sometimes called the voltage feed, or "input" wire. Then the sensor does its job (measuring something or another) and it uses its measuring to manipulate that 5v and return it on the 3rd wire which is called the "signal" wire. This signal is typically going to the computer, where the signal voltage (which is often between 0-5v) is letting the computer know that things are changing and how they are changing.

So what I was recommending was that you go to the harness where the connector for the particular sensor is, you can even disconnect the sensor if you want to, and check the harness-side connector to ensure that 5v is at least getting to the harness-side connector. Then one can reconnect the sensor itself and carefully back-probe the sensor-side connector and that will show that the voltage is getting through the connection and to the sensor itself. Wiggling the harness while this is being measured will help to show if anything is causing this voltage to be disrupted while the vehicle is bouncing around or moving down the road.

If you don't own a multimeter, or measuring voltage doesn't make any sense to you right now. That's ok, but it means you probably won't be comfortable doing these tests. They are not hard, and from scratch they can be learned with just a few evenings of watching youtube videos. I encourage you to learn more about it, but if that is not in the cards at the moment, then simple take it to a shop and ask them to diagnose the problem. At which point, they will start with the basics, such as measuring voltages just as described in this thread. (they may move on to more complicated tests, but they will start with the basics).
Thanks, I think I can pull this test off. I do have a basic multimeter and have measured resistance and voltage on other things in the past.

Now that I think about it, the CEL never came back on while the Jeep was idling in the lot. It wasn't until I began to drive and in consequence bounce the vehicle around that the CEL returns. As you said this may indicate a short that is only revealed when the wiring harness is sloshing around.
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post #9 of 23 Old 06-21-2016, 06:05 PM Thread Starter
AdamRice
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I performed the test and I'm not sure how to interpret the results. I probed the wiring harness connector by inserting a small paperclip into the back of it. I am taking readings with a cheap digital multimeter and did so with the engine cold and hot.

The orange wire is power and is delivering a constant 5v. I shook and rattled the wiring harness from the sensor all the way back to the ecu and there was no interruption. I also wiggled the ecu plugs.

The brown wire with yellow stripe is signal and consistently alternates between 1.5v to 3.8v. If I hold the engine at a higher rpm the range shortens to around 2.4 to 2.7v. Again I shook the wiring harness in multiple places between the sensor and the computer and it did not seem to affect the read out.

I still have a check engine light and I still have random 1/2 second losses of power.
The light actually went off while I was probing with the engine cold and idling. Once it was hot and I drove around the block a few times the light came back on. Heat or higher rpm may be triggering it.
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post #10 of 23 Old 06-22-2016, 05:43 PM
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Have you already bumped into this post? Anything helpful? Seems very similar (in both codes and symptoms):

http://www.jeepforum.com/forum/f11/c...p0340-1138855/

Things I keep around that help fix Jeeps:
AeroKroil and Fluid Film
BAFX Products 34t5 Bluetooth OBDII Scan Tool and Torque Pro OBD2 App for Android
Etekcity MSR-P600 Digital Multimeter
Bernzomatic TS4000 Trigger Start Torch + MAP Gas
1/2 inch sockets, Breaker, Cheater Pipe, and BFH
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post #11 of 23 Old 06-23-2016, 11:47 AM Thread Starter
AdamRice
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Yes, I already found it shortly after creating this thread.

The first person with the 2000 never stated if or how they resolved their issue. Plus they had the later distributorless ignition.

It looks like the later person with the 98 resolved their issue by installing a 2nd new cam position sensor. Check - already tried that.

Some of dukie564's suggestions were helpful.
I could try checking resistance in the power, ground, and signal wires between the cam sensor plug and ecu plug.
I could also try taking apart the cam sensor plug and recrimping the wires.

I will test those today.
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post #12 of 23 Old 06-23-2016, 08:03 PM
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I sure do wish I could help more. Since you are will to testing things, I've been racking my brain on this one to come up with other avenues.

The problem with quick intermittent loss of power ("fish bites") is that they be caused by a wide variety of things. However, your codes would imply that it is cam crank sensor related. The problem there is that beyond the basics of testing voltages, you have no easy way to observe what they are doing at as far as signals to the computer (and their timing) goes. So you'll have to start making some more pragmatic choices. For example, if you really want this to be a learning exercise, and time is not your main constraint, then perhaps getting some type of OBD2 scan tool (with live data) could help provide you with more insight. Although, if it really is a cam or crank sensor issue, it may NOT provide any additional valuable data. Personally, I would want to see the short and long term fuel trim values when driving at speed after having warmed it up. Just to see if the engine is compensating for a fuel or air issue. But they could very well be fine, and not uncover a cam crank sensor issue at all. To observe those signals is going to take a scope of some type. So it becomes one of those issues where you let a shop troubleshoot a problem that they are probably already familiar with, using tools that can help observe the signals from the sensors visually, or you continue to swap parts and make educated guesses.

If you have an android phone, I would HIGHLY recommend picking up the scanner and android app listed in my signature. If you already have an android phone, that would only run you about $30 total. And it will come in useful again and again. I actually leave one permanently connected with a old spare phone acting as a full time digital dash (so I can monitor coolant temp, rpm, fuel trims, o2 voltages, system voltage, vacuum pressure, speed, and a few other items) at all times. (Fuel trim values are worth their weight in gold, because almost any engine issue related to fuel/air is going to present in the fuel trims almost immediately).

Another option is to let a shop diagnose (and pay them for it), but do the fix yourself. So that you save your time and money focused on the right components.

Another non-shop option is to replace the distributor, cap, rotor, and a mopar cam sensor. given that the distributor play and sensor brand are still variables here (this is definitely into the part-swapping territory).

So it will just be a question of needs and values on your part. If you want your jeep back to running quickly, I would at least let a shop with a scope diagnose it for me, then probably apply the fix myself using parts of my choice. They will also be able to see/diagnose another possibility that won't be easy or possible for you without a scope, and that is the more rare possibility that both sensors are operating within spec, and producing valid/correct signals, but that the computer is not well. It is good to not jump to this conclusion first, but of course it is possible. Typically they would scope the signals from the sensors, and if they checked out, they would then probe the connector at the computer to ensure that the computer is actually receiving the signals. Then if all that checks out, they would call for replacing the computer, or at least testing it with a known good one to verify the diagnosis. Once again, not impossible to do at home, but pretty hard without the appropriate equipment.

I am hoping to get a scope this year (and of course learn how to use it properly), just so that I don't face the same dilemma that you are in.

Things I keep around that help fix Jeeps:
AeroKroil and Fluid Film
BAFX Products 34t5 Bluetooth OBDII Scan Tool and Torque Pro OBD2 App for Android
Etekcity MSR-P600 Digital Multimeter
Bernzomatic TS4000 Trigger Start Torch + MAP Gas
1/2 inch sockets, Breaker, Cheater Pipe, and BFH
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post #13 of 23 Old 06-23-2016, 08:11 PM
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And since you have nothing to lose, and because this -could- be caused by intermittent voltage irregularities at the sensors, you should cover the basics in this video before spending any more time or money:

I should have suggested this before anything else. Apologies.


Things I keep around that help fix Jeeps:
AeroKroil and Fluid Film
BAFX Products 34t5 Bluetooth OBDII Scan Tool and Torque Pro OBD2 App for Android
Etekcity MSR-P600 Digital Multimeter
Bernzomatic TS4000 Trigger Start Torch + MAP Gas
1/2 inch sockets, Breaker, Cheater Pipe, and BFH
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post #14 of 23 Old 06-26-2016, 11:15 PM Thread Starter
AdamRice
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1. Took apart cam sensor wiring harness plug, sprayed pins with electrical cleaner, and squeezed the crimp to make it tighter.

2. Checked resistance between sensor plug and ecu plug.
Signal (salmon + yellow stripe) to pin 18: 0.2 ohm
Ground (brown + yellow stripe) to pin 4: 0.2 ohm
Power (orange and no stripe) to pin 17: 0.2 ohm

3. Wire brushed and cleaned all grounds in the engine bay.

Still have a CEL and occasional 1/4 second losses of power while accelerating or cruising at speeds >25mph. I'm going to take it to a preferred shop tomorrow and explain what I have tried. Thanks for the help forum goers - this is no longer anything simple or obvious.
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post #15 of 23 Old 06-27-2016, 10:43 AM
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Would love to see a follow-up once you find out! Good luck.

Things I keep around that help fix Jeeps:
AeroKroil and Fluid Film
BAFX Products 34t5 Bluetooth OBDII Scan Tool and Torque Pro OBD2 App for Android
Etekcity MSR-P600 Digital Multimeter
Bernzomatic TS4000 Trigger Start Torch + MAP Gas
1/2 inch sockets, Breaker, Cheater Pipe, and BFH
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