|Topic Review (Newest First)|
|10-27-2019 01:09 PM|
|904block||i had the similar issue a few months ago i was at a dead stop and i went to press the gas and my jeep started going crazy and my check engine light came on so i pulled over did the key dance pulled the codes and noticed it was for the crank sensor so i made to the Autozone bought a new crank sensor installed it there in the parking lot and i went to start my jeep and it was worse multiple codes jeep started buckling it sounded like it wanted to die . so after switching out multiple crank sensors from Autozone i decided to go to the junk yard and pull one out of a different jeep which was the OEM sensor from the dealership installed it and everything went away instantly ! so when i returned the crank sensor back to Autozone a employee that worked there said the reason why it may have not worked is because the OEM sensors might have had a different output than the sensors Autozone sell .. but since then i had no more problems like that .. just sharing my experience .|
|10-27-2019 06:45 AM|
|10-26-2019 08:48 PM|
So, here's where everything has ended up:
I did a lot of searching for info on a "re-learn" procedure for the crankshaft position sensor install (just in case) to maybe get rid of the random misfire code.
I ran across a thread on DodgeTalk(dot)com called "Crankshaft Position Sensor Learning Curve". There was a list of three options that could perform a computer reset.
The following is the third option that I ended up using"
You can do what is often called a "hard dump".
We (techs) often do this when we need to totally reset the ECU and either don't have the proper tool close by (too lazy to walk to the toolbox and get it) or just are "in a hurry."
First, disconnect positive + battery cable at the battery and ground it to the chassis. Yes, the POSITIVE CABLE.
Wait a few seconds, 30 won't kill ya.
Now reconnect the positive cable. Careful, no sparks now.
Get in the vehicle, turn ignition key to ON (run) position, now depress fully and release the gas pedal 5 times to set the TPS to WOT. (Make sure the floor mats do not keep the pedal from going WFO0
Turn the key OFF, wait a min, and you should have cleared everything in the ECU except for the factory programming.
The hard dump does not effect the (factory) alarm, the only thing I noticed is my radio presets, as this method came from a working Chrysler tech, I doubt there are any negative effects.
I tried this after three days of trying to get the P0300 Random Misfire code to go away after changing the CKP sensor. I'm now two days into driving the WK and the code has yet to come back and there have been no other running issues.
As of now, I'm calling it fixed.
I did end up changing all 16 spark plugs and wires, but this was after the hard reset and the code was gone prior to changing the plugs.
|10-21-2019 12:00 PM|
|99sajeep||The FSM doesn't mentioned anything about a relearn procedure.|
|10-21-2019 10:47 AM|
|Avs||If Iím not mistaken, after you replaced the crankshaft position sensor you may have to run a relearn process using the scanner. I doubt you can do with the basic one way scanner.|
|10-21-2019 09:24 AM|
|RCS1300||I use autoenginuity software downloaded onto my laptop and it provides misfires by cylinder for my 4.7L. The cost is approximately $600 for one brand/make vehicle.|
|10-21-2019 07:28 AM|
I'm looking into the Torque app to try and maybe narrow things down a bit, but I don't know much about that app (and I'm an iOS person...). I have an old racing buddy that swears by it.
It looks like the Torque Pro app can be downloaded onto a PC, but I want to get some info from others about the extent of functions thru the app. Can it read individual cylinders in a misfire situation? I mean GPS, accelerometers, custom gauges, etc. are all nice, but if it doesn't get me further into my Jeep's computer, then it's a waste of money for right now.
|10-21-2019 07:05 AM|
Spark plugs only last 30,000 miles or 2 years in this vehicle. Make sure you replace them with the correct OEM plugs.
You need to find out which cylinder(s) is misfiring. I do not have your engine. In my 4.7L I would pull each plug wire one at a time while the engine is running to see if the engine idle changes to try and identify the cylinders. You could also use a spark tester on each cylinder. This assumes that spark is the issue.
Fuel could be the issue (fuel pump or injector). It is less likely but possible. For this you need to check fuel pressure first. If that is okay then you can try an injector leak down test.
Given that this is becoming more diagnostically challenging, you may want to find a great local mechanic and have the mechanic do these diagnostic tests for you. It will probably save you time and money in the long run.
|10-21-2019 06:46 AM|
Originally Posted by Avs View Post
|10-20-2019 07:54 AM|
Have you done any intake valve carbon clean? This can help with misfire issue at idle due to carbon build up on the back of the intake valves.
|10-19-2019 04:04 PM|
Well, it's been a rough week for me at work. Long contract negotiations all week, but I never had time to start looking at the WK before it got dark.
I'm finally looking at things this weekend. I got a crank sensor on order this week anyway and it arrived this Saturday afternoon.
Still, the only code showing up is P0300.
A couple things first:
- engine was low on oil. Apparently due to a leaking rear main seal that has just started showings signs. That might explain the MDS "activation" codes I got. I put the extra 1 qt and a half I had here in, but it still needs about 1 qt more. (Currently has about 5k miles since last oil change, but the seal issue wasn't there when I changed the oil.)
- I replaced the crank sensor. Sensor is a Mopar part. Was pretty easy. Went for a drive and the P0300 code came back. So no change.
- I'm checking plugs now and they are worn more than I would have expected. First two so far are reading a gap of .058" on the main firing one, and .050" on the secondary "wasted spark" plug. Current plugs have 52k miles and they are just over 2 yrs old. I'll plan for a new set. Wires also.
So my scanner does not have the ability to read which cylinder is misfiring. What next? Driving a short distance after replacing the crank sensor, the engine gets a definite misfire and runs a little rough. Stop and start it back up again and it's smoother, then will pick up the miss again shortly.
What else to look at?
|10-15-2019 05:35 PM|
In many instances, a bad crank or cam sensor won't throw a code, but since you were able to view it once, you can be sure there was a problem when it triggered and is likely the cause of your "thump" and misfire. Replace it and since it's high mileage, might as well replace the camshaft sensor.
|10-15-2019 04:57 PM|
|RCS1300||I would do basics - spark, fuel, air, compression. If you have a scanner that can read misfires by cylinder, that may narrow down the issue and save you some time. Do not throw parts at the car, even Mopar parts.|
|10-15-2019 04:41 PM|
Yes, stock 5.7 with only mod being the addition of a catch can. Most recent maintenance was replacing two rear most exhaust manifold bolts on passenger side (2 days before). Only other thing beyond that was oil change about almost 2 months ago.
My scanner can read most of the codes, but doesn't keep history after being disconnected. I looked thru the live data while running it, and most everything looked within range. Fuel trims didn't appear abnormal, but RPM's at idle (with engine loping because of misfire) were jumping around a lot. Figures.
Yes, currently the only code showing up (last 2 times I checked it) is the P0300.
I'm not driving it again until I can get this figured out. I'll be checking a lot of things once I get some time. I have a spare vehicle to drive, but I've been swamped with contract negotiations for a construction project these last two days. Part of the reason I had to drive it yesterday. I just didn't have the time to wait on a tow...
At first I thought the trans was in Limp Mode, but it wasn't. I could manually shift thru all the gears and it was running in 5th on the highway. But the misfire in the engine was very noticeable under load/acceleration. I don't think there is anything trans related, at the moment. Further driving and there could be. Another reason why I'm not driving it.
I was wondering about anything else beyond the Crankshaft sensor only because it's not showing the code as it did before. In my mind, that's the first place I need to start.
Oh, for what it's worth, the engine has over 219k miles on it. I'd be willing to bet that sensor hasn't been replaced before.
|10-15-2019 02:41 PM|
All of your symptoms are consistent with a bad crankshaft sensor. It acts as an input shaft speed sensor for the trans. If it suddenly loses communication, it will look for a lower gear in limp mode which is probably the source of your "thump". The RPM based vibration is also consistent with a misfire. When it regains communication, all may seem normal, but problems like that always get worse until complete failure.
Your scanner presented with crankshaft sensor codes. Is there a reason you want to look at something else? You're lucky you even got the code. The crank and cam sensors will often go bad and never show a code. It's an easy fix and easy to reach. One harness and one bolt. Just make sure you go with Mopar for that sensor. Had two defective Auto Zone crank sensors in a row. Thinking there's little chance of getting two bad ones, I wasted a lot of time and money looking for other issues.
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