Changed crank sensor and filter in fuel tank still didn't work
Per previous posts, my 2003 jeep cherokee sputters and loses rpms and speed and when going down to stop will just die but will start back up. Have changed fuel filter and screen in tank, crank sensor and drained fuel tank and cleaned. I am told by several mechanics it COULD be the PCM/main computer going out as when one mechanic had it hooked up to a 'flight recorder' and lost all communication. This started out sporadic and now seems to be happening quite frequently. Before going thru the expense of getting a new PCM, could this be the problem? This is getting very frustrating!
An expert who has achieved level 2 by getting 100 points
An expert that got 10 achievements.
An expert that got 5 achievements.
An expert whose answer got voted for 100 times.
Re: changed crank sensor and filter in fuel tank still...
This is possible however, the conditions you are discribing are not totaly consistant with that diag. the conditions you are discribing are more consistant with a TPS(throttle possition sensor) being faulty. If you Jeep is higher in milage this is quite common. They do tend to get gummed up. Have your tech remove it & clean it or replace it first with a "known good part" & try that. If that isn't it you may also have a poor connection @ the PCM or the crank sensor. The fact that the tech is losing communication is interesting & if this is happening only when you come to a stop would suggest a poor wiring connection & could be fixxed if the PCM is replaced just by messing with the PCM connector, everyone would think the PCM was @ fault but realy all it was was a bad connection with the PCM.
a 6ya expert can help you resolve that issue over the phone in a minute or two.
Best thing about this new service is that you are never placed on hold and get to talk to real repairmen in the US.
the service is completely free and covers almost anything you can think of.(from cars to computers, handyman, and even drones)
click here to download the app (for users in the US for now) and get all the help you need. Goodluck!
- If you need clarification, ask it in the comment box above.
- Better answers use proper spelling and grammar.
- Provide details, support with references or personal experience.
Tell us some more! Your answer needs to include more details to help people.You can't post answers that contain an email address.Please enter a valid email address.The email address entered is already associated to an account.Login to postPlease use English characters only.
Tip: The max point reward for answering a question is 15.
just a couple thoughts. Injector fuse and relay(does fuse and relay have power to and from them). My understanding is sometime Anti theft will shut down injection pulse so car can not be run. Maybe even timing chain broke. I assume there is no trouble code.
I could be the CKP (crank sensor), but it could also be several other factors including the TPS. The correct way to start a diagnosis would be to see if any trouble codes are stored in memory. I'm assuming all basic ignition components are ok ; spark plugs, etc.
you need to have it connected to an OBD2 machine and watch if you are missing the cam sensor showing RPMs or if your missing crank sensors RPMs, it could be a wiring problem or computer if your seeing the RPMs from both sensors,and the last thing i would check is hooking up a fuel gauge to the reed valve and watch what fuel pressure you have while cranking,if the cam sensor is the culprit it will turn the fuel off after the cranking.
It could do that with a bad switch if it was making poor contact before it disconnects, but that really sounds a lot like the fuel pump is going bad...they overheat and start to bind up, then stop...once cooled down they work just fine till it again gets hot enough to do the same thing all over again. I really hate doing this online because in real life, I'd be doing tons of testing instead of making "educated guesses"
From what you have written, the problem does at first, appear to be a possible crank sensor problem, however, If your mechanic drove it with a "flight recorder" on board and lost communication with the computer, I'd start looking for an electrical malfunction that is depriving the computer of power. Possibly a poor harness connection, ignition switch etc. Could also be an internal computer problem as well, but I'd hold that for last, after all testing has been completed.
If the problem began before you changed the plugs that they are likely OK...Some engines "like" certain brand plugs better than others. You may have a weak ignition coil. Poor spark will generally show up at higher rpm's. Spark should be blue and have good "snap" to it and should easily bridge a 1/4" gap or better. If fuel was contaminated, it should show up at lower rpm's as well. System cleaners sometimes work but often are added far too late to do any good. (tank can hold up to a gallon of water without noticing it.) I use 3oz of acetone and one oz marvel oil per 10 gallons of fuel about once a month...cheaper and more effective than most cleaners. (and does not "melt" gaskets and seals as legend has it) The vehicle speed sensor can also give you problems but needs testing to determine if it's got any problems. It's difficult to diagnose by remote control, but I hope you benefit form something here!
Sounds like contaminated fuel or bad pump/filter.
Now, just because I said that it's probably the crank sensor...Bottom line is do some testing. Or have someone test it. Begin with code scan...even if it shows nothing, that eliminates a bunch of stuff.
Fuel filter is the main culprit when you lose power going uphill. Going level or downhill means that the engine doesn't have to work all that hard and doesn't demand much fuel, so a partially clogged filter can usually flow enough to allow the car to run smoothly. Going uphill requires signficantly more fuel, and if the filter is clogged up, it won't be able to flow enough fuel. This will bog the car down and cause you to lose speed. Change your fuel filter.