SOS! I'm having serious safety problems with my car shutting off sporadically. Help? - JeepForum.com
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post #1 of 25 Old 09-17-2019, 07:53 AM Thread Starter
Nibroc99
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SOS! I'm having serious safety problems with my car shutting off sporadically. Help?

The people on reddit are out of ideas, so here's my reddit post for you folks to take a peek at. I don't know what to do from here. Edit 4 is the most recent one as of this morning. If anybody has ANY ideas I will greatly appreciate it. This is a serious safety concern and I need a reliable car. If my car shuts off and I lose power steering and assisted braking power, then it's definitely not very safe especially when it happens out of nowhere. Thank you all in advance.


Car occasionally shuts off when idling, then the starter motor turns just fine but the engine wont start - just keeps turning over. (2003 jeep grand cherokee 4.0l)
So this has happened several times, where I am stopped at a red light for a bit, then my engine just shuts off, but the electricals continue working just fine. When I go to turn the car back on (I put it in park and try to turn the engine back on using the key) the engine turns over but doesn't start right away or even at all. Sometimes it takes up to five minutes for the car to actually start again*, even stuck in traffic with cars behind me - causing a dangerous situation. The voltage readout looks normal when this happens, and the radio and blower motor all keep running, so it's not like the car is losing electronic power.

*See halfway through edit 2 (marked with another single asterisk)

My first thoughts are the fuel pump and/or relay or ECM. I've tried cleaning the alternator and battery terminals and I also tried putting dielectric grease on the contacts, to no avail. No engine trouble codes have been thrown when this happens. I feel like the fuel pump isn't the problem though because it does work just fine when the car is running, and when it dies like this and won't start if I turn the ignition off and then back on to the run position I can hear the pump priming.**
**See beginning of Edit 2.

Any ideas?

Edit: I replaced the Crank Position Sensor last year (about 1.5 years ago) because my dad thought it'd be good to do that right after getting the car since they are known to go bad/cause problems. This was done as preventative maintenance. The problem that this post is addressing, however, started about one month ago.

**Edit 2 (Sept. 9): So I've replaced the all-in-one fuel filter/pressure regulator unit, and tested the fuel pressure at the rail before and after replacing, and both before and after the pressure read normal (about 50psi, normal pressure should be between 44.2 and 54.2psi). This morning, the car shut off on me again while I was driving. I was decelerating and the engine just stopped, no sputtering or anything, it just turned off, just like before. I was still in motion this time when it happened, so I put it in neutral and rolled to the side of the road, stopped, put it in park, turned off the ignition all the way and restarted it and it was just fine. * If I turn off the ignition all the way and then start the car, it starts right up, but if I don't turn the key all the way to the off position and then try to start then the car won't start. My dad suggested that this sounds like a computer problem, do you think I need a new ECM to be installed and reprogrammed?

Edit 3 (Sept. 12): So, an ongoing problem that my car has had on occasion when starting the car is that the idle air valve doesn't work right away from a cold start sometimes, so I need to manually press the gas a bit for about 30 seconds until the valve kicks in. This same problem just happened to me yesterday when starting my car. I am wondering if the idle air valve may be my problem since the only time that the problem of the engine shutting off has been when decelerating or idling. I also feel like this could be a cause because the car's electronics don't change at all when the engine cuts out. I will report back on if replacing this seems to fix my problem.

Edit 4 (Sept. 17): I'm running out of ideas. I replaced the idle air control valve, and now it idles much more evenly and smoothly which I never even considered was possible. So that problem is solved when I start the car sometimes. I drove it for most of Saturday and Sunday, probably about 80 miles or so, without a problem. However, yesterday (Monday) and today, while ACCELERATING now and not just decelerating, my car has had hiccups. Yesterday I was doing about 30mph up a short hill, and halfway up the hill it cut out for a half-second and then kick-started itself back on and I was able to continue driving normally the whole trip after that. But then, I was late for work this morning, doing 80mph on the highway (my maximum comfortable speed in this car lol) and it hiccupped just like it did yesterday... Twice in a row. It died for about 4 seconds the first hiccup, and then about fifteen seconds or so passed, and it then had another 7 or 8 seconds on the second hiccup. I'm running out of ideas. Each time this happens, the electricals don't go out. Maybe I need to replace the crank position sensor again? Maybe the power control module has gone bad and I need to replace the ECM? Maybe my fuel injectors are clogged up, as somebody from r/grandcherokee mentioned. My fuel pressure isn't a problem but the injectors have likely never been replaced. I'm scraping the bottom of the pan now, guys... Thank you for all of your help so far. My dad seems to think PCM is the problem but that's just a gut feeling on his part.

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post #2 of 25 Old 09-17-2019, 09:45 AM
blueseasons
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Take it to a competent mechanic and ask them to see if the PCM is sending a signal. That should take them maybe 15 minutes. Randomly replacing parts and gut feelings typicaLLY take time, are expensive and rarely accomplish anything. Always use MOPAR sensors when replacing them.
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post #3 of 25 Old 09-17-2019, 10:26 AM
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First thing to do is clean/check your grounds, particularly G103 which is the PCM/ECM ground on the passenger side engine block to the rear of the motor mount. It wasn't on my 04 4.7 WJ but on my 96 4.0 ZJ this oily/corroded PCM ground took out 2 PCM's and 2 crank sensors to boot. I'm not saying to buy anymore new parts and you need to do further checking/testing. Below is a ground write-up giving info on the grounds/locations.

https://www.jeepforum.com/forum/f310...-info-4192594/

With all that troubleshooting problems have you checked for error codes and which ones were they? I'd think with all the current shut-downs it would still be throwing codes.

When you replaced your crank sensor was it an OE/Mopar crank sensor? That's the only way to go and we've seen major problems with aftermarket sensors, particularly the finicky crank sensor.

Below is a crank sensor resistance test and it's best to do when it won't start. You use a multi-meter set to low ohms and there should be no resistance between the ground & power pins/cavities in the sensor connector which is disconnected.
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post #4 of 25 Old 09-17-2019, 02:56 PM
Double E
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Sounds like classic fuel pump failing to me. Here is why listening for it to run when the key is on is not a good verification of it actually working: https://www.nagca.com/forum/showthread.php?t=34110

An easy verification you can do to rule in or out the fuel pump is to have a can of starting fluid handy the next time it shuts down and does not want to start... (the fluid is a couple of dollars at any parts store...) Remove the air filter, then have a buddy crank the engine while you spray some starting fluid in the intake.

If it runs on spray, it was a fuel delivery problem, if not, it is definitely something else.

'04 Freedom Edition HO & '04 Overland HO (previous '00 Laredo 4.7)
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post #5 of 25 Old 09-17-2019, 04:26 PM
blueseasons
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When my PCM went out, it did not show any codes. Thats why I suggested to rule that out first. Almost anything else will show a code except for fuel delivery. Even an aftermarket sensor will not show a code.
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post #6 of 25 Old 09-18-2019, 05:14 AM
rep-tile
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This awfully sounds like a bad crank sensor. If you replaced it with something else than Mopar, consider it garbage and that would be the first thing I'd replace. It may not throw a code because the crank sensor is the one that detects misfires. Otherwise, it could be a fuel pump failing intermittently. That won't throw a code either.

Check also your main battery cable connectors. WJ battery cables are notoriously crappy.

04 WJ 4.0 - Avital 4103, DB-ALL
91 XJ 4.0 - Avital 4103, Stage-2 aFe intake system, BBK high flow Throttle Body, Jones Exhaust A3518M-5
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post #7 of 25 Old 09-18-2019, 07:25 AM
Double E
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When my fuel pump was on the way out, it would shut the engine down in traffic. Not fun. Understandably, twice I got a bank 2 lean code.
Then it would no longer rev above idle, then it would no longer start.

'04 Freedom Edition HO & '04 Overland HO (previous '00 Laredo 4.7)
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post #8 of 25 Old 09-18-2019, 08:06 AM
JGCJeep
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When it stalls, do you hear the fuel pump start with key on engine off?
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post #9 of 25 Old 09-18-2019, 08:59 AM
broncoguy80125
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This was what mine did when the crank position sensor went bad.
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post #10 of 25 Old 09-18-2019, 10:35 AM
blueseasons
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I must be deaf. I have never heard my fuel pump make a sound in and of the injected vehicles that I have owned. Everybody talks about hearing it in these WJ's. But we do not.
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post #11 of 25 Old 09-19-2019, 07:24 AM Thread Starter
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Uniblurb: The only code being thrown is a bad oxygen sensor, which I'm going to be replacing this weekend. Last time I replaced the CPS I had gotten a code and that's why I replaced it last year. The car always starts up just fine now - I just had to turn the ignition off rather than putting the car in neutral, leaving the ignition in the run position nd then starting it from the run position as opposed to starting it from park from the off key position, if that makes sense.

Double E: I tested the fuel pressure, and it checked out good at 50-52 PSI. The engine goes from running 100% fine to 0% immediately when it fails, so wouldn't it sputter a bit or something before stalling if it loses fuel pressure suddenly? In response to your second reply, it idles perfectly fin, no lower than 600-700RPM and it idles nice and smooth.

blueseasons: I'm hopefully going to be finding a place that can test the PCM soon - that's high on my suspicions list. Thank you for the input! I'd rather not buy and install and reprogram a new one if I don't have to out of the interest of money.

rep-tile: Last year the CPS threw a code so I had it replaced, and the part at the time that I opted for was an OEM-Spec Duralast, built to be exactly like the Mopar part. I couldn't find anywhere even online at the time that had Mopar CPS in stock. It seems like it's been fine up until this problem over a year after having it replaced... It's first on my "parts to look into replacing" list though so I'm likely going to replace that, if anything, next. Also, I believe I mentioned this in the post that I keep my terminals very clean and well-insulated with Dielectric grease. There is no corrosion on the battery or alternator terminals or where the terminals meet the wires. So I've ruled out a bad connection to the battery, especially because the electricals continue to work when the car dies. Also, the car kick-starts itself back on when it's going fast enough.

JGCJeep: I do hear the fuel pump if I turn the key off all the way when it stalls and then back to the run position. The pump sounds like it runs solid, and I tested the fuel pressure at the rail when prin=ming the pump and it reads 50-52 PSI.

Thank you all for your input and I will be doing more testing and repairing until I find the problem.
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post #12 of 25 Old 09-19-2019, 11:06 AM
Double E
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When the fuel pump fails, it cannot keep up pressure enough beyond initial prime. At a standstill, it probably does have good pressure but it cannot maintain it. Read the link in my first post on what occurs internally to make it crank/run but periodically shut down and does not let RPMs increase.

'04 Freedom Edition HO & '04 Overland HO (previous '00 Laredo 4.7)
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post #13 of 25 Old 09-19-2019, 11:25 AM Thread Starter
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Nibroc99

Quote:
Originally Posted by Double E View Post
When the fuel pump fails, it cannot keep up pressure enough beyond initial prime. At a standstill, it probably does have good pressure but it cannot maintain it. Read the link in my first post on what occurs internally to make it crank/run but periodically shut down and does not let RPMs increase.
The thing is, I tested the fuel pressure both with the car shut off and after I started it for a couple of minutes, and it read very consistently between 50 and 52. When I'm idling, there's absolutely no drop in the RPMs, it idles smoothly and don't drop even under load (AC on, car in drive with the brakes on standing still. Also, the problem happens every few days, it seems, really never more than once in one day. So that's why I'm kind of feeling like it isn't the fuel pump, if any of that makes sense? The fuel tank is so hareally w rd to drop with all the rust on the bolts and it's such a big job for me to do right now that I really want to stay away from needing to drop the tank. I CAN do it, but with me being in college and having a job on the side and tons of homework, I really would prefer not to have to dedicate a whole day to doing that unless I'm absolutely positive that that's the issue lol...
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post #14 of 25 Old 09-19-2019, 11:27 AM Thread Starter
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Also just to clarify, I did read through your link, and there's definitely some awesome info as to what could actually be failing in there. If it comes to it I'll definitely follow that tutorial to repair the pump/o-rings etc.
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post #15 of 25 Old 09-19-2019, 01:18 PM
Double E
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I get it. That is definitely a big job. I applaud your looking at all else possible before settling on the pump. Sucks that you're having to spend all that $ on the other stuff though.

See if the starting fluid thing can help to rule the pump out entirely the next time it shuts down. Might need to be able to repeat that the starting fluid lets it run a couple of times just to verify.

I can tell you that in the normal way that the pumps fail, not related to the failure but by then, the sending unit will often act up as well and not read the fuel level right.

The pump will eventually not feed enough fuel to run at all, so there will be a definitive point at which you can verify it with fluid. Just be aware it may not fail completely at the most convenient time and using starting fluid to test it when you're alone is quite difficult. Maybe rig up a tube apparatus so you can spray while turning the key?

'04 Freedom Edition HO & '04 Overland HO (previous '00 Laredo 4.7)
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