On Friday, began to die with no warning while driving. Pulling over, letting it set for 15 seconds, and restarting allows it to start right up.
Saturday, it gets worse, so on Sunday, I replace the fuel filter. It then starts dieing every block or so.
Today I take it to a shop…they drive it around, it doesn’t die…put it on the diag. machine…nothing is wrong.
I drive it this evening for awhile, and it dies again.
it FEELS like it is running out of fuel (tank is full), kind of sputters for a second and dies. Could the fuel pump be going bad, but not show up on the diag. machine?
The two things you fellows have suggested are the top suspects.
It could be the fuel pump, or the ignition module. It could be any of a number of other things, as well, but those are the two most likely items in my experience.
Many ignition and fuel system components act up intermittently when they start to fail (and this can occur with any electrical or electronic device). And many, at any given moment, either work or don’t work. Testing while they’re working only verifies that, at the moment, they’re working. You’ve got to catch them in the act, running tests while the symptom is present.
I don’t know what kind of “machine” was used. There is no single magic machine that tests everything. Mechanics use a variety of test equipment and procedures, just as physicians do. Which equipment and which tests are appropriate vary with different situations.
With the suspicion that it may be a fuel pump, I’d be inclined to do two tests that will sometimes (though not always) reveal weakness in a fuel pump that might not otherwise be detectable. First is to test the fuel pressure and flow. If those test OK, next is a current ramping test, which involves measuring the pattern of fuel pump amperage on a lab scope. If the results of either test are poor, the pump is going out.
Is it possible that the timing belt is slipping. If it broke, the car wouldn’t work at all, but if it were to slip a little, that wouldeffect the timing enough to kill the engine, the question is, could it slip back (or further) to get the timing back to where it should be long enough for a mechanic not to notice the problem. IIRC 100,000 miles is about when those should be replaced (at least for cars with an interference engine.) BTW my guess is that a Jeep is a non-interference engine, but if I’m wrong, you’ll probably want to get that belt changed soon (even if it’s not the problem). Or you’ll have much bigger problems.
I’m with GaryT on this one… As for the timing belt, I could see the belt slipping and retarding the valve timing and making things worse, but not then slipping the other way to improve them again nor slipping enough to be right again.
This is just a WAG, but check your thermostat. Sometimes one can go bad and the whole cooling system fails, causing a remarkable collapse of engine functions. This may not be the case of course, I’d try a $3 bottle of fuel injector cleaner in a full tank if you think it seems to be the fuel system.
The noises and symptoms a vehicle gives before stalling and “dying” are very helpfull to know. Good luck.
Problem with it being the timing belt is that 15 minutes of cooling time really isn’t enough to make a difference…
You didn’t say if it was an automatic or manual, but you said it happens “while driving”, which I assume means while in motion.
I’d guess that the engine has a breating problem… oxygen sensor or mass airflow sensor, perhaps…?
manual transmission.
it doesnt make any noises before dying, it just loses all power.
I don’t know if the fuel pump tests will work, as it doesnt seem to be low on power at all…it runs completely normal, then WHAM shuts off…so I stop…wait 15 SECONDS or so, and it starts right up.
I’m going to dump a bottle of fuel injector cleaner in it and drive it empty…maybe I got some bad gas?
Gary–would a fuel pump work at 100% capability, then suddenly fail, then work normally again as it was going out? Or would it perform at 90%, then 75%, then 50, then fail?
I seriously doubt it’s the timing belt or chain. They can get loose enough to jump teeth, but they never jump back to where they were. The symptoms are not at all indicative of this type of problem.
I also don’t see it being the thermostat. Again, the back and forth works/doesn’t work situation is inconsistent with a thermostat problem.
Bad gas can cause poor running, but hardly ever causes dying. And the fuel mixture in the tank is constant (until more is added), so that doesn’t jive with its running normally for long periods.
…would a fuel pump work at 100% capability, then suddenly fail, then work normally again as it was going out? Or would it perform at 90%, then 75%, then 50, then fail?
Either way is possible. Fuel pumps have more capacity than is always needed, so a pump working at less than 100% might not cause any drivability symptoms. But being electric, they can go back and forth between working adequately and not working adequately. The specific tests I mentioned could show a weak pump even it’s working adequately at the time. It’s not a certainty that they would, but it’s about all that can be done without testing for the problem while the symptom is occurring.
This would create a mechanical problem easily diagnosed by the mechanics. They dont slip back and forth on the gears easily. Even if it did, it would cause poor performance and a rough idle at first and then after slipping another tooth or two and it would die. It wouldnt cause the sporadic off/on like the OP describes.
I would start with fuel line restriction or pump and then have the ignition checked. The computer which controls the spark and/or the injectors could be acting up too.
The test is to listen carefully when turning on the ignition key to see if you hear the fuel pump running - it’s in the gas tank so listen there for a humming noise. If you hear no humming but the car eventually starts and runs fine for a while, then replace the fuel pump relay.
This varies with the car. Some run the fuel pump when the key is switched to the on position, some do that but only for a few seconds, some don’t run the pump until key is switched to the start position. And unless you electrically test the circuits to the relay and pump while doing the above, you don’t know whether it’s a faulty relay or a faulty pump.
I’m pretty sure the 94 jeep would be somewhat obvious from the hum/no hum when turning key to on (yes, might not go on forever, but worth checking)…but back to my original point sans extra info:
The problem hints at the fuel pump relay in that it will start and run fine after it shuts down. Definitely worth checking into.