QuestionQUESTION: I have a 2000 Neon with 112500 miles on it that randomly stalls. It could be at high speed or coming up to a stop this usually happens when engine is hot but I have had it happen once cold. There are no codes set in the computer indicating any problems. I have done some replacing of parts that had problems but ended up not being this problem. They were the fuel pump and filter assembly; the ASD(auto shut down relay); the spark plugs, and the coilpack module. The car's RPM's seem to speed up when the car is about to stall. Also I change the last item because once when it died and wouldn't start the engine had no spark. The fuel pressure is 50psi so that is okay. I changed the ASD relay thinking that was causing the 12 volts to be dropped from the coil pak. (no help) The car sometimes runs for a few weeks and other times it may be a day,(very intermittent and very frustrating). I thought about the cam sensor or crank sensor but the fact that I don't see any codes set makes me think this is not the problem. I thought I had fixed the problem once when I replace the coil pak because prior to changing it I couldn't get the engine to start after 3 minutes of trying. I put in the new coil pack and the engine stated right up. I then put the old one back in and it started right up and ran for one hour without a hiccup. To be safe I re-installed the new coil pak and the car ran for a week before dying again moving 35MPh. Is there something else I'm missing? I hate to think it may be the engine computer module that controls the spark signal to the coil pak?
Thanks in advance for any insight!
ANSWER: Hi John,
I have reviewed the '01 Neon manual I have and can't find anything specific that would explain random stalling. A favorite for a non-monitored item is the egr valve but it doesn't look like there is an egr on that engine. How about worn spark plugs or spark plug wires? Perhaps a catalytic converter with a loose honeycomb that is shifting off axis and blocking the exhaust (does it rattle)? Have you checked the compression? How about the throttle body throat and plate, have those been cleaned? Other than those, I go back to the very basic: flaky ignition switch, flaky ground wire connection from the battery, loose positive cable at the battery. Particularly if the engine will start right up after a stall I would suspect something related to the battery voltage supply circuits or the ignition switch. How are you reading out the codes, with a reader or via the check engine light?
Please let me know if/when you determine the cause.
Roland
---------- FOLLOW-UP ----------
QUESTION: Follow-up to original question. I have the Dodge 2000 Neon service manual P/N 81-270-0025. I'm using a Actron cp9180 scanner/reader for reading of OBD-II codes (of which none show being set). As I mentioned I did replace the plugs and the wire set I believe is okay. The battery I relaced also and connections are good at the battery. The car usually doesn't start after it has stalled unless you let it cool down in most cases. I only had one incident where it wouldn't start when it was cold(Temp sensor was unplugged). I did have one quirky thing I found that may help to zero in on the problem but I am not sure that it may be just a coinsidence. One time when the stalling happened I was doing some under hood T/S and unplugged the engine coolant temp sensor (when I did this the check engine lamp came on,naturally) and the engine started to run for more then a few seconds. After doing this a few times the engine seemed to stay on longer. After getting the engine to stay running longer the fan began to run on the radiator(constantly). It seems like when this happened the car would run longer. In fact I was able to get the car home when I did this. One point I want to make on this thought is that anytime this car has stalled the engine temp seemed to be reading okay, a little less then mid-way(no over-heat condition). I did a resistance check on the temp sensor and at cold it read 28k ohms and when engine hot it read~1.2K ohms. Also when I was doing checks while sitting still after replacing coil pak the radiator fan was cycling properly. I was reading a IR temp of the engine block of about 205 degrees F max. Going back to the spark issue, when the car ran okay if you pulled one plug wire (while running)partly off you would hear the snapping of the electrical arc in the boot of the spark plug wire. When the engine stalled and wouldn't start there was no apparent arc sound when trying this technique. I'm sorry there is alot here, but I'm trying to give you all the facts and symptoms.
Thanks
ANSWER: Hi John,
I would suspect that the plug/wire connections from the coolant temp sensor may be compromised (either open or shorted together, or intermittent). Another possibility, perhaps also present simultaneously, it that either the cam or crank sensor is flaking out when hot, then recovering when cool. That should have set a code, however.
But the tie-in with your fiddling with the coolant sensor plug makes me suspect that would be the first thing to verify (between the sensor plug and ecm). The spark sensors can be checked, when the engine has stalled, by measuring between the tan/yellow and black/light blue (cam) and the gray/black and black/light blue (crank) while turning by hand the crank, via a socket on the pulley bolt and with the ignition 'on'.
You might want to carry a spare plug to check for spark by inserting it in one of the spark plug caps and then grounding its thread on the block while a helper cranks it over.
Thanks for the detailed report of your experiences.
Roland
---------- FOLLOW-UP ----------
QUESTION: If the temp sensor or wiring were bad I would have thought it would have set a code like it did when I unplugged it as mentioned previously. Also the gauge in the instrument panel reflects what the guage is sensing. (When unplugged the guage is at the bottom (cold)and doesn't move while the check engine lamp is on.) I'm not sure what a short would do other then possible show overheat. And if it was a short to ground I am not sure what would happen with that. Also a note on my last follow up of the no spark. When the engine stalled and wouldn't start I was having someone crank the engine while I listen for the arcing sound which wasn't present. So if seems like when it happens it is not letting the coil entergize to release the high voltage to create the arc at the plug's tip.
AnswerHi John,
I just offer the coolant sensor history for your consideration. I don't disagree with your observation about the gauge reading but the bottom line is there anything in the circuit that is falsely affecting the mixture.
The lack of spark may be the sensor issues a suggested, but also listen to whether the fuel pump runs for a second when you turn on the ignition to run so as to verify that the powertrain circuit to the fuel pump is working. That would help to verify that the spark coil is also being energized by the ASD which is also controlled by the pcm. That is about all I can suggest from a distance.
Roland
