I’m pretty sure your original alternator was perfectly fine until you pulled the cable off, which instantly fried the alternator. Then you took the car to the mechanic, he tests the alternator, it’s dead. He figured problem solved, and puts in a new alternator. At this point no one even thinks to look for a parasitic drain.
The intake tube between the intake manifold and throttle body may not have been secured and became disconnected, this will cause a check engine light, hard starting and stalling. Was the engine idling at a high speed?
The car was losing power while I was driving it, I had a check engine light as well as the battery light was flashing…that’s why the guys pulled the terminal to check the alternator. Wouldn’t that indicate the alternator was already failing before the terminal was pulled?
The mechanic couldn’t have checked the car before releasing it to me, else he would’ve noticed the dieseling and the check engine light glaring. I’m thinking someone else besides him, found the alarm system wired incorrectly (parasitic drain) after I took it back.
By stating I have a feeling the dieseling was something caused by a mistake on the part of the garage, I should’ve clarified to say I think they missed it. They couldn’t have checked the car before they released it to me, else they would’ve noticed the dieseling.
It didn’t have a hard start. It started as usual, I drove it and the warning lights came on, it started losing power. I brought it home, then when I tried to start it back up the battery was dead and was jumped. It started right up. It never did stall (though I was afraid it was going to), was just losing power.
I’m thinking the idle was previously set higher so as to compensate for the failing alternator. When the new alternator was installed, it resulted in the idle being too high and the subsequent dieseling. Would that seem a sound theory?
Wouldn’t the failing alternator cause a check engine light? Am I correct in stating that would affect the battery as well, and cause the battery light to flash at the same time as the engine light activating? The engine light came on first, then the battery light.
No experience w/2001 Neon, but on most modern gasoline cars, idle rpm determining inputs are
- A/C on vs off, increase
- Transmission in D vs P or N, increase
- Headlights on, rear window defogger on, increase
- Battery needs more charging, increase
- Steering wheel turning, increase
- Engine compartment fans on, increase
- Idle air bleed screw, increase/decrease (your car probably doesn’t use this)
An overly high idle rpm might cause the engine to keep turning a little longer after being switched “off” b/c of its rotational inertia, but that be a second or two at most, and it wouldn’t match the technical def’n of “dieseling”. For an engine to “diesel” a fuel/air mixture must be igniting inside at least one of the cylinders. So there needs to be a fuel source, and on your car that comes from an electrical fuel pump, which presumably completely turns off w/key in “off”. Could happen I suppose if fuel pump relay was faulty & sticking in the “on” position even after key turned to “off”. The only other temporary fuel source with fuel pump off is the pressurized fuel rail, so, another possibility, maybe a fuel injector is leaking. If fuel injector sticking on, that would usually cause a hard to start problem, which you say you don’t have. It’s a true mystery at this point. Hopefully issue is long gone and mystery doesn’t need solving.
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When a hot fuel injected engine is shut off at high engine speed, it can run-on fueled by PCV fumes. If the throttle body hose came loose, the engine will race.
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Three or four seconds, tops. So then it must not have been dieseling?
It’s starting up fine and shutting off fine, now. It’s driving a lot better than it was, seems to have more power. The true test will be when I use the sound system. I’ve always thought that’s wired incorrectly, didn’t even give a thought to the alarm.
I should think though, were the audio system wired incorrectly, there’d still be a parasitic drain. ???
I’m going to take it for a good run, tomorrow.
Thanks for the explanation! The engine wasn’t racing, so that means the throttle body hose didn’t come loose?
Before you even try it have a good audio shop just check for you . The alarm was a problem so this sound system might have been done by the same person . Why take a chance ?
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Good advice!