QuestionThanks Anthony. One follow up. I searched the archives for similar problems other people posted. I came across something called an IAC valve and a TPS. Could these be causing my stalling too? My speedometer seems to be working fine. I'll have a mechanic look at the reed switch, but was wondering if the TPS or IAC could be a likely cause of the stalling. I did take it to a mechanic. He said it could be IAC motor, TPS, or Air speed control (?) Anyway, the car passed all diagnostics since the check engine light was not on at the time. In fact, the car ran great all day. The mechanic suggested to wait for the situation to become worse to get a proper diagnosis. He could replace one of the 3 things he nmentioned but could not be certain the problem would be fixed. He said that by waiting, it would eliminate unnecessary replacement of parts. Plus, he mentioned that the mitsubishi parts are expensive (because he needs to order from the dealer) so by waiting, he may be able to pinpoint the problem, thus buying onlyt the necessary parts. Do you agree?
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Followup To
Question -
(97 Mitsu Gallant, automatic)THe car stalled after hesitating and jerking, while the check engine light came on. However, it started up immediately and ran normally. This happened twice. The mechanic couldn't diagnose it since the check engine light wasn't on at the time. I got a tune-up with new gas filter, and a fuel injection flush. The car ran fine for a week, but then started hesitating and stalling again. The check engine light comes on. But it starts right back up again. I'm concerned because it stalls while the car is in motion sometimes. When I step on the gas, it seems like it hiccups and I need to feed it more gas to prevent it from stalling. Is this a sign of a foreign substance in the gas tank? ECM? timing belt? Please advise. Thanks!
Answer -
Sharon,
So for the long wait in a reply. My AllExperts account has been giving me problems.
If the car starts up fine after it stalls, then I'd say both your gas and your timing belt are fine. I believe your ECM is fine as well. This is a symptom of a broken speed switch, which is a part of the speedometer in the instrument cluster assembly. With the switch inactive, the ECU (the car's computer) does not know the car is moving and doesn't keep the idle high enough to operate the power brakes.
First off, the idle speed for these cars is 750. When the car is moving, but the clutch is out, the ECU will keep the idle speed above that (possibly up to 1.5k, if you have ABS). This is so you have enough vacuum to run your brakes and steering. So the problem is that your ECU does not notice that the car is in motion. When you put the clutch in, it tries to take the the idle to 750. You turn the steering wheel and use the brakes, requiring vacuum and thus
killing the engine.
So how does the ECU get speed info? There is a "reed switch" that opens and closes whenever a magnet passes by it. Your speedometer is driven by a magnet shaped like a cross. As it spins, it drags the speedometer needle with it, to the right, against the pressure of the return spring. The faster it spins, the more the needle pulls to the right. It is called something like a "deArsenal" movement, and I might have mucked up the details, but that is how it works. So Mitsu put this reed switch next to the magnets in your spedometer, and wala! the ECU now knows your speed.
Two possible causes of your problem. Your speedometer is unhooked or your reed switch is broken. Though broken wires to reed switch not likely.
If the check engine light comes on again and stays on, see if there is an AutoZone in your local area. AutoZone will check your Check Engine Light for free. They will give more information.
Good luck!
AnswerSharon,
The IAC and Air Speed motor are the same thing. They allow air to bypass your throttle plate when your car is just sitting idle. So, if you can start your car when the engine is warm, and it idles fine, you IAC is not to blame.
The TPS is the throttle position sensor. That sensor tells your car's computer (ECU) where the position of the throttle plate is. Once the ECU knows this information, it knows how much air to expect that will enter the engine. If the TPS is telling the ECU a different position than where the throttle plate actually is, it can cause the problem you're experiencing.
Another possible problem could be your EGR valve; exhaust gas recirculation valve. This valve's job is to take any exhaust gas that was not burned up in the combustion chamber, and recirculates it back into the intake system. This is purely for emmissions purposes. Some people completely remove their the EGR valve and block up the hole. Not recommended, since it violates every state and federal emmissions law.
If your mechanic wanted to save you money, he can simply check your TPS, IAC, and EGR. All it takes is a little voltmeter and about 15 minutes. But he can make more money by charging you outrageous prices for dealership parts. You may just need to have your throttle body assembly cleaned. A good cleaning can make all the difference. And that may take an hour, total, to disassemble, clean and reassemble; no new parts needed.
So, I'd advise you to find a more competent mechanic, and ask your new mechanic to just check the items I mentioned and clean the throttle body assembly. But with your new mechanic, don't even tell them you're having a hesitation problem. If they don't think you're having a problem, they won't suggested unnecessary parts as your current mechanic is doing.
Good luck!
