1994 Mitsubishi 3000GT Engine abruptly quits and restarts m

Tiny
94BLK3000
  • MEMBER
  • 1994 MITSUBISHI 3000GT
Computer problem
1994 Mitsubishi 3000GT 6 cyl Two Wheel Drive Manual

Three mornings this week, my engine has stopped abruptly with in 1-4 blocks from home. If I cranked it over immediately, it wouldn't fire. Or two minutes later, it started and ran fine for the rest of the day. The fourth day, I couldn't get it to restart. The engine has 150k on it.

Had it towed to a local repair service with a good reputation. They couldn't get it to act up after leaving it out for 3 nights and driving it each morning with some diagnostic equipment attached. They found an error code for the crank position sensor, but insisted that that error could have been generated by several scenarios.

They are sure it is either the crank sensor, the computer or some other expensive electronic device.

Do you have any ideas as to what it may be or suggest a way to narrow the field? I can't afford to have them diagnose by part replacement.

Thanks
Do you
have the same problem?
Yes
No
Friday, May 14th, 2010 AT 6:45 PM

5 Replies

Tiny
CARADIODOC
  • EXPERT
Hi 94blk3000. Welcome to the forum. This is an easy one for a change. Have them install a new crankshaft position sensor. This is the most common cause of a stalling-when-warm problem in any brand of car, and the fact that it acted up long enough to set the diagnostic fault code is just "frosting on the cake". There are other possibilities such as corroded pins in its electrical connector, wires rubbed through and shorting out, or even a slim chance of an Engine Computer failure, but 99 percent chance it is just the sensor.

A good mechanic will perform tests first to eliminate other possible causes rather than just "throwing parts at the problem in hopes one will stick and fix it", (that is the most costly and least effective way to fix a car), but the likelihood of the sensor being the problem is so high, no employer would fault his mechanic for installing a new one and sending you on your way, even if it turns out to not be the cure. If the problem returns, THEN is the time to spend more money on diagnostic time.

Caradiodoc
Was this
answer
helpful?
Yes
No
Friday, May 14th, 2010 AT 8:34 PM
Tiny
94BLK3000
  • MEMBER
What test can preformed to isolate the part? He wants $600 to replace the crank sensor and if that is not the problem he wants another $1500 for the computer.
Was this
answer
helpful?
Yes
No
Friday, May 14th, 2010 AT 8:54 PM
Tiny
CARADIODOC
  • EXPERT
Wow, Unless I'm missing something, that seems WAY too high to replace the sensor. I know things are really stuffed into the engine bay, but that still seems like a lot. This is the same car as a Dodge Stealth, and I think I would have heard about it if that sensor was uncommonly difficult to replace.

As for tests, you will need a hand-held computer called a scanner that plugs into the wiring harness and can talk back and forth with the Engine Computer. The dealer's equipment can do that, but so can most aftermarket equipment that independent mechanics use. I use two versions of Chrysler computers. They will state "present" for the crankshaft position sensor and the camshaft position sensor when those signals are arriving at the computer during engine cranking. When a signal is missing, there are only three wires to test for the crankshaft sensor. With the ignition switch turned on, one should have either 5.0 or 8.0 volts, (I can't remember), the ground wire will have around 0.2 volts, and the signal wire will pulse between 0 and 5 volts while a helper cranks the engine. That signal wire can be hard to read with a digital voltmeter because it bounces around too much.

As a side note, most shops use a "flat rate" guidebook to quote labor times so they are in line with any other shop. I'm going to try to find one here, but if you can sweet talk the dealership repair department people or some other mechanic to show you the suggested time to replace the sensor, you will get an idea of what the repair should cost. Most shops are charging close to 100 dollars per hour now, (and if you could see the list of all their expenses, you'd wonder how they could afford to stay in business), and a TYPICAL crankshaft position sensor should cost somewhere between 50 to 100 dollars. That would mean they expect it to take them four or five hours to do the work. I don't want to second guess an expert without more information, but that does seem really high.

I had five laptop computers puke out on me in the last three months. With them, I could access the Chrysler web site and look at their flat rate guide, but I'm down to just this ten-year-old ultra-reliable tank of a computer, and something won't let me into that site.

Caradiodoc
Was this
answer
helpful?
Yes
No
Friday, May 14th, 2010 AT 9:26 PM
Tiny
94BLK3000
  • MEMBER
The following assumes that the sensor acts up when the engine is being cranked/run?

If this is the case, I 'm still no closer to isolating the problem. The shop had it for 4 days already.

"As for tests, you will need a hand-held computer called a scanner that plugs into the wiring harness and can talk back and forth with the Engine Computer. The dealer's equipment can do that, but so can most aftermarket equipment that independent mechanics use. I use two versions of Chrysler computers. They will state "present" for the crankshaft position sensor and the camshaft position sensor when those signals are arriving at the computer during engine cranking. When a signal is missing, there are only three wires to test for the crankshaft sensor. With the ignition switch turned on, one should have either 5.0 or 8.0 volts, (I can't remember), the ground wire will have around 0.2 volts, and the signal wire will pulse between 0 and 5 volts while a helper cranks the engine. That signal wire can be hard to read with a digital voltmeter because it bounces around too much. "
Was this
answer
helpful?
Yes
No
Friday, May 14th, 2010 AT 9:49 PM
Tiny
CARADIODOC
  • EXPERT
You now realize what the biggest headache is in finding intermittent problems. As a former tv / vcr repairman, we often ran into the same problem. In that situation we would connect a lot of test equipment, then work on other stuff until the problem acted up. With cars, it is not real practical to run beside the car with a tester in your hand in hopes it will act up! That's why you are lucky to have the diagnostic fault code that points to a common cause.

As I mentioned before, I don't like replacing a part unless I'm sure it is defective, but with an intermittent problem like this, and since it is so common, no one will fault you for taking this approach. The chances of it not solving the problem are very small. Unfortunately, sometimes this is all we can do, then if it does not act up again, you can never be certain it is fixed. All you can know is if it still acts up, it is not fixed.

It might comfort you to know that even if you didn't get the fault code, most mechanics would still head straight for the crankshaft position sensor.

Caradiodoc
Was this
answer
helpful?
Yes
No
Saturday, May 15th, 2010 AT 12:02 AM

Please login or register to post a reply.

Recommended Guides