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Frustrating Issue - Car shuts off randomly, runs for no more than 10 seconds


ktm

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Do you use an O2 sensor in closed loop? In other words, can an intermittent bad over-rich signal from the O2 sensor cause your ECU to want to lean out to the point of stalling the engine?

 

If the O2 signal is different for the ECU and your gauge, something may be up there.

 

The reason I'm focusing on the O2 sensor is that it's something that is ignored for the first few seconds or minute of running, depending how you've got it set in your ECU.

 

You haven't mentioned anything about logging the ECU yet. Please try it. That's why it's there!

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Major update. I think the problem is solved. Turns out that I had either a loose connection on a relay or a loose ground for one of the relays. The ground was loose enough that the ring terminals could easily move but still be in contact with bare metal though not tight. I also unplugged and replugged the coil and fuel injection relay plugs (two different relays) while testing out the relays with a spare.

 

I started up the car and waited for the customary shut down. The car ran fine for 1 minute, then 2, 5 and finally up to operating temperature. I shut the car down, restarted it with no problem, and allowed it to idle for 5 more minutes. So far so good.

Edited by ktm
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Mechanical Engineer's Bane: Electrical Problems.

 

"When in doubt, reseat all connections and clean/tighten all star grounding points."

Valeri Nugent, Instructor Block 10 A/N PSM-60A Gas Turbine Generator Set Course 3ABR423X5, Chanute AFB Illinois August 1984

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Mechanical Engineer's Bane: Electrical Problems.

 

"When in doubt, reseat all connections and clean/tighten all star grounding points."

Valeri Nugent, Instructor Block 10 A/N PSM-60A Gas Turbine Generator Set Course 3ABR423X5, Chanute AFB Illinois August 1984

 

Standard electrical problems are not too hard to debug. It's electrical problems that manifest themselves are mechanical problems.

 

It's akin to MS Windows problem matrix. All of the solutions are: shut down, count to 5, then reboot.

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Mrs Nugent did NOT like my 45 second troubleshooting technique... She installed problems in a circuit that was at the END of the 6 foot long wiring diagram. Many symptoms, all identified by the basic 30 second steps at startup. Sat back, thought 'what do all these points have in common' and they all went to the star ground out about 5' 9" from the starting point of the circuit on the wiring diagram. First thing I did (in violation of how we were 'supposed' to do it) was go to the start point and check it. Bad. Walked up "The star point is bad."

 

Shocked and more than a bit angry because she was going to 'teach me' she says "How did you come up with that so fast?"

 

It's the only common point for the six failures this unit is experiencing.

 

"You didn't do that the right way! You didn't troubleshoot the circuts!"

 

Why, they all go to the same point. I'd fix that point, and recheck operation. If it's fixed, I'm done, if it's not THEN I'll check individual circuits that have problems remaining.

 

It was hard to argue with the logic. I was told to sit down. Others went on troubleshooting 'the right way'...I knew then my time in the USAF may be harder than I thought... :D

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Minor update. I took the car for a quick spin since today was the first dry day we've seen in a week. It seems to be ok though I was nervous the entire drive. I live at the top of a hill on a dead end street. If the car stalls out 500 feet from home it means a tow.

 

I am happy to report that it drove fine for the 2 mile jaunt. Not a single hiccup along the way. I'll take it out for a longer cruise next week.

 

I would like to thank everyone who responded to this thread. Your insight and comments were very appreciated.

 

Happy holidays.

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