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Troubleshooting my 986's Random Shutdowns

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At the end of last year, I drove the car from ID to NC with two quick stalls/misfires going over a mountain in Montana. The rest of the trip, it was perfect. I had serviced it before leaving my parents' home there, as it had spent a good bit of time in storage. Now, when I'm on the road, it will occasionally completely shut down the engine. I roll to the side of the road, then can get it started after four or five tries (it always cranks). Engine temp really makes no difference. Occasionally, I can kill it immediately if I engage the a/c compressor at idle.


What I've replaced so far:


  • Idle Air Control Valve
  • MAF
  • Fuel Pump
  • Fuel Pump Relay
  • Coil/O2/injection relay (rear panel)
  • DME relay (rear panel)
  • Battery (my stepdad had the wrong one in there)
  • Accessory drive/serpentine belt
  • Air filter
  • Crank position sensor


I did locate an old mouse nesting spot between the rear trunk carpet and the firewall (near where the coolant hoses go through). That's all been cleaned up and I couldn't spot any chewed wiring, etc.

Interesting development with this car today. I went to start it up to point it the other way in the garage. When I went to position 1 with the key (where I always pause to glance at the oil level), a rapping noise started coming from the area of the right rear wheel well..."rat-a-tat-tat-tat-tat-tat". Like muffled automatic rifle fire. As it was happening, the cluster lights were flickering. I shut it off, then tried again.


It didn't happen again, but it did take ten or so attempts to start the car (it did crank every time). Once I got it going, textbook idle with no problems. I engaged the a/c compressor, idle adjusted as designed. I've made room for ignition switch replacement gymnastics (for this 6' 3" guy) tomorrow, and will hook up the laptop (Durametric) as well.

In the meantime, any thoughts or ideas are more than welcome. Thanks, all.

Edited by BobieMac
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I had an Audi that developed random stalls. Ran perfectly, and just before the warranty ran out the dealer said there was an interior oil leak in the engine ??? They replaced the heads and bingo, random stalls. I traded the car before the warranty ran out. A few weeks later I spoke with the tech (in the parts dept) that worked on my car for most of the last two years, something the dealer wouldn't let me do - speak to the tech, and he said the new sensors they installed had a different size vacuum fitting and the vacuum hoses no longer fit well enough so they would used clamps to make them fit tight.


Long way of saying check the vacuum.

Edited by ttocs
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