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P0300 Engine misfire reproducible only under very specific conditions...but why?!?

1264 Views 4 Replies 2 Participants Last post by  jk
2010 Traverse 180,000 miles. Runs well over all. This winter it started doing a P0300 misfire under these conditions:
1. Vehicle is started and run only ~30 seconds total time to move it to a new position on driveway.
2. Vehicle sits there w/o being started again overnight
3. The next am when you start it, it rumbles/ shakes a little with misfires and CEL comes on. After a minute it goes back to running smooth.
If you run the car for a normal trip of any distance and park it it will not misfire the next start up

Took it to shop and got complete "tune up" (new spark plugs, cleaned MAF, throttle body, air intake, had a few bottles of injector run through) and this did nothing to stop this issue.

Other than not doing this (!) how can we get this issue to go away?
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sounds like the very short 30 second run- leaves unburned fuel in the cylinders.

when you start it-- do you start it- and while its revving high-- do you immediately put it into gear and move it-- and then shut off?

when its running at high idle- the vehicle is doing double injector pulses (running rich) to get fuel to help warm up the CATS.

next time you move it-- wait till the engine idle is down below 900.
(I actually dont move my car until RPMs fall below 1000).
Ok interesting. I never knew it went from high idle to normal. I would say yes- we were moving it while in the high idle mode. I will give the car a moment to switch in the future and see if this solves the problem. Thanks for your time.
JK, do let us know.
Very interested to see if it is indeed extra fuel.
What I am wondering now is why it started do this now? My driving habits haven't changed so I am sure we moved the car briefly in the past 10 yrs without it misfiring the next day- so I am wondering what changed this year and is it serious?
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