P0302 / Fuel Pressure / Hot Start Issue

Rob11010

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Recently bought a '10 KK and just had a P0302 intermittent misfire (2x) . Nothing crazy on scanner snapshot from when it threw the code so figured it's due for coils & plugs (140k on ODO). Ordered and while I am waiting for shipping I swapped two coils to see if misfire moves to another cylinder (not yet). Pulled #2 plug and looks fine - Bosch double iridium which will be replaced w/ stock NKGs - seems illogical but based on forum research I'll try the coppers. In trying to narrow down the issue I measured the rail fuel pressure which was 50 psi when running and upon shut down dropped to 40 psi in a couple of minutes and down to 30 psi w/in 5 min. Leaky injector? Ordered new to replace but I wouldn't a leaky injector leave a wet or carbon fouled plug? Or does this sound like fuel pump (regulator) issue?

Also I have had the hot start issue appear on the car twice since purchased 3 months ago. Could the low fuel pressure and hot start be related? My thoughts are that low pressure could in fact cause true vapor lock in a fuel injected engine?

Any opinions or feedback appreciated.
 

Rob11010

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P0302 returns - so we're still on cyl #2 after swapping coils. Scanner freeze frame shows it occurred right at start up; OL, STFT=0, zero time etc. Leaky injector still a possibility?
 

lfhoward

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Following. I have this intermittent issue on my 08 and I also suspect a fuel pump seal is not doing its job well after 192K miles.
 

poor man

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mate think we all have that issue mine is when cold , i replaced the starter motor awhile ago and this did stop it for a while , since then have done plugs , coils and leads still does when it wants to , thinking of doing cam sensor next but could be a tipm issue with the fuel pump relay or the pump guess we just throw money at it and one day someone will find the answer
 

Rob11010

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Injectors, plugs and coils replaced. No misfire yet (still early). Fuel pressure still drops at the rail, but at a slower rate (or so I believe). Based on this I am inclined to chase the fuel pump / regulator next. Can anyone confirm that the fuel pressure should stay steady once engine / fuel pump turned off?

As for the hot start issue I would like to see whether it returns once I have steady fuel pressure in the rail. Then throw some money at that. I too was looking at TIPM or perhaps ECM. I would think electronic issue being that it is intermittent but the fact that many have claimed resolution by venting the fuel rail schraeder valve goes against that in my mind. Seems like many gave chased the hot start to no avail. As it only happened for me after a heat soak I may seek to minimize the heat via increased hood vent and delayed off radiator fan (mine is electric) .
 

Rob11010

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Just wanted to update on misfire issue, still clear after a few weeks. Also have not seen the hot start issue. Weather warmed up and I have been trying to instigate the hot start issue by running up temp and attempting restart after 10, 15 & 20 min. So far so good. Coincidence? or actually having fuel pressure in the rail prevents? Time will tell.
 

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