After sitting - hard start & missing

[Steve Pratel]

Interesting experience last night. I parked my M at our vacation house about a month ago, Put it under the cover, tucked in the garage, fresh tank on ethanol free gas. When I went to start the car, it would crank, felt like maybe 1 cly was catching, then stall. Once car was started strong smell of gas, so was a no spark situation. Took 4-5 attempts, better each time and then perfect. Drive to dinner, again all is good. No misses, pulls strong solid idle.

I initially thought it was the fuel pump or stuck injectors, but with the strong smell of gas, it seems like was fouled plugs, but they are new, maybe 3K miles, NGK platinums. ?? is was this a fluke? or is this the HG allowing some water/oil to seep while sitting a long time?

I will pull the plugs later to see if there are any signs, but as I am still an M neubie, and am pulling off my general knoweldge, figured I'd throw it out there for any M specific wisdom

[flyfishvt]

My guess is a leaky injector that allowed fuel to slowly leak in until the fuel pressure was zero. It could just be a fluky start. All cars do that once in a while even new ones. I wouldn't be too quick to jump to a catistrophic failure like a head gasket unless you have other evidence to push you in that direction. Some cars just don't like to sit for a long time.

[mboor]

Ive heard that our M3's arn't a big fan of platinum plugs, im pretty sure i replaced mine with irridum NGK's... possibly compounded by a leaky injector could def cause a hard start after sitting for a long time.

[rob22sf]

Ive heard that our M3's arn't a big fan of platinum plugs, im pretty sure i replaced mine with irridum NGK's... possibly compounded by a leaky injector could def cause a hard start after sitting for a long time.

+1

Iridium NKG or Denso you cant go wrong

[Steve Pratel]

Yeah, I'm normally a copper NGK guy, thought the Platinum's were the preferred for this motor. A very solid robust plug, change out every 30K. Not a big fan of Iridiums, though the 100K interval is nice. I have Denso Iridiums in my Wifes Outback, the H6 is a bear to change plugs unless you have a lift.

Thanks for the input, I'm going back to the copper NGK's and will see what happens, or the next time I let it sit. Could have been a leaky injector, but I'm betting a fluke related to the gas. This is the first time I've put the non ethanol mixed fuel in the car and I basically filled it up drove 10 miles back to the house and parked it Its definately not the gas as I have about 5 cars/motorcycles I store and use the same gas for all without issue.

[propcar]

My car would do this every time it sat for more than two weeks. When i d start it it would be very rough. I usually had to give it gas to keep it from stalling. Gas smell etc. The after a minute or so it would settle. Then perfect. A friends does the same. These cars don't like to sit I guess.

[hide1]

I'm attributing some rough idles to the SAP fan making the car run leaner. I need to get my dme remapped. It seems the conforti tune my car came with runs lean. When I disable mine by disconnecting the electrical connector on the vacuum valve on the intake side, it appears to smooth out my rough idle on cold starts. If connected the rough idle lasts as long as the SAP is operational. Just something to think about..

[Steve Pratel]

I've read in a few places that a rough/stumbly idle at cold start is normal for these cars. I've had that from day one and not too concerned. This was a complete no start no catch on 1st attempt had a slight catch on second and third, almost started on 4th and 5th finally caught on 6th but stumbled and stalled all previous times. I initially thought it was fuel supply problem until after it was started and I got out of the car to smell very strong fuel smell.. Thats why I thought spark as opposed to fuel issue. Others have chimed in that this is common. This may be, but if the injectors bleed down when sitting for a long time this needs to be fixed as the fuel will wash out the cyl bores and wipe out rings prematurely. Was a one time even so far. I don't plan to let the car sit until the winter, but will change the plugs back to copper as a preventative, and run a few bottles of FI cleaner before the next oil change as PM. Will see what happens in the future.

[hide1]

I hear people say that about the rough idle and smh. A rough idle needn't be normal if you don't want it to be. Unless there is some mechanical damage, 99% can be cleared up with one or combination of A) refreshed injectors, B) new (proper heat range), spark plugs, C) coils/ coil boots, D) cleaning of carbon build-up on top end, E) MAF, F) 02 sensors.

My experience has shown a HUGE improvement with properly cleaned and rebuilt injectors. A worthwhile place to spend $, like a mod in themselves. Injector cleaners due next to nothing unless you are using them every fill up. You're better off changing the $0.30 injector filters.

BTW, injectors typically fail due to condensation of hot fluids and cold outdoor temps combined with sitting making them 'sticky'. All typical replaceable wear items after 20 or so years of use..

[Casebrius]

Has it ever been overheated?