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Poorly 35i (Now Fixed)(sort of)

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Maniac
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Poorly 35i (Now Fixed)(sort of)

Post by Maniac » Mon Aug 21, 2017 5:25 pm

So I'm sort of hoping this is a bad tank of fuel but for the last week or two the car has had a really rough idle and misfires occasionally (as in stutters) under light load for the first few minutes. (Even tried, and it hurt me more than the car, a thrash from cold and it was absolutely fine at WOT)

When warm all is fine. No faults using a code scanner so looks like ill have to wait for it to develop before the men in the know can diagnose the fault.

Still hoping it's a batch of crap fuel.
Last edited by Maniac on Thu Apr 05, 2018 7:38 am, edited 2 times in total.

extrablatt
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Poorly 35i

Post by extrablatt » Mon Aug 21, 2017 5:44 pm

Sorry to hear. It sounds similar to the issues when my injectors were failing. I would always notice it from cold, but never once the engine has warmed up.

I don't think I was getting any faults through a scanner either, so I initially hoped it was a bad tank of fuel.
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Poorly 35i

Post by Maniac » Mon Aug 21, 2017 5:47 pm

extrablatt wrote: Mon Aug 21, 2017 5:44 pm Sorry to hear. It sounds similar to the issues when my injectors were failing. I would always notice it from cold, but never once the engine has warmed up.

I don't think I was getting any faults through a scanner either, so I initially hoped it was a bad tank of fuel.
What was your diagnostic path?

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Post by extrablatt » Mon Aug 21, 2017 5:53 pm

From the noise, I was certain it was a misfire. Was annoyed because the scan wasn't bringing up anything, but I knew the noise wasn't right. Took it to the dealer and left it overnight so they could start from cold.

They confirmed the issue and replaced injectors and coils under the warranty, so I was only out of pocket £100 or so for the sparkplugs.
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Poorly 35i

Post by Nictrix » Mon Aug 21, 2017 7:19 pm

extrablatt wrote: Mon Aug 21, 2017 5:53 pm From the noise, I was certain it was a misfire. Was annoyed because the scan wasn't bringing up anything, but I knew the noise wasn't right. Took it to the dealer and left it overnight so they could start from cold.

They confirmed the issue and replaced injectors and coils under the warranty, so I was only out of pocket £100 or so for the sparkplugs.
Before reading this my initial thought was spark plugs.
When were they changed last?
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Poorly 35i

Post by Maniac » Mon Aug 21, 2017 7:31 pm

Just had a major service. Oil plugs filters brake fluid you name it. Was rough before and is rough after.

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Poorly 35i

Post by R.E92 » Mon Aug 21, 2017 9:37 pm

Sounds exactly like my car before my injectors failed.

Symptoms are exactly what you are experiencing. Not sure how receptive BMW will be without a code unless the rough idle is really obvious.

It will probably go downhill really fast, my car went from rough idle to fuel leaking from the exhaust while the car was shutoff in 2 weeks.

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Post by Gaffa22 » Tue Aug 22, 2017 8:19 am

Based on what I have read do those symptoms also point to possible HPFP failure ?
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Poorly 35i

Post by R.E92 » Tue Aug 22, 2017 8:48 am

Gaffa22 wrote: Tue Aug 22, 2017 8:19 am Based on what I have read do those symptoms also point to possible HPFP failure ?
Both very similar symptoms but a bad HPFP would get worse at WOT.

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Poorly 35i

Post by Gaffa22 » Tue Aug 22, 2017 10:54 am

R.E92 wrote: Tue Aug 22, 2017 8:48 am
Gaffa22 wrote: Tue Aug 22, 2017 8:19 am Based on what I have read do those symptoms also point to possible HPFP failure ?
Both very similar symptoms but a bad HPFP would get worse at WOT.
Thanks R.E92 It's a learning curve for me.
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Post by dario » Tue Aug 22, 2017 11:31 am

i had a case a couple of years back with my 35i that was similar. I say similar but it was always when the car had been standing for a while, but it did not happen all the time. I thought it was some sort of temperature sensor that determined how much fuel to inject when cold as opposed to when it was cold (like whatever it is that causes the engine to run at fast idle on a winters morning). however, a few times it ran bad for a few seconds (30s max) and then it cleared and run as sweet as a nut. car had only covered about 22K miles.

as it was in warranty at the time i took it in to the dealers and they were not good at diagnosis as the computer said NO!

this happened for a while and they suspected coil pack break downs, but again wouldn't change anything because there was no definitive fault that they could see. They had the car for a couple of weeks and still couldn't find anything or get it to repeat itself.

so i took to filming the start every time i started the car hot of cold! and eventually got video evidence it this problematic startup.

Mine would start lumpy with the rev counter bouncing about at around 3-400 rpm and running rough and lump. widening the tail pipes i did witness in conjunction with the lumpy running black smoke!

having been a trained and timeserver mechanic of the OLD ERA B.C. (before computers) i was able to make a series of assumptions. Basically black smoke is either caused by either insufficient air in the combustion process of excess fuel.

doing some further research in the inter web, i found some reports of this that was traced to leaking injectors when at standstill. in other words when running at normal engine speeds the injectors were doing the job they were designed to do. BUT at standstill with a reserve of high pressure fuel held in the pipe network right up to the nozzle tip of each injector some of them were letting past the smallest volume of fuel in to the combustion chamber.

The erratic nature of why the engine did not start poorly each time in my opinion (and i think it makes sense) is that the problem depended on when the crank/cam shaft stopped in the 4 cycles. in other words, if No1 injector had a leak, and the cylinder stopped with a valve open in that cylinder, i believed that over a period of time the cylinder could dry off the fuel that had been leaked in to it and not cause the problem on the next start. However if the No1 cylinder valves were both closed on the next engine stop, then no way could the cylinder allow for free air movement and the drying of the fuel in the cylinder.

The upshot!

i commented on this the dealer and they undertook to remove the plugs and injectors after running the engine for a period (road test) when the removed all six injectors 3 were found to have wet nozzles. QED!

they replaced all 6 injectors and the problem has never returned.

this will never show up in a systems check, as its a mechanical problem.

I've no idea how had it is to remove injectors on your engine, however if the fault happens in the way I've described, it could very well be the problem.

Do give me feed back as I'm interested.

Dario

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Poorly 35i

Post by Maniac » Tue Aug 22, 2017 2:15 pm

I drove the car to the office today and despite the occasional non smooth idle all was well.

It's not severe enough to be reliably faulty if that makes sense. Just feels like it misses or chokes/may stall on occasion for the first minute or two.

I'm doubtful they'd find anything wrong so I'll have to wait until it gets worse.

It's never been 100% smooth at idle but now I have this occasional misfire or feeling of starvation/imminent stall that never happens.

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Post by Smartbear » Tue Aug 22, 2017 2:47 pm

Maniac wrote: Tue Aug 22, 2017 2:15 pm I drove the car to the office today and despite the occasional non smooth idle all was well.

It's not severe enough to be reliably faulty if that makes sense. Just feels like it misses or chokes/may stall on occasion for the first minute or two.

I'm doubtful they'd find anything wrong so I'll have to wait until it gets worse.

It's never been 100% smooth at idle but now I have this occasional misfire or feeling of starvation/imminent stall that never happens.
How about running a bottle of additive through the tank, injector cleaner etc? Think i'd try that before handing over to bmw :cry:
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Poorly 35i

Post by R.E92 » Tue Aug 22, 2017 3:08 pm

You can check the injectors yourself.

-Take engine cover off and get your tools ready
-Start car from cold, let it run for 30 seconds then shut it off
-Remove spark plugs and see if tips are wet with fuel

If you have had the car since new and never changed the injectors then they are overdue for failure!

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Poorly 35i

Post by Maniac » Tue Aug 22, 2017 4:18 pm

Overdue for failure at 34k miles?

Car ran fine other than a little inconsistent power coming home from the office.

Could well be different again tomorrow...

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