Engine 'Sputtering' at 1500 to 2000rpm...any ideas why? - BMW Luxury Touring Community
 
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post #1 of 8 Old Jan 15th, 2011, 11:34 am Thread Starter
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Engine 'Sputtering' at 1500 to 2000rpm...any ideas why?

Hi All,

My UK spec '99 LT with 62k miles on the clock has recently developed a slightly annoying problem that has me puzzled.

In any gear, at any speed, when accelerating through the range, the bike 'sputters' around 1500 to 2000rpm... it is most noticeable if you drop the speed right down but keep it in a high gear.

Fuel is good (running on 98 RON) - plugs, fuel filter, air filter etc were changed around 6k miles ago.

New battery was fitted around 2mths ago.

It had been left parked up for a while but is now back in daily use and MAY be a little better.

Any ideas?

The bike idles fine at 1000rpm, accelerates cleanly either side of the 'trouble zone' and seems that its MPG is still good.

On start up it does smell rich.. very 'fuelly' until warm.

Any thoughts or similar experiences out there in the wealth of knowledge that is the BMWLT forum?

Look forward to your views. - Andy
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post #2 of 8 Old Jan 15th, 2011, 11:57 am
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Re: Engine 'Sputtering' at 1500 to 2000rpm...any ideas why?

Clogged injector? Sounds more fuel delivery that ignition based. May take a while to get to the bottom of it. Do you have a dealer nearby or like to troubleshoot those things on your own?
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post #3 of 8 Old Jan 15th, 2011, 12:17 pm Thread Starter
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Re: Engine 'Sputtering' at 1500 to 2000rpm...any ideas why?

I was thinking maybe the same - clogged fuel injector - or maybe a motronic issue as battery was replaced. I have followed the TPS reset procedure when the sputter first started but didnt seem to have any effect at all.

Seafoam injector cleaner seems to be mentioned a lot - but to my knowledge not available in the UK.... any suggestions of good alternatives that maybe available in Europe?

I do have a dealer nearby but would rather try and fathom it myself... much more satisfying to work it out with help from the forum than lining the pockets of the dealer!
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post #4 of 8 Old Jan 15th, 2011, 12:28 pm
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Re: Engine 'Sputtering' at 1500 to 2000rpm...any ideas why?

Quote:
Originally Posted by andyfb
I was thinking maybe the same - clogged fuel injector - or maybe a motronic issue as battery was replaced. I have followed the TPS reset procedure when the sputter first started but didnt seem to have any effect at all.

Seafoam injector cleaner seems to be mentioned a lot - but to my knowledge not available in the UK.... any suggestions of good alternatives that maybe available in Europe?

I do have a dealer nearby but would rather try and fathom it myself... much more satisfying to work it out with help from the forum than lining the pockets of the dealer!
Hi, Andy - I don't know that EVERY '99 LT received the 'airbox sensor removal' treatment, butt ole Toad did and it stopped the sputter/hesitation while moving at the lower engine rpm . It would seem to me tho, since you have a lot of mileage on the bike, you would have experienced that sputter/hesitation long ago - not just recently. Butt, in case you've not removed the 'airbox temp sensor', that may be the thing to do anyway. You can do a little search on the forums for the procedure involved in removing the sensor (takes smallish hands, if you don't pull the tupperware pieces), and at least see if that solves your current problem. - or eliminates a possible cause. Good luck, Andy.
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post #5 of 8 Old Jan 15th, 2011, 1:05 pm Thread Starter
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Re: Engine 'Sputtering' at 1500 to 2000rpm...any ideas why?

thanks for your advice Dick - will add it to my list to ponder!

Its the 'sudden' start of the problem that has me foxed... I appreciate that items just fail... but if something had gone AWOL I would have expected something more serious to be occuring... what I have is an annoyance rather than a show stopper.... at the moment at least!

Will let you know what happens when I start to make a few tweaks and alterations...
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post #6 of 8 Old Jan 15th, 2011, 1:38 pm
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Re: Engine 'Sputtering' at 1500 to 2000rpm...any ideas why?

andy
i'm thinking it sounds more like a misfire. i suppose 12 year old plug wires could be weak. i would check them.
john
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post #7 of 8 Old Jan 15th, 2011, 2:59 pm Thread Starter
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Re: Engine 'Sputtering' at 1500 to 2000rpm...any ideas why?

thanks john - may well change the HT leads on next service just to rule them out - as you say 12yrs is a long time and could well be the issue (or at least part of it!) - Thanks
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post #8 of 8 Old Apr 27th, 2011, 6:42 pm Thread Starter
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Re: Engine 'Sputtering' at 1500 to 2000rpm...any ideas why?

HI All,

Just a quick update on the issue my bike was suffering. Carried out my annual service with the help of my friend and fellow BMWLT forum member Cookie at the weekend.

I had purchased new iridium plugs and lambda sensor as was convinced it was the sensor on the blink and this may have damaged the plugs also.

Got the plastics off and found that plug lead no 4 was very loose on the plug.. came off easily in my hands...leads 1 to 3 required needle nose pliers to pull them off the plugs.
Inside lead no 4 was full of corrosion, the surface that should have been making clean contact with the plug was buried under lots of white residue. Closer inspection of the lead also showed where it had rubbed through on its insulation and was most likely tracking/earthing out. I had recently detected a faint RPM linked interference on my Autocom headset which further helped me conclude that the problem was indeed the spark plug leads...

so... changed all of the leads...and have wrapped the new ones in self amalgamating tape to protect them as all of the old ones showed signs of wear from rubbing against each other and the cylinder head.

All of the plugs were in great condition so I put them back in - they had only done 10k miles so plenty of life left in them - the electrodes still looked like new.

Bike now runs like a dream again! Happy camper once more!!!

Hope that helps anyone else that have similar issues of a rough running / sputtering engine...
Andy
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