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1Back to top Go down   Help - Mis-firing 16V Empty Help - Mis-firing 16V Tue Apr 05, 2022 7:48 pm

stanthomas

stanthomas
Silver member
Silver member
One for the group...looking for suggestions for where to start. Lot's of info on the site but nothing quite matches my situation so I hope someone can offer some tips on the most likely cause(es).

Just fixed the oil/water pump. Was running fine and doing about 50 miles a day. Some dual-carriageway (highway) and some back roads.

On my way out, engine warmed up and about 5 miles in, briefly hit "good morning judge" speeds on dual carriageway. Just another day. Total of 15 miles up on journey, had slowed to 70-ish mph and rolling along in traffic when it started mis-firing. Fuel gauge was flicking into the red but low fuel light wasn't on. Stopped for fuel (E5 super as ever) but that wasn't it. Very, very lumpy pull away like it's lost half a cylinder but will roll at 70-ish on light thottle - bit rough and no get-up-and-go but sort of drive-able and I was able to get to my destination and home again. Won't really tick-over without some throttle and is very. very rough. All four exhaust pipes are hot. No water in oil or oil in water. Squirted  WD40 around the throttle bodies and intakes and no obvious signs of leaks.

In last 2000 miles it has had:
- new plugs and leads (pulled plugs and sparking on all 4. All plugs look fine and same.)
- new fuel filter and in-tank pipes (pulled pipe to injector rail and fuel pumps out - although it stops after a few seconds. And fuel returning to tank when connected.)

So guys, what goes bang, all of a sudden while rolling along, one moment fine, next moment terrible? And stays terrible but doesn't get any worse (although that would be difficult).


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K100RS 16V '91
    

2Back to top Go down   Help - Mis-firing 16V Empty Re: Help - Mis-firing 16V Tue Apr 05, 2022 8:50 pm

Point-Seven-five

Point-Seven-five
Life time member
Life time member
Two things.  First, check the battery connections and the grounds, including the one under the tank  Are they all tight and shiny?

Second, Check the four pin connector for the fuel tank.  Give the connections a shot of Deoxit.


__________________________________________________
Present:
1994 K75RT
1991 K100RS


Past:
1988 K100RS SE
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

3Back to top Go down   Help - Mis-firing 16V Empty Re: Help - Mis-firing 16V Tue Apr 05, 2022 9:26 pm

Dai

Dai
Life time member
Life time member
And thirdly the infamous crankcase breather might just have picked that time to split. Had that hacking around the Welsh mountains about six years ago - one moment I had a full set of grunt, the next I was running on 2.5 cylinders with all the symptoms you describe.


__________________________________________________
1983 K100 upgraded to K100RS spec, 1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

4Back to top Go down   Help - Mis-firing 16V Empty Re: Help - Mis-firing 16V Fri Apr 08, 2022 6:48 pm

stanthomas

stanthomas
Silver member
Silver member
While going thru cleaning and re-seating all the likely looking connectors, I found that I could leave #2 injector unplugged and it made no difference. Unplugging other injectors made things worse. I swapped the plug and lead on #2 for old parts - no difference and good spark on all cylinders. I pulled the injectors out, still attached to the rail and fuel pipes - when cranking on starter all injectors appear to be firing as expected. Only shooting an inch or so onto the cylinder head so no idea about spray pattern but definitely a good jet of fuel coming out of all of them. O-rings look ok. Measured the resistance on #2 injector at 16.8 Ohms (which seems to be ok) and voltage on injector supply plug is, as near as my DMM can register, 11.5V. Put back together - no change.

Maybe it's dropped a valve? Nope, all clearances are where they should be. I don't have a suitable adapter for my compression tester but the head gasket seems an unlikely candidate.

Examined the crankcase breather pipe (Z-pipe) in situ as best I can. Seems good and flexible with no obvious damage. I should take it off to be sure but getting at the hose clamp is going to be a pain. I don't understand how the Z-pipe can affect a 16V 'cos the Motronic doesn't have an air flow sensor - although I don't know how it does its magic without.

So what do people think?
Could an injector be superficially ok while causing a bad mis-fire thoughout the rev range? Motorworks have injectors at £123, a set of four "EV14"s at £130 or a second-hand one for £35. Are there better choices?

Is there anything else that just goes bad, in an instant, like this wiithout stopping the engine completely?


__________________________________________________
K100RS 16V '91
    

5Back to top Go down   Help - Mis-firing 16V Empty Rough running Fri Apr 08, 2022 8:30 pm

daveyson

daveyson
Life time member
Life time member
Instead of replacing The plug and lead for cylinder two, swap them with the plug and lead for cylinder one. If the problem moves to cylinder one, the plug and/or lead might be bad.

Check that the lead connections are clean, and the leads for resistance.


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

6Back to top Go down   Help - Mis-firing 16V Empty Re: Help - Mis-firing 16V Fri Apr 08, 2022 8:54 pm

MartinW

MartinW
Life time member
Life time member
Swap the injectors from the bad cylinder to a good cylinder and see what happens.
Regards Martin.


__________________________________________________
K75s Hybrid
    

7Back to top Go down   Help - Mis-firing 16V Empty Re: Help - Mis-firing 16V Sat Apr 09, 2022 1:50 am

Rick G

Rick G
admin
admin
A compression test would help it may have dropped a valve I had one let go about 10 years ago. A piece about 4mm wide about 90° of the exhaust valve.


__________________________________________________
"Man sacrifices his health in order to make money.
Then he sacrifices money to recuperate his health.
And then he is so anxious about the future that he does not enjoy the present; the result being that he does not live in the present or the future; he lives as if he is never going to die, and then dies having never really lived."   Dalai Lama


Bikes 2004 K1200GT 1998 K1100 LT, 1986 K75 GS.
    

8Back to top Go down   Help - Mis-firing 16V Empty Re: Help - Mis-firing 16V Sat Apr 09, 2022 3:32 am

Holister

Holister
Life time member
Life time member
stanthomas wrote:
Examined the crankcase breather pipe (Z-pipe) in situ as best I can. Seems good and flexible with no obvious damage. I should take it off to be sure but getting at the hose clamp is going to be a pain. I don't understand how the Z-pipe can affect a 16V 'cos the Motronic doesn't have an air flow sensor - although I don't know how it does its magic without.

You're right, a leaky crankcase breather has no effect on fuel/air. Air is metered with the Throttle Position Sensor on the throttle bodies which replaced the Throttle Position SWITCH and AFM used on the 2v.

***CHECK FOR WATER IN THE TANK***

Could be low fuel pressure. A quick check that doesn't need a pressure gauge is to take the fuel line off the rail and poke it into an empty 2 lit coke bottle. When cranking the fuel should gush out fairly well. Do the same with the fuel return line. Fuel should just bubble out.

I'd be taking the injectors right out so you can get a good look at how they're spraying. A good indication is that they spraying all the same. Worth going to the trouble of cleaning them. I've always had good success with a can of carby cleaner and a special adapter you can get off ebay. Replace the kit. They are cheap. The little filter basket on top of the injector could be blocked.

Just to be sure you can check spark plugs with a DMM. Info here... https://www.k100-forum.com/t10954-spark-plugs#130448

Make sure you've got the nuts on the top of the spark plug and there is no corrosion either end.


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1989 K100RT     VIN  0097367 (naked)  
1996 K1100RS   VIN  0451808
 Help - Mis-firing 16V Austra12    Fuel:  95 Octane
Engine Oil: Nulon Full Synthetic 15W50
Gear Box Oil:  Nulon Synthetic 75W90
    

9Back to top Go down   Help - Mis-firing 16V Empty Re: Help - Mis-firing 16V Sat Apr 09, 2022 3:38 pm

stanthomas

stanthomas
Silver member
Silver member
Hadn't thought of swapping injectors to see whether the problem moves with them. It doesn't.

#2 is runnning, kinda. Being careful not to move the throttle (have to hold it open otherwise it stalls), unplugging/replugging #2 injector does make a small difference to engine speed but not to the uneven running. Unplugging any of the other 3 makes things considerably worse.

Fuel comes out of the injector rail supply pipe like turning on the mains cold water tap. Haven't tried the return end but I had the rail off to swap injectors and it blows thru with an airline.

Finding an adapter for my compression gauge and doing that test seems like the next step...


Thanks for the tips.


__________________________________________________
K100RS 16V '91
    

10Back to top Go down   Help - Mis-firing 16V Empty Re: Help - Mis-firing 16V Sat Apr 09, 2022 7:46 pm

Laitch

Laitch
Life time member
Life time member
stanthomas wrote:. . . unplugging/replugging #2 injector does make a small difference to engine speed but not to the uneven running. Unplugging any of the other 3 makes things considerably worse.
If there is sufficient voltage supplied by #2's coil and its spark plug is in good condition, it seems to me like #2's injector is faulty.


__________________________________________________
1995 K75 81,000 miles
Help - Mis-firing 16V Usa-lo10
    

11Back to top Go down   Help - Mis-firing 16V Empty Re: Help - Mis-firing 16V Sat Apr 09, 2022 7:51 pm

stanthomas

stanthomas
Silver member
Silver member
Following MartinW's suggestion, I swapped injectors 2 & 4 but the problem didn't move with them. Sorry I didn't make that clear. Seems to be something going on with cylinder #2. Compression test next.


__________________________________________________
K100RS 16V '91
    

12Back to top Go down   Help - Mis-firing 16V Empty Re: Help - Mis-firing 16V Sat Apr 09, 2022 7:53 pm

92KK 84WW Olaf

avatar
Life time member
Life time member
Given that its an easy check I should swap the coils witrh each other and see what happens.


__________________________________________________
1992 K100LT 0193214 Bertha Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red 578 bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 689 58,645 now 106,950 miles Deceased.
1983 K100RS 0011171 Fricka 606 Alaska Blue 29,495 miles Damn K Pox Its a Bat outta Hell Now 49,840 miles. 
1996 K1100LT 0233004 Lohengrin Mystic Red 38,000 miles currently 42,640 miles.

Past:
1968 Yamaha 80 YG1
1971 Yamaha 125 YAS-1
1968 Honda 125 SS
1970 Honda CD 175
1973 Honda CB500-4
Honda CX 500
    

13Back to top Go down   Help - Mis-firing 16V Empty Re: Help - Mis-firing 16V Sat Apr 09, 2022 8:16 pm

Point-Seven-five

Point-Seven-five
Life time member
Life time member
When was the last time you checked the valve clearances?


__________________________________________________
Present:
1994 K75RT
1991 K100RS


Past:
1988 K100RS SE
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

14Back to top Go down   Help - Mis-firing 16V Empty Re: Help - Mis-firing 16V Sat Apr 09, 2022 8:29 pm

stanthomas

stanthomas
Silver member
Silver member
Point-Seven-five wrote:When was the last time you checked the valve clearances?
Friday. Checked in case valve bent. All ok, a couple right on the lower limit but nothing opened up like might happen if a valve had kissed a piston.

Olaf:
I'll try swapping the coils, easy to do as you say. Have assumed that, being a shared coil, a bad one would take out two cylinders.


__________________________________________________
K100RS 16V '91
    

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