K100 4v '92 long time to ignite & randomly hesitate, stutter, stalls.

[LeMoeur]

Hail, fellowship of the brick!


It's with pain in my heart that I start this thread. Mostly because I know how many of similar-titled posts like this already exist on the forum, and for a long time I've searched thoroughly thru them hoping for an answer and trying all your illuminating tips and trick, sadly without getting to a conclusion. But enought talk.


I've bought almost a year ago a    K100 RS 1992 16v, my first ride ever since a 50cc enduro when fourteen. So it is possible that the problems i noticed now were there much before i noticed, due to my inexperience.


The bike is working and takes me from poin A to B with no effort. But there's a list of things i know aren't right.


Problems:


1. It's very hard to get the motor to ignite, so that it takes about 2//3 secs of starter pressed to fire it up.


2. Once the engine is running it suddenly shuts off if i don't rapidly open the throttle OR open the choke lever. So that to ride it in the streets i need to open the choke everytime i stop at the redlight or manouver to park.


3. While driving i SOMETIMES very randomly feel hesitation in the response of the throttle, at times i felt myself in danger as the bike failed to get me away in a takeover or changed my lines when leaning for this very unconsistent throttle control.


4. Always very randomly the engine stalls, particularly when closing throttle or braking, even if clutch pulled in.


5. I'm not sure but i really feel gasoline smell when the bike's running, and (i don't know how it should be normally, to tell tghe truth, but...) fuel economy it's pretty bad... about 7km/l.


6. this is not a proper issue but maybe it's worth mentioning: not everytime i turn the ignition key the oil light would do the same, sometimes it does the flickers and die (randomly!)... ofc there's oil, over half, i can spot it from the window! and has been changed about 1k KM ago.


Last thing you'll have to know it's that my bike has an aftermarket gauge that i wired myself, following various explanations, and proudly wear an RPM filter & neutral relay as rbm teached... (god bless him)


Now i'll list the things i checked/tried with your precious advice:


Done:

1. Checked vacuum tubes (had the vacuum line fromfirst TB's disconnected, but easily re-tightened that) and caps, alongside with crankshaft hose (that was cracked, repaired with autosealing tape, now doesn't leak anymore).


2. Checked resistance @ motronic (MA2.1 non cat) female connector for:
    - air temp sensor & water ( 2k ohm @ about 20°C with 3% delta between them )
    - TPS values, in range as stated on that holy Frank Warner's fuel economy pdf
       ( pin 31-25 = 0,77kOhm / pin 31-13 = 1,07kOhm / pin 31-10 = 0,95kOhm )
    - CO2 Pot in range, if i've understood my homeworks right ( pin 32-25 = 0,99kOhm / pin 32-28 = 0,32kOhm / pin 25-28 = 0,68kOhm )
Still, when i try to run the error diagnosis from the three-pin connector the flashing overheat light shows me, in this order: error 1133 (HES n°1 fault), error 1122 (HES n°2 fault), error 1215 (TPS plug error) and lastly error 1224 (air temp sensor out of range).


3. Tried to run the bike without the air temp connector  ... same as with it on


4. Tried running it without the TPS ... perfect start, without having to long-press the starter, a bit of high idle (over 1k) but engine stalling when fast opening throttle, behaving "more normal" when slowly opening it.

.... it's all that comes to my mind by now. I'm puzzled and open to suggestions.
You are my hope! Good evening,
Alberto

[Gurujimmy]

Hi there,
I have just got my bike running after 11 years of sitting idle and have similar issue. I have checked every input and output on the electrical system and are sure everything is correct.
Getting a little desperate I have turned my attention to the fuel pressure regulator. Not having anything to test it with I decided to put locking pliers on the fuel return line to restrict the flow and increase the pressure in the injector rail, bingo bike starts easy and revs with no hesitation, although a little rich.
Now I will research a suitable replacement.


Cheers

[LeMoeur]

Hi there,
I have just got my bike running after 11 years of sitting idle and have similar issue. I have checked every input and output on the electrical system and are sure everything is correct.
Getting a little desperate I have turned my attention to the fuel pressure regulator. Not having anything to test it with I decided to put locking pliers on the fuel return line to restrict the flow and increase the pressure in the injector rail, bingo bike starts easy and revs with no hesitation, although a little rich.
Now I will research a suitable replacement.


Cheers

Thanks,
I'll try the very same diy solution right after lunch ^^!

Only one q... aren't fuel lines too stiff to effectively clamp them with pliers? I've already tried with heavy duty clamps, and it seems to me they don't move the hose a bit..

[Gurujimmy]

Lunch...wow I just put the kids to bed.
The fuel lines on my K are original and still quite soft. I didn't block it completely but quite a lot.

[Scott_]

LeMoer, with the 1004V, check the "heat sink paste" on the Ignition Amplifier. Clean and re-plentish.
It will dry out with age and cause funky ignition operation.
IIRC it should be mounted behind the ignition coils, mounted to a metal surface that will dissipate the heat, but not heat it, like the battery box.
For some reason, (like it didn't work out well)..... BMW only used these on the 4V K100's and K1's, and the '93 1100's.

[Laitch]

LeMoer, with the 1004V, check the "heat sink paste" on the Ignition Amplifier. Clean and re-plentish.
It will dry out with age and cause funky ignition operation.

This post shows what it looks like and the link with the post explains what to do.
http://www.motobrick.com/index.php/topic,8382.msg63872.html#msg63872

[LeMoeur]

Hi, guys!


After an happy afternoon spent in the garage with my beauty i have some unfortunate updates.


Did that Ignition amplifier thing: disassembled, sanded, cleaned, covered with dissipation paste..


Started the bike and... always the same.


So i moved on to clamp the fuel return from FPR, while applying quite a pressure with a multigrip plier i noticed a distinct fuel smell. fuel hose was well cracked and failed completely. At this point i bitten the bullet and went on to disassemble and replace every fuel hose, alongside with the FPR itself and replaced the vacuum tube (that was literally molten on the nipple from the first TB) with a not too tight fitting transparent hose i found lying around.


Went for a "test" ride (45km)... now the bike seems to act even worse. Long time to start, not keeping idle, and very unresponsive throttle.. plus (new) this time i found it hard to get the bike going over 6k RPMs making it quite difficult to reach speeds over 130//140.


I'm in black dispair..  more puzzled than before.


Thanks for the advice anyway, at least i can add to my "checked" list!

[Martin]

Bricks do not like sitting and the electrical connections seem to degrade from sitting. I used to work with an ex BMW technician who advised me when I got the bike to go over all the connections with Deoxit . I went a step further and against the advise of some inmates I smeared dielectric or heavy silicone grease around the connectors. I believed that by doing this I would stop the ingress of water air and road crap that leads to corrosion. The only electrical problems I have had was twice in the one connection I had not done due to limited  access. Just about everytime I pull a connection apart I spray and reapply the grease. I've had my brick twenty years and it has definitely helped.
Regards Martin.

[LeMoeur]

Bricks do not like sitting and the electrical connections seem to degrade from sitting. I used to work with an ex BMW technician who advised me when I got the bike to go over all the connections with Deoxit . I went a step further and against the advise of some inmates I smeared dielectric or heavy silicone grease around the connectors. I believed that by doing this I would stop the ingress of water air and road crap that leads to corrosion. The only electrical problems I have had was twice in the one connection I had not done due to limited  access. Just about everytime I pull a connection apart I spray and reapply the grease. I've had my brick twenty years and it has definitely helped.
Regards Martin.

Finally managed to get your suggestions practical. Bought a brand new dry contact cleaner, and sprayed all over ECU connector, air temp sensor & TPS.. no luck... still running crappy, long time to ignite, not idling, heavy gasoline smell, specially on starting up.

[wardie]

change the fuel filter make sure the fuel flow directional arrow is pointed in the correct direction.


Check the valve lash.


Wardie

[Martin]

Try removing the fuel pump fuse, and see if it will start. If it does start ram the pump fuse back before it dies.
Regards Martin.

[LeMoeur]

change the fuel filter make sure the fuel flow directional arrow is pointed in the correct direction.


Check the valve lash.


Wardie

Hi Wardie, i posted the image of the inside of the tank, filter replaced by me about 3 months ago, should be in the right direction...
As for the valves.. I read on the forums that 16V hardly needs to have them adjusted, that's why I never checked. Do you think I should?

Try removing the fuel pump fuse, and see if it will start. If it does start ram the pump fuse back before it dies.
Regards Martin.

Thanks Martin, tried your suggestion, as I expected the bike won't start without the fuse (n. 6, right?).
Can you please explain to me the reason for this check? What were we trying to test, exactly?

[wardie]

Many have mentioned problems with electrical connector underneath tank. I'd check that connector clean and reinstall.


Sounds like your not getting enough fuel consistently. You may want to reach in and pull the pump checking the screen for foreign debris possible restricting fuel pump flow.

[Scott_]

16v engines still need to have the valves checked. At the least after the 1st 25K miles then around every 50K after.

[Laitch]

Still, when i try to run the error diagnosis from the three-pin connector the flashing overheat light shows me, in this order: error 1133 (HES n°1 fault), error 1122 (HES n°2 fault), error 1215 (TPS plug error) and lastly error 1224 (air temp sensor out of range).

You have run tests that show these results in your first post, Alberto. It shows that errors at both Hall Effect Sensors. What does that mean to you? Does it indicate that their wiring should be checked, or that both sensors might need to be replaced?

[LeMoeur]

Many have mentioned problems with electrical connector underneath tank. I'd check that connector clean and reinstall.


Sounds like your not getting enough fuel consistently. You may want to reach in and pull the pump checking the screen for foreign debris possible restricting fuel pump flow.

It seems to me that I get too much fuel instead, that's just my thinking because I can smell unburnt fuel from the exhaust [emoji848]

16v engines still need to have the valves checked. At the least after the 1st 25K miles then around every 50K after.

It is possible to DIY it? Like in my garage...? And moreover.. if i take off the left carter, would motor oil spill out or it's a separate compartment? Sorry but i'm just a newbie selfmade mechanic [emoji28]

You have run tests that show these results in your first post, Alberto. It shows that errors at both Hall Effect Sensors. What does that mean to you? Does it indicate that their wiring should be checked, or that both sensors might need to be replaced?

For that results I just thought to bypass, because i read from the following doc that these two can be "spurious".. and then focused on the other two.. am i wrong?

I mean, I found very strange that even if the readings @ the ECU connector were perfectly in line with factory values (as given by the very same guide below), the output from the diagnostic pin from the ECU (once reconnected) showed me "Air Temp Sensor Out of Range" and TPS Out of Range" errors.

http://hrsbstaff.ednet.ns.ca/bvogel/K100/download/Motronic%20Fault%20Codes.pdf

[Martin]

If you are over fuelling removal of the fuel pump fuse will allow the bike to start without pumping more fuel into the combustion chamber. On the 2v bricks running rich can be caused by a faulty temperature sensor or connector which tells the computer it is running cold and needs more fuel to compensate. This results in a flooded engine which wont start. On the 2v Bricks you can get them to start by removing the fuel pump fuse and starting them on the residual fuel that is in the combustion chamber. As the engine uses up this fuel it starts to die, before it dies completely ramming the fuse home before it dies will keep it running. It will however be running rough and a bit of throttle manipulation is required. Two people can achieve this a lot better one to manipulate the throttle one on the fuse. Until I properly cleaned my temperature sensor connector it happened to my Brick twice. I'm not sure if the 4v are the same but it is worth a try.
Regards Martin.

[LeMoeur]

Sunday updates:

This morning I was thinking about that strage issue that occurs when TPS disconnected... so i decided to head to the garage and do further testing.

Came up that when i twist the throttle (while multimeter connected to measure resistance to both pins @ the ecu) the TPS sensors go crazily up (from 0,9 to 1,4kOhm) at the slightest movement, then reaches the apex (~1,7kOhm) at about 3/4 of the total allowed throttle travel then settles back to a medium value when completely open (~1,5kOhm).

I then tested continuity on the cable and seems allright.. I then have to assume my TPS is faulty... any way to disassemble & repair it?

Moreover, if it is the only problem? Why the bike still runs like crap when i disconnect it?

Thanks guys!

[Inge K.]

Why the bike still runs like crap when i disconnect it?

The Motronic needs the signal from the TPS to calculate the fuel mix, as you don't have a AFM as on 2V's.
Have a look in this link how to check and adjust.

[The Mighty Gryphon]

I have used the procedure described in the second link in Inge's post and can say that it works perfectly.  No need to even have to get a light, just look at the temperature idiot light.

[LeMoeur]

The Motronic needs the signal from the TPS to calculate the fuel mix, as you don't have a AFM as on 2V's.
Have a look in this link how to check and adjust.

Thanks Inge, firstly I must say that I found yours and rbm's words illuminating when had to figure out how to wire my aftermarket Koso speedo and get it to work with neutral and steady rpms needle.

Back to ours... Ok that I didn't know, it explains why the bike does not run with TPS disconnected. I did the test and settings as suggested by the page you posted, managed to get a clean and steady .375 V

...but the problems still remain, unchanged.

There's any way in wich I can open up and clean the TPS inner contacts?

[The Mighty Gryphon]

Where are you located?  It is nice to put your location and model of your bike in your signature line.  That way we can know what you are trying to fix.  U.S. bikes are different in some ways from others.

Having said that, do you have an OEM exhaust with the O2 sensor?  If not and you are in the U.S. you should have a CO2 potentiometer on the front of the relay box above the throttle position sensor.  This pot has a screw adjustment for the idle mixture to optimize it for CO2 % in the exhaust.  It may be that the pot, if present, is incorrectly adjusted for idle mixture. 

Have you tried letting the bike idle for a while at operating temperature, shutting it down and removing the spark plugs to take plug readings?  I don't recall seeing a mention of that in earlier posts.

With regard to the engine quitting when you stop, my 1992 RS has the same problem and even though it runs strong and smooth with good fuel mileage it srill wants to quit when stopping from a long run at high speed.  Over the past three years I have checked everything in the engine control system with no joy.  All I can do is be careful to downshift through all the gears and not just yank the clutch and brakes when coming to a stop. 

As a last resort, I may try replacing the voltage regulator on the alternator.  It may be that when dropping rpms quickly it is changing the voltage output enough to effect the operation of the motronic system.  I suspect this because I think I am seeing the alternator/battery idiot light come on BEFORE the engine dies.

[The Mighty Gryphon]

I don't see any mention of balancing the throttle bodies.  If one or more of them are grossly out of adjustment they can cause rough idling and other low rpm issues.

[Inge K.]

Having said that, do you have an OEM exhaust with the O2 sensor?  If not and you are in the U.S. you should have a CO2 potentiometer on the front of the relay box above the throttle position sensor.  This pot has a screw adjustment for the idle mixture to optimize it for CO2 % in the exhaust.  It may be that the pot, if present, is incorrectly adjusted for idle mixture. 

Check #2 under "Done" in first post.

[LeMoeur]

I've found this, while surfin' the mighty net...
http://www.ukgser.com/technical/nick/Throttle-Position%20Sensor%20%28All%20BMW%20models,%20'04%20on%29%20V1.0.pdf

I will proceed to apply this guide to my dear K (during the weekend) and see if it happens to be similar. I'll keep you guy updated!

@MightyGryph: Sorry i was quite sure of having update my profile with location data, i'll check asap... Btw i'm from Italy