Stuttering under part-throttle

[E30_Crazy]

The cutting off and not starting while hot presents a temp issue. Just looked more carefully at a more detailed wiring diagram. I had only checked my temp sensor and wiring at the FI computer plug. Gonna check the other signal and wiring going to the temp switching unit, the unit itself if I can, and the fuel injection relay. I can bear the pump running while cranking, and it sometimes want to start (when hot) but then dies. Pump or injectors may be cutting off as a result of bad temp input somsomewhere.


If these all check out, I'm back to the FI computer being shot (for a second time)

[Martin]

If the sensor is playing up the spark plugs will be wet. With the plugs out and earthed ( failure to earth the s/plugs can result in damage to ignition module) the check the spark, but be careful not to ignite the excess fuel. Remove the fuel pump fuse #6 while doing the test.
Regards Martin.

[E30_Crazy]

Temp sensor checks good at the temp switching unit. Wiring from temp sensor plug to the unit it good as well. Nothing burnt up inside the unit. Wiring from Temp switching unit to the FI relay checks good. I may try and pick up a new FI relay. Wondering if something inside is failing after carrying the power load for an amount of time.... And I may have the wrong one anyways. The part number returns as a BMW car relay. Reading around here and other forums, the K100 (or at least early ones like mine) had points reversed, and that the double 87 shouldn't have an "A" and/or "B" attached (double output vs alternating output IIRC).

[E30_Crazy]

Tested the fuel injection relay, and it turns out that it is a dual output relay.


Bike starts and idles fine. But after warming up a bit, if I try to rev past 4 or 5k rpm, and it stutters too much, or I try to ride it, it shuts off and won't start again until it cools off some. Temp sensor, and all wiring after it on both paths checks good. I'm thinking the FI computer has failed for a second time. If the signals and sensors are all correct, it must be the interpretation part that is bad.

[Laitch]

Test the coils according to the method within this guide. It's located just after the Hall sensor test. Have you done that yet?

[E30_Crazy]

Yes, that was done near the beginning of this whole debacle. Along with going up and down the troubleshooting guide several times now. Very informative, and I've used it on several occasions trying to trace the source of the issue. Nothing seems to present as "bad" or "broken" on all testable components and/or circuits. All voltages, resistances, and continuities are checking as the guide describes.


I have another ECU on the way. From there, the only thing I haven't changed is the ignition control module.

[rbm]

The purpose of the temp relay is to turn on/off the cooling fan, so it has no effect on your stuttering at 4K. Ignore that 1/2 of the temp sensor and that line of inquiry.  However, the other 1/2 of the temp sensor in the stand tube feeds the ECU, and that can be a problem for you if the temp sensor is acting up, or the wiring or mounting in the stand tube is corroded. Have you ever had that part out of the motorcycle for an inspection?

[E30_Crazy]

Yeah, had it out to make sure threads of the housing and the temp sensor weren't corroded, and to boil the sensor checking that it gave the proper readout to the ECU. Wiring to pin 10 on the plug checks good, too.

[E30_Crazy]

Finally gave in and bought another ECU. Ran great, been riding for 3 days now. Just tonight, however, it started down the same progressive path of failure as before. A little sputter here and there just around 4k, but will accelerate up to and past 4k no problem. Its just the cruising at 4k affected. Then it gets a little worse, not wanting anywhere from 3.5-6k rpm while cruising . Still runs and idles for now. I have already checked basically the whole bike for shorts and continuity.... But it very well seems like a short somewhere in the wiring harness, and its frying my ECUs (and wallet )

[Laitch]

I have already checked basically the whole bike for shorts and continuity.... But it very well seems like a short somewhere in the wiring harness, and its frying my ECUs (and wallet )

Have you disconnected, dismantled and inspected the ignition switch for dirty contacts or other faulty parts? That's been a fault of many used or neglected K-bikes recorded here many times. http://www.eilenberger.net/K75S/IgnitionSwitch/

 

[alexg]

Just a thought if you are frying Computers: have you checked the system voltage while running? Could it be too high?


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[E30_Crazy]

Have you disconnected, dismantled and inspected the ignition switch for dirty contacts or other faulty parts? That's been a fault of many used or neglected K-bikes recorded here many times. [size=78%]http://www.eilenberger.net/K75S/IgnitionSwitch/[/size]

Actually yes. As just some inquisitive/preventative maintenance, I did have it apart just the other week. All seemed in good order. I still freshened up there contacts a bit before reassembling.

[E30_Crazy]

Just a thought if you are frying Computers: have you checked the system voltage while running? Could it be too high?


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It runs right around 13v at idle, and drops a little with headlight on and upper RPM range. I had planned on changing out the brushes and voltage regulator in an earlier post, until I thought I fixed the problem with the ECU. It was still in the  plans in the close future. However, it was more so to see if it would keep the voltage from dropping, not having an overvoltage.


The bike does seem to run fairly rich now, in its current half-dead state. Either just a side effect of the failing ECU, or it could be receiving/sending an incorrect signal due to a short (I.e. the signal from the AFM is getting juiced up, and the ECU is sending too much fuel)

[timewolf]

Well, no change in the stuttering... Almost feels a little worse now. Can really power through it now. Stutters even with full throttle, and gets hung up around 5 or 6k. Almost starting to remind me of when the ECU failed. Hope it's not that, since that'll make me think there's a bad wire somewhere frying them. Or maybe just got unlucky twice? Still gotta finish checking the rubbers. Haven't got the intake manifold off yet to check the throttle rubbers. Can't very well see the back side of them. Fronts don't look too bad.

Next only list is the FPR and associated lines I guess.

slow down your check and changing to many things at once.
you ever mentioned how she idles ? steady? fluctuation ? popping ? smoking? white or black smoke present? these are tell tail signs


make a check list and eliminate as you go ! air , fuel , spark.
1. did you do the valve adjustment ? if you have a tight valve that could cause all kinds of problems
2. make sure your fuel flow is clean and steady! new filter and pump and is working right.
3. now if she idles right after valves are check / correctly shimmed.... you can move onto timing and throttle body sync.


you said you did the gas check for leaks and it didnt show leaks. leave that alone for a sec. just work on idle .
once thats right you can chase down the other issue.
1. mass airflow sensor ( could be stuck or a faulty unit) or just needs to be adjusted . there are articles here that walk you thought it . 
2.ECU maybe a bad unit or a short  ( probably not )
3.throttle position switch could be a culprit .


most important!!! only work on your bike on a full stomach !   
one thing at a time . make sure they are good. before you move on

[timewolf]

slow down your check and changing to many things at once.
you ever mentioned how she idles ? steady? fluctuation ? popping ? smoking? white or black smoke present? these are tell tail signs


make a check list and eliminate as you go ! air , fuel , spark.
1. did you do the valve adjustment ? if you have a tight valve that could cause all kinds of problems
2. make sure your fuel flow is clean and steady! new filter and pump and is working right.
3. now if she idles right after valves are check / correctly shimmed.... you can move onto timing and throttle body sync.


you said you did the gas check for leaks and it didnt show leaks. leave that alone for a sec. just work on idle .
once thats right you can chase down the other issue.
1. mass airflow sensor ( could be stuck or a faulty unit) or just needs to be adjusted . there are articles here that walk you thought it . 
2.ECU maybe a bad unit or a short  ( probably not )
3.throttle position switch could be a culprit .


most important!!! only work on your bike on a full stomach !   
one thing at a time . make sure they are good. before you move on

SOrry i didnt realize this threat was three pages deep and you guys where way past this point.  :dunno2:

[johnny]

greetings...

its the 4 pin... trust me on this... i have never been wrong... check my credentials...

j o

[E30_Crazy]

Wouldn't that just cause the pump to stop? Not over-fuel to the point of stalling? Or are you meaning there is a short frying ECUs possibly in the 4-pin and/or associated wires?

[E30_Crazy]

greetings...

its the 4 pin... trust me on this... i have never been wrong... check my credentials...

j o

Still not sure if you're just yanking the ol' chain?? Could the 4 pin cause the FI computer to over-voltage or short the system out enough to damage it?