Bizarre Problem - Will Not Idle!

[waehrik]

So it's proving impossible for my 1998 R1100RS to idle. I've tried everything I can think of for diagnostics and possible replacement parts and am out of ideas.

The bike starts up perfectly and will run but only with the 'choke' on or the throttle open.

I've tried two different sets of throttle bodies/throttle position sensor/fuel injector:
1) The first set was original to the bike and worked perfectly up until a month ago when the bike began to die when the throttle was released. Thinking that the TPS was set wrong, I did a 0=0 but it didn't help any. Same problem, as soon as the throttle plates hit the stop, the bike would die. I tried to raise the throttle stops to increase the opening at idle but after a looong time of doing this, I ended up stripping out the left side stop screw.
2) I bought the second set of throttle bodies hoping that a virgin pair would solve the problem. These had the tamper seal on both the stop screws and TPS, so nobody had ever mucked with them. I tested the TPS voltage and found it to be 0.402v, excellent.

But still no idle!

I replaced the spark plug wires with a new Nology set (cause they were cheaper than OEM)

I tested for vacuum leaks with an unlit propane torch. Nothing.

I've already removed my charcoal canister and have vacuum caps on the barbs.

I've adjusted the valves (they were good), opened up the brass bypass screws, everything I can think of.

I'm running without a cat code plug with no O2 sensor. The cat has been removed from the exhaust.

Oddly enough, rotating the TPS to a higher voltage (about 0.6v) will allow the bike to idle at about 1100rpm. But if it's shut off and restarted, it won't idle again.

Does anyone have an idea what this problem could be? I'm completely dumbfounded.

 

[pauls1150]

Fast idle lever on, or throttle open, or high TPS voltage... sounds like a fueling problem.

Did this come about suddenly (after what else?) or gradually?

Pull the Motronic fuse (#5, blue, 15A) for at least five seconds to clear out the faults, then when you put it back in, turn on the key but don't hit the starter:
Slowly turn the throttle all the way from full closed to full open, three to five times, all the way thru its range.
This "teaches" the computer the relationship between the TPS and the throttle position.

Let us know...

 

[waehrik]

Fast idle lever on, or throttle open, or high TPS voltage... sounds like a fueling problem.

Did this come about suddenly (after what else?) or gradually?

Pull the Motronic fuse (#5, blue, 15A) for at least five seconds to clear out the faults, then when you put it back in, turn on the key but don't hit the starter:
Slowly turn the throttle all the way from full closed to full open, three to five times, all the way thru its range.
This "teaches" the computer the relationship between the TPS and the throttle position.

Let us know...

I've tried the Motronic reset procedure and throttle learning, but unfortunately no luck with that.

I haven't thought of it being a fueling issue, but that makes sense. I had the tank off a while ago to bend the fuel lever float arm since it was reading one bar too low, but I was pretty careful not to disturb anything. The fuel filter was replaced at 24k, and I have 31k on the bike now. It didn't appear to be split or anything. I would have thought that the fuel demands would be higher at a larger throttle opening though - would a malfunctioning fuel pump/filter/broken line manifest itself only at idle?

I can pull the fuel lines off from the fuel injectors and gas pours out when the bike is switched on. I can't test fuel pressure, but it appears to be good.

I've tried pulling the connector on each side's fuel injector and it will run on each cylinder (as long as the throttle is held opening). So both cylinders are firing.

 

[bikerfish1100]

maybe too simplistic, but.. throttle cables need replacing? 30K is a bit low, but maybe they are just stretched out.

 

[waehrik]

maybe too simplistic, but.. throttle cables need replacing? 30K is a bit low, but maybe they are just stretched out.

I actually did that a couple months ago because I wasn't able to maintain throttle body sync throughout the entire RPM range. It made an enormous difference in surging!

But at idle, the throttle cables are completely slack and the butterflies rest on the stops, so worn cables shouldn't made a difference. They'll have a huge impact on running though!

 

[PGlaves]

I might be way off base but I do agree it sounds like a fuel issue, by process of elimination from what has been done previously.

Fuel delivery is a composite of three factors: cross section of injector opening; fuel pressure; and injector open time.

Injector open time is controlled by the Motronic and is probably OK of it runs semi decently above idle.

Fuel pressure is a result of pump pressure and any obstructions like a clogged filter. They will clog with one dose of crud or water so mileage on the filter doesn't mean much if anything to me.

Cross section depends on the injectors being not worn, and not partially clogged.

Conventional wisdom would say that if pressure or injector cross section were the cause it would appear more at high rpm than at idle. In my opinion that is not necessarily the case. BMW has made these engines very lean at low rpm so any extra leaning would be most pronounced at idle. The added richness at higher rpm might mask the fact that it is still leaner than it is supposed to be - but still rich enough to run.

Given that lean conditions can destroy engines, if that were my bike the injectors would be professionally tested and cleaned, and the fuel pressure would be tested. I would test it with the existing filter in place and if low, would replace the filter - even if it is almost brand spanking new.

 

[happy wanderer]

From everything you've done and checked already, I think Paul is probably right about fuel issues. It would seem weird that there was not enough fuel to run right at idle but it runs OK at higher RPM which demands even more fuel.

That said I just had my injectors cleaned and tested and what a difference it made at idle and 2 to 4K RPM.

You have spark, you have fuel and you have air. The only other thing that comes to mind is compression. You might want to check the compression just to cover the bases.

 

[69ZEFF65]

Might want to check engine timing

I would say Yep to fuel pressure tests and all but just to be sure your chain hasn't slipped one tooth on any of its sprockets I would give it a quick check to make sure everything lines up as it should. It will run up with a cam out but not idle. Something might have slipped enough to prevent idle but not enough for the valve to tap the top of the piston.

 

[Dave_Faria]

I ask this question because I haven't had to check fuel pressure on my bike. Is there a simple Test Jig for doing this on my R1150RT?? How do you connect it and what pressure would you expect to see???

Thanks

 

[PGlaves]

I ask this question because I haven't had to check fuel pressure on my bike. Is there a simple Test Jig for doing this on my R1150RT?? How do you connect it and what pressure would you expect to see???

Thanks

No, there is no simple test jig. To do the test right you need to "T" into the pressure line from the pump to the pressure regulator.

If your bike has quick disconnects you can buy another set and build up a gauge setup that has the gauge on the perpendicular leg of the T and a QD on each end of the through leg. I use an old metal T as used on the Airheads.

Don't just go into the pressure line without a T. The pump can exceed 100 p.s.i. and blow the gauge right off the end of the hose unless you are testing regulated pressure through the regulator.

 

[waehrik]

I ask this question because I haven't had to check fuel pressure on my bike. Is there a simple Test Jig for doing this on my R1150RT?? How do you connect it and what pressure would you expect to see???

Thanks

Thank you everyone for all of your suggestions! I'll look into the fuel situation today. It does make sense that since the fuel map is leaner at idle that any deviations from the standard fuel pressure would manifest themselves at that point. I didn't even think of it before since it was running alright at higher RPMs.

I have the same question as Dave though regarding fuel pressure, how does one test it?
One could stick a pressure gage on the tank's output line (where you'd normally put quick disconnects), but that wouldn't take into account the pressure after the regulator. The fuel system dead ends at the injectors - is there any way to test the pressure there?

I will send one set of injectors out for cleaning now that I have the spare set. It is strange though that the problem followed two sets of injectors.

I'll check compression - hadn't thought of that one!

I'll check out the cam timing too, but I'd be surprised if had shifted. Last time I did a valve adjustment I inspected the cam chain rails and they were all intact. I'd also updated the left side tensioner. What would cause the timing to shift?

 

[MOTOPERRO]

Injector Cleaning & Testing

Who is best for "professionally cleaning and testing" the injectors? MC shop, or anyone set up to do injector cleaning and testing?

 

[PGlaves]

Who is best for "professionally cleaning and testing" the injectors? MC shop, or anyone set up to do injector cleaning and testing?

Most motorcycle shops are going to take them or send them to an injector specialist. Years ago good shops were hard to find and usually did diesels. Today almost every good sized town has a shop that can clean and test injectors. Ask around.

 

[waehrik]

Alright, so here's the results of my testing this afternoon:

Compression is good at 125psi on the dot, both sides.

Cam timing is good, the arrows on the cams themselves which are visible when the little plastic covers are removed both point towards the bike when the flywheel is at TDC.

The fuel pump cycles when the engine reaches TDC on the flywheel.
BUT now here's something odd... it cycles THREE times as the engine is rotated through one complete revolution (from TDC and back again)
- Once at approximately 180 degrees of revolution
- Once just before the Z mark is visible on the flywheel
- Once when the OT mark is in the center of the window

Why would it be cycling three times? Does that mean it's sparking and giving fuel from the injectors at each of those points?

For fuel pressure, I'm making my own adapter that will mount as a fuel injector and give me a schraeder valve to use my standard fuel line pressure gage on. I'm making it from a spare injector I bought a while ago when thinking that going to a higher flow rate injector would richen up the mixture across the entire range and reduce surging. I ended up not needing them, so ripped them apart and am epoxying the valve to the injector.
In the mean time, I did a very basic test of holding my finger on the end of the fuel line while switching the bike on. The fuel pressure was very strong and I couldn't keep fuel from escaping.

 

[johncrute]

1100 Problems

I just had the same thing happen to my 1998 GS, and it turned out to be the curved fuel lin on the outlet side of the fuel filter. It had a hole on the underside of the curve that you could not see unless you took it off. Good luck.

 

[waehrik]

I just had the same thing happen to my 1998 GS, and it turned out to be the curved fuel lin on the outlet side of the fuel filter. It had a hole on the underside of the curve that you could not see unless you took it off. Good luck.

That makes perfect sense, I'll check for kinked fuel lines. Did the hole in your line cause gas to mist from under the tank when the pump was running?

Unfortunately the only schrader valve I had laying around was for a basket ball pump adapter and it had a hole on the threaded region. I tried to fill it with epoxy but it didn't hold. I'll look this weekend for another one without a break in the threads so I can make a functional adapter to do the fuel pressure test.

 

[bikerfish1100]

That makes perfect sense, I'll check for kinked fuel lines. Did the hole in your line cause gas to mist from under the tank when the pump was running?

should not have caused a spray or misting, as "outlet side of filter" is still within the gas tank. it would just cause a lack of full pressure, something every FI system requires to operate properly.

 

[waehrik]

should not have caused a spray or misting, as "outlet side of filter" is still within the gas tank. it would just cause a lack of full pressure, something every FI system requires to operate properly.

Oh gotcha, for some reason I was thinking of an externally mounted filter, which is something I'll convert mine to if I have to take off the tank again. It's just one more thing to be able to rule out in the future (if not just by simply replacing the $5 generic filter)

 

[waehrik]

Alright, so I can (finally) report back with additional information.

I was able to make an adapter out of a hollowed out fuel injector, some epoxy, and a basketball inflater with a Schrader valve to connect to my fuel pressure tester.
I measured 45psi at the injectors, which is right where it should be.

I pulled the hall sensor out and found the following traces on my scope. Any idea why there would be so much noise when the sensor is supposed to be pulled down to 0v? I suspected the power supply but tried two different supplies and a battery and found the same behavior.

Apparently I can only attach one file per post, so the trace from one sensor is here and the next sensor's output is on the next post.

 

[waehrik]

Here's the output for the second sensor.

At least it's consistent with the first, just a lot noisier than I would have expected.