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Discussion Starter #1
I rode my 2000 LT in to the office this morning for my 45 mile commute. This was the first longer ride following the main seal/clutch pad/gearbox/fuel filter job.

The shifting is smooth and there's a lot less vibration coming out of the gearbox now. So those are a major win! :D

She's a bit sputtery though. At high speed it feels like the throttle gets pulled a bit randomly when I didn't even move it. At low speed, it sputters in a way that makes me think I've got a cylinder not firing consistently and the power just isn't there. There are no warning lights.

Is it possible the pressure regulator on the fuel rail didn't like sitting dry for so long and is acting inconsistant?

I also know that the plugs have not been done in at least the last 5 years.

I just find it curious that this manifested after doing this work on it.

Any guesses?

-Steve
 

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I rode my 2000 LT in to the office this morning for my 45 mile commute. This was the first longer ride following the main seal/clutch pad/gearbox/fuel filter job.

The shifting is smooth and there's a lot less vibration coming out of the gearbox now. So those are a major win! :D

She's a bit sputtery though. At high speed it feels like the throttle gets pulled a bit randomly when I didn't even move it. At low speed, it sputters in a way that makes me think I've got a cylinder not firing consistently and the power just isn't there. There are no warning lights.

Is it possible the pressure regulator on the fuel rail didn't like sitting dry for so long and is acting inconsistant?

I also know that the plugs have not been done in at least the last 5 years.

I just find it curious that this manifested after doing this work on it.

Any guesses?

-Steve
How sure are you that you didn't swap one of the injector wires with the purge valve?
 

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Discussion Starter #3
I'm pretty sure I got that right. I would think it would never run smooth if that was the case. This issue seems intermittent.
 

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I also noticed that the rail on the back side of the throttle valve that comes from the crankcase breather seemed like it might be a bit cracked. #5 in the diagram.

11 15 1 465 009 DISTRIBUTION HOSE

I wonder if that could create this sort of issue.
 

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I think John mentioned something about making sure all the injector plugs were firmly seated on the injectors.

An intermittent miss could be plug wires arcing to ground or a lose injector connector. Are they still the original plug wires as I can't remember if you had replaced them yet?


The throttle pulling randomly could a cable routing issue as these LT's throttle cables can be quite sensitive to how they are routed and adjusted but I recall you working on that specifically during reassembly. It also could be an intermittent injector connection and one cyl is not firing consistently from a lack of a fuel charge. The fuel regulator would be of a lesser concern so I would focus on the injector connections and possibly plug wires. The wires may be able to be visually verified in the dark by seeing arcing with the cover removed. Those are fairly easy checks.
 
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I also noticed that the rail on the back side of the throttle valve that comes from the crankcase breather seemed like it might be a bit cracked. #5 in the diagram.

11 15 1 465 009 DISTRIBUTION HOSE

I wonder if that could create this sort of issue.
The breather tube won't cause any operational issue for the engine as it comes in above the butterfly valves and has no affect on vacuum or mixture. It will however leak condensed oil vapor on top of your engine through the cracks making a mess rather than being pulled into the venturi to be burned.
 

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Discussion Starter #7
The breather tube won't cause any operational issue for the engine as it comes in above the butterfly valves and has no affect on vacuum or mixture. It will however leak condensed oil vapor on top of your engine through the cracks making a mess rather than being pulled into the venturi to be burned.
This would explain the nasty mess that was there. It took quite a while to clean up. I'm gonna put that replacement on the short list just to keep it from making that mess again.
 

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Give a light tug on each of the injector wires, if one is not locked it will pull right off.
 
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Discussion Starter #10
Yeah, you guys were right. As I rode home I became more and more convinced I wasn't firing on all cylinders (in more ways than one really).

I popped the side panel off and disconnected and reconnected all of the injector connectors. I had to use a long pair of needle-nose pliers to get at injector #1 under the fan shroud, but I did it. I went for a test ride and all seems back to normal. The power is back, no sputtering, and the engine sounds smooth again.
 

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Discussion Starter #11 (Edited)
After the short test ride I mentioned above, I commuted to the office with her. Not good. The sputtering was back.

It seems like the behavior manifests itself after warming up a bit. At a constant speed, its enough to rock me back and forth a bit. During acceleration, its much more noticeable. When coming to a stop, and letting her idle, the RPMs will bounce around a bit for a few seconds before becoming constant.

Since I last posted, I:
1) replaced the fuel injectors with some refurbished Bosch 4-hole injectors
2) replaced the spark plugs with Bosch XR7LDC

None of those made a huge difference, albeit my old plugs were in pretty rough shape.

Yesterday, I:
3) replaced the spark plug wires with a new set from BBY

The initial short test ride had me filled with a great deal of hope. I rode her on the long commute this morning though, and it is STILL there.

I think all I've done at this point is lessen the symptoms of the underlying cause.

As I ride along at 80+ MPH I will, about every 10 mins or so, get a brief moment of what feels like FULL POWER. Its enough to tease me and let me know what she's capable of.

At this point, my guesses are:

  • fuel pressure regulator on the fuel rail
  • distributor or electrical connection thereto
  • fuel pump or electrical connection thereto
  • rail on the back side of the throttle valve that comes from the crankcase breather (EGR)
I'm thinking that that cracked rail could potentially create inconsistent pressure in the intake, which might manifest itself in this sputtering behavior. Given a blind guess, that will probably be my next move.

Any tips for common failures or diagnostics?

-Steve
Titusville, FL
 

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As I remember, you possibly stretched the engine temp sensor in lowering the transmission. Were you able to check that with a meter as I think I posted a chart with values made by Sailor on that thread. ( I think) Do the fans come on with the key before you start the engine? or do they come on at times when the engine is not hot indicating damaged wires? The one I did that on really ran like crap and the fans came on with the key indicating either an open connection. Jzeiler uses unplugging the sensor to test both fans as it causes them to come on with the key so that is why I am asking. We already verified that you don't have the purge valve connector on one of the injectors. I am in FL with you this week in Jax so I don't have my wiring handy to look at wire colors and the only pic I have is not good but it looks like a green and some form of yellow or something with on the purge valve. The injectors were something different. Just make sure they are all the same on the injectors and you are good there.

The EGR tube has no effect on engine operation so replace it if you want but it won't fix this. It plumbs in above the butterfly valves so it has no affect on manifold pressure.

Changing the plugs won't change the engine RPM at a particular speed, only changing gears would so I assume you were running in 5th versus 4th.
 

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Discussion Starter #15
I think I'll go ahead and order that replacement breather tube next week.

While I'm in there, I will reconfirm the wire coloring of the connectors on injector #1 and the pulse valve. At the very least, it doesn't seem to damage anything by having them swapped, so I can always try it for grins.
 

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I think I'll go ahead and order that replacement breather tube next week.

While I'm in there, I will reconfirm the wire coloring of the connectors on injector #1 and the pulse valve. At the very least, it doesn't seem to damage anything by having them swapped, so I can always try it for grins.
Sounds like a plan. The symptom of it occasionally feeling like full power could be caused by the pulse valve actuating an injector or a lose connection to an injector, both of which I believe you have checked but a doublecheck couldn't hurt. I was actually surprised that I managed to swap the pulse and injector connectors as I was replacing my injectors even knowing I could do that. A double check caught it before re-assembly so it didn't cause me any problem. I need to wear my glasses more often as I get older. After that, I followed Sailor's thoughts that the pulse valve can be entirely removed and the small 4 hoses joined with T-couplers with the cable just tied out of the way. Let us know what you find there.
 

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So, apparently I'm a blind idiot.

One of these is not like the other. I DID, in fact, exchange injector #1 with the pulse valve.

All of the injectors have green and yellow wires. The pulse valve has a green and blue wire.

Given similar symptoms, we have published this common error and the solution about 20 times here during last 5 years. Glad you found it!

P.S.:
every time I see questions / symptoms like yours on forums, one of my 1st or 2nd question is often:
- what maintenance was done on bike recently by you or the dealer?
- what area has been touched / dismantled recently ?

My best guess is that about 50% of these sudden "does not run right" issues are self inflicted - welcome to the club ;-)
The fuel filter hose popping out is the next one being very common - often appears following a filter replacement of course....
 
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So, apparently I'm a blind idiot.

One of these is not like the other. I DID, in fact, exchange injector #1 with the pulse valve.

All of the injectors have green and yellow wires. The pulse valve has a green and blue wire.
Like I said earlier, it is easy to do and I did it myself but caught it in a double check before covering things up. It should be running better now. :)
 
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