Rough Idle (here we go again)

[SWB]

I've written a bunch about my experience replacing my OEM coil, wires, and plugs on my 2001 R1100RT. I don't want to revisit this, but the idle still feels "off", i.e. a fairly steady, but very slight "miss". Any suggestions for a bike which runs great at every speed except idle (hot or cold), with no surging problems, with fast acceleration and good power??

 

To recap in a nutshell: At 54K, the bike was due for service (1st since I bought it), and was running rough, surging, weak at higher speeds and at throttle "snap". (Yeah, it just plain sucked.) The shop did the standard 54K maintenance, plus replaced the plugs, and added that the right cylinder plug wires was bad. They wanted $200 for a new pair of wires, plus $70 to install them, and I balked, and took the bike back home still running poorly.

 

About $230 and three weeks later, I had installed a Nology coil, Nology "Hotwires", AND picked up a "TWINMAX" ($90) to resync the Throttle Bodies. When I started the bike cold after putting it back together, it idled up strong to about 3K immediately, and I had to quickly crank the idle advance back. (I had increased the advance to get the bike to start and idle in the mornings, because it was running so poorly.) The immediate results were very encouraging. After resync'ing, I tested it on the road without the tupperware, and it ran VERY smooth and strong at any RPM range. Acceleration was terrific. Idle (hot) was right at 1100 RPM.

 

I washed the bike, slapped the tupperware back on the thing, started it up, seemed ok.. a little sluggish because (I suspected) it was wet. Next day; same problems. Rough idle cold and hot, a bit of hesitation at throttle snap, power was OK, but it sure wasn't like it was the night before. It ran like a truck.

 

I asked for some ideas on this forum, got some ("don't wash the bike"), and finally decided to retrace my steps to make sure I hadn't forgotten something (e.g. locking the throttle adjustment screw, hooked throttle cable on the adjuster, etc.). When I had just about given up, I reached over to double check the plug wires, pushed, and heard a "click". It appears that the left cylinder wire was not seated. That helped a lot, but it still wasn't completely smooth. The TB synch and other steps "checked" out.

 

There was some question whether the resister plugs were compatible with the Nology wires, so for the heck of it, I replaced the (new) OEM Bosch plugs with Autolites, and the problems seemed nearly fixed. Idle was still a bit hesitant cold, but was better hot, and there were absolutely no surge problems, it had great power, and in short, it was "good enough" to ride. (I have a problem with a crushed fuel regulator line, but figured I could get by until I replace the clutch around Christmas. I didn't want to dive back into tuning the bike until that problem was resolved.)

 

I spent some time tonight looking at other posts concerning "rough idle", and oh boy, there are enough problems described to make a guy become Beemer hypochondriac. So MANY problems, and solutions have involved everything from 0-0/resync to cam shaft scoring to vacuum leaks to excessive carbon build-up, but no one thing seems to be "the thing" that causes rough idle on the Beemers.

 

I don't have time to tear into the bike now; I could be working on this a while. The bike works well enough to ride if I kick up the fast idle, though the idle problem appears to be getting worse. The bike idled at 1100 after the work with the wires and coil (less than 250 miles ago), but now idles rough at 1000 RPM when hot.

 

The plug wires appear properly seated. I haven't pulled the new plugs yet. If I do go back into the bike, the first thing I'll do is check resistance at the coil and plug wires, as well as ensuring a secure fit of the wires at the coil. If I have further problems with the wires "unseating" at the plugs or coil, I'm heading back to talk to Nology for a solution, or may just replace the coil and wires with BMW OEM parts and be done with it.

 

I'm open to ideas. This Beemer wrenching is fun stuff! If I had time, I might even figure out what the heck I was doing.

[KMG_365]

Hi Scott,

 

I might have missed it, but did you already check/remove/clean the Large Brass Bypass (LBB) screws? They can get really caked with crud and with 54K (as dealers don't often go into that much detail) can clog up the narrow bypass air passage.

 

Odd that you mention the bike ran great (naked) before you washed it. I was amazed at how good my bike felt riding it naked (the bike, not me! ), and when I buttoned it back up (I try to never wash my bike if I don't have to! ) it ran just like always (that is to say, fine, but not WOWEE!! ) and I was a bit disappointed that it wasn't my FABULOUS tuning skills that were the reason for the difference I'd felt riding it stripped down.

 

 

A few other questions for you:

 

How many miles on your fuel filter?

 

Do you still have the charcoal cannister attached?

 

Have you ever run a bottle of Techron through it? (You run the Techron tank almost dry, fill with straight gas then immediately change your oil)

 

How long is your average trip? (short commutes near the cool coast?)

 

When was your last "Italian tune-up"?

[SWB]

Hi Scott,

 

I might have missed it, but did you already check/remove/clean the Large Brass Bypass (LBB) screws? They can get really caked with crud and with 54K (as dealers don't often go into that much detail) can clog up the narrow bypass air passage.

 

I assume that's the large brass screws used when sync'ing throttle bodies? No, haven't done that. Should the entire fuel injector be removed for soaking/cleaning like a conventional carb??

 

Odd that you mention the bike ran great (naked) before you washed it. I was amazed at how good my bike felt riding it naked (the bike, not me! ), and when I buttoned it back up (I try to never wash my bike if I don't have to! ) it ran just like always (that is to say, fine, but not WOWEE!! ) and I was a bit disappointed that it wasn't my FABULOUS tuning skills that were the reason for the difference I'd felt riding it stripped down.

 

 

A few other questions for you:

 

How many miles on your fuel filter?

 

Should have been done by BMW during the 48K service. Got the bike at 50K. External fuel filter mod is on my maintenance list. Air cleaner looked clean.

 

 

Do you still have the charcoal cannister attached?

 

Yes. CA emissions requirement.

 

 

Have you ever run a bottle of Techron through it? (You run the Techron tank almost dry, fill with straight gas then immediately change your oil)

 

That too, is on my list for 60K, since my oil is fresh. Hmmm.. I may just repeat the 54K maintenance early.

 

How long is your average trip? (short commutes near the cool coast?)

 

Have been riding 90 miles a day along the San Diego I5 coast.

 

When was your last "Italian tune-up"?

 

Are you an LEO?? Often enough, 0-80 shifting > 5500 RPM.

 

 

Thanks for your thoughts. I know I'm probably going to have to just break this bike down and go from A...Z., including all you've suggested. However, I hoped that the fact that the bike runs well except at idle might have jogged someone's memory over a likely cause. And, it REALLY idled well when I first put on the plug wires and coil - just perfect.

 

So many things can cause rough idling, and since I didn't do the 54K service myself, nor the service before I owned it, I don't have confidence about what's "not" causing the problem. I'm assuming that the engine is basically sound, because I had it checked out by two different dealers when I purchased it and at the 54K, and neither said "compression is low", etc.. Something like a clogged or dirty fuel injector, leaks around the airbox, or vacume hose leak could do it.

[Ken H.]

I've been following your saga for awhile (and trying not to be accusatory here) but I wonder if your chasing a ghost to some extent. The boxer really doesn't idle all that smoothly. Occasional 'missed beats' is something they all do at idle. Have you compared yours to several other same model / years to decide if yours idles significantly worse that all the rest of them?

[SWB]

I've been following your saga for awhile (and trying not to be accusatory here) but I wonder if your chasing a ghost to some extent. The boxer really doesn't idle all that smoothly. Occasional 'missed beats' is something they all do at idle. Have you compared yours to several other same model / years to decide if yours idles significantly worse that all the rest of them?

 

Unfortunately, nope. It might be inexperience on my part (and/or unrealistic expectations). I might take it by the dealer and ask them if it feels like a normal idle.

 

It seems like it idled smoother when I originally got it, and after the new coil/wires/plugs. The "tell tale" is the fast idle. I adjusted it up before replacing the ignition system parts so that the bike would start without stalling in the mornings. I had to adjust it way back down afterwards (and the idle was both way-too-fast and smooth). Since then, the idle is rougher and the bike stalls during starts unless I hold the fast idle past the "stop" (click position?) or unless I advance the idle using the throttle (and cruise control). It's not as bad as before the service, but the roughness "feels" noticible, and the difference in the fast idle setting is measureable. Occasionally, the hot idle makes the bike "feel" like it wants to stall at stop lights, and like I said, the hot idle dropped from around 1100-1150 RPM to 1000 now.

 

Short cuts rarely pay off. I only replaced the coil, wires, and plugs and resync'd the throttle bodies (since I had just had the 54K service). I need to pull this thing apart and check compression, maybe do a leak-down test, check the new coil, wires and plugs (yet again), clean out the LBB (good idea from KMG), do the 0-0 TPS adjustment, recheck the valve adj., then resync the throttles, etc.. The crushed fuel (regulator) line ("reopened", but still damaged) really bothers me. Since the fuel is under pressure, a slightly misshaped fuel line may not matter. But I can't be sure that's not the whole problem, i.e. constriction on one of the fuel lines. The fuel regulator gets replaced at Christmas, too.

 

Chasing ghosts.. yeah, maybe I am. I'll have something more intelligent to contribute here around Christmas when I do all of the above (but it's going to be a lot of work). I can do anything better than a "pro", it just takes me about ten times longer.

 

Thanks Ken - no worries - you can "accuse" all ya want.

[Slartidbartfast]

Firstly, regarding cold starts, you SHOULD have to hold the fast-idle lever past the click point to start the engine and maybe for a few seconds afterwards.

 

Secondly, per previous advice, make sure you are not trying to fix a non-existent problem. See how other oilheads idle.

 

Quick, easy things to check as a possible source for your erratic idle/and or other problems include:

 

A vacuum leak somewhere in the emissions vapor control system. Pull the two vacuum hoses off the undersides of the throttle bodies and cap the barbs either with vacuum caps from the local auto store or with short offcuts of rubber hose, plugged with screws or ball bearings.

 

Not sure if it would affect the idle mixture but you might want to make sure you have the correct Cat Code Plug installed.

 

Any sign of a vacuum in the gas tank (hiss when you open the cap) could indicate that some hoses were swapped when the fuel filter was serviced - this would defintely make the bike run badly.

 

As you noted, there are undoubtedly many, many other possibilites but these are free or very cheap, quick and easy to check.

[bmwmick]

Scott,

Ther very first thing I would recommend is a good valve adjustment. After that (which should always be the first step in your tune-up) I would verify the timing and then go after the throttle body sync.

 

Mick

[SWB]

Scott,

Ther very first thing I would recommend is a good valve adjustment. After that (which should always be the first step in your tune-up) I would verify the timing and then go after the throttle body sync.

 

Thanks, Mick. The dealer just did the valve adjustment, and since I was focused on the plug wires (per the service tech), I didn't recheck the valve adjustment.

 

It's time to stop "jawing" and start wrenching. I'm going to ride the heck out my Beemer this week (plus try the new startup/throttle advance routine mentioned above), and see if the idle and performance feels better or worse. If no improvement, I'll do as various folks have suggested, i.e. repeat a full tune up next weekend (valves, timing, TPS 0-0, throttle sync, etc., per the ibmwr "Oilhead Maintenance" manual). That manual also has an interesting section on increasing "valve lash" (as well as advancing ignition timing 3 degrees) which the author claims improves both idle and performance, which I think I'll try.

 

Thanks to all!

[SWB]

Quick, easy things to check as a possible source for your erratic idle/and or other problems include:

 

A vacuum leak somewhere in the emissions vapor control system. Pull the two vacuum hoses off the undersides of the throttle bodies and cap the barbs either with vacuum caps from the local auto store or with short offcuts of rubber hose, plugged with screws or ball bearings.

Are you suggesting that permanently disconnecting the emission's control system (by capping the barbs at the bottom of the throttle bodies permanently) might improve idle performance?

 

Thanks for the rest of your advice; will add it to my list of checks.

[ShovelStrokeEd]

It will if the hoses are leaking.

 

I'm kinda with Ken on this one. The boxer motor is never going to idle like a sewing machine. It just doesn't have it in it. The engine design is too sensitive and the flywheel too light. Small variations in combustion events, and they do vary, will cause (relativly) large changes in engine RPM. It is the price you pay for snappy throttle response.

 

The most important thing I did while following a similar quest a few years ago was to get that TPS voltage nailed. 0.380<TPS<0.400. I then redid the zero=zero thing such that my BBS were under 1 turn out to get idle at 1000 RPM. That had the effect of slightly richening the idle mixture and lessening the number of missed combustion events.

 

I have since stopped worrying about it. The idle just varies from day to day. It's at its best just after a good long day on the freeway. Something about 500 miles at 5K RPM really perks it up. It's at its worst when I spend a couple of days just going back and forth from my house to the office. 4 miles one way. Actually the trip home is 5 miles to the pub for dinner and then 4 miles from the pub to my house.

 

Anybody got a spare flywheel laying around? I'd love to see if I can build one a couple of lbs heavier. I've a feeling that you guys with RT's would eat them up. Much easier to pull away from a stop, smoother idle, no loss of top speed and, for that matter, minimal effect on acceleration, it might even help as your launch will be much better. Win/win situation. Long as you have it down for a spline lube anyway, its only a few bolts more to get the flywheel off. Should cut down on that pesky clutch rattle in neutral as well.

[Slartidbartfast]

Quick, easy things to check as a possible source for your erratic idle/and or other problems include:

 

A vacuum leak somewhere in the emissions vapor control system. Pull the two vacuum hoses off the undersides of the throttle bodies and cap the barbs either with vacuum caps from the local auto store or with short offcuts of rubber hose, plugged with screws or ball bearings.

Are you suggesting that permanently disconnecting the emission's control system (by capping the barbs at the bottom of the throttle bodies permanently) might improve idle performance?

Temporarily cap the barbs to check if your emissions system was leaking. If the idle improves then you had a problem. What you do about it after that is up to you.