Help! There's something I'm missing doing a TBS

[Bill Dennes]

Regular readers know I've been having a bit of difficulty getting a tune-up done. I got into this when my '02 RT (67k) became extra-gutless when starting off from a full stop.

 

I have done these things:

• Checked valve clearance, using the Anton method.
• Checked the compression (about 180, both sides)
• Changed the spark plugs.
• Messed with the throttle bodies about every which way a person could.

I have not

• Checked the coil, which is a 4-wire unit, part of the San Jose BMW dual-spark conversion.
• Looked at the Hall Effect plate, or at its wiring.

I'm about to go to the electronics store and get the parts to build the LED-based Hall tester that was described in last month's BMW Owners News. Before I do that, let me describe the remaining symptom in the hope that somebody will recognize it and save my hide:

 

If I ride the distance of a city block by accelerating for the first half and rolling the throttle all the way shut for most of the last half, the thing WILL NOT take off from the stop at the end of that block. It sputters and bucks, even with the throttle wide open. No power, lots of sputtering and bucking. The acceleration in the first half of the imaginary block need not have been wide open.

 

Occasionally this will not happen, but most often it does.

 

If I blip the throttle after the stop, the thing will clear, but not necessarily right away. If I just try to ride off, it goes berserk as described above.

 

If I coast up to the stop, avoiding engine deceleration, the problem is WAY less likely to happen.

 

The problem occurs whether the bike is warm or cold, but much more when it's warm.

 

Help!

[KMG_365]

Have you tried:

 

--pulling the LPB?

 

--pulling the Motronic's fuse and resetting the TPS?

 

--making sure your fuel filter is not clogged?

 

--making sure you've got good fuel pressure to the FI's?

 

--running some Techron through to clean out the FI's?

 

* Messed with the throttle bodies about every which way a person could.

If you pulled the TB's on a bike that old, it's very likely that the orings have stretched out and didn't go back properly to make a good seal (BTDT ). You might also try:

 

--cleaning out the TB's with FI cleaner?

 

--removing (or replacing) the LBBS's and clean out the hole with TB cleaner?

 

--removing your charcoal cannister and plugging the ports on the bottom?

 

--making sure you don't have a vacuum leak from one of the cannister lines if not?

 

If you've already done the cannisterectomy a while ago are the plugs/caps on the ports leaking?

 

I posted awhile back about troubleshooting a vacuum leak that I had slowly developed. It was exacerbated and really brought to my attention by a very bad tank of gas that I bought at a no-name station. I ran that tank out and filled up with Chevron and it got much better, but I couldn't get a good synch to hold on the next service. I replaced a lot of the rubber in the intake train, cleaned it out really well, replaced the air filter (I'd been knocking the bugs out of for 20,000 miles or so ) and it ran like a champ after that!

 

What does your synch say? Are you also having a hard time getting it to synch or stay synched while going up and down through the RPM's?

 

Are your throttle cables hanging up/binding? Is it time for new ones? How long ago was the dual spark conversion done (time and mileage), and did it work fine afterwards for awhile before the current problem? Were your bottom plugs fouled when you changed them out recently? How much oil are you using again?

 

Did the symptoms come on all of a sudden--especially after getting gas? It only takes one tank of crud to cause all kinds of problems.

 

I'm sure there are more questions that will come to me!

[bmwmick]

I'm about to go to the electronics store and get the parts to build the LED-based Hall tester that was described in last month's BMW Owners News. Before I do that, let me describe the remaining symptom in the hope that somebody will recognize it and save my hide:

 

If I ride the distance of a city block by accelerating for the first half and rolling the throttle all the way shut for most of the last half, the thing WILL NOT take off from the stop at the end of that block. It sputters and bucks, even with the throttle wide open. No power, lots of sputtering and bucking. The acceleration in the first half of the imaginary block need not have been wide open.

 

Occasionally this will not happen, but most often it does.

 

If I blip the throttle after the stop, the thing will clear, but not necessarily right away. If I just try to ride off, it goes berserk as described above.

 

If I coast up to the stop, avoiding engine deceleration, the problem is WAY less likely to happen.

 

The problem occurs whether the bike is warm or cold, but much more when it's warm.

 

Help!

 

Bill,

Dana has better test box instructions here:

http://users.rcn.com/dehager/service/oilhead_timing_box.pdf

About $16 of components at Radio Shack.

 

Can you tell if your fuel is being cut off with the engine above 2,000 RPM and the throttle closed? That little problem can cause your symptom. You should be able to feel it as you coast through 2K RPM.

 

Have you checked the Motronic for fault codes? Anton has a pretty good list of them here:

http://www.largiader.com/articles/motronic.html

I would suspect a 1215 error code of your TPS isn't set correctly.

 

Mick

[Bill Dennes]

Jamie:

Have you tried:

 

--pulling the LPB? Yes

 

--pulling the Motronic's fuse and resetting the TPS? Yes

 

--making sure your fuel filter is not clogged? Replaced it, did not mention

 

--making sure you've got good fuel pressure to the FI's? No. No gear for that.

 

--running some Techron through to clean out the FI's?

No

--cleaning out the TB's with FI cleaner? Yes

 

--removing (or replacing) the LBBS's and clean out the hole with TB cleaner? Replaced

 

--removing your charcoal cannister and plugging the ports on the bottom? Long ago

 

If you've already done the cannisterectomy a while ago are the plugs/caps on the ports leaking? Replaced 'em

 

I posted awhile back about troubleshooting a vacuum leak that I had slowly developed. It was exacerbated and really brought to my attention by a very bad tank of gas that I bought at a no-name station. I ran that tank out and filled up with Chevron and it got much better, but I couldn't get a good synch to hold on the next service. I replaced a lot of the rubber in the intake train, cleaned it out really well, replaced the air filter (I'd been knocking the bugs out of for 20,000 miles or so ) and it ran like a champ after that!

 

What does your synch say? Are you also having a hard time getting it to synch or stay synched while going up and down through the RPM's? Yes. Right side is jerky

 

Are your throttle cables hanging up/binding? Is it time for new ones? Replaced 'em How long ago was the dual spark conversion done (time and mileage), and did it work fine afterwards for awhile before the current problem? Two years, 30k miles, YES! Were your bottom plugs fouled when you changed them out recently? No How much oil are you using again? No change in rate

 

Did the symptoms come on all of a sudden--especially after getting gas? It only takes one tank of crud to cause all kinds of problems. No, but a tank I got recently made it worse for a while

 

I have replaced the little skinny o-rings on the TBs fairly recently. Using my "loosen the intake stub clamp" methond, it's fairly easy to put the tubes back on without hurting these.

 

BMWMick:

 

Can you tell if your fuel is being cut off with the engine above 2,000 RPM and the throttle closed? That little problem can cause your symptom. You should be able to feel it as you coast through 2K RPM.

I will test for this. What would it indicate?

[bmwmick]

BMWMick:

 

Can you tell if your fuel is being cut off with the engine above 2,000 RPM and the throttle closed? That little problem can cause your symptom. You should be able to feel it as you coast through 2K RPM.

I will test for this. What would it indicate?

 

Bill,

That would indicate that the idle voltage on your TPS is greater than 0.400 volts. It needs to be slightly less than that. I use 0.375-0.385 on mine.

What it causes is a fault code 1215 and an excessively rich mixture for a few seconds. It 'may' not be your problem but it's worth looking into.

 

Mick

[big-t]

Bill,a glitch in the TPS operation could cause the problem you describe.A TPS can often get worn or dirty in one particular spot within its range of operation.This shows up as a momentary loss of voltage to the Motronic as the throttle passes that spot.

 

Its an easy check,hook up a voltmeter just like you were checking the TPS voltage.key on,engine off,very SLOWLY roll the throttle thru its full range while watching the voltmeter.The voltage should rise in a smooth linear fashion to about 5 volts at full throttle.

 

Watch for a place in the throttle operation where the voltage disappears or jumps about in irregular amounts.Should you find a spot like that in the throttle,try opening the throttle all the way and let it snap shut several times,sometimes that will restore the contact within the tps and solve the problem.

 

Hope this helps>

[No_Twilight]

Maybe I read too quickly but nobody seemed to mention the fuel filter. A lot of them seem to be plugging up this winter. Second, I doubt it's the HES since it's somewhat rideable.

 

A severly mis adjusted throttle body sync would cause these symptoms. Do you have a Twinmax or what are you using. I assume you've checked for the classic cable sheath sitting on top of the adjuster ring, right?

 

Cheers,

Jerry

[bigboy]

hi bill

with the symtoms you describe i would be concentrating my efforts on the tps setting,s did you move it when you did the tbs the setting of it is critical if the bike is to run right.just had the very same problem with mine .hope this helps.

derek

[Bill Dennes]

The culprit was the TPS setting.

 

I didn't know that I had an evil twin, but that rascal set the TPS all the way down until the voltage was only 5 mv. Jeez.

 

I did have to put new batteries in my digital meter. This can't account for the adjustment, though, because the "where the screws have been" marks on the TPS were some distance from the screws.

 

I set the darn thing back to 385 mv and things were way better.

 

Thanks to all who helped!