Return of bucking. A jinx and a curse? Solved!

[aopisa]

and you confirmed TSII is nice and tight and resistance between connector and ground is there? how bout resistance from ECU main harness plug to ground? another thing to test is (-) side of coil to ECU main harness plug resistance?

I could not find my 13mm deep socket so I just bought another one. It seemed tight. I think I want to remove the spacer and connect the new sensor directly. The tin thing is a problem. I know Colin said I can loosen the screws and move the tin. I will have to take a closer look. Every little project seems to take about 3 times longer than I anticipate.

[aopisa]

Maybe I just need to fly up there and motivate this boy to get his wagon ahoy!

That would be so great!

Really, I am a bit embarassed that I have not been able to track this down yet. You know it is probably going to be something very simple that has been staring me in the face the whole time.

[luftvagon]

We are all rooting for you!

[TrollFromDownBelow]

Really, I am a bit embarassed that I have not been able to track this down yet. You know it is probably going to be something very simple that has been staring me in the face the whole time.

Don't be.... it took me close to two years and a Colin visit before i figured it out....it can be very vexing.

[56ovalbug]

Every little project seems to take about 3 times longer than I anticipate.

Yea... that sounds about right.

[Lanval]

it is probably going to be something very simple

Simple needs some qualifying here; it's often extremely difficult to figure out what's happening when there exists a range of variables. While the problem may be "simple", it doesn't follow that the process to discover and/or repair the problem is "simple".

I feel, based on what you've done, that it's most likely electrical. "Electrical problem" is still a rat's-nest of issues. Everything from bad circuits to faulty connections; not easy to check "everything" including the lengths of wires. Patience and thoughtfulness; compartmentalize your work, and verify one element at a time. Possibilities must be reduced over time. Per Sherlock Holmes:

"How often have I said to you that when you have eliminated the impossible, whatever remains, however improbable, must be the truth?"

ML

[aopisa]

You are correct. To clarify, I feel that it is likely something that once discovered will be an easy fix from a time, difficulty and cost perspective. However, the path to its discovery may have many more twists and turns.

I am trying to find some time in the next few days to refocus my efforts. Next up is the replacement of the TSll sensor which I anticipate being a problem because of the 'slipped tin' issue.

Thanks to everyone for hanging in there with me.

[Westy78]

Maybe I misses it somewhere in the past pages but have you tried a different AFM yet? I chased a bucking issue for a year before discovering high resistance in a recently refurbished AFM. It's a quick easy thing t rule out if you have a known good spare to throw in there.

[aopisa]

I have already checked the resistance per Bentley and tested the voltage as the stator flap opens.

Randy in Maine loaned me his spare AFM.

As I stated earlier, hope to devote some more focus on this in the next few days.

The spare AFM is second on the list after the TS ll. Randy stated that little is known about this AFM so I am not sure what conclusions can be drawn from it.

Thanks and stay tuned.

[Westy78]

An AFM on loan from Randy is what got me back on the road.
=D>

[aopisa]

I made a little time today to get back to diagnosing.

I found an analog multi-meter the other day while digging around the garage. I re-ran the AFM stator flap test looking for a voltage drop as the flap opened. No voltage drop detected.

I decided to install "The Randy in Maine Commemorative Loaner AFM" since it was basically plug and play and I know the TSll sensor is going to be a cursing, tool throwing endeavor.

Randy's AFM did not change the bucking. I got almost immediate bucking as soon as I took off down the road. I swapped back in my AFM and the symptoms were exactly the same.

Next up is the TSll and then chasing wires I guess.

Stay tuned.

[Gypsie]

The tsII can be worked with a 13 mm open end wrench used kind of like a screwdriver. this way the wire can be unmolested during installation. a screwdriver through the closed end will give the last bit of cinch needed. it can be cumbersome but once you get the 1/4 bto 1/2 turn rhythm going it goes pretty quick. I did a little "coercion" with the tin to clear a spot for a good mating surface by putting a screwdriver/drift along the edge of the tin and tapping it out of the way. Be careful of the head surface.

The TsII should be one of your first tasks to get out of the way. Get it on there good and confirm that it is giving proper readings. Then move on to the other stuff.

2 cents.

[aopisa]

Let's just say I am cautiously optimistic at this point. About 95% cautious and 5% optimistic. I almost hesitate to admit what the problem may have been and considered constructing some elaborate story in order to save a small shred of self esteem. Since you have all stuck with me this long, you deserve to hear the real story.

I finally had my friend come over to help. Cliff has a lot of experience with fixing cars, but no real knowledge about air cooled engines. So, with his mechanical knowledge and my VW book learnin' we worked on the problem together. I will have to say it was mostly Cliff who gets the credit of the possible solution to this problem.

First off was to get the new TS ll in just to rule out another thing on the list. He used a long screwdriver to lever the tin up a bit while simultaneously screwing in the sensor. Got a nice tight fit.

After the new TSll was installed the bus ran worse than it ever has. It idled fine and the throttle could be advanced for the first few minutes without any issues. After that I could barely get it out of the driveway. Not only was it bucking, but it had virtually no power. I could hardly limp it back the few dozen feet to get it home.

We turned to checking the FI wires. The TS ll wire that leads to the ECU plug was suspect. Even last year I replaced a section of the wire since it was very brittle and crumbly. So Cliff spliced in a new longer section. Still terrible performance. We tried grounding out the sensor with no change in performance. We tried disconnecting the sensor which made the engine die.

Pulled the ECU just to say we checked and it looked surprisingly good for a 36 year old electronic component.

So, just idling was fine if maybe a bit low on the RPMs. As soon as I jumped in the seat and depressed the accelerator the engine would start bucking. We joked that we finally pinpointed the problem to the driver's seat! My son had remarked earlier that when I revved the engine when it was bucking the lights would dim and get brighter. It turns out that as soon as I jumped into the driver's seat, I would automatically switch on the headlights. We revved the engine with lights off, bucking diminished, lights on, bucking returns. Took it for a drive. Lights off on the pitch black road, less bucking. Lights on, bucking returns.

We turned our attention back to grounds again. Cliff rechecked, cleaned and tightened the FI grounds and did a much more thorough job than I had. Now, the negative battery ground is a nice shiny braided strap. It always looked fine to me. I have always removed it from the battery terminal and cleaned it while it was off. I never really removed it completely and only checked it for tightness where it attaches to the body in the engine bay. As I said it always looked brand new and in excellent condition.

Well, my friend decided to remove it completely . When he did a lot of sand came out from behind the strap contact point. I don't know much about the past history of this bus. I am fairly certain it is a former California beach and surf bus, hence the sand. I have long suspected that the bus has a deep resentment for being forcibly relocated east to snowy Vermont.



In addition, the negative strap attachment point was covered in the black engine bay paint and under that was the sage green body paint. What? You mean silica and paint are not good conductors? Cliff sanded it down to bare metal, cleaned the strap and reattached it.

The bus ran great with full power and acceleration and no bucking at all. It even seems to start up more powerfully and faster. We were able to drive it longer and farther than it has gone in over a month. We stayed on the dirt road up here on the mountain as I did not want to chance AAA waking up our local tow driver at 2:00 am.

Since then I have driven it several times still staying close to home. I have made sure to get the bus good and warm and to run it with the high beams on to be certain there was a significant electrical load on it.

I am quite ashamed that if indeed the problem has been solved, this whole mess could have been avoided if I checked more closely and carefully what should have been checked as the first item on the troubleshooting list. Not to mention it is the quickest, cheapest and easiest thing to do. I am quite ready to be stripped of my rank of novice air cooled mechanic.

This problem has unexplainably gone underground many times before and I will not be surprised if it returns suddenly again.

After a few more test drives, I will begin to expand the radius of travel since I still have a fairly high level of distrust that this bus will get me from point A to point B.

I will give further updates as I rack up hopefully more trouble free miles over the next week or so.

[Lanval]

That seems likely though; that's exactly the sort of early bottleneck that can be such a pain to track down. Hence my earlier comments... you start with the battery and work your way forward. Don't feel bad; that's the sort of lesson I have to learn all to often ~ and it's more true the more "expert" I become. I've had a hard time absorbing some of Colin's teachings, because his standard (and it's the best approach) is to set the basics first, then get into more complex issues. But that's so time consuming... and I don't feel like I'm an expert... and etc., etc., etc.

Drive it for awhile, and you'll find the distance gradually expands with your sense of safety. When you're ready (as I am now with the ratvan) to drive long distances and expect it to work, you'll know. And you'll do it.

Crossing my fingers...

ML

[luftvagon]

Good job.