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

[aopisa]

I cant believe it! Today the hesitation and bucking returned.

Last year's IAC appointment was spent chasing down a severe bucking issue which was finally solved by Colin making some significant enrichment adjustments to the AFM.

viewtopic.php?f=66&t=11001

The bus has run flawlessly since then. As a matter of fact, I said the very same thing to my son earlier today as we cruised down the road. As we pulled in the driveway I noticed the alternator light glowing faintly. I have heard this is a common problem, but never before with my bus.

Later, as I left to run some errands the bus began to lurch and hesitate just as it did last year. It only seems to do it under load when starting from first and after shifting into second. Last year over time it turned into a condition that made it undriveable until Colin came. I think I jinxed it.

Every year for the past 3 or 4 we have tried to go to a Westy camp out about an hour from home. Every year we have to cancel for some reason. Last year it happened as we pulled out of the driveway to go to the camp out. The bus bucked so badly that we had to cancel the trip. This year may turn out the same as the trip is less than a week away. Is this the Curse of West River Westies?

So, I am looking for guidance on where to start since I don't want to go through the failed experience of a year ago by just trying things to see what it might be.

Here are the only variables that I can think of that may or may not have affected the situation.

- I fueled up with Sunoco today and I almost always use Mobil
- The alternator light is glowing faintly for the first time ever
- Today is the warmest most humid day this year that I have driven the bus

Thank you very much.

1977, 2.0L FI, running on points

[Amskeptic]

I cant believe it! Today the hesitation and bucking returned.

Don't panic.

Be methodical.

If the weather is due to cool, see if symptoms go away. (conclusion: too rich for ambient temps)

Because of alternator lamp:

Check grounds from battery to body, transaxle to body, fuel injection harness to crankcase, double relay brown wires to double relay bracket.

Check actual battery charge, 12.7 minimum with engine off, 13.4 + with engine on at 2,000 rpm let's say just after start. Your alternator may not be charging battery fully, fuel injection hates that.

While battery is disconnected during post/terminal cleaning, do all the connections at the starter too.
Clean! Then grease with dielectric gel.

Ignition switch works correctly?
Any vacuum leaks?
Colin

[aopisa]

First Report:

Immediate bucking under load at cold start up with ambient temperature of 71F this morning.

Battery:

13.1V engine off

11.66V - At start up, idling. Alternator light glows steady red (has always done this). I alway have to give it a little gas right after starting to get the light to go out.

14.6V - After revving engine and letting settle back to idle. Alternator light is about 1/2 brightness

14.0V - With engine at approx. 2,000 RPM. Light steady at about 1/4 brightness.

All grounds checked and appear to be OK. Connections at starter look pretty dirty. I will not be able to clean and grease everything until later.

Ignition switch functions properly.

No apparent vacuum leaks, but will have to check later as well.

We are bummed again. This has been a recurring issue on this bus from just about the beginning of my ownership. It was almost exactly one year ago where this problem shut us down for the summer. I just hate the prospect of canceling this trip again and spending the rest of the summer chasing this problem down while not being able to drive the bus anywhere.

The alternator light has added a new wrinkle. Although it may be coincidental, the bucking started as soon as the light started glowing.

[Lanval]

OP, I see you're over on the Samba trying to track down some help: kudos to you. I add a bit here. I have a vanagon, so a little later FI but I think not to different, seeing as how I've had similar problems. Short history: bought it out of a field where it sat for 7 years; wires mice/rats chewed, etc.

My van, if it rains, bucks like a, well, like a severely bucking van until things get warmed up. Talking about revs going to 0 then redlining, engine dying; severe. The fact that this occurs nearly 100% if it rained anytime in the preceding 24 hours, and that it stops after the engine gets warmed has always suggested to me that it is humidity in any of the connections from coil to plugs to dizzy.

My van ALSO has another bucking; historically, at low revs, when you stepped on the gas, especially in 1st or 2nd gear, it would buck in the low rpms. The only way to avoid this was to rev up then let out the clutch. Colin went this way and that and eventually decided that I might have to live with it a bit (it's not a deal-breaker in terms of driving around, but annoying in parking lots). However, I noted that shifts in timing and the AFM seem to have eliminated this issue, which suggests to me that it was fuel supply and/or timing/detonation that were responsible for that issue.

I think that you're on the right track checking the voltage in your system ~ the glowing alternator light is probably the meaningful sign here. since the problem and the glow arrived simultaneously, it's not unfair to link them. Do check to make sure the connection to the light itself is good. Here's a link to a vanagon discussion of a similar issue, though the OP doesn't report bucking:

http://www.thesamba.com/vw/forum/viewto ... ator+light

Let us know how the tests turn out (or we can follow here too: http://www.thesamba.com/vw/forum/viewtopic.php?t=561789)

I want to see you take that bus and gooooooooooooooo!

ML

[aopisa]

Thanks for the reply.

Yes, I did post something over on The Samba. Since there was a member having a similar problem, I thought I might see if whatever happens there might apply to my issue as well. The Samba has a lot more traffic and while everyone is very helpful, the information tends to be more of a broad approach. Over here things can be a bit more measured and methodical. I went through the try everything and see what works method last year and I find I do not have the energy or appetite (nor the time) this year to go that route. I do learn things in the process and I am now pretty good at finding out what is not the problem.

I have been through this so many times. It used to be a problem that would crop up occasionally and then hide for a while. Now when it returns, it returns to stay. It is my feeling that we have been 'fixing' it by attacking symptoms while the root cause has never been addressed.

I know the FI system really does not like inconsistent voltage and yes I am thinking that the alternator light and the immediate recurrence of bucking are linked. I am pretty bad when it comes to electrical knowledge. However, I can follow directions pretty well and will certainly take a look at the Vanagon link that you sent.

As I said, it bucks pretty hard in 1st and 2nd, but can be felt in 3rd and 4th and only seems to get worse over time. I used to be able to 'nurse' it, but the bus seems to have gotten wise to that tactic. Climbing hills becomes a problem. When cruising on a flat road, it begins to buck at about 45 mph and I cannot get it to go much faster. Yesterday we were cruising along at 60 with plenty of power in reserve and life was good.

I am going through one thing at a time so I can pinpoint it if indeed it somehow miraculously fixes the issue. I started with the FI grounds. Took it for a spin and not one buck was felt no matter how hard a tried. I decided to take a ride to the bank into town and barely made it back home because of the bucking.

I noticed some of the coil connections looked not so good. Cleaned those. Same story again. Performed well on a test drive. A few minutes later more bucking.

That might lead one to think that it has something to do with the engine being warm, but it bucked right off the bat this morning after sitting in the garage all night.

Thanks again. Today we were going to start preparing for our camping trip. I hope I can solve this on my own and we can still get out on the road.

[Lanval]

Imma go out on a limb here, but... have you ever checked the fuel pressure and fuel filter? Same van experienced issues related to low FP supply to crap in tank. If you filled it and let it sit for a day or two, would even out. Let it the gas get low, it'd start having trouble. Having seen the inside of the vanagon tank, I know it wasn't the actual level ~ suspect that it was the difference between the relatively high pressure of a full tank of gas sitting on the fuel supply, and the bucking/etc. started when there was less pressure on the tank side due to less gas in the tank. FWIW.

ML

[aopisa]

Yes, this is one of the things on the exhaustive list I went through last year. The fuel pressure was spot on at 28psi if I recall correctly. I also replaced the fuel filter and all all fuel lines one year ago. Also, I filled it up yesterday, the bucking started after that.

FYI- Checked and cleaned VR ground. I have a new Bosch (made in Germany VR) and plugged it in. No change in the alternator status light situation. I did not drive the bus with the new VR installed because I am pretty sure that it was still going to buck.

[satchmo]

Here is what I have learned:

If the bus is acting like something is turning off the electrical activity of the engine, then turning it back on again (just like you were turning the ignition key back and forth), then that is exactly what is happening; the electrical circuit is breaking somewhere. I'd bet there is a wire connection somewhere in your FI harness that is iffy. There may also be an iffy connection (ground or other) somewhere in the alternator circuit that is making your light glow. Or perhaps it is the same wire responsible for both.

In my case (78 bus) with awful bucking, there was a wire connector backing out of the connector block at the double relay. Check every connection in your engine bay. Pull/push on every wire in those connector blocks to make sure a wire isn't loose or backing out (it isn't enough to make sure the connector block is seating properly on the wire spades). You need to know each wire is fully seated onto its partner.

I hope you find the issue soon.

Tim

[Lanval]

I'll note that Satchmo's point is a LOT easier to verify if you have a tach like I do... I can see the revs drop to zero, so I know something is going on.

Maybe an aftermarket temporary tach would help to ID this issue...

ML

[aopisa]

Thanks Satchmo and Lanval.

I have been thinking that myself that there is a wire or connection that is loose or not making full contact. Since I went through just about every other possibility of fuel, air, spark stuff last year I have been leaning more toward that theory. That's not to say that any of the things that checked out before haven't gone bad this year on a 35 year old vehicle. I do know that when I work on some of that old wiring the copper just disintegrates.

I suppose I could hook up the Multi-meter through the top hatch while having someone sit in the back to watch it to see if the RPMs drop when it bucks.

However, I don't quite understand how Colin richening the mixture through the AFM made the problem disappear for an entire year.

[aopisa]

Update:

Still stumped.

I hooked the multi-meter as stated earlier while my able assistant sat in the back and reported his findings. The RPMs did not drop when the bucking started. Actually I had a hard time getting it to buck as severely as before. It does start consistently at around 3,000 RPMs while moving and only while moving.

[Amskeptic]

Update:

Still stumped.

I hooked the multi-meter as stated earlier while my able assistant sat in the back and reported his findings. The RPMs did not drop when the bucking started. Actually I had a hard time getting it to buck as severely as before. It does start consistently at around 3,000 RPMs while moving and only while moving.

Humor me:

TS - II what is the cold morning ohm reading? Please unscrew and retighten in head just for grounding

Did you really and truly check every terminal in the double relay white molex blocks to see that none have slipped down?

Unplug, check terminal fingers all for correct position and replug ECU terminal.

I will trust that your grounds on the crankcase, transaxle, double relay are good and clean and secure.

This red light issue might be a blown diode in the alternator if all checks have checked out. You can test at dusk or with a multimeter when you clean the starter solenoid terminals.
A) keep red/white wire that leads to the fuse box OFF the 13mm post, just hook up the battery cableand the alternator output cable.
B) Check for a little spark at the battery negative post when you touch it with the negative terminal of the ground cable/strap. It is subtle.
C) Rehook all wires back to starter solenoid (do not overtighten)

I dearly want you to fix this damn thing and go camping!
Colin

[aopisa]

Update:

Still stumped.

I hooked the multi-meter as stated earlier while my able assistant sat in the back and reported his findings. The RPMs did not drop when the bucking started. Actually I had a hard time getting it to buck as severely as before. It does start consistently at around 3,000 RPMs while moving and only while moving.

Humor me:

TS - II what is the cold morning ohm reading? Please unscrew and retighten in head just for grounding. 2150 Ohms at ambient air temperature of 72F

Did you really and truly check every terminal in the double relay white molex blocks to see that none have slipped down? Yes

Unplug, check terminal fingers all for correct position and replug ECU terminal. Yes

I will trust that your grounds on the crankcase, transaxle, double relay are good and clean and secure. Yes

This red light issue might be a blown diode in the alternator if all checks have checked out. You can test at dusk or with a multimeter when you clean the starter solenoid terminals. Cleaned and dielectric greased all terminals. Small red/white wire attached to spade was cracked and broke when I removed it. Replaced with new 1/4" spade.
A) keep red/white wire that leads to the fuse box OFF the 13mm post, just hook up the battery cableand the alternator output cable. There are six wires on this post. I will have to figure out which one is which. I will disconnect battery again and attempt this test.
B) Check for a little spark at the battery negative post when you touch it with the negative terminal of the ground cable/strap. It is subtle.
C) Rehook all wires back to starter solenoid (do not overtighten)

I dearly want you to fix this damn thing and go camping! Me too. Trying not to hate this bus right now.
Colin

[Lanval]

Trying not to hate this bus right now.

I laughed at this out of sympathy; I live in that space.

For example. My van will randomly decide that starting is a one-shot affair. If it doesn't catch at first, push start or wait an hour. I fixed this by going for a long drive. Why does that fix it? I don't know.

When my van runs well it is truly a pleasurable experience. That is not as often as I'd like. When it doesn't run well, I repeat your statement above like a mantra.

ML

[aopisa]

Maybe I am on the right track, maybe my bus is just messing with me.

I took a test drive after inspecting and cleaning a lot of connections. The connections at the starter were pretty bad and there was that nearly broken small red/white wire. The bus seemed to have more power and better acceleration. I could not recreate the bucking no matter how hard I tried. I was getting ready to slap a big SOLVED on the topic subject line and to call my kids to say the camping trip was back on when it started up again. This time it was not as bad and mostly in second gear. It was more intermittent and harder to reproduce. Perhaps I bumped or moved some wire somewhere while performing the inspection which made a better connection? I don't know.

Lanval, I echo your thoughts. When my bus is running well, I feel like we can go coast to coast. However the elusive nature of this problem makes it so I can't trust it to get me to the grocery store.

The alternator light still glows faintly. Is it a bad thing to run with a possible bad diode?