Running Issues: sputtering, bucking, etc. [SOLVED!]

[vanagonforever]

I've got a stock 86 Vanagon that has run like a champ for over a year of daily driving. Silky smooth and glorious. A couple of weeks ago I noticed a subtle change to the power curve. It felt weak under load and had a reduced top speed. Later it started bucking while accelerating. I've noticed this gets a lot worse as the engine heats up. Now my idle has started sounding rough with occasional sputters and misfires. I can still drive it and it has never completely stalled but it will buck if I drive up a hill or accelerate too much. I can chill it out pressing in the clutch a bit but yeah, no bueno. Turning it off and restarting it has no effect. This problem is consistent and occurs on every drive. The Vanagon seems to perform best after a cold start and doesn't start exhibiting the problem consistently until it gets fully warmed up.

So here's what I've done to try to fix it:
- checked the battery cables
- replaced spark plugs, wires, distributor cap, rotor
- replaced air filter and fuel filter
- cleaned engine and transmission grounds and then replaced the ground strap with GoWesty's replacement straps
- cleaned the ground and contact point for the fuel pump
- replaced the temp sensor in the thermostat housing
- replaced the O2 sensor
- installed the gowesty signal filter for the air flow meter
- installed a rebuilt air flow meter

About a year ago I installed GoWesty's mechanical throttle position switch so that's basically new and glorious as well.

So far none of that has had any consistent impact.

I'm running out of ideas to check and about to throw my hands up and book some shop time with my mechanic. I'd love to tackle this myself though. Any other ideas of things I can check?
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1986 2WD 2.1L WBX Vanagon Weekender
1983.5 1.9L WBX Vanagon Westfalia

[vanagonforever]

Oh and I detached the ECU and shook it just to see if I could hear a rattling sound and nope. No rattle noise at all.
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1986 2WD 2.1L WBX Vanagon Weekender
1983.5 1.9L WBX Vanagon Westfalia

[Ahwahnee]

You've certainly covered a lot of the usual suspects with that list - I agree you should try to avoid turning it over to a mechanic as the mystery (though it could be something simple) could be time-consuming to solve.

Two things come to mind that I do not see on your list -

1) Partially blocked cat converter (back pressure measurement is one way to assess).

2) ECU connection - I do not have a Digijet but some have reported dodgy connections that can be resolved by simply flipping the ECU 180° (upside down) to strain the connector the opposite way.

[dobryan]

I would borrow a known good ECU and swap it in just to be sure it is not the ECU. Solder joints going bad do not rattle. Does not cost anything and takes a few minutes.
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Dave O
'87 Westy w/ 2002 Subaru EJ25 and Peloquin TBD

"To travel hopefully is a better thing than to arrive." Robert Louis Stevenson

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[vanagonforever]

My heroes at Desmond's Auto here in Baltimore are going to let me borrow a working ECU to give that a shot. I'll update with the results tomorrow. Seems like a long shot. I've read when your ECU is bad that the van doesn't generally run at all but I'm out of ideas and ready to beat this thing.
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1986 2WD 2.1L WBX Vanagon Weekender
1983.5 1.9L WBX Vanagon Westfalia

[stormforge]

Get a PDF of the Digifant Pro manual (available free to download on a variety of Vanagon sites). It has some good procedures to debug these sorts of problems. Check the key sensors/signals with a multimeter and there's a good chance you'll find the problem.

Other ideas:

Bad fuel? Maybe add a bottle of gas drier?
Bad coil? They sometimes fail with temperature...
Bad fuel injection relay?

Can you get the problem to happen when the engine is warm in the garage? Have you checked the fuel pressure at high RPMs?

-Bill
'89 Syncro 2.2 WBX

[MattyBUS]

I've seen rotor, cap, plugs, wire... Change your ignition coil.

[Mathew Zelezen]

I just posted the same issues I'm having with my 86 Syncro.

I've updated all the items on your list (as well as some others) and still have this mysterious stumble.. you may want to throw a timing light on and see if you have any misses.

How old is your distributor?
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87 Syncro Tintop
~Rocky J Motor
~Steedle Trans


Of all sad words of tongue or pen, the saddest are these: It might have been.

[Howesight]

You have eliminated many of the key items that cause or contribute to running issues. Now it is time to test a few things. These further tests are intended to check for things that happen to vanagons that are stored for extended periods, which I assume is what occurs to your Baltimore area van.

1. Do a compression check. The eninge must be warmed up fuly in advance, all spark plugs removed, helper must fully depress accelerator and crank engine (with injector connectors disconnected) until compression tester gauge no longer increases. Only this approach will yield test results that can be used for diagnosis and comparison.

2. Compression test results might indicate, say, one weak cylinder. If your van has sat unused for several months, old gasoline with varnish may have sprayed varnish-laden gasoline on the intake valve stems, causing intake valve or valves to not fully close. This can cause running problems. Varnish-laden gas also contributes to clogging injectors to the point that volume is reduced and/or spray pattern is turned to a "squirt" pattern as opposed to the atomized pattern the EFI system was designed to use.

3. If the injectors do have unequal injection quantity, then the cure is to send them to an injector servicing company for ultrasonic cleaning. Don't go with new injectors since the factory units are the highest quality and 99% of the time are re-usable after ultrasonic cleaning.

4. You may have some undetected vacuum leaks (I assume you have checked all the more common leak points). The most difficult one to detect is a vacuum leak at the "PCV" valve in the crankcase vent tower. You can check for this by blocking off the hose connecting the vent tower to the intake tract to see if idle quality changes. Otherwise, you need to remove the vent tower and physically inspect it.
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'86 Syncro Westy SVX

[vanagonforever]

OMFG.... well the good news is that I solved the problem. The bad news is that I'm kicking myself for not catching it sooner.

So I tried the ECU that Desmond's graciously loaned me but it turned out to be a dud. I couldn't even get the Vanagon to start with it so we figured it was just mislabelled (they were clear that the only reason they thought it was a good one was because somebody wrote "good" on the front of it )

Striking out there I decided I'd just throw caution to the wind and order a rebuilt one from GW. I hovered over checkout and said to myself that I was being stupid and impulsive and I just need to dig deeper. Maybe I'll reclean the grounds or something..

Anyway, I just went out to poke at it and visually check every square inch of the fuel injection system. That's when I noticed that hiding under my new air flow meter somehow the little wire clip holding the injector next to cylinder one wasn't there. I stuck my hand under there and was able to push the injector clip in ever so slightly. After a big face palm I fired it up to let it get warm and take it for a test drive.

Well, I took it on a drive and didn't hesitate or buck at all. I'll need to do a bit more testing to be positive but I think the problem all along was a bad connection to that injector. That's consistent with what I was seeing and the wire clip is for sure gone. That engine bucking would likely just make the connection worse and I could imagine that the plastic getting warmer under operating conditions could make the problem worse.

Lesson learned: visually check every single connection and then do it all again before you go spending money.
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1986 2WD 2.1L WBX Vanagon Weekender
1983.5 1.9L WBX Vanagon Westfalia

[Viva.Sabata]

Hi everyone. We just experienced the same thing on a windy ass no shoulder road in Mexico! Fortunately we were able to make it to our daily destination safely.

Turns out my throttle position switch was not closing at idle. It’s a GW refurb throttle body that I’ve had for about eight years. It just needed an adjustment per digifant pro training manual and she’s running perfectly again!

I think this reinforces the inner mysteries of the digifant ECU, as I would expect an open circuit would only affect idle and not mid throttle operating range.

Cheers
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Sabata
1987 Westy Full Camper, Peloquin 5-Speed 2wd

[Viva.Sabata]

Well, I figured that had to be too simple as we experienced the same hesitation and bucking symptoms. Classic dreaded intermittent electrical problem.

After digging deeper by measuring the obvious items (fuel pressure, temp 2 resistance, AFM response, throttle switch, etc.) I can’t find anything out of spec. I even hooked up my analogue multi meter between pins 2 and 4 down stream of the AFM signal filter harness and routed the leads to above the engine lid. The idea being if it starts bucking again I can have the wife drive while I look for voltage drop outs that might occur at higher temps. I did notice that the high tension lead from the coil has about 2k ohm resistance, where I remember it should be around 6k ohm. I left it alone for now.

Last night I realized that the issue seems to occur in the heat of the day (90-95F) and sometime after filling up, so I’m suspecting an issue with the fuel vapor recovery system. So today we drove with keeping the fuel tank below 3/4. She ran nearly perfect, with just a bit of off idle sluggishness that powered right out.

If I get the balls to fill the tank completely in the next day or so and if I get the same bucking again I’ll try disconnecting the fuel vapor recovery vacuum lead from the throttle body. The hypothesis being I’m getting rich mixture from the vapor collection system

I will report back on the outcome regardless.
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Sabata
1987 Westy Full Camper, Peloquin 5-Speed 2wd

[leecat]

"Last night I realized that the issue seems to occur in the heat of the day (90-95F)"

Wait...um...what part of Alaska are you in, exactly, that's hitting 90F in late February? Cuz I want to live there!!!

[Viva.Sabata]

[dobryan]

[danfromsyr]

take the gas cap off, see if behavior improves
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[Viva.Sabata]

[Viva.Sabata]

Greetings everyone,

Further inspection of my evaporator emissions system showed vacuum at idle on the port where the purple line connects to the throttle body. So I ponied up $35US for a vacuum gauge and adjusted the throttle stop screw per Digifant pro training manual. What I think happened is the rivnut securing the screw to the throttle arm has worked itself a bit loose and caused the throttle plate to close past the teenyweeny hole midsection in the throttle body. Need to JB weld it next I suppose.

Anyway, no more bucking or hesitation - my idle is improved and throttle response is no longer sluggish out of the hole!

To be fair, it’s much cooler here in Oaxaca that it was on Costa Michoacán.
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Sabata
1987 Westy Full Camper, Peloquin 5-Speed 2wd