On road, van bucking

[dan vandenheede]

'89 syncro, stock. Left Mich. On way to Memphis and new Orleans, van started MFCO (mother f' cutting out) like you are switching key off for second, violent buck, tach drops, comes right back. Has done this on rare occasions for the 3 years I have had it, now is much worse and more frequent, sometimes several times a mile. But, like before, if I shut it down for awhile, on start up it is usually gone. My wife got behind wheel an hour ago and has not had a problem. I did complete tune up, new Bosch coil, cleaned grounds, vanagon syndrome capacitor fix, all trying to fix this with no luck. Hard to diagnose because it goes away. Just before my wife took the wheel I pulled computer to make sure connection was good, harness seemed bent up so I left computer laying on floor to take strain off harness, thinking maybe broken wire, like I said has not returned since. Any ideas or help around Memphis or there a bouts?

[Baxta]

I'm fighting the same sort of thing. In my case I'm pretty sure it's a bad connection to the ECU, but you might want to look at your Hall Sender on the distributor. I had these exact symptoms (and worse - complete shut down of engine a couple of times...) on my Corrado a few years back, and replacing the distributor took care of it.

Good luck! I know how frustrating tracking down intermittent electrical gremlins can be, doubly so (or more) on the road!
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Greg
'87 Syncro Westy 'Bastian'
2.2l

[GWTWTLW]

If it is working with the strain off the harness, I would suspect a connection issue there. With the tach dropping and bucking, it sounds like the Hall connection. My guess it would be where the hall wire is connecting into the ECU.
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89 Syncro Westy - GW 2.5, now with a double knob job
@gwtwtlw

[dan vandenheede]

Thanks for the thoughts, 100 miles since last buck, knock on wood. One other possibly related tidbit, last night while idling a couple of times idle jumped up tp 2000 plus for no reason for just a second. Does not have a real smooth idle either. Oh yeah, and the battery was dead yesterday and again today, even after I ran it for half hour or so to charge yesterday. Related draw or three year old battery dead???

[78BayDriver]

Replace relays in the back engine comaprtment. 40amp relay, will fix the issue. Relay is failing. Please replace. the right relay in the little black ignition box...
_________________
1987 Vanagon GL 2.1 Flat Stanley (present)
1991 Golf GTi Forest Green
1981 Vanagon L 1.6 Diesel
1978 BayWindow Bus
1974 Bus
1990 Jetta
1979 Dasher Wagon
1972 Beetle

[bjrogers86auto]

I have mentioned before about alternators and grounding. The alternator has to ground through the engine to charge. If it's not grounded it will charge at a low rate. It happened to mine.

I'm not sure if a low charge rate would cause your symptoms, seems unlikely, but I thought I'd mention it. It might be the cause of the battery drain.

I had to add a ground wire to my alternator to frame.

Brian.
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2020 T@B 320 Teardrop(Has been van guy)
21 Ford Ranger XLT
19 Honda Civic Hatchback

A little rudeness and disrespect can elevate a meaningless interaction to a battle of wills and add drama to an otherwise dull day. Calvin and Hobbes.

[climberjohn]

Clogged fuel filter, maybe?
A cheap and easy thing to replace.
Might as well try it . . .

-CJ
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'86 Westy, 2.5 Subaru power
Know your limits. Exceed them often.

[78BayDriver]

the number 54 relay in the ignition relay box is failing closed, cause of battery drain... Please check... Replace both if you can. Most Auto stores carry them. 40amp SPST relay. I would bet dollars to your van that is what it is...
_________________
1987 Vanagon GL 2.1 Flat Stanley (present)
1991 Golf GTi Forest Green
1981 Vanagon L 1.6 Diesel
1978 BayWindow Bus
1974 Bus
1990 Jetta
1979 Dasher Wagon
1972 Beetle

[IdahoDoug]

78Bay,

Just looking for clarification because this is a great tip to know about. Are you saying his bucking is likely going to be fixed by replacing this failing relay? Or just that it's highly likely to fix his battery drain?

Thanks!!

DougM
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1987 2WD Wolfsburg Vanagon Weekender "Mango", two fully locked 80 Series LandCruisers. 2017 Subaru Outback boxer. 1990 Audi 90 Quattro 20V with rear locking differential, 1990 burgundy parts Vanagon. 1984 Porsche 944, 1993 Toyota LandCruiser, 2002 BMW 325iX, 1982 Toyota Sunrader

[Howesight]

Hey Dan:

I had exactly the same symptoms a couple years ago. Although it can also be caused by a bad Hall sensor in the distributor, in more cases, it is caused by the torque forces of the ECU harness connector fracturing the printed circuit board in the ECU. Bear in mind that the ECU side of the connection is merely a piece of the PC board.

See my previous post cut and pasted below for my fix:

"I had similar problems on my '86 syncro. John, of Van Wonder auto service in North Vancouver BC told me that the problem was likely my ECU. He said that the harness attaching to the ECU exerts pulling/pushing on the ECU circuit board where the harness attaches to it. It then creates a small crack in the circuit traces and if the harness moves, or heat causes expansion, then some of the circuits go open and the ECU goes into limp-home mode or causes a stall, depending on which circuit goes open and for how long.

The most important tell-tale sign that your problem is the ECU is that when the engine is acting up, your tach needle will bounce all over the place as though your ignition was being turned on and off.

If anyone you know can lend you their ECU (one that is known to be good) for a test, do the swap and test. Otherwise, do as follows below.

The fix:
1. Disconnect and dismount the ECU;
2. flip the ECU so the side that was at the top is now at the bottom, but the harness connection is still facing rearward;
3. Drill new mounting holes as necessary to attch the ECU;
4. Turn the harness 180 degrees and re-connect it to the ECU;
5. Re-install the ECU mounting screws in the new holes you drilled.
6. Enjoy your no-dollar repair.

This worked for me and apparently for John on 90% of ECU's with the same problem. The harness now puts an opposite force on the circuit board, thus closing the cracks that were previously opened with movement or heat or what-have-you."
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'86 Syncro Westy SVX

[dan vandenheede]

Howesight thanks for the tip, sounds likely as since I dismounted Ecu and laid it on the floor we have gone 600 plus miles with no issues, anyone between Memphis and new Orleans have a spare Ecu I could buy?

78bus, you refer to the relay as battery drain issue, not bucking, correct? It started this morning, but a relay failing could also be intermittent

Thanks for all the advice, keep praying to Ben Pon for us!

[78BayDriver]

I refer it to both. I had the same exact issue. Thought it was my hot going to the relay, but infact it was the relay overheating and failing. Let the bus run, and then feel the relay. I can almost tell you that it is HOT to the touch. AND if it is overheating, it can also stick itself, so that the relay can actually close without being closed completely. A very slight contact enough to drain the battery, but not completely energize the ignition system. What I am saying is check the relay. When the relay coil gets hot, it cuts out opening the ignition circuit breifly, enough to shut off the coil and fuel, and then back on, and it is not regualr either, but predictable. It tokk me about 5 min to figure it out, go in my garage and grab a relay when I got home from picking the kids up from school. A huge pain in the ass. It scared me really bad, but after tracking it down, I got it really fast. Please check the relays in the back. Could save you a few days tracking down...


Michael...
_________________
1987 Vanagon GL 2.1 Flat Stanley (present)
1991 Golf GTi Forest Green
1981 Vanagon L 1.6 Diesel
1978 BayWindow Bus
1974 Bus
1990 Jetta
1979 Dasher Wagon
1972 Beetle

[strawhouse]

you should have included a poll to see how many other owners have the same problem... My wifes van is exactly the same it drives me absolutely nuts.
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Pacifist with a gun

[Cygnus]

I am experiencing a similar issue - but in my case it regularly happens on a sweeping RH curve - So when the van has any tilt to the drivers side it starts bucking - really annoying - I am guessing it almost has to be a ground - so I will hunt those down and clean them this weekend. We'll see. Good to know about the ECU - maybe I will unmount it and let it bounce around on the floor to see if anything changes.

'86 syncro

-Brian
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'86 Syncro Timbertech Hightop "Cygnus"

[0to60in6min]

ignition switch?

[Cygnus]

If its in the ignition switch would I lose power to radio/lights etc? What would be a good way to rule that out?

Thanks,

-Brian
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'86 Syncro Timbertech Hightop "Cygnus"

[kuchiman]

Symptom for ignition switch failure is partial cutting out and/or complete shutdown of engine; van may or may not restart. Since radio power is independent of ignition, this shouldn't be affected. Regardless, as many others have lectured on other posts, if you haven't done it, replacing the ig swtch is a must do - before you get stuck on the road in BFE. Its low cost and easy to do. Instructions are conveniently located on BenPlace (don't forget to donate!):
http://www.benplace.com/dash.htm

Ig switch failure is somewhat different symptoms than bucking brought on by 'vanagon syndrom'. I thought I had the syndrom and did a # of repairs including the capacitor fix - all to no avail. Took it to the mechanic who found a bad fuel line vaccuum hose.

[Cygnus]

Its kind of acting like vanagon syndrome only I have cleaned and adjusted the TPS - all good there - and replaced the rear relays - I have a spare AFM and ECU - might try that - but I am leaning towards engine/transmission grounds since it ALWAYS bucks on a sweeping RH turn. must be some kind of shifting of the engine and or tranny that is pulling a ground at that angle. weird. AND DAMN ANNOYING.

I just replaced the starter motor on this (its an 86 syncro) and OMG that sucks. Rates right up there with major dental work...

-Brian
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'86 Syncro Timbertech Hightop "Cygnus"

[Bassyaks]

Howesight is correct.
also the draining of the battery leaves the ECU with low voltage which will cause another problem.
If your on the road and you have it in a posisition where it works leave it alone. You can also pull the harness out about 1/2 " and that will change the strain on the connecter. A little dielectric grease carefully applied to the connecter will help.
Don't waste your time with the Ignition switch it not the problem
Bserrett,Brian you have a fuel pickup problem, does it only happen when the tank is close to empty?, a quick turn to the left will allow full back over to the fuel pickup on the right side and keep it from stalling

Good luck
Steve

[Cygnus]

Thanks for the tip Steve, its happening with a full tank or low - its really acting like its electrical. I have replaced both rear relays, and cleaned ECU grounds etc - I will try repositioning it. It doesn't seem to have any load on the connector. It also cuts out (bucks) on washboard or rocky areas - could be the hall sensor or an engine ground. real PITA to narrow down. The grounds look good on the side of the firewall but I haven't got a visual on where it ties to the block yet - the tranny ground is REAL greasy - like totally black - I'll pull it and clean it up tomorrow. Not a lot of rust anywhere though. I should mention I have the slightly toasted D15 pin issue - I cleaned it and reseated it but if it was that then I wouldn't get the fuel pump prime when the key is turned on and that has been consistent since I cleaned it.

<sigh>

-Brian
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'86 Syncro Timbertech Hightop "Cygnus"