Vanagon bucking / hesitating at certain rpm's while driving

[ericpmurphy]

Hi all... My new '87 vanagon westy is having some running issues that i'm having a heck of time sorting out. I'll post below a series of parts etc that were replaced while fixing what I think was vanagon syndrome and is now fixed.. but now I'm having new issues.

The van mostly runs very well except that when reaching 2800-3200 rpm's while driving it starts to hesitate/buck in each gear. Also I took it on a 70 mile ran trip and nearly went through a tank of gas. Just put in a new rebuilt AFM from GoWesty which didn't seem to fix this but other issues like surging idle got a bit better. Any help would be much appreciated as I am cross eyed from reading forums!

Oh and have a tencent TPS coming next week along with new fuel pressure regulator.





Sorted by most recent
2014

-Replaced o2 Sensor
-Replaced Temp 2 sensor
-Replaced Air flow Meter with GoWesty rebuilt
-Replaced alternator
-Replaced water pump
-Replaced some of wiring harness that had water (this is what ultimately fixed the stalling/ vanagon syndrome type problems)
-Installed Volt regulating Diode ito wiring for temp sensor
-R&R Fuel Pump

2013 (approx mileage 154k)

-Tracing and testing wiring harness
-Replaced ECM Unit
-Installed Signal Filter between Mass Air Flow Sensor and main wiring harness
-Added ground from distributor to engine block
-R&R Mass Air Flow Sensor (with used one so this could still be issue)
-R&R Thermostat
-R&R Water temp sensor
-R&R ECM Unit
-R&R Starter and Bushing
-R&R Instrument Cluster and Changed out Voltage Reducer (used part) Traced our wiring and grounds
-Cooling System flushed
-Set Idel and R&R Both Coolant Temp Sensors
-R&R Aux Fan Switch and Fan Resistor Control

2011 (approx mileage 153k)

-R&R Spark Plugs, Distributor Cap, and rotor button
-New O2 sensor

2008 (151k mileage) (looking at records it looks like the syndrome started about here)

-R&R Water pump and temp sensor
-New Belts

2000 (103k miles)

-R&R Cylinder heads, fill corroded surface on cycle head, resurface, new head gasket

[Ahwahnee]

I would be checking to see if the grounded coax shield on the green O2 wire is shorting to the center lead on that wire.

there are many posts describing the specifics - a search should turn up details.

the main clues suggesting this are your running issues and gas mileage. this condition will cause very rich running and low single digit mileage.

good luck.

[ftp2leta]

[insyncro]

DigiTool time

[davevickery]

Was it always doing that, or did you notice after doing some work. It is usually something you did when it is a new symptom.

Maybe remove the ECU plug and work it in/out a bit to get better connections and put it back. (I've heard you should disconnect battery first, but I have gotten away without but i'd say do it)

Maybe AFM is not good even though rebuilt. Have you got a spare you can try?

Does it have a tach. It is dropping way down each time it bucks?

Does it feel more like fuel or electrical? I believe electrical is more harsh cutouts.

Disclaimer: I don't know as mcuh as these other guys, but maybe it's helpful.

[ericpmurphy]

thanks all..

I've tried 4 air flow meters including the newly rebuilt gowesty so I think its fair to say that it is not the problem.

I'll try some of your suggestions and check back..

But to be a bit more descriptive of the driving condition:

At running temperature the van will start to hesitate/hiccup/buck/stumble as you get close to 3k rpms, if I floor it while its stumbling it will "catch" and push through and be fine... once in fourth and past the stumble it will start to stumble again if you let off throttle and come back to the low 3ks rpm.

Seems like this would be something to do with the throttle body or fuel system being told the wrong things at certain points??

[ftp2leta]

Bang the ECU at idle.... not with a hammer use a screw driver hand side.

Tap on the ECU. If you see some miss or hiccup...

Ok, I just read back your post:

[ericpmurphy]

Tried the following today:

-new fuel filter
-new fuel pressure regulator
-swapped ecu

none of the above helped with the stumbling

will try to have fuel pressure tested but i'm not equipped to do so.

would throttle body be causing problems if its bad? seems like when i'm mid throttle and at the stated rpms I have trouble but if i floor it through the stumble its fine.

[insyncro]

Yup, the TB can make the van act as you describe.

[ftp2leta]

Hi, it's the fact that you did 70 miles and used up almost a tank that bug me.

You don't have a heavy smell of fuel in the back, smoke at start up?

Is your oil level ok? Smell of gas?

What you could do is remove the injector rail (1 screw), pull them out and pry the pump a few time to see if one (or more) is leaking.

here is the screw location:

Bad millage is caused mostly by a faulty O2 sender.

you could also check plug to see if any are wet.

Ben
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[Ahwahnee]

[ericpmurphy]

well my coaxial wire on o2 sensor (ecu end) is compromised as some of the inner wire is exposed to outer.. I will get this cleaned up tomorrow but I have run the van without the sensor plugged in and the stumbling still occurs... The o2 sensor is probably a very good reason for the bad gas mileage but would it explain the stumbling?

thanks

[ericpmurphy]

Ahwahnee - just been getting familiarized with multi-meter.. put red lead on green wire (connected or unconnected from the ecu end)? What setting on meter and what reading would i be looking for?

thank you

[Ahwahnee]

which color lead where doesn't matter when using the ohms function. almost any 'ohms' setting should work.

with green wire disconnected touch one lead to the center wire [or spade connector] and the other to ground [or the coax shield].

the should be no continuity -- infinite ohms -- may simply read '1' on some meters.

if you read continuity -- zero or some number -- then there is a short. even one strand of that coax touching the connector or center wire is enough to cause the engine to run very rich all the time.

if this condition exists then disconnecting the O2 sensor would make no difference - this is 'up stream' from the O2 signal.

sorry for the ee cummings style here - just had arm surgery and typing 1-fingered and left-handed.

no guarantee this is your problem, just a 'usual suspect' that can be easily ruled in or out.

[ericpmurphy]

well the o2 was shorting so I got the wire cleaned up and now reading correctly on meter... BUT still running rich and stumbling

[vanonimous]

I once bought a van with a symptom like that but was not apparent untill engine was hot. PO had spent a couple of grand replacing every single Digifant component to no avail and finally threw his hands up in the air and gave up. Turned out to be high resistance in Bosch secondary wire from coil to distributor. It was 9K Ohms and rising in heat causing occasional loss of spark...It is supposed to be 1K Ohm with built in resistor on a good wire. Rest of wires from distributor to plugs 5K Ohms trough resistorized caps.
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If happiness is being a mechanic, owning a Vanagon is nirvana.

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[nacradriver]

[kaeferman]

You might trace all the wiring harness legs out in the engine compartment to make sure something is not melted somewhere. I believe extreme heating of the vw wiring can render the insulation useless and your electrical components get improper signals from shorts or partial shorts. rewrap any burnt looking spots well in electrical tape.

But starting with the grounds (cheap and easy) is important. Use dielectric gel on them once you shine everything up. I use that gel on all my connections. Sometimes too, just clipping off the end and reattaching a new connector can fix an intermittant loose wire that might be arching.

[ericpmurphy]

Thanks to everyone that chimed in to help with my Vanagon.

The previous mechanic that was working on this van really jacked some stuff up so there was not one fix as we found many vacuum and exhaust issues that were causing problems, some water in a wiring harness, etc...

BUT when I thought it was all good to go I took a road trip to Central Florida (about 400 miles each way) and about an hour into the drive started having some running issues and was getting terrible gas mileage... the van would not hold a steady speed (i.e. I would try to go a steady 60 or so mph and the van would run good then start to go lean(or maybe rich) and stumble in search for mixture losing a little power then "catching" and pulling good again).. it was not Vanagon Syndrome as restarting car didn't help and we never had to actually pull over as I could just accelerate or decelerate and force the car to "catch" and pull fine.

Got back home and had a friend helping me do some work to my Mercedes 300d and was explaining my headaches of the vanagon and I pointed out a brown wire coming out of the wiring harness to the distributor. I've been suspect of this wire for a few weeks as it leaves the housing and then disappeared under the AC compressor and engine block. I had pulled on it and it felt as though it was securely held down but just didn't make sense that it would be on a compressor bolt or anything else under there...

we decided to lift the compressor up some and investigate and sure enough it was just sandwiched in there not actually attached to anything... cleaned it up and attached to proper ground on block and now getting 18mpg and no stumbling!!

So now I have pretty much all new FI components so she should be good to go for sometime!

Thanks again for everyone help.

eric