Engine misses, surges or bucking (FI related only)


New member
My current digifant 87 Westy just experienced these FI missing, surging, and bucking problems for the first time at 222,000 (original engine) miles. I'm very frustrated. I purchased and installed the "Vanagon Syndrome" harness and it made a major difference. However today I replaced the O2 sensor which has been disconnected with no obvious ramifications for the past 20K miles, and vehicle is again running poorly. Question: Do I need to reset my O2 sensor to have it work properly? I removed the LED hundreds and thousands of miles ago simply thinking it as a dumby light? Thanks!


The O2 senser light has no effect on the O2 sensor opperation. It is just a timer that clicks on at designated intervals, (I think it is 60k miles) If you are having poor running with the O2 sensor connected, I urge you to read the F/I section on O2 sensors. Especialy look at the shield braiding at the plug where the sensor plugs into the wiring harness.

As to having the sensor unplugged for 20k miles, I suspect that your fuel mileage has suffered. Since you said you replaced the sensor, I would look carefully at the wiring at the plug

Good luck.


Capt. Mike

Transferred to consolidate same topic.

James W. (Bill) Harrison Posted August 07, 2006 01:08 PM

I certainly hope this is the right forum and apologize if it is not. I tried to get as close as possible to my problem. 1990 Westy, runs good when it runs. Can never tell when I am going to lose power. I have had the following done: First drained the oil and replaced it with engine restore; replaced oxygen sensor and spark plugs. Tested all items on fuel and ignition systems. In spec per Bentley. Problem did not occur while in the shop, but mechanic experienced it on road test. He found the engine running rich per oxygen sensor readings, but all delivery systems tested normal. There is no rhyme or reason to my Westy's antics. It is great for awhile, then out of the blue, loses power to the extent that it won't run. Then will run great for another while. I read in one of your postings about an asbestos flap in the muffler causing a similar problem. Funny thing, this problem started on the way home from having a complete exhaust system (not VW( installed. Thanks very much for any assistance possible.

Bill Harrison

Capt. Mike

Before abandoning the exhaust system to get into FI, do check the ENGINE forum, "Exhaust . . ." topic. Just to be sure that they didn't damage your CAT during the exhaust work.

Capt. Mike

Transferred to consolidate same topic.

Fast Jack Junior Member Posted January 16, 2007 02:43 PM

Hi there,

I'm in Pheonix, AZ from BC, Canada hopefully going to Mexico.

I have a 1989 Vanagon Westfalia. for the past few days it has been having problems with the RPM's dropping about 400-600 and then kicking back in again. I've been driving at a steady 3200rpm. It is intermittent. It first started after 7-8 hrs driving in a day and then started right away when starting out on the highway agein. Yesterday, it jerked up and down for about an hour and then ran fine for another hour. Do you have any ideas what it could be? It feels like the ignition is cutting out. It has also stalled upon stopping which it hasn't done before.

Please let me know asap if you have any ideas.


icarus Super Member Posted January 16, 2007 05:05 PM

It sounds like "vanagon" syndrome. Find more information in Fuel injection threads. It also sound like the symptom I had with a bad O2 sensor. Next time it does it, try quickly turning the key off and on and see it it re-sets the FI. O2 sensor should re-set to default setting. If this cures it, check the O2 sensor. Also check the shield braid on the O2 sensor wire.(Particularly where it plugs into the harness) If it shorts it can cause similar symptoms.

Good luck, Icarus

[Moderator Note: Vanagon Syndrome & O² Sensor have their own topics.]


New member

Hello All. I’ve got an ’84 Westfalia that has a GoWesty 2.2 engine in it and was then upgraded to the Digifant fuel injection system. This included new (rebuilt GoWesty) injectors and a new catalytic converter. The original conversion to the Digifant system improperly left the Digifant ECU in the engine compartment. About 6 months later, my new mechanic moved the ECU to under the back seat, cutting a hole in the firewall and using a soft gasket to line the hole as prescribed. Immediately after moving the ECU, the van began to buck hard. Buck – did I say buck? What the engine really does is hammer! For a split second the tachometer dives towards zero, and the engine hammers in a manner similar to what it feels like when you pop out a clutch. Instantaneously, there is lots of resistance to the cars momentum – it hits like a hammer – really shakes you up. Lasts for just a fraction of a second, then returns to normal. It can be very severe. At its worst, a series of such hammering seemed to affect the alignment of the linkage for shifting – I’m postulating that the “hammering” moved the engine some and messed up the linkage (later adjusted).

From reading posts on this site, I haven’t read a description of how severe the “bucking” of Vanagon syndrome actually is. What I’m experiencing is not a stutter or a hiccup or a hesitation – it is a hard and sudden buck or hammering. My mechanic “poo-poo’d” it until he experienced it himself – then he got a bit concerned. Between hammerings, engine power is not otherwise lost. It can happen several times consecutively within a minute, or intermittently several times over an hour, or it can not happen for days, weeks or months! The hammering/bucking does not happen a given RPM or a given degree of engine warmup. While I have shut off the engine and restarted – I don’t recall the time lag until the problem expresses itself again – but I think it is relatively short. Very difficult to diagnose – but makes it hard to use the Vanagon for any real travel.

In the beginning (2 years ago), the problem could occur while I was driving (thus causing a hammer) or while I was idling (you would just see the tachometer drop to near zero and then bounce back up). A lot of diagnosis was done. Both mechanics who looked at it felt was an ignition problem – that somehow the ECU thought the engine was off for just a fraction of a second, and all systems instantaneously shut down. Mechanics checked the air flow meter (swapped out), oxygen sensor, idle control unit, all the wiring for bad grounding, the coil, ECU (swapped out), spark plug cables (replaced) – nobody could find anything wrong. About a year ago my mechanic noticed that the ECU was making a loud buzzing so we swapped in a new ECU – same buzzing. We decided if it wasn’t the ECU or any of the parts, it was probably the harness – perhaps it had been damaged when it was twisted to get it through the hole in the firewall. Installing a new harness instantaneously made the bucking go away – and we thought we had solved the problem.

…Until 6 months ago, when it happened again. I checked the connection b/t the wiring harness and the ECU, noticed that the soft gasket had slipped so the harness was in contact with the sheet metal firewall (no damage to insulation), fixed that – and the problem went away again. Then it came back recently. Again I checked the connection between the harness and the ECU. Cleaned all the contacts with contact cleaner, made sure the gasket was in place, made sure there was no stress on the harness/ECU connection. This time it didn’t solve the problem. In addition, the problem may have shifted some in that the hammering feels the same, but it only happens when the van is driving. So far, I have not observed it during idle. My mechanic suggests that while it feels like the same problem, it may actually be different. In my gut, though, I feel like it is the same.

I just checked the air flow meter, and it does not have one of the “transformer” patches on the wiring harness used to treat Vanagon syndrome. We will try that – but we did try it 2 years ago without success. Like I said, everyone who looked at it thought it was a problem with the ignition system. I’m taking it back to my mechanic this week. Does anyone have any ideas of what it could be or any suggestions for what I should ask my mechanic to look at? I will ask him to check all the electrical connections and grounds, try the “transformer” on the air flow meter, check the O2 sensor. Anything else? Please help! Thanks.

Capt. Mike

Vanagon Syndrome bucking is severe -- the engine is shutting off but the vehicle is still in gear & rolling, so it is "restarting" with all the jerking & black smoke one would expect. See Vanagon Syndrome topic.

Guideline #7 addresses modifications. You've done two -- an aftermarket engine modification and attempting to change from one generation of FI to another. Why, I'm not sure as the Digijet was quite reliable, too. Doing so adds a host of other possiblilities of incompatibility and factors introducted by the modifications themselves. So many of the sensors have to be changed and the wiring carrying their signals checked for identical resistance since most sensors are resistance carriers.

You mention rerouting through the firewall and some problems. This may have caused damage inside that caused wires to fray or be broken. They now get contact most of the time, but not full and subject to interruption. The insulation and bundling is holding them together but they no longer consistently carry the correct resistance or power as the vehcile shakes and twists. See the <Power windows> post in BASIC VAN WIRING forum as an example. This diagnosis will be quite tedious as you will have to have a very sensative ohm-meter and watch its readings as you massage and bend the harness over its length to make the broken but touching wires inside change and create a resistance variation.

However, an ECU should NOT buzz; that two did it does not mean it's OK. Was the replacement brand new? If so, it may be an indication of getting a bad signal from somewhere. If used, it may be coincidence of two in a row -- it's 'used' for a reason.


New member
Thank you Capt. Mike so much for your response. I think I can answer some of the questions.

Modifications - yeah, I think I got some bad advise when I decided to get a GoWesty 2.2. rather than just stick with stock. When we got the new engine in, there were significant problems with idle and emissions. Idle was very rough, loping, sometimes it would just die out. It wouldn't pass emmissions. Eventually, this was diagnosed as related to the camshaft design that was put into the 2.2. Apparently, I was not the only one with this problem on the 2.2 as some of the after market camshafts were too aggressive and were made for performance at speed not at idle. I wanted a van that idled well and could pass emmissions. GoWesty was working with my mechanic at the time, and rather than fix the camshaft issue, they elected to "give" me a whole new fuel injection system to try to fix the problem. We did replace nearly everything: rebuilt injectors, air flow meter, ECU, O2 sensor, harness, plenum, throttle body, air intake boot, air filter box, idle control valve, idle control computer, distributor. The invoice from GoWesty also notes that they had to modify the digifant harnesss so the coolant temp sensor reaches the 1.9 location - I guess my new mechanic had to do the same thing with the replacement harness they put in. Anyhow, switching over to the digifant system did not fix the idle/emmissions issue, and GoWesty (to their credit) paid my new mechanic to put in a different camshaft. That problem was solved.

So yes - sensors, wiring, components have changed. Given my list above, are there any others that were not changed from the digijet/1.9 system that we should pay attention to?

I do agree that re-routing through the firewall may have damaged the harness. The "buzzing" in the ECU went away when we swapped out the harness, as did the bucking (for six months). It seemed like the problem was indeed a damaged harness (not either of the ECU's). But now that the bucking has returned (6 months later and then 4 months after that) - I am questioning whether the second harness might be damaged or whether it is something else. In the time it takes to twist the harness around and measure voltages or resistance, is it not easier just to put in a different harness? Is it about the same level of effort? It seems odd that the second harness would fail after 6 months of working fine, and cause the same problem when it failed. But indeed, the first failure (after 6 months) I did twist the harness around at the firewall, try to relieve stress, and it held OK for 4 more months. By the way, I note that currently, if I put my ear to the ECU, I hear a slight ticking sound, around 5 tics per second I would guess. I can only hear that by putting my ear right on the ECU.

So, on the current visit to the mechanic, besides the obvious things like checking the O2 sensor, the air flow meter, all the wiring for poor connections or grounds, and adding a "Vanagon syndrome" fix on the harness - any other suggestions? Are there any potentially incompatable relics from the Digijet system that we should just replace to eliminate potential electrical mismatch? At what point do you think we should embark on the time consuming process of analyzing for transient shorts in the harness? Or is it better to just replace the harness again and hope for the best.

Thank you Capt. Mike, and any others who may contribute.


New member
My parents are driving their 78 westy camper down here to Florida from South Dakota. About 200 miles into the trip as they were tooling along getting peace signs from everybody, the van started bucking but did not stall. They pulled into a gas station and put in a can of something called sea foam. They said it helped but after another hundred miles it started to do it again. So they have been just putting this additive into the tank and the problem goes away for awhile. It does not stall out and starts and idles fine. Also when it does start bucking it happens in every gear. Where is a good place to start trying to find the problem. Thanks for any help.
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Capt. Mike

Sea Foam® is basically alcohol, naptha & pale oil. It's only signifigant use to to absorb moisture in fuel (alcohol), solvent type cleaner (naptha) and provide some lubrication (pale oil) to fuel injectors. It does NOT solve the problem, which appears to be water in the fuel tank, but may mitigate it for a single tank. Only draining, changing filter and refilling with fresh gas fix any significant amount of water in a tank. This does not appear to be a fuel injection problem (this forum). See the FUEL SYSTEM forum for topics on draining & cleaning fuel tanks, filters, etc.
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New member
88 syncro blowing white smoke, power loss, temp gage out

HeLLo, I have an 88 syncro which recently has lost some power and seems to be blowing alot of white smoke at times ~ I also noticed yesterday the temp gage wasn't working but it has been recently while this occurs. It also seems to have a vibration when giving too much gas or in lower end of RPM green zone or in 4th gear ~ Don't know if that could be related? Any advice is greatly appreciated. THank You!


New member
2.2l stalls on starts inconsistant idle

My 88 Westy with a new GoWesty 2.2l has been hesitating on initial taking off from a dead stop. I have messed with the idle adjustment that seems to change things abit but eventually the hesitation returns and seems to be inconsistant. Some mornings it starts right up and no problem and no hesitation, other mornings it has a hard time starting and idleing until it is warm. I have read that the throttle switch might be the problem, or maybe even a worn out throttle bushings.
This is the final thing that I have thought might be the problem. We have solved other fuel problems like water in the tank from bad expansion tank valve gaskets, plugged fuel filter and fuel pump from from rust. The fuel pump, fuel pressure gauge are all ok, even checked out the injectors and they are all fine. I also checked out the idle control valve, and the idle speed stablization switches and replaced the Air mass control, they all seem to be fine. We also had a bad oxygen sensor that was also causing very rich mixture and bad fuel economy,fixed that. It seems that all the other problems now solved still haven't totally eliminated the hesitation, though the engine is running much better.
From all this do you think that it is a badly adjusted/malfunctioning throttle switch and valve, or is this what is called the Vanagon Syndrom?
The van is in storage until next january, and in Uruguay. Our mechanic in Buenos Aires says that it is probably a bad throttle switch and out of adjustment. So, what parts do I take back to south america with me to solve this problem?
Thanks for any help,
Gary Peebles

Capt. Mike

Vanagon Syndrome symptons are different than you describe. I don't see any indication you have done the full step-by-step troubleshooting of the FI system (Guideline #3)