Ever drive down the road in your 86-91 VW Vanagon, all is well, stars are aligned, moon is in Venus (whatever that means), then all of the sudden: Hiccup. At first you think it was a gust of wind, or a maybe you just drove over a racoon. Then moments later: Hiccup. After that, maybe back to blissful wonderful aligned stars and moons, or maybe a total loss of power, and to the side of the road you go. You check the fuel level on the gage, tire pressure, stars and moon, get back on the road, and all is fine again! Then: Hiccup. Damn it all to hell!
The dreaded Vanagon highway hiccup syndrome has to do with the Digifant fuel injection system found on 86-91 Vanagons (and some other VW vehicles of the same vintage). The culprit is the air flow meter (AFM). The AFM is the metal box attached to the air filter housing, that has an electrical fuel injection harness plug attached to it. This device does just what its name implies, it meters the air flowing into the engine. There is a spring-loaded, swinging door inside this contraption that is displaced by the air rushing into the engine. Just about all electronic fuel injection systems from around 1974 into the early '90s use a device like this. This swinging door rotates around a pivot point, above which is located an electrical “wiper” that rubs on a semi conductive strip. The Digifant computer sends a 5 volt signal to the AFM, and depending on how much air is entering the engine, this electrical wiper arm and semi conductive strip send back a fraction of that voltage, proportional to the amount the door is displaced. It’s a pretty simple, fail-safe idea, right? Wrong…
For reasons not fully understood, the Digifant computer can be confused by the signal coming from the AFM. And, because of its antiquity, the Digifant system cannot simply work around it like a modern system would. Instead, it goes into shut-down mode. The problem can be exacerbated by a worn-out AFM. That is, the electrical wiper and semi-conductive strip inside the AFM begin to wear and add to the confusion. You are probably thinking, "Okay, so what? Everything wears out. As long as it lasts long enough and you can get a replacement when the time comes." Herein lies the problem. New replacement air flow meters have been discontinued by Bosch. Even with a new air flow meter, these symptoms would return in as little as 20K-30K miles (or a year or two). VW recognized the problem early on, and back in the late '80s/early '90s they introduced a "filter cable" that plugged in between the air flow meter and the fuel injection harness. Now equipped with a (very expensive) filter cable and a (very expensive) new air flow meter, the problem would finally be solved until the AFM was really worn out.
Several years ago we came out with our GoWesty Hotwire AFM replacement system. It was a complete departure from the original system and employed an air mass sensor (AMS) and additional conversion computer so it would operate with the rest of the Digifant system. It was a bit pricey, but compared to the alternatives at the time—it just made sense. Then we landed a very nice supply of brand-new air flow meters for a decent price, so the Hotwire system didn't make sense any more. Well, we've sold out of those brand-new AFMs, and now we're back to square one... sort of.
As time has gone on, we've recognized that the days of the Digifant system are numbered. Besides the AFM highway hiccup problem, availability of the air flow meter is becoming an issue... as well as that of the ECU, the ICU, and the TPS (just to drop a few acronyms!). Coupled with an aging wiring harness and the antiquated Digifant system, it just seemed pointless to invest in a partial-fix system like the Hotwire. Instead, we felt two approaches were necessary: 1) Continue to offer the most cost-effective replacement parts to keep the remaining (and otherwise serviceable) Digifant systems alive, and 2) put in a serious effort to get away from the Digifant system altogether.
To that end, we will continue to offer replacement parts for the Digifant system for as long as humanly possible, improving them whenever we can. Also, we are working on a completely new fuel injection system to completely replace the Digifant system. Our new GVW-EFI system is due out by the end of 2015. To read more about that, click here.