ECU and electrical FI malfunctions


New member
I seemed to have put myself in a dilly of a pickle. I'm traveling in my '81 westy, across Canada, starting in Halifax, N.S. I've just made it to Thunder Bay Ontario, and this happens... When I start driving from 0 mph, before I need to up shift, the van begins to shake violently, and loose all power, until I either step off the gas, put it in neutral, or up shift. If I push deep on the gas pedal when this shaking happens, there's no more power, the engine doesn't rev, or get louder. So, to continue driving, and to avoid this from happening, I find myself in fourth gear, when I should normally be in second, but even then I can't even get up to 35 mph before it happens again. This has happened before, on a rare and unpredictable occasion. It also would happen if I turn on my interior fan, or sometimes when I turned on my windshield wipers while driving. I think it is happening now because of the severe cold here. The van has never been winter driven before, but I don't suspect that's the reason for this happening. Clearly it is an electrical problem, but I can't put my finger on it. I brought it to an electrical place before, and they said my points were corroded, and "fixed" the problem, but they really didn't fix anything.

I don't mean to put the pressure on anyone, but I am stuck here until this problem gets resolved. The VW dealer here was very unreceptive, (perhaps being 22 and on my "great adventure" has something to do with it). So, I'm afraid that if I don't know the problem, they're going to take my climbing gear budget away!

Thanks in advance,
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Capt. Mike

Without being there, the best I can guess is that you've got a failure in either the power supply to the FI brain box or it's signal to the air-flow meter. To be shaking from just acceleration sound much like the air flow meter is running amuck, flapping open & closed. In a way, very similar to the Vanagon Syndrome posted elsewhere. Although true Vanagon Syndrome can't happen except to the late digital FI, the problem of erratic air-flow meter can, just different cause.

I'm also concerned that you say use of any electrical appliance can trigger it. This would indicate your voltage TO the ignition or FI is unstable. It could be something as simple as a dying battery or bad voltage regulator. Also a bad coil or condenser that is breaking down under load. What I'm getting at is the shaking could be caused by not getting smooth ignition and, in effect, misfiring but doing so often and with many cylinders so it causes the engine to shake. I'd have them also check distributor advance -- yours should be 7.5 BTDC but has both a centrifugal and vacuum advance. In fact, now that I think about it, this might be more probably than the FI. Failure of advance causes the engine to fire at the wrong point in the stroke.

It's always a problem when you get a VW dealer that wants to sluff off a hard to diagnose problem, but have you gone direct to the Service or General Managers? Checking ignition, coil and even the FI isn't that difficult. If that doesn't work, demand to call VW Canada Headquarters and tell them you've got a bad dealer that won't fix a VW. Dealers don't like getting calls from headquarters.

Keep all replaced parts, and if one doesn't fix it, make them take it out and not pay for it.
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New member
ry charger dropped to under 2 amps, and all of the cells were full and bubbling. I then installed the battery in the vehicle, and accidently grounded the positive terminal for a moment there. The engine started up, but immediately would stall. I then found a disconnected hose somewhere after the AF meter. This fixed the stalling problem, the engine fired right up and was running great.
/infopop/emoticons/icon_biggrin.gif Over confidance and cockiness got the better of me, and I pulled out of my neighborhood to run some errands. :cool: I was so happy to be motoring around in my Westy after 2 weeks of it sitting in the driveway, that I motored onto I-40 for a quick jaunt into the mountains. As the grade
steepened about 20 miles from home, the engine started losing power abruptly and shaking pretty hard as described by westyjohn's post. I exited, and figured my battery was dead, and I would be walking soon. I pulled over, and found that the engine was idling smoothly at 900 rpms, and my oil was around 215 F normal for a 90 degree day in NM. My headlights worked fine, and did not affect the idle when switched on.
This made me rule out the battery. I then thought it might be the accelator cable, so I tightened it up a little. I then limped home
(luckily it was all down hill) and fine tuned the accelator cable with someone up in the driver seat pushing down the accelator. That
wasn't it.
So, before I swapped out the starter, the engine ran great. I imagine the problems are unrelated, but am afraid I fried something in the fuel injection when I grounded the pos. terminal installing the battery. I am making the transition from doing only minor maintenance myself to doing some trouble shooting, and more complex repairs. Should I check the distributor advance first and then do the AFC FI trouble shooting in the Bentley? Could a slight knudge on the distributor throw it out of whack? I don't remember touching it. Could it still be the battery, even though the engine starts, and I can run my headlights. I forgot to mention, the starter was a reman. by autolite. The wierd thing was that there was an extra electrical connection on the solenoid of the rebuilt starter on the left side. The connections I needed from my old solenoid were on the reman. in the same places so this didn't bother me to much. It was the same dimension etc.. The parts guy basically said beats the heck out of me. I hope someone can point me in the right direction, since I'm not sure where to start but want to trouble shoot this myself. Thanks for the help.

-Zach DiCicco

Capt. Mike

I don't ever rule out anything; I just recategorize them in the order of least likely. I'd put the battery short in least likely. Electricity is like a water -- flows in the path of least resistance. If you shorted the + terminal of the battery to ground, it flowed right around the battery box to the ground cable. There's no reason for it to head anywhere else. I'm not saying that super excess voltage to the chassis, like welding, can't back up into other components, but a quicky short isn't likely to. That lights, etc. are doing fine puts battery problems way down the list.

Timing getting knocked out is way overrated. It's BOLTED into place. Unless you've screwed up last time it was adjusted, it won't change. And it will be consistent. Now knocking a vacuum line off or getting a leak is further up the likely list.

Starters have two basic connections. Power to the starter motor itself usually runs direct from the battery. Then an ignition switch controled circuit puts power to the solenoid, which also needs power to operate the plunger. Look at the wiring diagram in the Bentley, 97.20.

The 1 gauge black wire to the starter is the main battery supply. Only one other wire comes off the battery to feed the fuse box circuits, including the solenoid circuit. The alternator feeds recharge current back through that starter connection, and the engine management & ignition system get their power from that terminal, #30.

Usually the big black #1 and often the red 10 & 12 gauge connections are eye type with a nut. Some starters may have a male plug tab set under that nut for the smaller wires that use spade terminal connections. But look at your diagram codes. Both wires at the solenoid #50 are colored. R/BK from the ignition, and Bl/Br that feeds the fuel pump Starter and solenoid grounds through the body so there are only 2 terminals with any connections.

IF your aftermarket starter has more, they might be ground terminals for the solenoid, or some other application feed. It's possible that might you might be messing up your power to the fuel pump & AFC, which would give you the low power symptoms you have. Get back to the original wiring diagrams circuits #26-31 and see if your problems don't go away.

I'm sorry if this eventually involves replacing a wrong starter, but it's more likely a case of connection differences. One of the hazards of going with the cheaper aftermarket. A Bosch reman would have been correct with all the correct terminal numbers.


New member
Thanks for getting me re-focused on trouble shooting this problem! I referred to the wiring diagrams and relevant circuits in the Bentley manual as you suggested. After studying the diagram, I was fairly sure I had
swapped the wires going to terminal 50 to the funky extra terminal of my non-bosch rebuilt starter. I was sure that I had made the connections to terminal 30 correctly however, letting the info that "the alternator feeds its recharge current back through that starter connection, and the engine management system and ignition get their power from that terminal." Although the pessimist in me was certain that I had a big $ fuel injection on my hands.
I crawled under the van as the light was fading, and shined a flashlight up at the solenoid and verified that the connections at terminal #50 were correct. Then I noticed that the connections on terminal #30 were very hastily connected. I must have just screwed the nut on the bolt just enough to secure it while I worried about making the other 2 connections correctly. Thrown off by the extra connection no doubt. I tightened up the nut on connection 30, and a quick start and driving test showed that my former symptoms were fixed!
Next time I'll triple check all of the connections. I'll also lay out a few more bucks for the bosch rebuilt part. Seems like I'm always enrolling myself in the school of hard knocks. I think I got off pretty light this time though. Thanks again for the help.

-Zach DiCicco

Capt. Mike

The Vanagon Syndrome is a distinct malfunction caused by a loss of voltage stability from the CPU to the AFM in Digifant systems. Digifant is a digital system and the fix was to install an inline microprocessor into the control harness that corrected and stabilized the electric signals and did some rerouting.

The older Digijet systems were analog, thus the CPU generated a different type & quality of signal that did not suffer the instability of the digital signals.

[I'm learning more than I ever wanted to know about digital signals when I switched my cell phone service from analog to digital -- what a nightmare. Digital signal stability and strength DECREASE with the quantity of signal being handled!]

The Vanagon Syndrome symptoms, however, were not from the CPU signal, but the EFFECT thereof. The AFM can still misbehave and flutter; the CPU can still generate poor or unstable signal; you can still have a wiring defect effect on the CPU-AFM control circuit; and finally -- the more common -- you have some power supply or signal generating sensor malfunction that is feeding the CPU bad info, thus being processed into a bad control signal to the rest of the FI system.

So wiring & other FI problems can create the symptoms of Vanagon Syndrome, but the microprocessor fix won't solve the problem. The Digijet and AFC systems had a lot of similarities. I'd suggest reading all the info available about those two systems -- including Bosch's own tech manual. (See SUPPLIER forum for sources.)


New member
flypdx, I was wondering if the new connection "fixed" your problem. I am having somewhat similar problems for the last month with my 83 westy (130,000 miles, 50,000 on a canadian reman engine). On very warm days (85 and up) after about 30 - 40 minutes of stop and go driving, when the engine is completely warm, I will experience surging and hesitating on acceleration. The engine will idle roughly, but will not stall. There is no discernable exhaust (i.e black, etc), though the exhaust smells rich when this occurs. The problem does not occur on cooler days. It has only occurred once at full-throttle and that was again on a hot day on a moderate (wisconsin) climb. It typically does not occur at highway speeds.
Assuming this was a fuel injection problem, my voltmeter and I have checked the temp sensor I and II and the air intake sensor, and auxilliary air regulator. Everything was within Bentley specs. The only abnormality I could find was a cracked connector attached to temp sensor II. Despite the crack, then connection appears to be intact (I could be wrong).

The dealer also checked out the van, unable to duplicate the hesitating/surging problem much less find the cause.

Is there some component of the FI system that would stand out as the cause, given the intermittent nature of this problem, which only seems to occur under fairly consistent conditions. I'm not sure where to look next. The dealer is suggesting that I replace the ECU, thinking there may be a short that only shows up at the warmer temps. I am not a fan of the "replace parts until you find the problem" approach and would like to locate the problem, if possible, before I start randomly replacing parts.

thanks! :confused:

Capt. Mike

Nor I unless he's buying the part back AND labor if he's wrong!

That cracked connector is one likely source. Electrical connections that have been subject to stresses like that can develope a temperature related intermittency because they do expand and contract quite a bit during temperature changes. The crack can also allow moisture in which does some very unexplainable things, remembering heat does allow a higher humidity before it reaches the point of driving it out. One of those deep thermodynamic things.

Vanagon Syndrome is capable of 'mild' symptoms as you describe -- in fact if you check that thread you'll see VW's original wording was for symptoms more to what you describe than the complete undriveability or shut-down many of us have experienced.


New member

Unfortunately, I have only driven my van about 20 miles since I posted the message about the broken plug and I hesitate to say that the replacement solved my problem. After closer inspection of the broken plug I am beginning to think that it was damaged by the mechanic trying to troubleshoot my problem.

It does sound like you are having the exact same problem so, between the two on us, maybe we can figure this thing out! Please keep me posted and i'll do the same.


New member
flypdx, thanks for the reply. I have yet to fix the problem, though I have done more troubleshooting. I currently have the god of vanagon parts at my local VW dealer working on getting me a new connector for Temp sensor II. It may be the problem, we'll see. What strikes me about the problem is the seemingly complete relation to engine temperature. It only occurs when the engine is fully warm, and then, only on warmer days. It never occurs on cooler days or during night time driving. Two weekends ago, I was on another trip when the problem occured. To test my engine temperature theory, I turned the heat on full force (to much whining from my traveling companions)just to see what would happen. After 10 minutes with the heat on, the problem stopped. I have tested this "theory" twice now, and both times, turning the heat on stopped the problem. This has led me to think that there is some temperature-related mess up in one of the sensors (or connectors). I may be going down the wrong path, but i ordered a new Temp sensor II even though the current one tests within bentley specs. I will replace that and the connector and see where that gets me. The van runs great otherwise, and the intermittent and temperature-related nature of this problem is pretty amazing. I'll keep you posted.
BTW- does anyone know if I need to put any type of sealant on the threads for the new temp sensor II? seems like it wouldn't be necessary, but I would hate to create another problem by not doing so.....

Capt. Mike

The Temperature Sensor II uses an O-ring for sealing. Do not coat the threads with anything that is not electrically conductive as that is your ground point the sensor relies upon to complete the circuit. (You can usually coat the threads with WD-40 or silicone spray to ease installation without losing ground.)

Capt. Mike

Computer glitch lost first part of message during board update.
. . . For instance, the fuel guage would drop to zero. And sometimes the coolant light would begin to blink. But then these phenomena would disappear but the engine would still be erratic. Someone who has a different kind of vehicle said to me that the jerky performance happened to him when his vehicle needed a new timing belt. But I don't believe Vanagons have timing belts. Could this problem have been caused when the body was completly repainted several years ago? In other words, could an electrical contact been covered up? We love our Westfalia a lot and depend on it for summer vacations in Canada so we want to help it be better. Please offer any suggestions that I can pass along to my mechanic.

Capt. Mike Moderator Member # 11 posted 05-27-2000 09:53 PM

Simplest first, it is not a timing belt; the Vanagon waterboxer has none. It is not related to a long-ago repainting.
Slight variations in idle -- hunting -- are a normal feature of the O² sensor controlled part of the FI system. O² sensors are a service item and should be replaced every 90,000 miles.

The symptom you describe is closest to an erratic air-flow meter. The '85 will not have Vanagon Syndrome -- that's only on Digifant systems, but an erratic air-flow meter is possible on older models and will do that jerking at mid-range speed. You can test the air-flow meter with an ohmeter per the Bentley shop manual.

That you are having erratic gauge and ignition controlled electrical problems indicates a deeper problem. The most common cause is a deterioration of the electrical side of the ignition switch. It is no longer feeding power to all key-on systems. Usually this will also show up in such other ignition-controlled circuits as headlights & wipers. This is a relatively easy & inexpensive item to change as it does not require changing the keyed ignition switch, just the electrical contact module.

mjrly Junior Member # 74 posted 06-07-2000 11:50 AM

My feeling is ignition switch as well, especially about the coolant light blinking. I bet it blinks about the same number of times as it does when you turn the switch 'on' before starting the engine.
Let us know what your fix is if you can.


dwolterd Junior Member # 47 posted 06-08-2000 09:21 PM

Thank you. I passed along your comments to my mechanic who has considered them but doesn't see an answer in them. He is, at this time, open to all ideas. He suggested that I use more detail in describing the problem and gave me these comments to pass along.

"Here are the symptons:

Engine starts and runs perfect when cold. After aprox. 2 minutes, engine will not run between 1000 and 2000 RPM's. As soon as Rpm's drop below 1000, it idles perfect and also if reved up above 2000. At this rpm range (1000 - 2000), I found that fuel injectors DO NOT get any pulse from ecu. It does not loose spark in this range. If coolant temperature sensor is disconnected, engine will run perfect at ANY rpm's. In 30 years experience as Auto Mechanik I have not seen anything like it, Your help is much appreciated! Laslo Bozoky.

Work done so far:

Coolant temp. sensor replaced; Air flow meter tested and replaced; ECU replaced; All ground connections cut back, and replaced ends; TPS replaced; Ignition Module replaced; Idle stabilizer box eliminated."
These are his own words. Thank you for your initial comments and thank you in advance for any additional comments based on this better description of the problem from a mechanics view.

Capt. Mike Moderator Member # 11 posted 06-19-2000 08:52 AM

The Bosch FI has a dual brain setting for idle and for full throttle. It amounts to a transfer switch to change from the idle mode to the throttle load mode. A failure, including getting wet, can cause the engine to refuse to operate across that changeover range but be OK at the two extremes. Tell your mechanic to check the switches shown in circuits 10 - 12 in the Bentley wiring diagram. On the later water-cooleds it's located on the right side above #2 cylinder between case & head.

It amounts to a transfer switch to change from the idle mode to the throttle load mode
This switch is currently the subject of investigation. According to my mechanic, when replaced, the new one immediately failed. It seems to be getting 12 volts instead of 5. Currently looking at wiring harness at various spots to see where this wire it is tapping into battery strength current. Again, thank you for your helpful ideas on this subject.


New member
Following the current diagram, it seems as though you may want to check the following:

- if you are getting 12V (normal 4.5-6.5 per Bosch) it could be a couple of things:

1) A bad resistor in ECU is over powering the switch, (you should have a "dual load" ECU on your Vanagon). See test circuit 10 per the Bentley guide.
Note: I do not believe the 12V will 'fry' the switch, it will just provide a false reading.

2) Grounds, grounds, grounds, grounds. Make sure everything is grounded.

3) Temperature sensor circuit: Could be giving CPU false info due to a wire that has melted to something, rubbed itself and is now grounding out the circuit.

My roll-up guess is that your temp. circuit has a fault in the wiring, albeit the MPC (plugs getting corroded). There may be a short, which will give the ECU a false command.


Bad ECU resistor letting too much voltage out the floodgates. (Test the resistance on the PINS per Bentley)

In my experience, the ECU's are well protected and are pretty durable. There is also a relay (double) with a resistor and two diodes. The resistor operates the fuel pump correctly; the diodes keep the 'turn the key' current from running current, mostly when the intake air sensor kicks in and takes over.

It's a long-shot, but check it out. Bad diodes would be relavant to the ECU, and sensors. The resistor just 'hands off' the fuel pump to the air sensor.

Good Luck.

Capt. Mike

Transferred to consolidate same topics.

AC0T Junior Member posted January 31, 2003 01:31 AM

Hello, I have a '84 1.9L DIGIJET with CA emissions.

I just rebuilt the engine after 157k miles.
Prior to the rebuilding I had some idling problems and poor gas milage (15 - 16 mph). I still have the problems now only worse.
The engine always starts up easily, even in cold weather, but after it warms up and the Temp SensorII tells the ECM to slack off, it will hunt. And I don't mean 50 rpm hunt, I mean HUNT like 200 to 400 rpm, and generally run very rich over the driving range. Also when driving at city speeds it will occasionally buck (probable fuel shut off, but if I stomp on it and run up to hiway speeds it doesn't buck at all. It just doesn't have the pickup it used to have. (like it is running to rich) I checked all the FI components using my Bentley and everything checks out, with a few exceptions. Namely test #3 on the throttle valve switch, 24.33. When I operate the throttle valve switch by hand and slowly accelerate, the engine speed accelerates smoothly. This is just the opposite of what it should be. In fact, these conditions are reversed. It surges at normal warm idle and runs smoothly with the switch held closed and engine speed over 1500?? I then checked all the wiring back to the ECU plug and it was fine. I cut off and replace all the ground lugs and the lugs on the throttle valve and enrichment switches. No change

So I bit the bullet and ordered a new "improved" ECU from the Bus Depot (025 90621E)
After installing it I had a new problem. The engine would run for about 20 or 30 seconds, shut down and would not start up again. I found that if I turned the ignition off for 5 or 10 min. it would start up again, but again shut down after a few seconds. I found that after it stop running that I had spark but no fuel. I pulled the injectors off one bank and cranked it to be sure. Yep, no fuel. This new and improved ECU is shutting of my injectors. I reinstalled the old ECU and it fired right up and after it warmed up went right back to its shurging. I think this new ECU doesn't like the CA emissions?

I guess my question is... What components comprise the CA emission system. How do they differ from the rest of the world and can I get rid of them??

Thanks for your patience and sorry for the dissertation.

Capt. Mike

Some possiblities:

1. Excessive hunt can be caused by failure of the O² sensor or its circuit and function to the ECU. O² sensors have their own topic in this forum.

2. That you can get past the bucking by full throttle may indicate a failure/misadjustment of the Idle/Full throttle switch. They have their own topic in this forum. Note there is a difference in Digijet versions per pg. 24.23 of the Bentley. Later models have throttle body with 1 switch.

3. "New & Improved?" Says who? Go to your VW dealer and find the proper, current ECU for your CA vehicle on his fiche. A lot of aftermarket discount vendors buy whatever is cheapest and might work. I'd be surprised if VW and Bosch got together and designed a new & improved just for the CA market of a 19 year old vehicle. 025 90621E is not a valid VW number. Have you read the "Bus Depot" topic under PARTS? Ken Willard at Van-Again (PARTS forum) seems to have one of the better grasps of FI, ECU's, etc. Although he & I disagree on some facets of Vanagon Syndrome (not applicable to Digijet), I've found most of his advice pretty well right on. He carries one of the better selections of FI electronics.

4. There are "Fuel Mileage" & "Surgin" topics in this forum that may provide some clues.

5. By the time of advanced FI systems, the differences in CA and 49 are minimal. CA required 30K plugs so VW went to heavy-duty in all. Quite probably is a difference in ECU's as they program the entire engine management system. Many of CA's EPA differences are in evaporative and other emmissions, not necessarily the running electronics. Again (GUIDELINE #8!!) your dealer can be your best friend, just ask to look for the parts that are different in the CA version. In reality, you will probably be better staying with the CA version -- they differences aren't significant and you retain originality, and thus diagnostic continuity & parts compatibility.

6. I notice you live in CO. Do include an check of your fuel. CO is NOTORIOUS for bad fuel. They have mandated some of the weirdest octane ratings I've ever experienced. There is a "Gas Octane . . " topic in the TIPS forum. I don't give a darn what 'grade' it says on the pump, R+M/2 must be 87! I found "regular" as low as 83 octane in CO and even middle grade below 87. My own Vanagon wouldn't run worth diddley when I put in a tank of their substandard regular by mistake.
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Capt. Mike

Transferred to consolidate same topic.

CW Junior Member posted March 19, 2003 08:51 PM

I am having a problem getting a new VOA engine running. After the engine was replaced by an independent shop now out of business, it ran several months (virtually no miles) then began quiting and refused to restart. Sit an undetermined period of time and after you worked on this or that would restart only to fail again unexpectedly. This required 3 rollback ventures home, one was 50 miles away. Not a happy camper. Two years have passed since it was done and last summer a VW dealer finally gave up telling us to convert to carburetors. I will not give up. One part resembling a relay - 4 wires plugged into it &(California only - no longer available)was defective, that is why we decided to change. We purchased a Federal ECU #280 000 178 to replace the original ECU #280 000 192. Fuel injection harness was changed from California to Federal and added items such as the resistor unit then deleted oxygen sensor and so on. Distributor is a factory rebuilt points unit #231 170 093. The air flow unit remains #280 200 020. How critical is the ECU unit being matched to the system? Is the air flow unit specific to each model ECU. And if the air flow unit is slightly out of specification when compared with Bentley's resistance readings in one catagory, would it keep the engine from running? Thanks for any help or thoughts.

carlosthecatcatcher Junior Member posted March 20, 2003 05:24 PM

probably not much help but the air flow meter on my 78 westy has the same bosch code as yours and i'm sure they must of made some changes over two years-if only to annoy everyone in the future.
i've just had a LOT of problems with my injecion system but finally fixed them today (hurrah).one problem i have had and several friends is restarting particularly after a long journey, this turned out to be a poor connection in the red/black ignition wire due to corrosion 4 inches down the wire i.e not visible ! i would certainly doulble check out your double relay for any faults as most of my problems seem to stem from there.


New member
HI Everyone. I am going to be installing a new ECU in my 1987 Westy Vanagon GL Hopefully this will be the answer to my problems
Anyway, I wanted to know if replacing the ECU was just a matter of unplugging the old one(as shown on page 24.48 of the Bently repair manual) and plugging in the new one? (Disconnecting the battery first seems wise as well). The Bently
as far as I can see doesn't provide any additional information. I guess it just sounds too easy. Thanks!!

Capt. Mike

Sounds like a plan. Other than the "ignition off" warning, I haven't heard of anything else and have seen shop mechanics just swap EDU's out. The battery disconnect might be overkill, but that's better than ECUkill, huh? I have connected & disconnected one in a Type II without ill effects.