Engine misses, surges or bucking (FI related only)


Domokos

New member
I have an 87 syncro Westfalia that I purchased at ~30k miles in 1994. I have since that time had a bucking problem that goes away for long periods of time (years). It is back. I see from the posting that it might be the Westfalia syndrome. This only happens if I drive it for more than 2 hours and if I stop and get gas or some such short cool down it goes away for a hour or maybe for the rest of the trip, or it might return. Sometimes in frustration I keep driving and it goes away again for an indeterminate amount of time. The revs seem to go to zero. Is there a checklist I could follow on this issue?
 

Capt. Mike

Moderator
The first 'check' of Vanagon Syndrome are:

1. Will it quite after just shutting off the engine and restarting immediately? Even if just runs without bucking for a few minutes. With Vanagon Syndrome, the shut-off and restart seem to perform a "reboot" the microprocessor in the harness fix until the voltage instability returns.

2. Will putting the accelerator to the floor provide normal full throttle response? With Vanagon Syndrome, the bucking and dieing occur at partial throttle. It will usually respond to full throttle. (Not a practical way to drive but perhaps a was to get out of traffic to a safe stop.)

3. Per the Vanagon Syndrome topic, the harness fix is not infallible -- like any micro-processor, especially in a hot, vibrating environment, can fail. Refer to the Vanagon Syndrom topic to explore that further.

If you can eliminate Vanagon Syndrome, then begin the ECU system checks. Also, look at the Decel/Idle switch, FI Troubleshoting, Air Flow meter and Inection & sensor topics as the underlying causes are often related.

[Don't rule out moisture in the fuel!]
 

kevininseattle

New member
I have an 1988 Westy w/ 2.1 at 93k. This van has been in my possesion for about 3 months. Here is the problem.....

After driving for 15 minutes (if outside temp is hot) or 25 minutes (if outside temp is cool.) the engine occasionaly bucks. It ONLY bucks when driving at light throttle. The bucking has only happened in 3rd and 4th gear. (Those are the only gears that see light throttle action.) The bucking seems worse in 3rd than in 4th. (probably due to the wheelspeed/enginespeed ratio.)

It was bad enough the other day that I drove for an entire hour to get home by accelerating hard to 70mph, pushing in the clutch, releasing the accelorator pedal and coasting down to 50mph, then accelorating hard again. Over and over all the way home. **The van never bucked once using the hard accelorate/coast method.**

Things I have done to the van since I bought it 3 months ago:
-seriously cleaned the very dirty engine
-new battery,
-new cap, rotor, plugs, filters, oil
-new clutch, and throwout bearing
-vanagon syndrome: added 22mF, 25volt, tantalum capacitor under the black Air flow sensor lid. Soldered in place across terminals 2 and 4. Resealed lid ontop with silicon.

Known remaining problems:
-lower pitch (but not very loud) rattling as engine is accelorated. Mechanic thinks this is a slighly loose wrist pin. He was not concerned.
-poor idle (idle control unit?)
-leaking coolant (of course)
- /infopop/emoticons/icon_mad.gifbucking after warmup at light throttle

The first 3 I can live with, the bucking I can't. Does this sound like vanagon syndrome even thou I soldered in the capacitor fix? Or do I need to search elsewhere? The air flow meter itself? ECU? Faulty/loose wiring? I have found my Bently manual not very helpful in this matter. Is there a section that might help?

Thank you, Thank you, Thank you for ANY help....
Kevin
 

michaelmaxp

New member
Kevin I experienced the same symptoms with my '84 westy 1.9. It only happened when warm. Testing showed a bad Air Flow meter so I bit the bullet to replace it. I was happy as a clam for about 2 weeks and it started bucking again although not as often and not nearly as bad but only when warm. Further testing showed that I had one bad plug wire and although I didn't believe that a bad wire could cause the problem, it did. New plug wires and no more bucking/surging. It's been about three months so I know it wasn't a fluke. Added bonus: 3 extra miles per gallon of fuel!

Michael

MichaelMaxP
 

Gary Calaba

New member
Hello:

I'm a new member (87 Westy owner; 135,000 mi.) and missing or bucking occurs at altitude. It's been doing that for several years, the last time going up to mountain the engine missed so badly that the van nearly stopped at the 8,000 foot level. I changed fuel (92 octane) and that seemed to help, the the problem still persists even travelling straight-aways but at altitude.

Any insight to a fix would be helpful.

Gary
 

Capt. Mike

Moderator
CO is altitude dependent; check your CO at the higher altitude per Bentley 24.52. Note the adjustment procedure requires connection & disconnection of the O² sensor & idle stabilizer control valve. These are what signal the ECU to adjust for changes in altitude. If your's doesn't change, then one of the three is the mostly likely culprit. The O² sensor is a service replacement item; see "O² Sensor" topic.
 

Gary Calaba

New member
Capt. Mike, thank you so much for the advice. So I go over to "O2 Sensor" to take a look, and low and behold there's a relationship between a leaky exhaust and 02 sensing. Well, I have a leaking exhaust so I'll replace that first before I go on.

Thanks, Gary
 

lexluthier72

New member
Intermittent miss 85 vanagon
85 vanagon 135,000 miles on broken OD.

My vanagon has an intermittent miss, when both cold and hot. Here is what I have done so far…changed plugs, wires, cap, rotor. checked timing, new fuel filter. I pulled the plugs after about 500 miles, and they look good. Since it is winter here, I get some water out the exhaust till it warms up, and then all is good. it will idle fine for a few moments, and then a “larger blast of air out the tailpipe” is the only way I can describe it, almost like there is water in the gas. It sort of burps intermittently. I have not done a compression test yet, but it is next. The van does have a drip of coolant coming from one spot on the head,(no puddle on the ground) but no coolant in the oil, and vice versa. At highway speed it does fine, and does not cut out, and is not at a loss for power. I do have a leak at the pushrod tube, on the #1 cylinder, but no noise coming from the lifters (at least not audible) Could the pushrod leaking oil cause this in a roundabout way? I did fill up with fresh gas and put a can of seafoam in the tank, thinking maybe it was dirty injectors, or water in the fuel. Any thoughts would be great. I took it to a friend of mine, who said it sounded like I got a bad tank of gas, thus the seafoam. Wouldn’t most issues show up on the plugs? It also has about a 2 second shake on shut down, but again I did do the timing, and the plugs don’t show any fouling or carbon buildup, and the tailpipe doesn’t seem to show an excess of carbon, or running too rich….any suggestions would be great. For now, it seems like running thru a couple tanks of gas is the first thing.
-Erin R.
 

lexluthier72

New member
Intermittent miss update 85 vanagon

Well, I Started poking around in the wires the other nite, and seemed to be a grounding issue to the temp sensor on the thermostat. So i tried to undo the bolt holding the ground on, and the head broke off. Drilled out the bolt, replaced the ground wire connector on all the grounds, put back together, and now i have no spark at all. Finally fed up, towed to the mechanic...I'll let him fix both issues. =(
-Erin R
 

lexluthier72

New member
85 vanagon intermittent miss update 3
Turns out the ignition coil fried in the cold. When i went to pick it up from the mechanic, he said it ran good, so he did nothing. the only difference would be the heated shop....what gives? I am mystified. Things changed, or new include:

new tranny (not related)
new clutch (also not related)
new plugs, cap, rotor, wires
new ignition coil
unplugged O2 sensor NO change
checked timing and readjusted 5 ATDC
new ground to the temp sensor on the thermostat..NO change
On first tank of gas with Seafoam added, have not seen any change yet.
My bently manual went missing so, in the next week i will order the manual on CD (found on Ebay for 20$) Any help would be great...
-Erin R
lexluthier72@yahoo.com

p.s.-This is probably in the wrong forum, please move accordingly.
 

Douglas

New member
Hi Everybody. I have a 1986 Westy and for the last 1 1/2 years I have had the bucking problem--minor at first but lately--with wx getting warmer--it has become serious. My mechanic and I have tried various things--I even printed out pages and pages of this message board hoping that my mechanis would find the answer--no avail. But after 2 days of his own diagnostic he found the problem--in the computer-- and replaced it--everything works fine now---but what I wanted to share is the way he found the problem--He put a bag of ice on top of the computer and as long as the bag was there everything was OK but the moment he took it off and the regulators in side were allowed to heat up the problem came back. So there you go another high tech diagnostic approach.
 

brkhnu

New member
I've an '87 2.1L w/at on which I rebuilt the engine this past Winter. While at it I also replaced both mass air flow meter and O2 sensor. We went out west putting on about 10,000 miles and all worked well. Upon our return while using it locally I began to experience an unusual problem. Warm or cold when negotiating a left hand turn the engine skips and misses while the throttle is off idle.It happens sometimes and will then go for weeks with out any problems. Again this only happens during left hand turns. HELP!!!
 

Capt. Mike

Moderator
Chances are your problem is not FI, but a loss of contact or ground while under the stress of the corner. It could even be ignition/distributor wiring. Check all your wiring, including such items as the fuel pump. Since all engine management electrical current is fed off the starter, is that set of wiring & connections all the way up to the ignitionswitch good -- they can flex with engine movement. Presume you have checked your engine mounts & ground stap. Be sure you are not running into a fuel water/contamination or loss of pick-up problem. These subjects all have their own topics on the site.
 

brkhnu

New member
Thanks for so prompt of a response. Unfortunately I had company from up north and until today have not returned to the site. Your reference to pick-up problems. Is that fuel being picked up in the tank or ignition distributor pick-up? I have replaced all of the engine mounts (on the rear cross member)and had not noticed a seperate ground strap. After having previously had a problem with the starter solinoid not getting enough current (I installed a seperate Ford solinoid to power the VW solinoid). A friend (who had a repair shop) informed me that the only time he had experienced that solinoid problem was when the engine was not properly grounded. Perhaps I should install a grounding cable from the engine to the body/battery.
 

Capt. Mike

Moderator
Definately supposed to have one -- look at transmission removal section of the Bentley -- there's a picture. That would not be an FI problem for this forum.
 

Capt. Mike

Moderator
Transferred to consolidate same topic.

vw-traveller Super Member Posted February 28, 2005 06:37 AM

Everytime I head up to to Lake Tahoe in the winter to get some winter camping and skiing in, my 1979 CA westy tends to lose a lot of power, I'm not sure if it's realted to the cold (around freezing) or to the alltitude (6200-7000 feet).

The symptoms are wierd, when i'm on the freeway, at higher & medium speeds (from 35mph to 65mph) it buckels constantly (like when you have a bad fuel pump or clogged fuel filter). When i'm in town, i need to rev up the engine, before i can get going in first gear, otherwse it will stall. And even when i rev it up in neutral, it lags a few seconds between the time i hit the accelerator and when it revs up, and even then it sounds like it only hits low rmps. As soon as I come out of the sierras though I'm cruising along just fine wih lots of power to spare. Oh yeah and btw, my engine oil temp is about 160-180 fahrenheit up here

I've read before that you can expect about 10% power loss every 1000 meters. Which would leave me with about 57hp from the original 70hp. It feels like i end up with a lot less power than that.

I'm sure everything FI related is running fine, since I just passed the rigourous new Californian Smog test quite well.

So finally my question: Is there some way I can adjust something to compensate for alltitude, I'be heard increasing the advance in the timing forum, and when I still had my 1976 dual carb bus in germany my mechanic would let the engine run more "fatty". But that was before I worked on my car and I dunno what that meant.

Type 2 T2b driver
 

Capt. Mike

Moderator
The multiple symptoms indicate this is a FI problem, not likely fuel delivery to the FI or distributor/ignition harness (limit of the FUEL/Ignition forum) .

First, the fact that it passed an emissions control test means little -- that is a very narrow test of just a couple of functions at a pre-determined rev & (no) load state. What you described are classic of multiple problems long before you get to any sort of altitude compensation. Go back and do the full FI check-out per the Bentley, Section 10.4-10.8. Testing specs of the AFC are posted on this site in the Tech Drawings link. I'd suggest you do so in sequence, too. One bad section can throw off all the others.

One side thing to do before you start the testing is to check your fuel octane. See the topic posted on fuels, octanes & additives, but there are often huge differences between fuel octanes in the mountains, not to the Westy's liking.

The FI system does a remarkable job of adjusting for altitude for smooth running but cannot compensate completely for the lower O² content of the air so power loss is enevitable. It is magnified by your other FI problems. Adjustment is not wise with FI. If you adjust ignition timing or attempt other adjustments, the entire FI system will try to compensate, thus introducing one error to counter the other. The results are almost always bad --any attempt to richen the mixture for the power in the higher altitudes will cause the FI to try to lean it down. Too lean can ruin an engine in short order.
 

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