Bucking, lurching leads to no camping and bummed out kids

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aopisa
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Bucking, lurching leads to no camping and bummed out kids

Post by aopisa » Fri Jul 13, 2012 4:48 pm

So we were all packed and ready to take off on our first real camping adventure with a bunch of other bus owners.

As soon as we left the driveway, the bucking, lurching and hesitation and eventual stalling started. This bus has been very reliable over thousands of miles of nearly daily 3 season driving. I had this problem when I first bought the bus about 3 years ago. I was never able to duplicate it in order to try to fix it. Had to have it towed and the next morning it started right up and never repeated the problem. It seems to idle fine when parked. Under load of gears 1-3 (more so at shift points) it really does not want to go, fighting all the way. If I can get it into 4th, it will cruise relatively well with minor occasional bucking. It also appears to do it when warmer out. Today it was in the low 90's.

Checked for vacuum leaks, but could not detect any.

My technical knowledge is still quite primitive. It was suggested at one point it might be the Temp ll sensor. I had a spare so I decided to change it. The old one came out easily enough, the new one did not want to go back in. I was parked outside the local parts store since I need a 13mm deep socket for the job which I did not have in my toolbox. An old acquaintance who has worked on a lot of VWs happened to stop by. We finally noticed that the engine tin had 'slid' down to block the hole for the sensor by a fraction of a mm. It was hell trying to pry that up in that tight space to get the sensor seated. We finally did. And still no improvement.

I thought next that maybe a blocked fuel filter might be the problem. That wasn't it either. And I destroyed the fuel line that leads from the tank to the filter in the process. So I had to change that which was not fun.

I certainly don't want to just swap parts, but I don't know enough how to proceed logically at this point. I don't have a lot of diagnostic tools at my disposal right now either. I spent 6 hours on things that would take most of you maybe an hour to complete and now I can barely make it out of the driveway and past the house.

The kids are disappointed as am I. I really wanted to get this bus over to the campout since I would have met a few folks to help me troubleshoot. Instead, I have emptied the cooler and cracked a beer. I smell like gasoline.

I realized a short while ago that today was Friday the 13th and I speak truthfully when I say that there was a black cat in my yard this morning staring at me through the bedroom window. :pale:

1977 2.0L FI with electronic point replacement.
1977 Westy 2.0L F.I.

Flow with whatever may happen and let your mind be free. Stay centered by accepting whatever you are doing. This is the ultimate. - Chuang Tzu

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Amskeptic
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Re: Bucking, lurching leads to no camping and bummed out kid

Post by Amskeptic » Fri Jul 13, 2012 6:40 pm

aopisa wrote:bucking, lurching and hesitation and eventual stalling started.
Start simple.

Right after vacuum leaks, bad grounds/loose wires can cause holy hell. Check especially the double relay grounds and the three grounds under the intake plenum. Clean and secure. Battery posts must be clean and secure, so does the battery and transaxle ground strap.

Connection between the AFM and its plug is important. Check to see if the little female "tines" are all accounted for and in line with each other. Sometimes, a wire terminal will get shoved backwards.

I will torment you with diagnostics when I get there. You get me a nice cup of coffee, and I will treat you to an engine that won't start by the time you get back.
Colin :alien:
BobD - 1978 Bus . . . . . . . . . . . 112,660 miles
Chloe - 1970 bus . . . . . . . . . . . 206,845 miles
Naranja - 1977 Westfalia . . . . . 112,885 miles
Pluck - 1973 Squareback . . . . . . 55,570 miles
Alexus - 1991 Lexus LS400 . . . 78,899 miles

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aopisa
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Re: Bucking, lurching leads to no camping and bummed out kid

Post by aopisa » Fri Jul 13, 2012 7:15 pm

I checked the double relay ground earlier this afternoon to no avail. I will recheck it more carefully along with your other suggestions. The last time I had this problem, I shined up the transmission ground strap as bright as a new penny. I meant to inspect it today when I was under the bus, but was overwhelmed by all the gasoline in my face and burning my armpits.

I will report back.

:salute:

I will indeed give you a nice cup of coffee, but hope we are working on a running bus by September.
1977 Westy 2.0L F.I.

Flow with whatever may happen and let your mind be free. Stay centered by accepting whatever you are doing. This is the ultimate. - Chuang Tzu

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Re: Bucking, lurching leads to no camping and bummed out kid

Post by luftvagon » Fri Jul 13, 2012 10:01 pm

I've had a similar problem, and my problem turned out to be bad ECU -- water got in, and all she wrote.
The likely hood of you having the same issue are slim, but here are couple of things to check as any of these, or combination of these could give you same symptoms.

This is what I have done to get to the conclusion my ECU is bad:

Check all grounds.
Check voltage on the AFM. (Ignition on, engine off; Check to make sure voltage is incrementing without any dead spots as you open the flap).
Check resistance on Temp Sensor II.
Check resistance on Temp Sensor I (inside AFM).
Check fuel pressure, fuel filter, and ultimately all injectors.
Check ignition switch.
Check the coil.
Check the voltage regulator.
Check the ECU (open it up, look for obvious signs of damage).

Good luck. Colin will figure it out.
1981 Volkswagen Vanagon Westfalia - air-cooled Type4 1970cc CV (hydraulic lifters, 42x36 valves, stock cam, microSquirt FI with wasted spark ignition)
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Randy in Maine
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Re: Bucking, lurching leads to no camping and bummed out kid

Post by Randy in Maine » Sat Jul 14, 2012 5:52 am

I still like a poor electrical connection at the TSII.
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aopisa
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Re: Bucking, lurching leads to no camping and bummed out kid

Post by aopisa » Sat Jul 14, 2012 7:40 am

Amskeptic wrote:
aopisa wrote:bucking, lurching and hesitation and eventual stalling started.
Start simple.

Right after vacuum leaks, bad grounds/loose wires can cause holy hell. Check especially the double relay grounds and the three grounds under the intake plenum. Clean and secure. Battery posts must be clean and secure, so does the battery and transaxle ground strap.

Connection between the AFM and its plug is important. Check to see if the little female "tines" are all accounted for and in line with each other. Sometimes, a wire terminal will get shoved backwards.

I will torment you with diagnostics when I get there. You get me a nice cup of coffee, and I will treat you to an engine that won't start by the time you get back.
Colin :alien:
-Rechecked for vacuum leaks - none detected
-Rechecked and recleaned double relay ground - looks OK
-There were only two grounds attached under the intake plenum, one single wire and one with a double wire, the third had no wire attached - cleaned and reattached.
-Battery posts are clean and secure
-Removed and cleaned transaxle ground strap - the strap still looked pretty good, but the terminal ends were a bit dirty.
- Checked AFM plug. Looked OK, but it was a bit oily

Still behaving badly. It felt a little better after an uncharacteristic hard start. I still seems to be temperature related and I think it will be worse once the day and the engine heats up. It almost seemed worse after the new Temp ll sensor was installed. It also does it more during gear changes. Sometimes when going from first to second it really cuts out to the point of almost stalling. I have to wind out the clutch and give it quite a bit of gas to 'power' through it while it protests the whole time.

Next steps? We will most likely be getting into the realm of the unknown for me, but I am willing to try.
1977 Westy 2.0L F.I.

Flow with whatever may happen and let your mind be free. Stay centered by accepting whatever you are doing. This is the ultimate. - Chuang Tzu

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aopisa
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Re: Bucking, lurching leads to no camping and bummed out kid

Post by aopisa » Sat Jul 14, 2012 7:43 am

Randy in Maine wrote:I still like a poor electrical connection at the TSII.
You may be right. It actually seemed worse after we installed the new sensor. It also is worse as everything gets warmer (see my response to Colin).

What/how do I check at this point?
1977 Westy 2.0L F.I.

Flow with whatever may happen and let your mind be free. Stay centered by accepting whatever you are doing. This is the ultimate. - Chuang Tzu

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Bleyseng
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Re: Bucking, lurching leads to no camping and bummed out kid

Post by Bleyseng » Sat Jul 14, 2012 7:58 am

Swap in some points to see if its timing related
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Randy in Maine
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Re: Bucking, lurching leads to no camping and bummed out kid

Post by Randy in Maine » Sat Jul 14, 2012 11:08 am

Try grounding the electical harness (where the TSII plugs into the engine wiring harness) to a known good ground or a wire you just attached. That will sucker punch the ECU into thinking the engine is warm and will lean out the mixture.
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aopisa
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Re: Bucking, lurching leads to no camping and bummed out kid

Post by aopisa » Sat Jul 14, 2012 11:22 am

Randy in Maine wrote:Try grounding the electical harness (where the TSII plugs into the engine wiring harness) to a known good ground or a wire you just attached. That will sucker punch the ECU into thinking the engine is warm and will lean out the mixture.
That doesn't sound too difficult, but I am not near my bus to picture how to do this. Can you please give me just a little more detail? I hate to plead such ignorance of things mechanical. It's just that I'm about 3 decades behind everyone here on the learning curve. Thanks.
1977 Westy 2.0L F.I.

Flow with whatever may happen and let your mind be free. Stay centered by accepting whatever you are doing. This is the ultimate. - Chuang Tzu

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Randy in Maine
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Re: Bucking, lurching leads to no camping and bummed out kid

Post by Randy in Maine » Sat Jul 14, 2012 2:48 pm

The TSII is a black wire with a female crimp connection that fits into an off-white plastic connector (with 2 male ends). The other female crimp connector goes into the wiring harness.

You are going to remove the wiring harness connection female end using your needle nose pliers and touch that to a known good ground and see if the bucking goes away.

If it does, you are going to clean all of connections using some sand paper until they are nice and shiny and re-insert them in the cleaned white connector.

Let us know what happens.
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Re: Bucking, lurching leads to no camping and bummed out kid

Post by SlowLane » Sat Jul 14, 2012 4:20 pm

Though I understand that you've been all over looking for vacuum leaks twice, please check your AAR albow again. Remove it from the AAR and give it a good inspection in the light of day.

The bucking and lurching is exactly the symptom that I had when I first encountered this problem. Even if you've replaced it recently and are convinced that it couldn't have gone bad that quickly, be assured that the commonly-available aftermarket elbow can give out within weeks, they're just that bad.
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Re: Bucking, lurching leads to no camping and bummed out kid

Post by DjEep » Sun Jul 15, 2012 12:26 pm

Bleyseng wrote:Swap in some points to see if its timing related
:withstupid: I've seen more than a couple faulty electronic ign units.

Can you get it to act up w/o load on it? i.e. rev it up to about 3000 rpm and have it feel kinda sputtery? If so, a simple bump of the AFM wiper in both directions will tell you if it's a too lean/rich condition. Bucking is usually a too lean symptom, unless it's a badly dribbly injector or something. On that note, make sure you don't have plugged/sticky injectors by pulling them out of the manifolds and checking the spray pattern while a helper turns it over. (fire precautions please!)
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aopisa
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Re: Bucking, lurching leads to no camping and bummed out kid

Post by aopisa » Sun Jul 15, 2012 12:46 pm

OK, when the key is turned to the ON position I can hear the double relay click, but do not hear the fuel pump turn on. I assume I should.

The rubber boot at the fuel pump electrical connection was torn and the connection itself looked pretty beat up by the elements. I cleaned the connections and still nothing. I do not know which scale to use on the multimeter, but I do get a reading at the wire with the key on and with the key off.
1977 Westy 2.0L F.I.

Flow with whatever may happen and let your mind be free. Stay centered by accepting whatever you are doing. This is the ultimate. - Chuang Tzu

luftvagon
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Re: Bucking, lurching leads to no camping and bummed out kid

Post by luftvagon » Sun Jul 15, 2012 12:49 pm

On Vanagon, the fuel pump will not come on until you move the fuel pump switch inside AFM
1981 Volkswagen Vanagon Westfalia - air-cooled Type4 1970cc CV (hydraulic lifters, 42x36 valves, stock cam, microSquirt FI with wasted spark ignition)
1993 Ford F-250 XL LWB Extended Cab 7.3L IDI

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