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No Power in Reverse at Elevation
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blackglasspirate
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PostPosted: Tue Jun 08, 2021 1:31 pm    Post subject: Re: No Power in Reverse at Elevation Reply with quote

When I left my spot today I put some rocks in front and behind the tires and tested simulating going up hill both ways (there's a dad joke in there). I was at 8,500ft and the engine idled for a minute or so before I gave it gas. Surprisingly there was no problem in forward or reverse.

I did remember on my way to town that I forgot one important bit of info (whoops) that may lend more weight to the running rich theory. Besides the time it did this at much higher altitudes, the one time it did it lower at 6,500 I had the O2 unplugged for testing something else and had forgotten to plug it back in. That would have meant it was running super rich, which maybe means when it happened again at higher altitude that it was running rich as well (even though the O2 was reconnected for that).

I will check the S-boot later today when I make it to camp but I was in there a few weeks ago and inspected the boot. No tears or anything, although it's possible it came loose or popped off. I'll check that later.

As for the mounts, the trans mount is definitely good. The motor mounts, maybe not. I replaced them in Chile about 2 years ago but one of them already looks like it may be going south. Aftermarket parts.....

Anyway, I'm going to check the boot later and may unplug the o2 before I get going tomorrow morning to see if I can recreate the issue.
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Wildthings
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PostPosted: Tue Jun 08, 2021 2:09 pm    Post subject: Re: No Power in Reverse at Elevation Reply with quote

The O2 sensor doesn't come into play until the engine temps get to be something like 160°. However if the TSII was for some reason reading very low, the O2 sensor would come on line much earlier
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PostPosted: Tue Jun 08, 2021 2:37 pm    Post subject: Re: No Power in Reverse at Elevation Reply with quote

Wildthings wrote:
jimf909 wrote:
blackglasspirate wrote:
Like, does reverse put more load on the engine than 1st and maybe the engine is having such a hard time at altitude that the extra little bit of load is too much?


FWIW, yes, reverse is a (slightly) taller gear than first and is harder for the motor to turn (this surprised me).

Oldbluesblog is always my first stop for Vanagon gear ratios (thanks, Kamz!).
http://oldbluesblog.com/files/VanagonTransSpecs.pdf


If his inability to move in either reverse or first was mainly caused by the gear ratios, he would be able to rev the engine to the stall speed of the torque converter, 2400-2700 rpms, but he says this is not happening.


I'm not saying this has anything to do with the OP's problem but it is a direct answer to one of the OP's questions (nested among other questions).

Thanks for making the point on the torque converter which wasn't something I knew.
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blackglasspirate
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PostPosted: Wed Jun 09, 2021 8:08 am    Post subject: Re: No Power in Reverse at Elevation Reply with quote

Wildthings wrote:
The O2 sensor doesn't come into play until the engine temps get to be something like 160°. However if the TSII was for some reason reading very low, the O2 sensor would come on line much earlier



I was under the impression based on past posts from tencentlife that the o2 and lambda feedback kicked in around 2 minutes after starting, regardless of temp. Is that not the case? I may have misunderstood.


And thanks for the info on the TC and gear ratios - that helps clarify some of my questions.

Like I said, I did make some adjustments to the AFM recently when troubleshooting hesitation (mixture screw, board placement, and spring tension...). However, I thought I adjusted more to the lean side than anything, but who knows - I'm an average backyard mechanic at best.

All my spare AFMs are not close by so I can't swap them to test, but will do more testing today.
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Wildthings
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PostPosted: Wed Jun 09, 2021 9:56 am    Post subject: Re: No Power in Reverse at Elevation Reply with quote

blackglasspirate wrote:
Wildthings wrote:
The O2 sensor doesn't come into play until the engine temps get to be something like 160°. However if the TSII was for some reason reading very low, the O2 sensor would come on line much earlier



I was under the impression based on past posts from tencentlife that the o2 and lambda feedback kicked in around 2 minutes after starting, regardless of temp. Is that not the case? I may have misunderstood.


Certainly not an expert on fuel injection, but I thought there was a temperature input that effected the O2 operation. I know the exhaust needs to get up to 600°F+/- for an unheated sensor to work, but I though it needed a reading from the TSII as well, someone will surely let me know if I am wrong.

My Vanagon Bentley is not close at hand, should pick up a second copy.
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PostPosted: Wed Jun 09, 2021 1:31 pm    Post subject: Re: No Power in Reverse at Elevation Reply with quote

The lambda system kicks in once a threshold coolant temperature is reached, but I can't recall what temp that is. Obviously, cold ambient conditions (on a cold engine) mean the time before the lambda system kicks in is longer.

I think a poster above identified the most likely source of the OP's problems - - the "S" tube between the intake plenum and the AFM. When the engine moves, a crack in the tube opens enough to cause the power loss. In another stab at the "elevation connection", it's just plain cold up there and this affects rubber, like the rubber "S" tube, so the crack opens further.
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PostPosted: Wed Jun 09, 2021 5:08 pm    Post subject: Re: No Power in Reverse at Elevation Reply with quote

Quick update on this. I checked the temp2 sensor reading cold and hot - both checked out. I also checked the S boot and it was snug with no cracks that I could find. I twisted it around a bit and held it up to the light but couldn't find any holes/cracks.

Regarding the coolant temp and lambda, when this happened last time I did let the engine warm up for about 10 minutes, maybe more. I think, but am not positive, that the coolant gauge was reading operating temp, though the oil temp was only between 120-150 ( I don't recall exactly ). It also wasn't a particularly cold morning and I think I even had shorts on at the time, so ambient temps weren't super cold.

Seems like I have more troubleshooting to do. I did try testing my only available spare AFM and it was a bust - I think something internal is wrong or it was previously adjusted way out of range. I adjusted my running one to run a little bit more lean and so far so good. I'll be heading up into the high mountains again tomorrow so we'll see how it goes. This time I know to arrange myself so I don't have to back out of a spot!
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PostPosted: Wed Jun 09, 2021 8:00 pm    Post subject: Re: No Power in Reverse at Elevation Reply with quote

Maybe a shorted or broken spark plug wire? Wiring to distributor? Plugged muffler or cat.?
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blackglasspirate
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PostPosted: Wed Jun 09, 2021 9:55 pm    Post subject: Re: No Power in Reverse at Elevation Reply with quote

The cat/o2 are new, and spark plug wires aren’t too old either (I’d have been o check my logs but I wouldn’t say older than 2 years). Wiring to to the distributor could be suspect and I’d need to test. In the past I had noticed one or two of the wires had broken insulation. I cut and respliced those wires a while ago but I haven’t really check them since. Worth a look for sure.
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PostPosted: Thu Jun 10, 2021 5:45 am    Post subject: Re: No Power in Reverse at Elevation Reply with quote

we had an air cooled van with CA hall distributor
that would stutter and lose power only on left hand turns.
only on specific degree of a left hand turn (speedXangle)
attacked so many parts of the fuel supply system..

in the end it was the wire(s) to the hall sensor inside the distributor
would flex by the force only in one direction and contact the spinny parts and short out.


or maybe there's a walnut husk in your AFM from a pack rat.
it only gets in the way of the flapper in a slight reverse motion.
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PostPosted: Tue Jun 15, 2021 6:20 pm    Post subject: Re: No Power in Reverse at Elevation Reply with quote

Just an update on this. I haven't had the issue happen again since when I posted this. The closest I've had is sputtering and almost dying in reverse when I don't let it warm up for a minute or two, but it has always moved. I've spent the last week or so between 8000-12000ft and have tested reverse first thing in the morning (after a few minutes warm up) with no problems.

The only changes I made were turning the AFM screw out 3 turns, cleaning the charcoal canister out with compressed air, and cleaning the idle stabilizer valve with carb cleaner. Not all of that was done in relation to this problem, but figured I'd include it anyway.

I'll update this if it happens again, but so far so good. Now if only tuning the AFM could give me some more low end power, because I've had to back down a few steep dirt roads over the past few days and am really hoping I can make it back up the one I took to get to tonight's camp spot. Tomorrow may be an interesting day.
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PostPosted: Wed Jun 16, 2021 7:57 am    Post subject: Re: No Power in Reverse at Elevation Reply with quote

The waterboxer has something like 8hp at idle, 22hp at 2000rpm. There is nothing you are going to do that is going to give you more low end horsepower.

Maybe lean your butt out of the window and fart. Laughing
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PostPosted: Wed Jun 16, 2021 3:59 pm    Post subject: Re: No Power in Reverse at Elevation Reply with quote

Luckily I ate beans last night and was able to get the fart boost up the hill and make it out of there. Laughing
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?Waldo?
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PostPosted: Wed Jun 16, 2021 5:14 pm    Post subject: Re: No Power in Reverse at Elevation Reply with quote

4Gears4Tires wrote:
The waterboxer has something like 8hp at idle, 22hp at 2000rpm. There is nothing you are going to do that is going to give you more low end horsepower.


Your comment applies to vehicles equipped with manual transmissions but does not apply to the automatics. When fitted with an automatic, you have access to RPMs up to the stall speed of the torque converter and the resulting higher HP of those rpms even when you are stopped and just starting to move.
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PostPosted: Wed Jun 16, 2021 5:33 pm    Post subject: Re: No Power in Reverse at Elevation Reply with quote

For low end power a Subaru kicks butt. At sea level a 2.2 is fine but about 7000 ft a 2.5L or something turboed would be the way to go. The extra power can damage the tranny if not used judiciously. At 10,000 stomping on a 2.5L isn't going to hurt anything, but at sea level regularly using all the power from a 2.5 would likely shorten tranny life.
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PostPosted: Thu Jun 17, 2021 3:01 am    Post subject: Re: No Power in Reverse at Elevation Reply with quote

Wildthings wrote:
For low end power a Subaru kicks butt. At sea level a 2.2 is fine but about 7000 ft a 2.5L or something turboed would be the way to go. The extra power can damage the tranny if not used judiciously. At 10,000 stomping on a 2.5L isn't going to hurt anything, but at sea level regularly using all the power from a 2.5 would likely shorten tranny life.


This has been anecdotally proven to be the case for manual transmissions (which are demonstrably less robust than the VW automatics), but I have seen no accounts of higher output engine conversions damaging an automatic transmission.

kourt
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PostPosted: Mon Aug 02, 2021 7:32 am    Post subject: Re: No Power in Reverse at Elevation Reply with quote

Got a little update on this.

I hadn't had the issue happen since my initial post until this weekend. I am using a different AFM from last time which had been running without issue for a few weeks and I also adjusted the timing to 40 degrees advanced right before my weekend camping trip (it was slightly higher before, maybe 43deg).

The issue happened multiple times this weekend at a range of elevations (8k-11k) but this time it happened in drive with the engine hot. As in, coming to a stop sign after a while of driving, then giving it gas to go and getting nothing.

As before there's no rev, there's no change in RPM, there's nothing. It's in Drive, was working a second ago, but I give it gas and nothing happens. What I've found works in this case is to put it in neutral, rev it, and then before the revs come all the way down, pop it into drive. I know that's probably not the best thing for the transmission, but it was the only thing that got it going again.

It's weird that the neutral trick works. Any ideas why?
I'm likely going to email GTA later today to see if they can explain any of this.
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PostPosted: Mon Aug 02, 2021 8:03 am    Post subject: Re: No Power in Reverse at Elevation Reply with quote

Mmmmm neutral slamming! I remember the days when I was a young man thinking I was a hot street racer in my convertible Chrysler LeBaron and the tailgating Audi that got peppered with bits of my transmission when it exploded.

How old is your fuel pump and filter?
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PostPosted: Mon Aug 02, 2021 8:17 am    Post subject: Re: No Power in Reverse at Elevation Reply with quote

Have you checked to see if your O2 sensor is working?
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PostPosted: Mon Aug 02, 2021 1:49 pm    Post subject: Re: No Power in Reverse at Elevation Reply with quote

The o2 was working last I tested, a few weeks ago. I replaced it in January. The fuel filter has about 25k miles on it. The pump, not so sure since I've swapped it a few times with good spares that I've had. I did do all the fuel tests (pressure, quantity/output, spray patterns, etc.) a few months ago and everything was fine.
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