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No Power in Reverse at Elevation
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4Gears4Tires
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PostPosted: Mon Aug 02, 2021 3:58 pm    Post subject: Re: No Power in Reverse at Elevation Reply with quote

Does it go away by shutting the van off and then turning it back on again?

Does it go away if you disconnect your o2 sensor? And your idle control valve?
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blackglasspirate
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PostPosted: Tue Aug 03, 2021 7:34 am    Post subject: Re: No Power in Reverse at Elevation Reply with quote

I am not sure about shutting the van off. I believe when this happened the first time (in reverse) I tried that and it didn't work, but I'm not 100% sure. I did not try that this past weekend. Every time it happened was, of course, a very inconvenient time so I didn't really troubleshoot much in the moment.

One of the very first time it did this I had the O2 unplugged, so I don't think that will help. That's what made me think that it was running too rich in the first place, but I could be wrong.

The ICV I cleaned out with carb cleaner right before this trip. It seemed to be working fine and every other time I have had issued with the ICV it caused stalling when in gear and idling, but I had none of that. I have spares I can swap in if needed though.

It's a difficult issue to reproduce, which makes this very hard to troubleshoot. There doesn't seem to be any correlation between the various times that it has done this, other than elevation. But I also went camping the weekend before at the same elevation and had zero issues. So it's still a big mystery, I have no idea what's going on but will keep investigating.
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4Gears4Tires
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PostPosted: Tue Aug 03, 2021 7:56 am    Post subject: Re: No Power in Reverse at Elevation Reply with quote

When putting the engine in reverse it torques different and can cause loose grounds to stop grounding well. With it coming to a stop, that is less likely, but it could also be loose grounds since then the motor isn't torqued over on load. So grounds are certainly something you can chase.

You already replaced the AFM, was the gowesty rebuild you mentioned? Can anyone confirm if the AFM is how the Digifant reads barometric pressure at first start? I think I read that somewhere. I am wondering if the elevation really is a contributing factor.

Random/hard to reproduce issues can be caused by the Digifant computer itself. If you have a spare or can get one, try that and see if anything changes.
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blackglasspirate
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PostPosted: Tue Aug 03, 2021 1:14 pm    Post subject: Re: No Power in Reverse at Elevation Reply with quote

I'll check the ground on the trans, though I'm 90% sure it's fine. I'm pretty religious about cleaning those regularly. I know the grounds in the engine bay are good. It's possible the trans ground came loose or something, so I'll check.

The AFM I put it was one of my used ones I had lying around. I used it because it had never been opened up or had the adjusting screw messed with before. I opened it up and moved the board just a tad to get it on a new track, cleaned off the sensor and board with contact cleaner and installed it. Unfortunately my gowesty one started giving me issues a few months ago and I no longer have it.

Luckily, I have plenty of spare ECUs, so I can always swap and see if it makes a difference. I just haven't found a way to reproduce the problem so it's a crap shoot at this point. If I could reproduce the issue then this would be much easier.

The only other related factor I can think of is moisture. The first time it happened it wasn't raining but I was high up in the mountains and there was morning dew/humidity. This past weekend when it happened multiple times it had been raining a LOT and I had been driving through a lot of mud puddles, though it still happened the morning after the rain when stuff had dried. Probably not a factor but that's the only other thing I can think of. I heard back from GTA and they didn't offer any more insight into the issue.

So it seems like I have a couple things to check/try, but then it's just waiting to see if it happens again.
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