As of last writing the Wagovan was doing some... weird stuff. I laid out a long list of possibilities and you guys offering some additional opinions. I think I figured out what the problem is....
Ok so... despite my better judgement, before heading home from work I went ahead and adjusted the mix to be a half a turn more rich, figuring if there was a mix problem, that might solve it. The drive home was uneventful, but the idle was still too damn high.
Home, I popped the hood and started looking things over. Despite having recently been adjusted, I figured it couldn’t hurt checking the throttle cable. Turns out it was actually way too tight. I added about a quarter inch of slack to it and suddenly was actually idling a little low! Success! I upped it a touch via the idle adjustment screw, and called it a win.
So what happened?
I made a rookie mistake. I adjusted the everything with the choke partially closed, not fully open. With the car fully warmed up, readjusting got us back where it is supposed to be. That is my best guess anyway.
Ok so... winning? Not quite...
I’d like to say that was an end of it, but I also mentioned a stumbling issue. I decided it must have been a fluke...
It was not.
Our local ORV park is about a 30 minute highway drive away from my house. We got the Xterra, Suzuki, Renegade, and Wagovan together on a convoy and headed that way.
The Wagovan was running great right up until we hit a tricky highway exchange.
Then it died.
On the highway.
The problem is preceded by a sudden lack of acceleration, followed by some backfiring (intake and otherwise), and then complete death. Luckily it restarts without much effort, but that is cold comfort when you’re trying to not die.
I pulled off, but by this time it was back running and seemed to be doing ok. I tried adjusting the mix a bit, and then headed out again.
I made it to the first rally point without a problem, but I was taking it kinda easy. I checked fluids, topped off the oil, but otherwise left it and decided to try for the park.
I did not make it far.
Right after getting onto the highway I started stumbling again and knew I was in deep shit. I pulled off again and tried leaning out the mix, as I’ve been only making it more rich. While that did smooth out the idle, I wasn’t confidant it was going to solve the problem. A quick run down a side street confirmed that it had not.
Against my better judgement, I decided to take surface streets to the ORV park, as the problem seems to be isolated to the highway.
On the way in the problem persisted, but only occasionally.... and then it hit me...
Can you guess what I think the problem is?
While helping another 3rd gen Wagovan owner diagnose some problems with her fuel system (yes, I apparently already doing that) I noticed that while my Civic has an inline fuel filter in the engine bay, the manual shows one near the tank.
After seeing this I made a preliminary check and couldn’t find one. I then foolishly assumed the PO bypassed it long ago.
Can you see where this is going?
So yeah, on the way to the ORV park I developed a new hypothesis: Fuel flow is restricted. The OEM fuel filter is still hiding in the system somewhere, having never been changed, or at least not recently. A dirty old filter, or the dual filter setup, was causing not enough fuel to be delivered under load. This wasn’t noticeable under most conditions because the carburetor bowl has to drain before the problem becomes apparent. So only under sustained high throttle, like going up a hill or getting on the highway quickly, the bowl empties out, the car starts running lean, and then we have a bad time.
Against all odds, I made it to the ORV park. Recalling the fuel system diagram I checked for a filter again and...
Boom. Little bugger looks OLD too.
After some debate I decided to leave the new, in bay, filter where it is and delete the OEM filter. I have some fittings on order so... we’ll see.
In the meantime I apparently picked up something at the ORV park and have a flat tire now. Boo...