1977 J10 Honcho "Magnum"

[speedkills]

Helping Ty with his leaf springs was my penance for suggesting I could help Jim change his leaf springs with a spring compressor

[TyTheJeepGuy]

Well we were pretty exhausted by the time the difference in U bolt size came up, all it would have taken was a quick peek to see why:

[TyTheJeepGuy]

The night before the trail run Trent came over to help me line up my steering wheel is at it was off after the lift. I put in a new steering stabilizer and a new set of spark plugs. Spark plugs are gapped to .045 because the distributor is an HEI, I guess they can handle the bigger gaps because of the higher voltage and it makes for a better burn.

The test drive the night before was enough to convince me to go on the run, unfortunately the service engine light was on for the entire drive to Idaho Springs and the entire trail and rest of the day. I had a blast despite this, this truck is SO fun to wheel. Sure its bouncy and noisy but engaging the low range on it is just instant fun; even with a barely running engine.

I rewarded myself for tidying up the garage tonight by taking it on another test drive, this time with the air cleaner off. I had a theory that the air cleaner being metal it was interfering with the potentiometer that is the Throttle Position Sensor, which is what was throwing the code and putting me into limp mode all day. Sure enough with the cleaner off I had a fun little drive around the neighborhood with no codes being thrown. So now the hunt is on to either shield the TPS or get a different cleaner. I'm currently using an adapter to lift the cleaner up away from the TBI and throttle bracket anyway so it might be time to just find one that fits better.

Here are some awesome photos from the club, and one from tonight to show how close the Jeeps are in height now:

[Jim]

So you think the metal in the air filter assembly is causing issues with the TPS? You're certain there is no physical obstruction at play. If electrical, do you think isolating the metal of the air filter assembly from the throttle body with some electrical tape / duct tape (as a temporary test) might give good results? If fruitful, perhaps find some permanent isolation material (gasket material?).

I believe you commented about photos of the car's odometer moment - here ya go:
www.JimWilliamson.net/automobile/2021-09-12--odometer-moment-honda-333-333-3/
.

[FINOCJ]

Would have been more interesting to have an odometer photo on Devils Canyon this weekend...is the YJ running?

[FINOCJ]

TyTheJeepGuy previously posted:

[Jim]

FINOCJ previously posted:

[TyTheJeepGuy]

Maybe your whopping 15 gal will pack a bigger whallup if I told you the big ol J truck Honcho Magnum Ultra is packing a 10 gal

To answer your question, I do not think it is a clearance issue because I can fit a finger under there and move the TPS blade. Not very scientific... I think tomorrow after work I'm going to paint the underside of the air cleaner to ensure that it is not able to affect a potentiometer

[FINOCJ]

Jim previously posted:

[TyTheJeepGuy]

Actually I think its pretty appropriate for this thread since I'm definitely going to be looking at a fuel cell upgrade at least at some point in the J10s future. It might be earlier than later, since I am unsure if the current tank has the kind of connections I need to set up emissions systems

[Jim]

Not looking at a Holly pump - just their hydramat - interesting method to have all available fuel scavenged from low corners to the pump. I thought there was some competition to hydramat but I am not finding it in my bookmarks.

The larger tank, designed for FI pump mounting, is probably where I'll end up / what I should do now and get off of the fence. The only time I needed extra fuel, that I recall in 10 years, was the Maze trip. Sure, extra range on a daily basis would always be used - though not needed. Tank ($240) + Sending unit with pump ($153) + vent valves / hoses (~$70). But yes, in the end I should just do it.

The pump location is centered so it won't match my "cut in the jeep" access panel. I believe my current tank uses one strap over the center - the larger tank uses two straps - outboard. I'll want to check into modifying strap connections at the body (probably a trivial mod). A skid plate to match the larger tank then comes into the picture ($$) as I imagine I'll have ~6" of poly hanging out of the metal skid plate by the leaf springs.

Why is Johnny Cash's "One Piece at a time" coming into my ears... One of these days this 90 will become a 94.

[TyTheJeepGuy]

You guys aren't going to believe this. Once again, not very scientific because I changed two parameters at once, but its easily testable later if someone is really dying to know.

The two changes:
1. Painted the underside of the aluminum air cleaner with the same paint I used on my bumpers, its like a near-bedliner.
2. I found a little extra spacer that came with the air cleaner spacer kit I used to fit the old aftermarket cleaner to the new TBI and clear the throttle body

I took it for a test drive and no service light, and I *may* have roasted those BFGs on Wadsworth. Allegedly.

I am convinced now that the aluminum air cleaner was interfering with the TPS. I don't believe physically, but electronically by messing with the resistance measurement somehow. There is a flat area of the TBI itself that hangs out by the TPS, and the spacers and air cleaner go on that. The TPS is just barely shorter than that, so I don't think physical clearance could have possibly been an issue because I can't see how the air cleaner would reach down in there, and I was able to physically move it with my fingers.

Maybe I should post this on one of the insane amount of unanswered "GM Code 21 and 22" threads.

[Trevor?]

This sounds a lot like EMI. Maybe the throttle body assembly and air-cleaner formed a resonant circuit excited by RF from the ignition system. Injectors can be pretty noisy too. I kinda wonder if the issue would also have gone away if you had a larger or smaller air cleaner or if you clipped a couple of ferrite chokes around the TPS leads or added a coupling capacitor in parallel with the TPS.... or changed the length of the wiring between the TPS and the ECM. It's probably not the best use of time to play around with it anymore if your solution is working.

Nice catch.

[TyTheJeepGuy]

I think like you said with the injectors, the throttle body, plastic spacer and aluminum air cleaner I somehow created the perfect storm for throwing off the TPS. Luckily it has driven enough times with no hint of an issue since this change that I think its good, otherwise I would move on to more shielding / isolating options.

[TyTheJeepGuy]

Was able to take the rig out wheelin yesterday with no issues, engine felt great even at elevation and the 4x4 worked really well. Icing on the cake was no leaf springs fell off either!

https://photos.app.goo.gl/MXhpNPBGGbq6GzGy8

[TyTheJeepGuy]

The exhaust leak was bothering me. Not messing w/ 44 year old exhaust replacement sounded nice to me, so I eventually found a shop that would put in two pipes with no converters (confirmed with emissions tech I didn't need them because it never had one) and flowmaster mufflers. I love the result! Its weird hearing engine sounds behind me now instead of all around me.

https://photos.app.goo.gl/CmUhcJu2JmS5Q6xx5

[Jim]

More steps checked off - getting closer!

[FINOCJ]

Nice...keep working it a bit at a time

[TyTheJeepGuy]

Great news! I am only one step away from passing emissions. I think. The 1977 service manual states that non-California trucks like mine did not use the closed fuel tank vent system so I don't need a charcoal canister (though I already bought and "installed" one thinking I did) and that is a big relief because my tank didn't seem to have any vent lines for making it work. So I hooked up the PCV system (positive crankcase ventilation) which turned out to be as simple as taking leftover 3/8" fuel hose I had from the EFI conversion and taking it from the correct port on the TBI to a new valve pushed into the grommet on the manifold.

Despite that being super easy, I made it difficult at first by misidentifying the correct port on the TBI, and scratching my head and tearing through the garage to be able to find a converter for 1/4" hose to 3/8" from the PCV valve that still had a short length of 3/8" hose on it plugged up with a bolt from when the engine went in to be rebuilt. There might not have been anything wrong with the old valve but new ones are cheap and the service manual recommends changing them often so I put in a new one and trimmed up the 3/8" to the correct port and I think its probably the cleanest system in the engine bay right now. I had the other end of the PCV hooked up as the first thing I did on this emissions journey, its some loosely fitting hose around a fitting that I found for the aftermarket air cleaner that hooks up the oil filler cap vent to the air cleaner.

I am very happy to have the PCV system hooked up now because not only does the truck run cleaner but as I understand it there is less pressure in the crankcase now, and so maybe some of my oil leaking issues should end. The oil filler cap was previously pumping a good amount of dirty crankcase vapors into the engine bay and probably dirtying it up in addition to the eventual destination of the atmosphere. Now those crankcase vapors get sucked out of the intake manifold at idle, and with drop in vacuum pressure I think that the flow actually reverses. The crankcase vapors that get sucked into the TBI get re-exploded so I suppose its almost like the EGR system that I have yet to hook up.

[FINOCJ]

TyTheJeepGuy previously posted: