[tristessa]

Getting back on this once again.

Last time I started the car, I think I was still chasing my tail with the ignition even after setting the timing to a verified 10°BTDC. Realtime monitor in TS was showing engine RPM jumping all over the place, and the idle was rough most likely because of that. I'd originally failed to run shielded wire to/from the ignition system, stupidly hoping I could get away with it because I didn't have any shielded wire on hand larger than 23GA. This was clearly wrong. That part of the harness has been replaced with shielded 4-conductor 18GA wire. Shield is tied to the sensor ground of my NO2C Speeduino, and shielded wires are now connecting distributor points to VR1+, IGN1 to PRW-2 module, PRW-2 to coil and PRW-2 to ground though I realize that last is probably overkill but it was easier than trying to separate the old ground wire from the rest of the old wiring.

Once that was rewired, it started fairly easily, idles and runs OK and doesn't try to stall out/fall on it's face when I put the transmission into R or D. I'd like to get the idle speed up a bit from where it is without resorting to something crude like the throttle stop screw, and I can tell it needs work on the fueling because I can smell richness in the exhaust plus the realtime monitor was showing AFR in the 11-12-ish range.

Still, best it's run so far. I took a bit of a log at idle so y'all can see what it's doing, attaching it here with the current tune.

[tristessa]

Additionally, I've got parts on the way for the down-the-line distributor replacement that will let me have Speedy control the advance. I've got a complete new Chineseium Vanagon 2.1L distributor on it's way because they're cheaper than a replacement Hall sender for the OEM unit I have on the shelf. Might adapt that one, might just rob the Hall sender for what I've got on the shelf, but either way I'll need to machine a 20MM longer drive dog to make up the length difference between the VW distributor and what this engine uses. Should be able to carve it out of some 1" round stock, and I need an excuse to get more practice on the milling machine.

[LPG2CV]

There is still something wrong with MAP! Until that issue is fixed, you can't tune.

is it possible you have added the MAP sensor upside-down? You wouldnt be the first, and you wont be the last .

It should be flat side up.

[tristessa]

Rechecking things this morning to verify things are as they should be, and all seems to be correct from what I understand.

Flat side of the MAP sensor is up:


Vacuum hose to the MAP sensor is connected to the port labeled "J", which is for the MAP sensor according to the vacuum diagram for the donor vehicle this TBI unit came from:


Port J is the nipple closest to the fuel line fitting in the lower part of this photo:

(photo is of an NOS TBI unit of the same p/n as mine)

I had originally connected the MAP sensor to the large port farthest from the fuel line fitting by mistake because I was sort of standing on my head to make the connections at the time. That port is for the charcoal canister, and is currently capped. The middle port has a hose to the distributor for vacuum advance, but it's currently disconnected and plugged.

There is a vacuum nipple on the intake manifold by the rear intake port (cylinders 3 & 4) for the Mercedes vacuum system, and a larger connection at that port going to the vacuum pump that runs the brake booster. There's also a disabled EGR valve physically present on the intake, and a large nipple going to the "crankcase separator" which has a tee on top that connects to the valve cover and effectively to the air cleaner, goes into a rubber boot just the other side of the TB. Just to give a rundown of anything between the TB and cylinder head that might have an effect on this MAP funkiness.

[PSIG]

Either the diagram is wrong or the ports are mislabeled. Your MAP appears to be functioning, but connected to the "ported" distributor vacuum source. Note in your logs that it is reading, except at closed throttle. This is representative of how ported vacuum works. Move it to another source that shows full-time manifold vacuum.

[tristessa]

Got it.

If there isn't an appropriate vacuum port on the TB, would it be acceptable to connect the MAP sensor hose to the intake manifold, or should I drill the TB adapter plate and add a nipple? I do have a vacuum connection on the manifold, though it only reads from the 3&4 intake port not the whole engine.

[PSIG]

Test which of the 3 ports on the throttle body provides vacuum at any throttle setting. Use that one if you don't need it for anything else. Otherwise IMO anywhere in the plenum, just drill & tap, or epoxy and stake a nipple in there.

Anywhere from the throttle body to the runners (the green area). Closer to the center or throttle body tends to be a bit more stable, but anywhere in there will work:

W115 230.4 manifold.jpg (82.39 KiB) Viewed 958 times

[tristessa]

That's a diesel intake with way more plenum than I have, but I get the gist of what you're saying. My manifold looks more or less like this, not much of a plenum, mostly a Y between the carb/TB flange and the two siamesed intake ports:


I'll check the third TB vacuum port, and if that isn't workable I'll pull the TB adapter and add a nipple there. It'll also give me a chance to clean up the adapter and make it look a bit less homebrew, right now it's just a square piece of 1/4" aluminum with some holes drilled in it. "The port that has vacuum at any throttle setting" is what I thought I had with the large "charcoal canister" port, which has a nice wide channel to the area behind the throttle plate as seen in the TB photo I posted. I'll give things another look before I go to work in the morning, before it gets hot. It's cooled off to 95° here, which is offensively hot for the Portland, Oregon area.

[tristessa]

Rather than check the vacuum ports on the TB, because they're a royal pain to access with the way the TB hangs on the manifold, I pulled the adapter. All three ports now have short lengths of vacuum tube connected to them, plugged, so I have easier access in the future if needed compared to just putting caps on the nipples. Interestingly, Rochester used a small plate bolted to the TB with the vacuum nipples in it, so if I never need any of the ports I could make a blanking plate and not have rubber vacuum caps to worry about deteriorating or falling off.

Probably a good thing I pulled the adapter off anyway. There was a burr on the backside of the plate, causing a small vacuum leak. Smoothed off the burr and made sure there weren't any others I'd missed, reshaped the visible parts of the plate to make it less homebrew-looking, drilled into the edge and added a 1/8" brass tube to have a known manifold vacuum source, cut new gaskets......and ran out of time to work on it this morning before having to clean up and go to work.

[tristessa]

It seems much happier now, both idling and driving up & down the block. It started easily and idled fairly nicely once I bumped the stepper up some. I realize there's definitely still work to be done just for the idle and possibly the injector flow rate settings, but even though it's cooled down some from earlier in the week it was still too effing hot & gross this afternoon for me to do much in the driveway. Idle dropping 3-400 RPM when I put the transmission in gear has been normal behavior for this car/engine/transmission the 12 years we've owned it......when the stupid carburetor worked correctly, at least.

Does this log look like I'm now in a place where I can start tuning from, or is there still a problem with the MAP signal? Anything else that's a big red flag to correct before trying to get things better set up?

I'm actually starting to get excited.