I do NOT know how it happened but this is the first time I didn't have to hack into the idle mixture screw caps. The 84 H/O's original carburetor was messing up and couldn't really figure out why it was acting up. I had rebuilt it years ago. May be some dirt or crud or something that made its way in there, or the throttle shaft's a bit worn, I don't know. Bad gas maybe? It's been a good while since I've driven it.

With the gas tank nearly empty, I drained what was left in the tank and put in 5 gallons of fresh, non-ethanol gas and a bottle of Heet.

I had an NOS 84 H/O carb just laying around without a job so I decided I'd put it to work. I first wanted to ensure every bench adjustment was done, so I went through all the procedures to ensure they were within specs before installation, plus pull the adjustment plugs on the rich/lean stops and TPS. Float level, check. M/C solenoid lean stop, check. Rich stop, check. Total of 4/32" paddle travel, check. I just GUESSED at a TPS idle position and bench set it to 0.41volts on the bench, but I figured that would just get me in the ballpark.

All the choke settings were set within specs, all that. Put the top back on and figured the idle mix screws would need re-adjusting, I'd take it back off and drill out the tamper plugs and deal with that later. Since it's a lettered idle air bleed, I figured the factory knew how to set these with the gauge and I didn't remove the IABV cover. Again, if it HAD to be adjusted, I'd deal with it later as well. Regardless, you have to check nearly everything on the carbs to ensure the settings are in spec. Follow the CSM procedures when messing with computer carbs. Again...in case you missed it...follow the CSM procedures.

Bolted it on, and hooked it all up. Filled the bowl up with a couple syringe shots of gasoline through the D-slots to put some gas in the bowl. Pumped it twice and it fired right up. Not great as the idle speed was off, but it was a win. It hadn't been run in quite a while, so I let it get hot and ready watching for leaks, etc, and get rid of that old gas in the supply line.

I whipped out the GM Tech 1 and went to work. It's been a minute since I've used it and did a carb tweak with it. As suspected, I needed to adjust the idle speed and the A/C kick up solenoid to underhood decal specs, and was at 0.26 v on the TPS @ 550 RPM in drive. Adjusted it to 0.42 V and that was done (0.41 V @ 550 RPM is the spec). Next I unplugged the compressor put the HVAC in NORM, and adjusted the A/C kickup solenoid to 700 RPM in drive. I then adjusted the fast idle to 750 RPM in drive.

The most amazing part is that while it COULD be tweaked a little on the dwell, I'm not going to worry too much about it. It came in bouncing between 29-33, staying mostly between 30-32 at idle speed in park. I have NEVER seen that before right out of the box. Checked out the O2 cross counts and it was around 7-8 so it seems to be ok. Kept flipping rich/lean so I'm calling it good. Might change the O2 sensor out anyway just because I got a slew of them. The technical spec for dwell is 25-35 degrees, and 30 average would be perfect, but I'll take it not having to pull the carb off again. I'm probably going to double check the Tech 1 using an analog dwell meter (my trusty old-school Sears Diagnostic Analyzer 21045).

Again, the IABV is a lettered version, which means you set it by the gauge and forget it. The roller cam E-Qjets don't use the lettered versions so you may have to tweak the IABV on those cars. But they don't have an adjustable rich stop as it's built in. I've seen people mess with these right off the bat and you probably shouldn't unless it's a last resort.




Cranks right up. Lovin' it.

But, words are worthless without pics...



Final TPS voltage in Drive:




No removal of the idle mixture screw caps or the IABV cover:






And here's what I was getting closed loop at idle. Averaging just a tad north of the 30 degrees, but within specs. Not worth taking it off to muck with idle screw caps. I'm rollin' with it.