Howdy, y'all. Long time googler, first time writer :o)

[xsdg]

After getting lots of useful info from this forum and Ratsun, I figured it's high time I joined, asked some questions, and (hopefully) gave some answers.

To start off, here's my history so far with this truck:

I picked up a 1985 California 720 off Craigslist at the beginning of the month. 2WD, Z24, 5MT, base model, electronic carb. The previous owners didn't smog it, which I figured meant that it wouldn't pass. So I've got 30 days from the date of sale to get it to pass. Here we go!

It ran okay at speed and once it was warmed up, but it'd idle pretty poorly, and would stall at idle until warm. It was also lacking power in the low-mid RPM range, but felt fine off the line and once it got going. I'm pretty handy in an engine bay (thank goodness for the 24 Hours of LeMons), but this is my first carbureted vehicle :o)

So, first, I replaced all the plugs. The Intake side looked okay, but with large gaps; the exhaust side were some of the worst-fouled plugs I've ever seen. I then used the carb cleaner trick to find a vacuum leak at the two vacuum switches on the PS in front of the firewall. That's when I discovered that if I pulled that hose and folded it over, the truck ran a _lot_ better. I left it that way for a week, and it no longer stalled at idle, but it also ran rich basically all the time. I replaced all of the vacuum hoses, and didn't see much change (but they were pretty much all cracking, so it was only a matter of time).

I got a friend who knows carbs to take a look, and he said to rebuild the carb. He noticed some fuel leaks and whatnot. I got a kit and followed fastboatman's awesome carb rebuild tutorial. There was lots of stuff gummed up in there and thankfully, I discovered that Harbor Freight sells an ultrasonic cleaner for $85 just in the nick of time. Saved me a ton of scrubbing. Anyway, got everything cleaned up, got the carb back on the manifold, and the truck fired on the first try. Huzzah! And this time it ran fine with the vacuum switches back in the loop.

I had started off with a Chilton's manual, and during the rebuild, my eBay shop manual (for a 1986.0) showed up and I finally figured out what the different parts on the carb are supposed to do. It's awesome how everything on this truck is, like, a half-step before the technology you see on modern cars.

I used a 12V battery and verified that the anti-dieseling solenoid and the AF solenoid were working. I also tested the choke resistance (in spec) and checked that the throttle switch was working (working). At some point, I checked the light on the computer and it was solid on, even with the truck fully warmed up. At that point, I figured the O2 sensor was bad (which makes sense, given the plug fouling). I replaced the O2 sensor with a new Bosch, and also replaced the broken exhaust manifold ground strap, and now the light blinks like it's supposed to.

And that's where I am right now. The fast idle is definitely high (~2700-2900 RPM), and the normal idle is sometimes fine, and sometimes a little high. Timing is 1deg BTDC, and I have yet to figure out how to rotate the distributor :o). It's got an exhaust leak, but it looks like all the pre-cat piping is fine, thank goodness.

Anyway, I'm going to check the PCV valve today, set the idle so it's right with the engine warmed up, and take it for a smog pre-test. For now, I just want to see what the numbers are like so I can figure out what else might need attention. I've done most of the major stuff, and that seems fine. The O2 sensor is switching, which _should_ mean that the computer is controlling the AF ratio, but I have yet to check the voltage to the AF solenoid while the truck is running.

[PEZi]

Quick learner! Glad to have someone like you on board. Good luck with whatever your plans may bring, man!

[Rev_D21]

I found on my old 81 720 that my fast idle stepper would get stuck and keep it idling at 2500 all day. If I got out an physically pushed on the throttle with my fingers I could getit to idle down. This was long before I knew anythnig about cars...let alone carbs. High idle could also be a vacuum leak, just throwing that out there.