Couple idle questions

[Chihua33]

So tonight on my 82 I hot wired my fan to make sure that was working, and it does in fact work, I've been trying to diagnose a overheating problem. So I'm assuming I will have to get a new stat, because when I flushed my coolant I noticed that my stat didn't look like all of the ones I see on here where guys drill the hole??

I was letting my car idle to see if the fan would kick on, well it fired right up and idled good for a bit, but then once it just started to warm up the idle dropped almost to nothing and it was surging up say from 100-400 on the tach. I guess my question would be why would it surge like that? would this be a distributor problem?

I'm pretty confused on what is actually causing this? I'm thinking I might have to take it in somewhere for a tune up

[courtenay]

Can't comment on the idle issue, but there are a few different thermostats out there. Mine doesn't look like the ones that other folks have been drilling holes in either.

[So Cal Mark]

if indeed your idle speed is 100-400, that is WAY too slow. Your car needs to idle about 900rpm. The idle speed gets set with the air bypass screw, not the idle stop screw, nor by taking the slack out of the throttle cable

[Chihua33]

Air bypass screw? hmmm I'll have to look that one up. Thanks Mark!

[Chihua33]

Any ideas in why it would surge like that?

[Chihua33]

Courtenay, did you have problems with your stat?

[124JOE]

Any ideas in why it would surge like that?

a coolant leak internal might cause that
try some barrs stop leak

[RRoller123]

Does anyone know: How do you adjust the air bypass screw without an O2 gauge on the 2L? Also a pic of the location of the screw would be really appreciated. Thanks.

Pete

[So Cal Mark]

the air bypass screw is on the throttle body. If someone has used the idle stop screw to adjust idle speed it will surge at idle

[Chihua33]

How do you re set the stop screw?

[RRoller123]

I got the car in November and it was idling a little low and rough, like 400, so I adjusted the cable to about 800-900 but it is a little rough, misses here and there. Runs great for about 30 seconds when first cold started, then starts to miss somewhat. Plenty of power at throttle, accelerates fine, just a rough idle. Seems to hesitate a little until warmed up too. Not sure if those are common symptoms that point to something specific? New plugs properly gapped have been installed, plenty of fresh fuel, air cleaner filter is fine, plug wires are fine.

Pete

[rlux4]

The stop screw should be set so that there is a little slack in the cable. About 1/2 to 3/4" of free play in the pedal. The air bypass screw allows a little more air to pass the throttle plate and will raise the idle speed. The screw is just aft of the throttle position sensor plug. It would be a good idea to take the screw out and inspect the o-ring and spray carb cleaner in the hole, clean the screw and lube the o-ring with a lube suitable for rubber. I use pool and spa lube because it's formulated specifically for rubber.
Ron

[RRoller123]

Thanks Ron. Is there a starting point for the screw, like 2 turns as is typical in a lot of carbs? I will obviously take careful note of where it is right now when I remove it for cleaning. Is there a spring or anything to watch for that could go flying?

Pete

[rlux4]

They probably will vary according to the condition of the engine, but on my car it idles at 800-900 rpms with the screw turned about 3/8 of a turn from seated. (Not quite a 1/4 turn).
Ron

[Chihua33]

I got mine to idle at about that when in drive. But in park it goes up to 1200ish is that okay? I took it for a ride and it ran real good! Temp stayed at 190 but when I got home let it idle and it kept climbing with no fan kicking in. I hit wired my fan and it does work. All rad hoses are hot. So does this mean bad stat?