Crappy fresh idle

[Ol'Scratch]

Hello Folks!!...
While I'm busy saving to get my "diffy" rebuilt ( I've just gone through ALL u-joints and rear wheel bearings).. I have an issue with my cold idle. When I first initiate a start (after gently pressing the accelerator to the floor and letting up). She runs real rough. As she warms she smooths out. What could be making her run rough? A vacuum leak??..:confused She has new plugs and wires...

Thanks in advance
Fred from Columbia City, Or

 

[Yoda]

Fred,

I would start with the simple items first

Clean the butterfly valves in the carb, paying special attention to the front choke butterfly valve, then move to the linkage's. Also see if the idle corrects itself with the air cleaner off (check filter and bypass) also check to see if the valves in the fresh air intake are working properly (vacuum operated).

If all these items are working correctly and the rough idle persists, check the choke on the side of the carb. If it is the original, it will be riveted, you can adjust it, but I urge you to be VERY CAREFUL when trying to move the settings. I used a small pipe wrench, YES a small pipe wrench to move mine, as it probably hasn't moved since February of 1982 (did the same proceedure to 81Mako's to get his working again) to replace the coil in the choke, and if it is original, you'll need to drill out the rivets and use small bolt and nuts to assemble it back together

Good luck and let us know how it turns out ..

Bud

 

[74bigblock]

I was having the same problem after fresh plugs and wires... rough idle at start up... a little bit of run on after shut down... and hard starts all the time (she used to just bump over). I adjusted the timing and all was good.

 

[Ripp 73]

I'd have to agree with Rare81. Sounds like a problem in the carb somewhere. The choke or something. As I'm guessing that when you say she smooths out after warming up. Or your other solution could be to never let her get cold (ie. run her all the time). Hope something works out for you.

 

[Tom Bryant]

One other thing you should do every time you make a tuning change or add new tune up parts is to erase the computer memory. The ECM remembers all of the setting it has initiated in order to try to make your engine run right when it was malfunctioning. It will try to correct for that weak choke, bad plugs and ignition parts or gunky carb as well as several other things. When you replace the bad parts with new and start the car the ECM is still remembering the old settings. In time it will usually relearn but the easy way is to disconnect your battery for around 15 minutes to erase the memory. Now when you start the car it will learn all new settings based on the engine with the new parts. This shortens the learning curve drastically. Sometimes the ECM never self relearns so erasing is the only way to a smooth engine.

In the spring when we get out the '81 we'll drive it for a few days and then erase the computer. I almost always notice a smoother idle after doing this.

Tom

 

[Ol'Scratch]

Thank you Bud, Ripp76, 74BB and Tom... for your replies. Bud..if I can, I'll take a couple of pictures of the choke flaps before and after initial activation, to see if you think the setting is close. I think I can thumbnail them so that they'll fit up here. Breather "on/off" makes no difference.

I've not touched the timing 74BB...but it's worth looking into.

Tom...I never even considered the ECM. I must have overlooked that this car had a computer. I'll try that also. Hell...I'd even caper atop the castle walls and trade japes with the moon if I thought it would help...

Thanks again fellas
Fred

 

[snk1994]

Had the same problem Just recently. The Choke cam gear was getting stuck. Basicly just junk on the carb. Once I cleaned it really well it wouldnt idle very good. I unplugged the battery for about 15 minutes and started it back up. It idled at about 300RMP so had to bump up the idle. Once that was done it idled perfectly and havnt had any problems after that.