daverino Posted August 13, 2011 Report Share Posted August 13, 2011 Hey guys. So the other night I was cruising and out of no where, the engine started idling crazy high on its own (probably around 3500-4000). I played with the throttle cable and nothing looks to be stuck. When I shut the car off, it kept chugging, rocking back and forth and back firing. It would barely turn over for like 15 min until I finally went in there and manually shut the carb down. Has anyone had this happen? If so what was the diagnostic? Thanks guys! Quote Link to comment
datzenmike Posted August 13, 2011 Report Share Posted August 13, 2011 Not enough info> Do you have the stock carb? 1/ Auto choke failure. High idle is the fast idle caused by choke being slightly on. The over rich mixture will carbon the plugs up and lead to run on as you have described. May seem higher but it's really 1,600 to 2,300. Take air filter top off and look at the choke plate with engine warm. The choke butterfly should be full open and vertical. 2/ The secondary has stuck slightly open and won't close. Very high idle. L20Bs tend to run hotter and will run on. Because of this an idle cut solenoid was installed to cut fuel off with the key. 3/ Float is stuck or inlet needle stuck and carb over filling and leaking into primary. Will run rich, difficult to shut off and will run on. No high idle though. Quote Link to comment
daverino Posted August 13, 2011 Author Report Share Posted August 13, 2011 Thx Datzenmike. So yes stock carb on a 1976 620 with a L20B. Before this happened, I have had trouble getting the car started when the engine hasn't run in a couple hours or more. I have to really pump the gas before the engine starts and then I have to keep a little weight on the pedal before it can run on its own. Usually takes 2-3 minutes and then it's fine. After that, it runs fine on it's own but has always idled a little high. Now it starts right away and goes straight into hyper idle! I just started it again and it gradually idles higher as the engine gets warmer. Attached are some photos I took of the carb like you mentioned after the engine ran for a bit. Im not sure if this helps but I thought I'd throw them in there :) Quote Link to comment
ggzilla Posted August 13, 2011 Report Share Posted August 13, 2011 A large air leak will cause both symptoms: very high idle, plus "dieseling" where it keep chugging along after the ignition is turned off. By the way, just dump the clutch to kill the engine. Take the air cleaner off and inspect the linkage, as your throttle may be sticking open, dashpot may be loose or some other visible problem. If none are spotted, start looking for an air leak (vacuum leak). Quote Link to comment
daverino Posted August 13, 2011 Author Report Share Posted August 13, 2011 So I kind of took every ones advice and took out the air filter compartment so I could really see what was going on with the carb and the hoses. I decided to remove and replace all the old hoses and it fixed the problem. One of them must have been leaking. Thanks for the advice guys!! I really appreciate it!! Quote Link to comment
ggzilla Posted August 14, 2011 Report Share Posted August 14, 2011 Air leak is the #1 carburetor problem. Often caused by cracked/split hoses. Glad to hear it is fixed! Quote Link to comment
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