This is driving me nuts. When I start my car (LG4) first thing in the moring (engine cold) it runs great. Once the engine is warmed up to operating temp, it's fine too. But, if I shut it off it diesel's a tiny bit. If I restart the engine after it has been sitting hot for awhile without cooling completely, I get a really low idle (~ 400-450 RPM's) and it stumbles from about 800-1050 RPM's. Above that range it's fine, and if I "get on it" for a few seconds the idle RPM's return to a more normal range ( ~700RPM), but it still seems to miss and sputter.

The engine itself has 165k miles on it. I have recently replaced the CTS, O2 sensor,PCV valve, and carb (Holly rebuilt E4ME). The plugs all look good, the ignition is all new (HEI module, coil, cap/rotor, wires, etc.) and the timing is set about 4 degrees advanced. I haven't been able to locate any vacuum leaks, and the fuel pump was replaced about 6 weeks ago.

Could this be a fuel problem? Heat soak? My fuel lines are routed in the stock locations. The rubber pump inlet (supply) line runs about 1 1/2" from the #2 header tube (Hedman shorties), and the line to the carb is a steel braided line with AN fittings (-6).

Any ideas or suggestions?

 

Whats your choke setting like? It working good?

 

Mine used to have a problem something like that. The fuel line was just about touching the header in one spot. I cut out the hard line and put in some -6AN line with a heat wrap on it up to the carb. For the carb I just got a 1/2 inch phenolic spacer. Now after driving the car, parking it and going back to the car 5 min later it runs perfect. Before it would run like crap till some fresh fuel went through the carb I guess cooling things off. A choke wasn't a factor with mine since the carb doesn't have one

 

If its fine on cold starts, but is low idle on warm starts, it sounds as if the choke is staying on to long. Try adjusting the choke thermostat to the lean side a bit.

 

Thanks guys. I'll set it a more lean and post back with the results.

 

I set the choke leaner. No real change though. Today I drove about a 15 minute drive to an appointment I had (water temp was ~210-220 and steady); after about 1 3/4hrs I came out and restarted the car. Initially it idled at 400RPM, once I kicked the throttle it bounced back up to ~1000RPM. When I put it into gear, the idle dropped again to ~500RPM and slowly fell off to ~380-400RPM.

Next I'll try some heat wrap on the fuel lines to see if it helps any. If I added a spacer, would my stock air cleaner still clear the hood? I'm guessing it wouldn't. Any other ideas? And thanks for the help so far.


Oh, one other thing I noticed today; once the engine is hot I can smell fuel vapors with the windows down. I don't see any leaks, so could that be the fuel boiling off in the carb?

 

What is the voltage across the choke? The choke pull off is functioning as it should?

When's the last time the carb was cleaned up?

 

Stekman,

I haven't checked the voltage across the choke. The pull off seems to be working fine, and the carb itself is a brand new reman version. The idle was set to specs (700RPM in gear 1kRPM in park/neutral) when I installed it.

What should I see for VDC on the choke? I assume 12VDC when engaged and 0 when off, is that correct?