Good Morning,

I have a 1985 HO L69 305 Camaro, unfortunately I am dealing with a few issues here and I would certainly like to know your opinions.

Recently, I had rebuild my E4ME Quadrajet due to the car running rather lean. On my dwell scale, I was not able to adjust my mixture screws nor idle air bleed to obtain 30 on the dwell. I maintained atleast 5-10 on the scale.

After I rebuilt the carb, I also replaced the TPS. My current MCS travel is approximately 1/8 and TPS at idle is 0.4V. MCS also reads 23 Ohms. The dwell was then set to 30, and it can be easily changed by the idle air bleed. Idle air bleed as of now is somewhere within 2.5 & 4 turns out. Mixture screws are 3 turns out. Since this, I ran the engine and it was flawless for 2 days. Idle was as steady as I have ever seen it and throttle response was perfect. Now, still at around 25-35 on the dwell, it idles like crap wandering & shakes from {730-780} Rpms but power from 750 to 5000 is perfect. I have went after every vacuum hose for leaks as well as the intake manifold. The only leak that I have and have had FOREVER is the airhorn due to being warped. Mind you car ran great in the past with a slight leak from the airhorn.

As of now, I am wondering whether something might have broke in the carb or if a sensor is not functionating correctly. I have checked CTS and this checks out fine. I also disconnected the MCS and the car steady idles but of-course has a lack of power. I plan on checking next 02, MAP, BAR & Knock Sensor, Canister and the Egr valve. I had also thought about trying to play with the initial base timing. Stock from factory is 6 on my L69, and I am at 8 now.

If anybody could add to this, I would certainly appreciate your thoughts or if you have dealt with a similar issue?

 

I'm having a similar issue on mine--could be the same issue. I've been able to identify it and it turns out that my fuel is getting too hot on its way to the carb. What happens, especially with 10% Ethanol fuel, is that the fuel starts to boil in the lines going to the carb. When this starts to happen it'll create variations in fuel pressure that the carb can't effectively deal with. What I'm running into is that any carb adjustment I make is only temporary. As soon as conditions change, the carb is again out of tune. The addition of a fuel pressure regulator that returned unused fuel to the thank helped a little, but in the grand scheme of things it is ineffective.

My solution to this will be to install a heat shield between the exhaust manifold on the passenger side, and the fuel lines located mere inches away. I think this will give me a more consistent fuel supply.

FYI, there is no adjustable idle air bleed on the Quadrajet. If you're turning the screw that is recessed under a plug in the front of the carb, you're actually adjusting the APT (Adjustable Part Throttle). This setting moves the primary metering rods in and out of the primary jets to control flow. When vacuum is high, the rods dart down into the jets creating a restriction. When vacuum is low, the pop out of the jets to provide fuel. Best not to mess with that setting.

In a Quadrajet, the idle air bleeds are fixed. They are tiny brass pipes that are pressed into the main body of the carb. You can extract them and change them out (or drill them larger), but that is the extent of the idle air bleed adjustment.