You may have more than one thing going on. I put the screw back to 2 turns out. Perform this check with a new camshaft and lifters in place and the valve covers off. The resistance in the sensor is high when cold and drops about 300 ohms for every degree Fahrenheit as the sensor warms up. Whenever you get a Varajet-equipped engine that surges or runs poorly during light-throttle or part-throttle driving, check basic engine condition, check for fault codes in the computer control system, and then check the mixture solenoid dwell at 3000 rpm in neutral. I wonder if anyone has a ballpark of where this screw should be. Clogged passages could be the problem, but you check for them in every carburetor you disassemble, right? The idle mixture screw is recessed in the throttle body and is sealed with a hardened steel plug to prevent alteration of the factory pre-set mixture setting.
If you can't get it right, the main metering circuit probably has a leak or restriction. The plunger cycles up and down approximately 10 times per second, controlling air and fuel mixtures. Remember to dab some grease on that air valve spring where the arrow is pointing. Also recall that the only thing that keeps fuel well vaporized at cruising speeds is the high venturi vacuum produced by the speed of the air rushing through the carburetor. This may sound contradictory, but try hovering the carburetor with a shop rag at curb idle to see if you can keep it running. The plug should not be removed or the screw setting disturbed.
Did the float appear blistery when you had it apart, or ooze fuel with a light squeeze? The number of vacuum and electrical connections to the carb became downright ridiculous. Because when the throttle is opened in the absence of a load, engine speed can build smoothly and quickly. The only time you should adjusted it is when the engine is cold and warming up. When the plunger is in the lean position, fuel metering is controlled by a lean mixture screw located in the float bowl. You'll get a reading drift of 5 deg. Given these expensive circumstances, there's little doubt that you'll be fixing these late model carbs whenever possible rather than just taking the simple route and bolting on a new or refurbished unit. I try to dial in as much intake vacuum as possible closed throttle with these screws.
I started at 1 turn out and went all the way to 8 turns, one full turn each test. Add StarTron to your gas. Also, when the vehicle is parked on a hill or side slope, high float level may cause fuel spillage through the vent or main system. They are: Engine Displacement - specified in cubic inches. Whenever you get a Varajet-equipped engine that surges or runs poorly during light-throttle or part-throttle driving, check basic engine condition, check for fault codes in the computer control system, and then check the mixture solenoid dwell at 3000 rpm in neutral. In my experience, a fuel line hose works very well and does not get mushy with age.
Considering their complexity and small mechanical parts, no wonder. The electric choke spring begins to heat up and expand, and as it does, it begins to open the choke until it is all the way open. Ill research around and let ya know if i can find it. All products containing or displaying the trademark brands are licensed through their respective manufacturer. Neither Karl, Rochester Products Division, or anyone else contributing to this site advocates or in any way recommends altering or disabling your emission control equipment in any way. Make sure the engine is cold for this procedure and the ignition key is off. So manifold vacuum returns to its normal 14 to 17 in-Hg rather quickly.
It tells the computer just how far the throttle is open or closed. The 4M has a manual choke. Throttle Position Sensor: yet another variable resistor. Retain the air cleaner element to diffuse the incoming air's turbulence, or a high speed miss may occur. This is called a hot soak and there are instructions for it on the can.
The spark plugs were changed and a new oxygen sensor was installed. Throttle Body If engine modifications have caused a low vacuum condition at idle, you may need additional airflow while keeping the throttle plates closed enough to prevent an overrich mixture. Take her out of the highway look at the rpm at 100k and see if it needs adjusting. The fast idle is only suppose to be engaged when the engine is warming up. But on carbs with venturi boosters, shooters are usually aimed right at the booster. The better the breathing ability - the higher the volumetric efficiency.
The carburetor you are exchanging must be the same type you are ordering. The electronics were added within two years. If any spring binds, stop immediately and back up slightly. But while where chatting about carby settings, just for a future thought. Rochester Varajet carburetor technical help guide, including helpful tips and videos.
None of the settings allowed the truck to idle. The primary rods and jets can be changed for various sizes and styles, and so can the secondary rods. I know because mine used to be like that. Due to the increased travel, the valve spring coils may hit together bind causing considerable damage. Hold the rpm at 3,000, then watch your dwell meter while turning the lean mixture screw -- you want 35 deg. Too low a level causes a lean mixture, resulting in late or hard starting, a flat spot in acceleration, or stumble. I pulled the carb apart and ran a guitar string through the idle passages so that I could visually trace them.
In the past, this meant a simple examination of the ignition system and maybe compression. I don't have a tool that will allow me to adjust this screw while the carb is on the engine which is a huge pain. Ive found that one before abba, thought i was in the right spot, though it says allot more on how the carby operates with certain parts and cars etc. When the sensor is replaced, it must be adjusted to the specified reference voltage. Back the screw out to raise the reading.