SkyWarrior

what would cause an LG4 to run better with the mcs unplugged? I have a friend with an 86 auto with the LG4 and the mcs was unplugged, the car ran very smoothly, I couldn't tell it was carbed! So I told her she should plug it in. Well I plugged it in and the car wouldn't idle after that and it died at every stop sign. Would my car run better if I unplugged by mcs?

Homer

iTrader: (1)

My car does the same thing. Here's my theory:
When you disconnect the mcs, it goes full rich. Full rich, all the time, regardless of rpm, tps sensors, oxygen sensors, whatever. The primary rods are suspended on springs which pull them out of the jets. The mcs, when energized, pulls them into the jets (which leans the mixture) for a short period of time (I think it's 10 times per second). If the mcs is disconnected, it never pulls the rods into the jets, and the rods float on top of the springs, giving you a richer mix.

My car takes a LONG time to warm up, doesn't idle too strong, and bogs at any speed under about 35mph (probably when the secondaries kick in and straighten out my fuel mix). Sound a lot like your friend's car?

You've therefore determined that the motor runs better on more fuel than less. Look under the tech articles for "tuning for performence with your computer controlled quadrajet." It contains a section near the bottom for primary enrichment, which is what I think we both need. Pep boys still has the cheapest tool I can find to adjust the rich mix stop screw, but it's now $9 instead of $4, and they have to special order it. When I get mine next week, I'll let you know if my theory was right.

SkyWarrior

her car idles fine, right at 800 or so, with no rpm searching. Thats what I found to be wierd, but as for the bog under 35 that sounds about right, her car feels like it doesn't have much power when I give it the gas, but wouldn't she be able to plug the mcs back in and have it run better? I'm interested in what you find out, let me know how it goes.