A/C and Carb.

[RottenDog]

Since I put a completely rebuilt 4350 (my mechanic did)on my 401, it performed pretty darn good (caught second gear with an auto)once my truck was warmed up. There were the occaisional hesitations,pops and sputters, but nothing significant. Last week I had a aftermarket air conditioning system added on. Since then, the frequency of my carb spasms have increased and intensified. Without the A/C turned on, I feel a slight "miss" or hestitation now while I am driving at freeway speeds. I can actually feel a decrease in the overall performance of the motor even without the A/C turned on. I know the addition of the compressor and components would steal performance, but I am concerned about these other symtoms. This is a completely rebuilt motor with all new or rebuilt acccessories.

Question 1. Could the installation of the A/C have any effect on the carb?

Question 2. Should the timing or some other electrical component be examined for possible failure or adjustment?

Ideas or reommendations?

[Joe H.]

Isn't there an a/c compensation circuit that bumps the idle up when the a/c is on? Check with your mechanic...I'm pretty sure there's some type of switch on the carb that adjusts the idle to fit the power demands of the a/c system.

[wagdriver]

If you can get your hands on a Haynes manual 50029 they have a pretty good carburator adustment procedure outlined in it. It looks pretty good. If you have the electric solenoid throttle positioner it is used to gain the extra rpm to keep everthing running smooth. Basically make all the base idle adjustment with it disconnected (on my 88GW its 500rpms). Then hook it up blip the throttle so it can extend put it in drive and block the wheels and adjust the curb idle (again on the Wag it is 600rpms). I don't know how this plays out on the 4350 but it should get you in the ball park. ;)