old's school carb problem ??????

[chevman1961]

I'm working on a 1984 olds delta 88 with a 307 4 brl carb. The car runs fine at cold start but after warmup car starts to stumble and dye at an idle.I replaced all the vacum lines and checked carb gaskets for leaks.The car runs fine out on the road after warmup but dyes at a stop.Also how do i tell if this an open or closed loop carb? stumped

[Tony Silva]

Ok...first warm up the car. Turn the car off. Next, turn the air/fuel ratio screws all the way till they are both bottomed out then 'loosen' them 1 and a half turns. Then, adjust the curb (regular) idle screw. Adjust it so that the idle is high enough to keep the car running at say......... 1,600rpm's. Next, adjust the air/fuel ratio screws. Loosen the air/fuel ratio screws one turn at a time each, alternaterating between the 2. The engine rpm will get higher and higher. Adjust the curb idle screw down so the engine will still idle with out any gas pedal pumping. Repeat this turn by turn till there is no change in the idle rpm when you loosen the air/fuel ratio screws. Once there is no more rpm raising when you adjust the a/f screws turn them back in a half a turn and then set the regular idle to 700 rpm, or whatevet it is supposed to be set at.

[maxwedge]

Actually that may not be " it", this is a CCC system using a tps and mc solenoid in the carb, with an o2 sensor and basic ecu. The mc solenoid could be bad or the carb loaded with dirt, when it gose to closed loop and depends on these sensors that could trigger the problem, the egr could be leaking thru also.

[doug1430]

Another thing is to pull your EGR valve and make sure carbon isn't holding it partially open.

[chevman1961]

I'll check the egr and get back to you
Thanks

[chevman1961]

Is there any easy ways to check these sensors and controls

[mfre1111]

I always start with the fuel filter in the Rochester Quadrajet. It costs about a buck and is directly behind the nut that the fuel line goes into. They have a tendency to come apart, especially with the new fuel. They do make one that is not paper, if you ask for it.(It looks like a brass strainer) Then I check fuel pressure (should be 4 to 7 lbs. If that is all good, my next step is to start the engine and let it run until warm. Then remove the air filter and plug all the vacuum lines. Rev the engine and then choke it off with the choke plate. Do that a couple of times. If the engine runs differently than it did before, you have got dirt in the carburetor and it needs to be cleaned/rebuilt. That is what they taught me at GM Training. They said that everyone tries to over complicate things when it is usually not complicated. I always check the simple stuff first, like the fuel filter or the EGR, before I start tearing things apart. Good luck.