Hi everyone, I've noticed that after my Buick has sat overnight that if I stepped on the gas before starting the engine the next day that it felt like something was stuck before pushing through and then clear. I did this also pushing the throttle by hand before a start up and the same issue. Only the first time I push the throttle does it seem to really stick. Once I push through it the throttle is fine and it won't stick again. Today I removed the throttle cable to isolate where the issue lies and the same issue so now I now it is in the carb. Any ideas? Also, I've noticed lately that sometimes when I come to a stop sign or red light that my engine will sometimes suddenly drop in rpms. It is usually idling around 600-650 rpms. I tried adjusting the fast idle screws and have them three turns out now but the same issue. The Buick runs great on the road and this issue is only when the car is stopped. If I put the engine in park the rpms go up a little bit and the engine will be fine. Could there be gunk stuck inside? I was thinking of trying a carb cleaner on it. This is a rebuilt quadrajet that has run great in the past (the rebuild was probably around three years ago now).
the sticking feel sounds like a bad accellerator pump cup. check for the squirts of fuel. sometimes the cup sticks in the bore and messes things up, jumps off the pump. Also, sometimes the plastic end on the pump shaft starts sticking to the shaft. this causes a sticking feel that breaks free.
It almost sounds like the primary throttle plates are sticking in the bore. Were the throttle shaft bushings replaced during the rebuild? If the bushings are worn, both of your symptoms could be caused by the same thing. I would try pushing down on the accelerator pump plunger with a small screwdriver after an overnight sit, to condemn or acquit it, and then go from there.
>>I have looked down the primaries when pushing the throttle and I a few squirts of gas and then just a spray.
Most likely the accl pump cup is swollen and sticking in the bore. We went round and round with the suppliers over pump cups in the past few years for this problem. The one we sell currently is impervious to ethanol, even fine in E-85.....Cliff
>>Hi Cliff, I had two questions regarding this. One - could a sticking accl pump cup cause loss of power? Two - I assume the carb will have to be taken apart again to install the new cup?
Hi Chris. 1. With a bad accelerator pump, you can experience an initial stumble when driving, when you press the gas pedal, so it could be loss of initial power feeling. 2. Yes, you would have to take off the top of the carb to replace the pump. Hope this helps.
The accl pump is there to cover any potential lean spots cause by quick movement of the throttle where there would be a momentary delay in fuel delivery from the main system(s). It also helps get the huge secondaries on line by continuing to supply fuel (duration) till things get flowing well there. The accl pump is NOT a player for "normal" driving in the cruise range with very light/slow throttle movements, and at heavy or WOT throttle after the first initial shot of fuel is delivered......Cliff
Thank you for the information guys - my Buick is a cruiser so I'm not stomping on the gas peddle much but I do need to fix the idle dropping at stop lights so the cup will need to be replaced.
Had the exact same thing on a Q-jet I just recently rebuilt. I felt the same sticking in the pedal and also when moving throttle by hand. Took the top off and checked the accelerator pump. Pump plunger seal cup was good but the plastic piece on the rod that the seal goes around was cocking from side to side and was not tight on the shaft. Replaced with another and presto-magic problem was solved. By the way, these parts were all new about 6 months ago. So new doesn't necessarily mean good.
Did you check to see if the primary throttle plates are sticking in the bore or if the primary throttle shaft bore is good?? A bad accelerator pump cup can't cause an idle problem, only an acceleration problem. If the accelerator pump cup is indeed bad, it should also make for miserable cold starts.
I would try pushing down on the accelerator pump plunger with a small screwdriver after an overnight sit, to condemn or acquit it, and then go from there. >>I just tried pushing down the accelerator pump plunger and it stuck also. Pushed the throttle by hand and pushed through the stuck feeling until it operated freely. I should also mention that upon first start up I do have the give the carb some gas or it may die out.
Sounds like you have at least 2 problems, maybe 3. The pump is bad, so that's one. There is a cold start problem, which oddly more pump action from a bad pump seems to help, for problem #2 and an intermittent hot idle concern for problem #3. If you grab ahold of the throttle lever where the throttle cable attaches, is there a lot of up and down movement or back and forth movement? If so, a worn throttle body is the cause and will need to be repaired by installing throttle shaft bushings. The throttle body is aluminum and this is a real common problem on Quadrajets that have seen a lot of use.
>>There does not seem to be any excessive play in the throttle lever as I just checked it out. I'm sending the carb to Ken to replace the accelerator pump to see if that will help the issues.
Got the carb back from Ken and took the Buick out for a test drive yesterday - no more sticky throttle and the Buick ran great. Thank you Ken:TU:
