Guest Posted June 5, 2001 Share Posted June 5, 2001 Well, I actually rebuilt my original Q-Jet and put her back on. She really runs pretty good since this is the first time I have ever dove into such an undertaking. My problem is that when I am driving around 30 m.p.h. and in 3rd gear (just cruisin') when I give her some gas, the engine hesitates before the RPMs increase. If I try to kick her in at that speed the engine almost dies. I am guessing it has something to do with the accelerator pump??? I put in a new one when I rebuilt, so what else could it be? I did some adjustments with the idle screws, but when I try to back them out to find the rough idle, it never happens. It does when I screw them in, but not out. Any suggestions? Link to comment Share on other sites More sharing options...
Guest Posted June 6, 2001 Share Posted June 6, 2001 What size motor are you putting this Q-jet on? When adjusting idle screw always screw them in till you get a rough idle then back out about a turn or turn and a half. Thats the way it should be. Also,is the motor doing this on the front barrels or does it cough when the rear barrels are trying to open? When you put in the new accelerator pump did it have a spring deal under the rubber or not. The good ones will have a round spring-like thing under the rubber skirt to keep it from turning inside out. If you can answer a couple of these questions it would help narrow things down. Link to comment Share on other sites More sharing options...
Guest Posted June 6, 2001 Share Posted June 6, 2001 It's on a stock 350 and it only does it with the primary barrels. When I am driving along the highway and kick her down into passing gear, she runs beautifully. It is only at low RPM and in high gear such as cruisin' through the 'burbs. I did turn in the idle screws until the rough idle and backed them out the one and a half turns. I'm not sure of the accelerator pump "spring deal" but I did work the rubber seal prior to putting it in to ensure it wasn't cracked or hard. I don't think it had one, though. ------------------ Adam She ain't quick off the line, but she sho' cruises fine. Link to comment Share on other sites More sharing options...
iceman Posted June 8, 2001 Share Posted June 8, 2001 I don't believe that adjusting the idle screws will help the hesitation. They only control the idle air/fuel mixture. I had this problem on a Holley and increased the jet size to correct it. I believe that Q-Jets us metering rods although I haven't had one apart. Try adjusting the metering rods to richen it up. Be sure to drive it for a while after making the first adjustment, not just around the block. After driving, let the engine cool and read the plugs. If the plugs are OK now, keep going on the accelerator pump. Most of all, be patient and record all of your adjustments. It is very easy to get lost if you make too many adjustments and don't keep track of them. It realistically could take quite a while to get the car running the way you want it to. Link to comment Share on other sites More sharing options...
Guest Posted June 8, 2001 Share Posted June 8, 2001 She also is hard to start and runs like crap until warmed up. I haven't had a chance to check the choke yet to ensure it is adjusted right. I figured since the choke wasn't changed from swapping out carbs, that it would be alright. I'll let you know on that, but she still has problems with acceleration even after getting warm. ------------------ Adam She ain't quick off the line, but she sho' cruises fine. Link to comment Share on other sites More sharing options...
Guest Posted June 9, 2001 Share Posted June 9, 2001 Definitly check the choke vacuum pull off. Push them in and plug the hole and see if it holds,if it doesnt,replace it. And also check the choke itself.Not running well when its cold sounds like the choke may not be controling the front butterfly correctly. As for the stumble when its warm at low rpm, You may have to pull the top off and check the power piston.If the spring under it is too light it will not overcome the vacuum to force the metering rods up to richen the mixture and cause a lean spot.Also make sure the piston moves freely up and down. Check the accelerator pump when you pull the top. Make sure its not a cheap one that will turn inside out. Make sure that your vacuum advance is good and make sure that it is hooked to the right vacuum source at the driver side front of the carb. Slow timing advance could cause driving problems too. Well Ive rambled long enough and thats all I can think of right now. Hope you track it down. Link to comment Share on other sites More sharing options...
Guest Posted June 9, 2001 Share Posted June 9, 2001 Well, I sprayed the choke linkage with some Liquid Wrench and that did the trick; she starts up great. I also checked the accelerator pump by pushing down from the top and it stuck a little and the spring is weak compared to the new one. I sprayed that too and it works much better, but the spring is still weak. Will this cause the hesitation? It doesn't seem to do it now, but I don't want a quick fix. If this is the problem then I need to know if I can just buy the accelerator spring. Something I need to ask my parts guy. Thanks for the help and if it starts doing it again, I will have to take it apart again. ------------------ Adam She ain't quick off the line, but she sho' cruises fine. Link to comment Share on other sites More sharing options...
Guest Posted June 10, 2001 Share Posted June 10, 2001 The spring I am talking about is under the piston that the main metering rods( the tiny brass ones) are attached to. The power piston (or power valve)is made of brass and slides in the aluminum well of the carb and sometimes gets in a bind and doesnt slide smooth.Unless you have a vacuum pump and guage to set the spring,I would first just check to see if it is moving up and down smoothly and completely.Glad it starts better for you now.Let me know if you have any questions. Link to comment Share on other sites More sharing options...
Guest Posted June 22, 2001 Share Posted June 22, 2001 Check your timing. If it is retarded you could also have these problems. ------------------ George Lines Link to comment Share on other sites More sharing options...
Recommended Posts