Cliff's Quadrajet Parts and Rebuild Kits
Quadrajet Problem Solving => Diagnose a Quadrajet carburetor problem => Topic started by: Jesse_E4ME on March 26, 2019, 11:38:54 PM
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Carb is an E4ME on an
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Okay, I don't know why my post got cut off like that. TLDR, my issue is an off idle stumble that appears when the car's warmed up and when the ambient temperatures are above 70-75*. On really hot days, it'll surge a little as you advance the throttle, but once you get good and going, it's fine. Cruises great, accelerates great (generally), but I'd like to cure this warm weather issue I'm having. Fuel filter has 27,000 miles on it, and I plan to change at the next opportunity. Curb idle mixture is appx. 3.5 turns out from lean, and the idle screw is almost all the way out. I haven't tried to get too liberal with the curb idle mixture, and I've heard that newer Q-Jets like more than pre-'73 units. It seems like a heat soak issue, but I'm confused as to why it's happening. The engine's running at normal temp, and while I have a nonthermal fan clutch, it's never given me any overheating issues. Car's a 1986 Chevy Caprice, 305 (E4ME). It will do the stumble in park, as I've tried to see if maybe it was the torque converter. It doesn't rule out a worn distributor issue, but it only does it at this very specific time and not all the time. @Cliff Ruggles
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Intermittent problems can be difficult to diagnose.
Is the timing advancing like it's supposed to?
Have you tried adjusting the upper idle airbleed to give it a little more or less fuel to the idle/off idle system? That can be a pretty big player in fuel delivery in the range where you are having issues as fuel flows from the transfer slots as the throttle plates uncover more of them........Cliff
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Intermittent problems can be difficult to diagnose.
Is the timing advancing like it's supposed to?
Have you tried adjusting the upper idle airbleed to give it a little more or less fuel to the idle/off idle system? That can be a pretty big player in fuel delivery in the range where you are having issues as fuel flows from the transfer slots as the throttle plates uncover more of them........Cliff
Last I checked, timing was advancing properly. I'll recheck it just to be sure, though. At 272,XXX miles, it might be time to preventatively replace the distributor with a remanned Delco-Remy. To answer the latter question, no I have not. I'm no expert when it comes to the intricacies of the Quadrajet, but I'll do my homework on this particular setting. The carb was supposed to be dialed in when it was remanufactured a few years ago, but you never know... Thanks.
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Remanufactured?
Is it the original carburetor completely/correctly rebuilt or something purchased from a parts store as a remanufactured unit?....