January 25, 20251 yr My 85 gl with the dcz carburetor idles like crap and I honestly can't figure it out. It'll still idle sometimes with the idle mix screw bottomed out etc and I'm honestly not experienced enough to figure it out
January 25, 20251 yr Probably lots of old vacuum hoses and even a small leak can make your idle rough. "To detect vacuum leaks in a carb car, the most common method is to use a carb cleaner or a similar spray around suspected leak areas while the engine is running; if the engine RPM changes noticeably when the spray is applied, it indicates a vacuum leak at that point."
January 25, 20251 yr Author 3 minutes ago, kayakertom said: Probably lots of old vacuum hoses and even a small leak can make your idle rough. "To detect vacuum leaks in a carb car, the most common method is to use a carb cleaner or a similar spray around suspected leak areas while the engine is running; if the engine RPM changes noticeably when the spray is applied, it indicates a vacuum leak at that point." I'll do that because I'm sure it's part of it, but could that cause it to run even with the idle mix screw tightened down all the way?
January 25, 20251 yr 3 hours ago, Nunyabis12 said: I'll do that because I'm sure it's part of it, but could that cause it to run even with the idle mix screw tightened down all the way? I would think so. Find the air leaks first then back that idle screw out appropriately. Good luck
January 25, 20251 yr Yes. When the idle mix screw is turned in, you richen the mixture. With vacuum leaks it leans out the mixture.
January 25, 20251 yr Author 4 hours ago, 88SubGL said: Yes. When the idle mix screw is turned in, you richen the mixture. With vacuum leaks it leans out the mixture. I thought a tightened idle screw meant leaner and loosening it meant richer?
January 26, 20251 yr Author On 1/25/2025 at 8:18 AM, 88SubGL said: Yes. When the idle mix screw is turned in, you richen the mixture. With vacuum leaks it leans out the mixture. Okay so, I've been overthinking it a little, the throttle is getting physically stuck open a little. The spring isn't returning the throttle all the way closed
January 26, 20251 yr Author 2 minutes ago, Nunyabis12 said: Okay so, I've been overthinking it a little, the throttle is getting physically stuck open a little. The spring isn't returning the throttle all the way closed Other than that, I finally gotten it to idle evenly at about 800
January 26, 20251 yr Author Just now, Nunyabis12 said: Other than that, I finally gotten it to idle evenly at about 800 Now the question is how do I get it to stop getting stuck open
January 27, 20251 yr It’s a good possibility that the throttle shaft has play in it, which is causing the throttle to hang open. It’s a 40 year old carburetor and no doubt worn. You can try hosing down the carburetor, especially around the throttle shaft, with carburetor cleaner. It might help it.
January 28, 20251 yr If there’s play in the throttle shaft you can usually find this by physically wiggling the shaft with your finger or gently levering against it with a screw driver. Any lateral movement tells you there’s play in the shaft. Otherwise I could be some grit, or a burr on the shaft, butterfly or a frey in the cable that sits in the throttle linkage round piece (clear as mud I know, I can’t think of a name for it). Or there could be a missing/broken/stretched spring that’s not applying its full pressure on the throttle shaft to properly close it. At least you have a lead at this point in time! Cheers Bennie
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