Hey there,
I'm looking for some help investigating the idle on my Renault 11, 1.7L with Weber carburetor. I have vacuum gauge to help me tune for leanest smoothest idle and AFR gauge AEM UEGO 30-4110 to tell me the reading of the mixture.
When I tune with the vacuum gauge I get nice smooth & quiet idle but the AFR shows 12-12.5, gas here is about 8% ethanol, so the mixture seems rich to me.
When I tune for AFR I screw in the mixture needle a bit to bring the idle AFR to about 14.3 but then the vacuum gauge starts bouncing around, car feels crappy and the exhaust starts making some popping sounds at idle, goes away when I rev it up.
Any ideas what can be wrong - bad timing(ignition module controls advance, there is no distributor - only finger & cap)/exhaust leak/vacuum leak/...? AFR gauge and sensor are promised to be calibration-free. I tried spraying starter fluid around to check for vacuum leaks but nothing came up changing the tone of the engine.
I had the same thing happen to me with my Weber 32/36 DGEV carb. Turns out, a piece of junk got stuck in the idle jet. Unscrew it from the side of the carb, spray some carb cleaner and compressed air through it and reinstall. Also, count the number of turns out your idle mixture screw is now, remove it and spray some cleaner through the passage. If dirt is getting into the system, it's time for a new fuel filter and a carb rebuild kit soon. If it's a 2 barrel Weber, you probably have two idle jets, one on each side for each barrel. Clean both of them. They are attached to the brass, slotted screws.
I would assume your carburetor needs replacing or overhauling if you can't find any vacuum leaks
Thanks for the advices Doc & Scotty, I will take it apart to clean and review the carb and report back.
So the problems were many:
- vacuum leak at carburetor base gasket
- idle channels blockage as Doc mentioned
- wrong idle jets as well
- heavy carbon buildup which is aggravating the bad idling even more and needing richer mixture to mask up the problem
Things got better after I refurbished my original carburetor and fixed the first 3. I will have to do an Italian Tune Up after a whole winter of few minute trips and check the valves with the boroscope camera again to see if it will need additional cleaning. Thanks for the tips I completely dismissed the carb as the problem!