Keeping it short, I rebuilt this carburetor about two years ago, since then I’ve put about 20k on it. Past couple of days I’ve noticed a rough idle problem that’s progressively gotten worse. At first I thought the idle screw backed out again (did that once before). I checked the idle speed (no tach installed yet) with my analyzer and it was set right where I left it at 720ish rpm. Thought maybe a little low, so I cranked it up to 800 and drove to work this morning. That didn’t work, on the way home it died several times. So, I started putting in neutral at all stops, then shift into drive and didn’t have any problems the rest of the way home. Here’s what I found when I got home, idles fine while in park or neutral, as soon as shift it into drive it spews gas down the throat every time, when I shift it back to park or neutral the spewing stops and idle normally. This is only at a standstill, stopped. At normal operating speeds I have no issues that I know of. I think it’s coming out of the pump jet but not 100% sure that’s what it’s called. I was also thinking maybe some trash clogged a passageway but now I’m leaning toward a vacuum issue? Anyway, any recommendations at this point are appreciated. I’ve posted a couple videos so you can see what's happening (apologies for the shaky cam!) / (200 inline six, automatic)
I believe I figured it out this evening, I pulled the idle mixture screw out all the way, it appeared to be clean but I wiped it anyway. I re-installed it and it runs like a champ. I think I’ll get another fuel filter, a clear one so I can see what’s going through and monitor things going forward.
No worries, I was extremely motived after lasts nights commute. Drive, neutral, drive, neutral wash rinse repeat for 45 minutes solid. I was fully expecting a carbectomy and dissection last night, I started with the simplest checks and found it fairly quickly. Really thought it was going to be more difficult because there is no mechanical linkage between the carb and transmission. The only time it would present itself is when the car was shifted into drive, logically that linked the two. The only thing that really changed was the load while in drive, I believe the load caused the vacuum pressure to become so low it would not atomize the fuel within the idle circuit. Once I pulled out the mixture screw out, I think it cleared the passageway and everything resumed to normal. May still have a problem but I’ll know for sure over the next few days. At least at this point I know for sure the problem is in the idle circuit, if it happens again I’ll blow it out with some air and see if I can clear it. Who knows, there may still be some type of blockage.
