Been trying to figure this out for about a month now, but after the car is up to operating temps and it’s sitting still idling for a while (like at a traffic light or in a drive thru), if I haven’t touched the gas for a while and then I suddenly blip the throttle like I’m about to engage 1st gear, the car will belch this big embarrassing cloud of smoke, and it is SUPER rich unburnt exhaust. Smells like an old boat starting up, or a cold 2-cycle engine. It has a JHM 91 tune on it, their IM spacers, and the TB coolant bypass, and VAG COM is not showing any codes.
Engine-related things I’ve replaced:
- HPFP’s
- Fuel filter
- NGK Spark plugs
- Air filter
- O2 sensors (all four are brand new from Bosch)
Also, as long as I’ve owned this car (2 years), I’ve noticed that if I’m just cruising on the highway for a while and then suddenly down shift and floor it, I will clear out the local mosquito population with the cloud of black smoke behind me for a few seconds. On track, the car runs fine, no smoke.
I sorta seems like a bad fuel pressure sensor or regulator, or maybe some bad injectors, but the smoke will come out of both tailpipes equally, for what it’s worth. My best guess is it started doing the puff of black smoke after sitting for a while thing about two months ago when I ran a bottle of Seafoam through the gas tank. Sometimes I think it’s a bad injector, but the car starts/idles/runs fine, short and long term fuel trims look perfectly good in VAG COM, and no misfire codes. What should I try next? Fuel pressure regulator and/or sensor? MAF? TB? Get the injectors cleaned? It kinda worries me when I see that occasional cloud behind me, would appreciate any input.
Thanks!