Stall and strained start after Carbon Cleaning

Just finished a carbon cleaning on another 2.0T (not my GTI) and had a small issue I was unable to reproduce- figured I'd ask here before investigating further-

First start after everything was reassembled- engine turned over for about 3-4 seconds before starting---> I presume that is normal, I disconnected a fuel hard line and imagine that it would take that long to get fuel to the injectors.

The car ran for about 4 seconds afterwards with no hiccups, no rough idle, sounded fine-- then sputtered and stalled. Not violently like it was fighting to stay running, it sounded almost as if I had simply turned the car off- I hadn't.

Started right back up and idled, pulsing the throttle brought no issues. Performed a few on/off cycles and couldn't replicate the issue.

No CEL, no EPC light, nothing out of the ordinary.

I thought it could be a lack of pressure in the fueling system, but any leaks would've been noticeable while I had it idling, so my only idea gets thrown out the window.

Something to worry about? Or just a fluke?

Probably a pocket of air trapped somewhere in the fuel system. If it doesn't happen again I wouldn't be too worried.

If you want to avoid long(ish) cranking times after you've had the fuel system open like that open and close the driver's side door a few times. Each time you open the door the ecu sends a prime signal to the in tank fuel pump.

Lol the first start after my carbon clean was interesting. Turned over for a good 5 seconds, started up kinda smooth aside from some rpm fluctuations. Then cyl2 had some chronic misfiring - it didn't want to light at all. Turned the car off, started it 5 minutes later and it was smooth as butter. :iono:

Haven't had a problem in the 1k miles since.

Sounds like air trapped in the line. Did you run VCDS on it? I feel that it would of recorded any issues that you had.

that is totally normal to have it act a lil funny like that at first. let it idle for 5-10min n it'll seem like somethin is wrong cuz it idles rough but after a lil while it'll be normal.

so i wouldnt worry bout it.

Totally normal. Everytime I do a carbon cleaning it takes a long time to start and hacks and coughs until it smooths out. It's a combination of lack of fuel pressure, air in the lines between the HPFP and the injectors, excess carbon and gunk that was left behind falling into the cylinders and possibly some of whatever chemical you used getting into the combusiton chamber. Either way, don't worry, it's fine!

Até you 100% sure pcv hoses are all firmly connected?

mfractal said:

Até you 100% sure pcv hoses are all firmly connected?

Click to expand...

100% everything is connected.

Update- This morning after letting the car sit for about 10 hours, took about 3 seconds of cranking to start, ran rough for a few seconds while the CEL flashed, then got a misfire on all 4 cylinders.

After that, it ran completely fine. Cleared the codes and nothing popped back up, haven't had any issues since and I put about 40 miles on it to be sure, a mix of highway and city driving.

Thinking it was a fluke.

Someone must have sprayed a whole can of cleaner into the valve chambers.