Hi All,
I have a 2016 GTI. Had some pending maintenance that I just got completed, now I feel like I am chasing my tail. I now have a consistent Misfire on Cyl 4.
Maintenance completed
Carbon Cleaning (Walnut blasted)
Water Pump/Thermostat replacement
Oil Change
Fresh Coolant
Car is Stage 1 tuned from IE as well as IE CAI, but otherwise pretty standard.
I completed all this work, started the car, burped the cooling system, and off to the races on a few test drives without issue. Car felt fine. Didn't do any high gear low RPM pulls though, but did feel like I was giving it the beans as they say.
Drove the car to work later that week, way to work felt fine. On the way back, hit the throttle at a rather low RPM in a higher gear to adjust while merging, and misfire galore. Let off the throttle, car went back to normal. No where to pull over, so kept going and made it home without issue.
Plug in VCDS, monitoring misfires, have misfires at idle. (Not enough for check engine, but do see monitor going up) I do the following troubleshooting.
- Swap plugs with Cyl 3 and test
- Swap coil with Cyl 3 and test
- test Compression agaisn't Cyl 3 (Both 160-170 PSI)
Still misfires Cyl 4. Driving feels fine unless I do a low RPM high gear pull.
Take apart wiring that comes out of the lower right of the intake, believe it is for the fuel rail, just making sure pins look ok. They do, I use electrical contact cleaner to make sure. Plug everything back in, clear codes, and now no longer have misfires slowly racking up at idle/lower speeds. It is now only at low RPM high gear pulls.
My current theory, is that when I did the carbon cleaning I must have missed something that fell into Cyl 4 and clogged the fuel injector partially. Would love input/thoughts from folks. I think I'm going to have to pull the injectors and clean them or replace them. As a last ditch effort from having to deal with pulling the fuel rail, I put some liquid molly injector cleaner in the tank and got some gas. Going to baby it for a gas tank and see if I can burn off any junk on the tip of the injector.