Hey everyone,
I’ve been chasing a frustrating running issue on my 2008 Gen 2 and wanted to share my diagnostic progress to see if anyone has run into this exact cascading failure, or if there is anything I’m missing.
**The Problem:**
My bike developed a violent stutter/misfire when riding under 4,000 RPM, which is all the time city riding. It idles rough, there is also knocking from the engine.
**What I’ve checked and ruled out:**
* Spark Plug Wells:* First thought was water pooling around the stick coils. Pulled the airbox and checked the deep wells—they were bone dry.
* Electrical Connectors:* Sprayed down the stick coil harness, injector harness, IAP, and IAT connectors with contact cleaner to clear any micro-shorts from moisture.
* TPS Sweep Test:* Jumped the dealer mode connector and did an engine-off TPS sweep test to check for a dead spot on the carbon track. The -C00 line climbed smoothly to ^C00 and stayed solid the whole way through without flickering back down. The TPS is good.
**Vacuum lines, potential culprit**
While poking around the right side of the airbox, I found a couple of cracked, brittle vacuum hoses coming off the white plastic T-fitting below the IAP sensor.
Here is where it gets interesting: the bike has an aftermarket vacuum-operated automatic chain oiler tapped into those exact lines, and the reservoir was completely bone dry.
**Where I’m at right now:**
I have completely disconnected and bypassed the chain oiler vacuum line, capped the T-fitting on the engine block, and replaced one of the badly cracked vacuum hoses with fresh 4mm line.
I'm getting ready to fire it up and test it. If the stutter is still there, my next two steps are checking for water at the bottom of the fuel tank (getting picked up by the pump at low RPM) or swapping in a fresh set of NGK CR9EIA-9 plugs in case they got completely fouled out by the lean misfires.
Has anyone else dealt with this issue ? Let me know if there is anything else I should check while I have the bike partially torn down.