So when I'm applying moderate throttle between 2-3K rpm in 4th gear and above, I hear some sort of rattling or ticking sound that doesn't sound like it's coming from the tensioner but more so from the driver side, or even from the exhaust area. Its not noticeable under heavier throttle, anyway it got a lot worse the other day when merging onto the highway on an on ramp. I wasn't giving the car heavy throttle, just easing into it when the sound got much louder and the rpms kind of stumbled (no engine light) and I saw a quick plume of black smoke out of my tailpipes, then there wasn't another issue the next 25 miles up to college and 25 miles back. I traveled at about 70mph while being very careful to listen for anything unusual but there wasn't after that episode. The sound is still there, but it hasn't had that hiccup/smoke issue under identical merges since then (which was about 3 days ago). There's no engine light, and I did the carbon cleaning about 8k miles ago. Could this be just a piece of carbon/dirt rattling around in my engine, and finally made its way out an exhaust valve? Or is my hpfp going, or does this sound more like a tensioner issue or a bad cat? I suppose it could be a bad clutch as that is a bit noisy during idle (replaced it about 50k miles ago). Any help is appreciated, this issue is very strange and while it doesn't make the car undriveable, it has me on edge and seems to get worse in warm weather and if I have the A/C on too. The car is an 07 MCS with the 6sp manual btw, and the only real engine mod has been the WMW diverter valve.

 

This sounds somewhat similar to what I've been experiencing. Not exact, but similar.

https://www.northamericanmotoring.co...ats-wrong.html

 

When is the last time the plugs were changed? Are they correct and a quality plug? The interval on those is every 60K miles.

What grade and quality fuel are you running? 91 octane minimum, from a reputable station, none of the Sam's Club garbage.

I would hesitate to say your HPFP is failing, because black smoke is an indicator of running rich.

Does the car seem to be laggy, or short on boost? Depending on when you installed the WMW diverter valve, could this be caused by it?

Nick
Detroit Tuned