Acceleration Loss
 

My car runs sluggishly under 6k rpm (outside vtec). Vtec gives a significant power boost, making it feel like it’s throwing you into the seat. The car revs through the rpms fine but doesn’t accelerate. The rpms climb slowly until 6k rpm, then vtec hits and pulls hard again. I have changed the spark plugs and air filter, unplugged coils to test they’re functioning, same with injectors. They all cause the engine to stumble when unplugged. Just replaced the fuel pressure regulator today, but still same issue. Have tried the map whack and cleaning it with maf cleaner, still no solution. I did pull out the spark plugs and noticed 2-4 were dark and sooty, but no oil present. Cyl 4 was the worst.

Try a compression test.

Try a compression test. Or check the valve lash.

I just ordered a compression tester, will be checking compression as soon as it comes in.

Has it always been like this? Or is this a recent problem?

Just a note, this car doesn't have the low-end torque grunt of many others. Even your wife's SUV. :)

If the loss of acceleration is a recent problem, how old is the clutch?

Thanks!

Just recently, a problem within maybe the last month or so. It doesn’t feel how it felt when I first bought it, so while they might not be the torquiest cars, it’s definitely not running properly at the moment. As for the age of the clutch, I couldn’t tell you; it’s currently at about 165k KM (102k Miles). I’ve owned the car only for about 8 months, with no records of previous maintenance.

Try this test. Drive around in 4th at a cruising speed. Then shift quickly into 3rd (drop the clutch). Does the car instantly decelerate? Or does the car not slow down?

A slipping clutch will show the latter.

Just tested this out a few times, car seems to immediately start decelerating after dropping the clutch into 3rd from 4th gear at cruising speed.

Probably can rule out the clutch being worn out. See if you get good engine deceleration when the car has been thoroughly warmed up. Sometimes, the clutch will only slip when warm.

Good luck! :thumbup:

Tried again after the car fully warmed up and got the same result. Appreciate the help!