brauhaus313

My C55 felt a little low on low end torque for it's manufacturer ratings, especially compared to my other M113 engined cars with substantially lower hp/tq ratings. My car doesn't throw any codes so I had to go fishing for potential issues. Checked all the usual suspects and found nothing. Long story short, I decided to buy a new dipstick tube cap for the heck of it as part of a larger order as mine felt a little too easy to pull off and had a few millimeters of play up and down before pulling off the tube. In comparison, the rubber plug end of the old cap is visibly shrunken compared to the new and the new plastic fingers hold onto the tube tighter. Installed the new cap and voila. The low end torque I thought was missing showed up. I did nothing but open my hood, install the new cap, then shut the hood and go for a drive.

On the C55 I never bothered with the dipstick tube because there's no dipstick, unlike my other M113's for which oil filters usually come with a replacement o-ring for the dipstick tube. On my car at least, it seems I had a vacuum leak because of the shrinking and looseness of the dipstick cap. Wasn't expecting a change just from changing the dipstick cap so I didn't take any fuel trim measurements before, and I don't remember what they were the last time I looked, but they weren't terrible or indicative of a massive vacuum leak. I'll be checking what my fuel trims settle to after a few days.

Perhaps the car will revert to it's old ways for whatever reason, but for today's driving the torque has returned and it's the best $6.50 I've spent on the car so far. Well worth changing out periodically and something I pretty much completely disregarded.

tlambert

Cool deal. Glad it worked out!

brauhaus313

Thank you. After a few days of driving, the car still drives as it did after changing the cap.