[GAM]

Hi guys,

I am about to sell my car and found a little issue. The car runs great on accelerations but sometimes (and I cannot reproduce the issue whenever I want, yet) the car jerks like mini misfires for a few seconds and then everything goes to normal. Either like mini misfires or if fuel doesn't come in right.
It happens on steady cruise at low RPM, like 2,000rpm at 70mph and sometimes on very light accelerations. No problem on regular accelerations or when pushing her. I drove 200 miles yesterday, mainly highway and couldn't reproduce the issue. I drove her back yesterday and leaving publix after letting her sit for 10min she did it for a few seconds.

The problem is that I am selling my car this week to a private guy and don't want to sell it with an issue. Have you guys experienced that?
I was thinking maybe an O2 sensor or plugs (plugs have been changed 20,000 miles ago)
Mods are JB4, DP and running map 2 and Auto Clear Off. 335 coupe with 70k miles.
Here are the codes I got but didn't throw a service light:

• 2A15 DMTL diagnosis module tank leakage, fine leakage (I do get the Fuel Cap open light someimes and goes out after a few seconds)
• 29F4 and 29F5 Cat converter
• 2C27 Lambda probe in front of catalytic converter system check
• 29E0 Fuel mixture control

[Sans]

Cruising at 2000rpm in 6th gear is more like 58mph. (I know this bc that's where I get my best mpg- 36mpg) 70mph would bring your tach closer to 3k. Your issue sounds like carbon build up on the intake valves or fouled plugs (or both). 20k miles is about the lifespan for plugs on a tuned 335.

[GAM]

Originally Posted by Sans

Cruising at 2000rpm in 6th gear is more like 58mph. (I know this bc that's where I get my best mpg- 36mpg) 70mph would bring your tach closer to 3k. Your issue sounds like carbon build up on the intake valves or fouled plugs (or both). 20k miles is about the lifespan for plugs on a tuned 335.

I don't know why our cars would be different but checked tonight 2,200rpm shows 70mph and 3,000rpm is 98mph on mine.
Got a new code tonight 2C3D Lambda probe in front of catalytic converter, control failure even tho I changed the front driver side O2 sensor 3 months ago

[Sans]

Originally Posted by JB4 PWR

I don't know why our cars would be different but checked tonight 2,200rpm shows 70mph and 3,000rpm is 98mph on mine.
Got a new code tonight 2C3D Lambda probe in front of catalytic converter, control failure even tho I changed the front driver side O2 sensor 3 months ago

I am positive that 2k is 58mph (in 6th). It's possible that 6th is so long that a small increase in rpm (200) can produce a large mph difference (22mph). I guess that's about right seeing as though 6th can go all the way to 190+mph. And the tach only goes to 7k.

To get back on topic, I can't add much insight on that code or what a faulty o2 sensor can do to performance. I would imagine if it were bad it could make you run like that. I still suspect dirty valves are at play, possibly plugs too. If it were me I would address the code first, which might mean changing an o2 sensor again, and take it from there.

Good luck!

[GAM]

Issue was a burnt O2 sensor wire that was sitting too close to a pipe

[tphss]

Originally Posted by JB4 PWR

Issue was a burnt O2 sensor wire that was sitting too close to a pipe

Wow nice find, you would be replacing a lot of parts if you didn't find that.

[GAM]

Originally Posted by tphss

Wow nice find, you would be replacing a lot of parts if you didn't find that.

That was the first thing I started with because of this code which indicates that the front left O2 sensor has an issue:
2C27 Lambda probe in front of catalytic converter system check