Rough/Jumpy Idle, Increased exhaust noise under accel

[edhogan1224]

Okay so im not that new to cars, but I am pretty new to the Nissan/240 scene. I was driving home from work the other day, trying to merge onto the highway but the car next to me wouldn't let me. I got on it in order to get past him, taking it to redline before shifting. Not pinging off of redlimiter or anything other than driving the car hard. Didn't notice anything until i got to a stoplight, where, once i had stoppped, i noticed that i now had a very rough idle that would jump a few hundred RPM's then back down, jump a few hundred RPM's then back down, etc. Upon pulling away from the stoplight, i noticed that the exhaust was much louder under acceleration. So, i made it home without incident and i opened the hood to see what the damage was. The exhaust leak sounded as if it was coming from forward of the front of the door, but behind the engine block itself. Since my 240 sat for 10+ years before i got it, and still has its original exhaust, I'm guessing that I popped a hole in the exhaust in front of the secondary O2 sensor and the secondary O2 is getting fresh air readings from the hole and causing the car to run funky. Am I right in my assumptions, or is this a more serious issue? Ive read about the sticking fuel injectors and whatnot so i wanted a second opinion. Also, there was no overheating/oil or coolant leaks/etc. that would leave me to believe that the headgasket had blown.

[PapaSmurf2k3]

It sounds like your assumptions are correct. I would guess exhaust leak giving funky readings to O2 sensors to start with.

[GoodzKouki]

Agree with both you guys, but you say you have a 1993 240sx under your cars listed? I could be wrong, but I don't recall s13's having a rear o2. However yes a leak right were the header meets the downpipe could maybe cause the primary o2 to pick up some fresh air and trick your car into thinking it's running lean. Pull the spark plugs and see if they look fouled. Just my $0.02.

As a side note, since you have a leak you might as well put a new cat back on the car. At that point you might as well put a nice header on too. I guess at that point you should just put a turbo manifold, turbo, and turbo-back exhaust on.

[edhogan1224]

exhaust leak giving funky readings to O2 sensors

put a new cat back on the car. At that point you might as well put a nice header on too. I guess at that point you should just put a turbo manifold, turbo, and turbo-back exhaust on.

100% Unmolested 240 w/aftermarket exhaust
Tis the season for no money, so some adhesive-backed aluminum sheet it is!

[edhogan1224]

For the reference of anyone who comes to this thread with a similar issue,what actually happened is the EGR tube directly in front of the drivers side firewall (coming off of the exhaust, roughly an inch around) was rusted and split in half. I simply unscrewed the bung (about a half a million threads) and plugged the hole on the exhaust and unplugged the EGR valve. No more issues

[PapaSmurf2k3]

Thanks for the follow-up!