So, I had a muffler delete done a while back and after a bit of driving around and stopping at a light, the car will go from its 600rpm idle down to 500 and back up to 700 and then down back to 600 again. It fluctuates like this almost everytime. Also sometimes when its just idling, it starts to shake a bit but at random times. Before the muffler delete I didn't have this problem. Also, on startup, the car will fire up and then the rpms will suddenly dip and then go back up again, I am wondering if this is normal?? I think the muffler delete screwed up my car?

 

Maybe an exhaust or vacuum leak?

 

I would suggest you do a exhaust timing relearn. Flat ground, turn everything off except the engine (minimum load, no head lights, radio, climate control etc). While in Park, rev up the engine between 1900 rpm and 2000 rpm for 20 seconds and you're done. I didn't exactly have the problem you had when I got my muffler delete but after this relearn it felt a lot smoother for me at least.

 

does this have to be done on the first startup of the day or anytime? I did it after driving around for a bit and as of the few times I driven since that, I haven't had noticed anything yet. Also, I don't understand why this would create a problem for the engine, as the muffler delete should let the engine push the exhaust gases out easier, making it run better no?

 

yea the engine has to be warm. Well I'm not 100% sure but my logic is that muffler delete will cause exhaust gases faster and easier like you said, but you are also losing back pressure. Most people would say a muffler delete doesn't do anything which makes sense but when I got mine done I had a engine code pop up as well and I did the relearn/clear and it never came back.

 

Well thankfully I didn't get a code, and I did the relearn thing, and for the few times I drove it after that, I didn't have the idle issues but I'll see if it lasts. Also, can you explain to me how that exhaust timing relearn thing works? I mean just holding it at 2k rpms for 20 seconds doesn't seem like it would do anything.

 

it's just a build in procedure in the ECU. I have the car manual that someone on G forum sent me awhile ago. It was described on there and it was just called exhaust timing relearn from what I remember I'll have to look at it again. But from what I remember it has to do with the exhaust timing retarder and it relearns the timing or something like that. I can send you the manual if you give me your email

 

Manual is easy to find if you search on Google for Infiniti FSM.

 

Ok, so the exhaust relearn lasted for about a few days and then the car went back to the same issues as before. It doesn't it bother me so much but I am just wondering why the muffler delete caused these issues.

 

Seriously? You've changed the entire flow characteristics of your finely tuned (stock) exhaust system, and you wondering why it cares?