Hey guys i havent been on the forums in a while. I have a 2001 maxima se with 207,000 miles and have had this car for a yr and a few months now. Never had any issues with it really, always had it maintained regularly by my mechanic thats been into just maximas for yrs. i needed an exhaust recently, so i had him put a y pipe and tsudo cat back on it. Ever since i did this the car seems to have loss of power. My car always has been quick off the line and even on the highway. Now it seems if i am cruising at 65 mph in 5th gear and go to full throttle it takes a bit before it starts to accelerate, and seem to have lost power. If i drive at 45 mph in 5th gear and go to full throttle it doesnt really accelerate much at all. Before it seemed to just get up and go like a raped ape. Im running 93 octane fuel and always change the oil regularly. Car doesnt burn oil, doesnt leak any fluids, or anything. If u start accelerating in the low gears its ok but still seems to be missing something. I dont know if its just a cooincidence that now that i just put the exhaust on it started doing this or what but it seems like it lost power due to the new exhaust.. Someone told me it could be due to loss of back pressure from the huge *** muffler that these tsudo exhausts come with but It doesnt make sence to me, but im not a pro at these cars. Does anyone have any info or can anyone relate to what my problem may be? It idles at about 7-800 rpm is this normal? Any help would be greatly apreciated..

 

Idle speed is good. I would check o2 sensors and plugs. Both can cause loss of power. With the hesitation that I'm understanding from your post, it seems like it could be a plug issue. I would check the o2 sensors regardless especially after changing exhaust systems. Are you using anti-foulers, o2 sims, neither? Do you have any codes at all?

 

My mechanic also told me thAt it could be a bad 02 sensor and bad plugs. If i run 87 octane it spark knocks on acceleration, but if i run super 91 or 93 it doesnt do it at all. Could my maf also be dirty or something?

 

Certainly could be. And it certainly won't hurt to give it a quick once over with some MAFS cleaner.

 

First get an obd2 scanner and scan for knock sensor codes. Replace knock sensor if needed.
Also, replace your primary O2s