My car misfires and loses power? I own a.

TINATU1

MEMBER
2004 NISSAN SERENA

My car misfires and loses power?
I own a 2004 Nissan Sentra SE R Spec-V with a cold air intake installed and a 4-2-1 exhaust installed also. The new exhaust has no precat and catalytic converter. Upon removing the old exhaust only 1 O2 sensor survived, the upflow (closest to the head). I went to the track and had 5 runs no problem, then on the way home it started misfiring and I felt a loss in power. I took the spark plugs out and saw they were dirty, I cleaned them with a wire brush then sea foamed the intake manifold, then I ran lucas fuel injector cleaner through the gas tank. The car doesn't misfire now but I still feel a lack of power. MAF checked out working perfect. I'm waiting on the down flow O2 sensor in the mail. Any ideas what might be the cause?

Additional Details
I also am getting really shitty gas mileage. After I cleaned it, the gas mileage increased by about 10mpg. I top out around 30 mpg at 55 on the highway. Any faster and it goes down about 2 mpg per every 1 mph.

5 Replies

AUTOSCANNER

MEMBER
4 POSTS

Well if its miss firing then it has to do a lot with the spark plugs but a lot of people make the mistake to just clean them or put in new ones u have to also buy brand new spark plug wires not only that but also the coil it has to do to much with it without the coil it doesnt send the spark threw the spark plug wires to spark the spark plugs change it all. The second thing with lack of power involves the fuel filter if its dirty the gas isnt going to pass threw the correct way causing it to not start, lagging to start, and lacking power cause of lacking fuel to combustion and maintaining it to run with power. The third thing I would check and change if still causing problems is the injectors they get clogged up no fuel passing threw them as well there not spraying properly so therefore lack of power or not starting. Are u smelling gas? If u are one of ur fuel lines is dripping it will cause it not to start if it gets to big could cause lack of power. Weak battery? Check it buy a cheap muti meter put the negative on negative terminal of battery n positive on positive while car off it should read 12 v cause its a 12 v battery if less means battery is weak going bad so lack of power then turn it on it should read over 12v around 13 or 14 if so means the alternators working good and charging battery cause a weak alternator or one that is goin bad cause lack of power as well I know this is a lot to read lol but hey its good knowledge if u dont no hope this helps

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Wednesday, January 9th, 2013 AT 8:47 AM

AUTOSCANNER

MEMBER
4 POSTS

There are a few things to do to when trying to diagnose a misfire. All vehicles are different, but there are a few places to start.
1) If possible use an auto scanner on newer vehicles. The misfire counter function can help you determine which cylinder is behaving badly. Clearly this is not an option for all people and vehicles though. Fcar F3-W is an advanced auto scanner. It can diagnose all kinds of petrol control systems quickly and easily, and it Supported Nissan.
More for Fcar F3-W:

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Wednesday, January 9th, 2013 AT 8:48 AM

ASEMASTER6371

MECHANIC
52,797 POSTS

Have you done anything else besides the cold air and exhaust?

The downstream is not needed now as its only job was to monitor the cat converter. Does not effect the running of the car.

I would go back to basics as drag racing the car may have damaged something internal.

Start with a compression test, fuel pressure test

Roy

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Wednesday, January 9th, 2013 AT 12:04 PM

TINATU1

MEMBER
3 POSTS

Thanks for you advise, helps me a lot.

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Thursday, January 10th, 2013 AT 1:05 AM

SNIKREPN

MEMBER
17 POSTS

The problem with the car may not be what you think. Most of such cases are due to lack of compatibility of exhaust systems and the car engine. Yes, you may have acquired the car with the exhaust in talk at ago, but the fact is that it never works for all the sames well. You need to check how the two components are performing so as to find out what exactly might be the problem.