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Hello, i use a nissan primera as my daily drive
Recently its fuel economy got quite a bit worse, usually i could go 650+km on one tank
now for a few tanks i couldn’t manage more then 550-600km. (i’d say a drop in mpg of 10-15%) With today’s fuel prices i’m not too pleased with this…I did not change my driving style, also i’ve been recording mpg for quite a while so its not based on one tank.
My car is a 1997 nissan primera 1600cc petrol, manual transmission.
No changes/repairs were done to the car.The only change is a new exhaust system, the old one was rusted and leaked, so a new one was installed an aftermarket one, garage owner recommended it. (costed about 250€)
the middle muffler, rear muffler and the piping in between was replaced.So this is my main suspect, is it possible that this new exhaust gives more backpressure?
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How soon after the new exhaust did you start experiencing problems?
Have you checked your air filter and tire pressure?
Does your vehicle have the catalytic converter, O2 sensors, EGR valve, etc for emissions that we have here in the U.S.? Are there any CEL/MIL/SEL codes that have come up?
I started noticing the problem about 2 tanks after the new exhaust was installed, first i thought it was a coincidence or something…
-I check my tire pressure on a regular base, it stays within specification
i looked at my air filter, nothing special about it-My brakes make no noise, also i checked if they were (too) hot after a drive, nothing special here too.
– oil is changed every year
– fuel filter is about 1.5 years oldI don’t really know what my car is equipped with emission wise, it has 3 box like things in the exhaust system.
I do have a sensor in the exhaust manifold, also in the intake manifold.
No check engine light has come up…The easy answer it would seem is that it has something to do with the new exhaust system but that seems like a pretty significant hit for just that. I will say that a good exhaust systems can do wonders where a bad system can cause all kinds of issues. You seem to have covered the basics such as your tire pressure and tune up items so I’m at something of a loss really. If it were me I might hook up a scanner and get a look at the long and short term fuel trim numbers. They should be as close to 0 as possible. Positive numbers means it’s adding fuel such as with a vacuum leak or something. Negative numbers mean that it’s taking fuel away for a condition like a leaking fuel injector or bad fuel pressure regulator.
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