Nissan Primera P11 144 New exhaust affecting MPG? |
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Colin1976
NPOC Guest Joined: 28 Dec 2012 Location: Newcastle upon Online Status: Points: 5 |
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Posted: 09 Sep 2017 at 7:56am |
Hi guys
So i needed to replace the front section of the exhaust on my p11-144 2.0se+ because the flexi pipe was in tatters. To cut a long story short i kept finding minor blows everywhere so decided to just do the whole exhaust. A few challenges along the way but got it done and she sailed through the MOT. Thing is, I've noticed a drop off in my MPG in the week since i did it. I was getting bang on 35mpg but it's slowly dropping. Should i disconnect the battery to reset the ecu? Have i put the cat on backwards? Should i have replaced the o2 sensor? Any help much appreciated Cheers 👍 |
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d60_tag
NPOC Guest Joined: 18 Jul 2015 Online Status: Points: 533 |
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o2 sensor maybe ok as it passed the MOT with it, where they measure the range, think is 0.97- 1.03 or so to be 'within range'.
'Cat on backwards'.... probably unlikely as think they sort of guard against this on cars by having the mounting plates so that it can only be mounted oneway- (I think). Probably no leaks as again think the MOT would have picked up on those if you did still have leaks. Yes, maybe try disconnecting battery, to reset/ relearn ECU stuff. Also maybe could imagine there could be a slight drop (or gain come to that)- just because the new system in clean / new CAT etc, may run otter or colder temps. Yes- possiblly a small change in MPG but would think it should not be too much from what it was. |
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Colin1976
NPOC Guest Joined: 28 Dec 2012 Location: Newcastle upon Online Status: Points: 5 |
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Hi guys, an update to this........ Its now 3 months down the line and the lack of MPG is now a huge concern! I'm down to 31.6mpg and dropping. £20 used to get me roughly 150-160 miles depending on the kind of driving but my driving doesn't really change much. I put £20 in last week and i'm almost empty.... I've done 90miles!!!!!!!! I tried resetting the ECU by disconnecting the battery but I'm guessing that does nothing? Can anyone PLEASE offer any advice. I don't have the money for a new o2 sensor right now so would like to rule out other things before I start down that route. Could I have done something wrong? I'm not a mechanic by any stretch and this is the first full exhaust i've changed. can oil/oil filter/air filter/spark plugs have any significant effect and could it happen all of a sudden?? i'm seriously concerned now and need to have something to try. Here's hoping someone can help.
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d60_tag
NPOC Guest Joined: 18 Jul 2015 Online Status: Points: 533 |
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Ok- firstly, some calculations :- if you were previously getting 150-160 miles for £20(3.66 gallons @£1.20 litre), then that would mean the car was doing about 41-43 mpg. Being a 2.0 I would think that is maybe unlikely. My little 1.6 only does about 35-38mpg on a run and sometimes only 28-30mpg round town. I would think if you get 30mpg out of a 2.0se+ then that is quite okay and normal. So if the computer is saying around 30mpg odd, as it seems it is, then this would be about right. You state that your put £20(3.66 gallons) in last week and have only done about 90 miles odd (say it does maybe 10 miles more before becoming totally empty) then that is still 27.3mpg- again being a 2.0- 27.3mpg maybe sort of what it may do. That being said- I think my 1.6 did used to sometimes even do about 40-45mpg(max) on a run but now it only seems to do about 38, never more than 40mpg now. Not sure why it did sometimes do 42-45mpg and I too have went over many things and car seems in good order. However, on the few times it did 45 odd, that was only on occasions(always long distance A roads/ motorway driving) and would also more times be about 35-38mpg. So mine doing 38mpg on runs nowdays, is still pretty good for quite a big heavy car(mine is a wagon). Motorway versus town driving you can sort of knock 6-10mpg off, so if you get say 35mpg on motorway at 60mph odd, then you would probably get maybe 25-28 round town. Defo change the air filter if its not been changed for a while and also a set of new plugs may help mpg and smoothness of power delivery. What kind of condition/ age is the MAF? Hope this goes someway to helping and maybe don't expect it to do 41-43mpg (150-160miles for £20). Being a 2.0se+, would think this unlikely. |
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d60_tag
NPOC Guest Joined: 18 Jul 2015 Online Status: Points: 533 |
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... I did also have a fuel hose split slightly, probably caused by a slightly blocked fuel filter and it was putting the hose under load where it was blocked.. eventually the hose slighlty split and it took me about 3 months to notice because it was only leaking slightly and never noticed it- until it got worse and then I smelt fuel and found the split. Think when it was running with the split hose for 3 months, mine went as low as about 30-33mpg and after I sorted the split and new fuel filter it went back upto the 38mpg I get now.
Yes- my 1.6 does about 38mpg on a run and about 30mpg round town. This is probably quite good for an old car. Me too would like to see the 45mpg it seemed to do on occasions but also when it did occasionally do this it also sometimes only did 35mpg. So 38mpg for me is quite acceptable for a heavy big useful car. |
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p11primeragt
NPOC Guest Joined: 29 Jul 2011 Online Status: Points: 18750 |
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O2 sensor first,and if no better compression test the engine.A worn engine can drink fuel.
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