Would a vacuum leak really drascally decrease MPG in our cars?
04-01-2012, 02:14 AM
#1
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Would a vacuum leak really drascally decrease MPG in our cars?
I am trying to figure out other then a tuneup what needs to be done to improve my 16-17mpg maxi. okay yeah I know it is an old car with 213k miles but really. $40 bucks of 93 and I only get 204 miles until orange light. Granted I do live in the city and do some highway driving but this is "MADDNESS" lol
I hear a little vacuum sound when I put my head near the engine but I really can't locate it but I never had this leak before I decided to rip off half the upper manifold to fix and clean out the EGR issue these cars love to have. I have year old Michlian tires that have proper psi, I gave it a tune up 2 years ago with all plat lasers. I will do another one this summer. I changed the fuel filter from a 300zx I did 2 years ago to a maxi one this past fall.
There is only one thing that makes me think this is causing an issue and my mpg but I am not entirely sure if the knock sensor would have anything to do with it. I have had knock sensor codes in the past. Tons of them. Went to junkyards and put like 3 different ones on through out a few years span and they would go. I know, I know, I could of spent $50 bucks on a new one, but I didn't wanna spend $50 bucks on these things if the junkyard ones up to 3 kept throwing codes after a while.
So I decided to do the Resistor mod on here because the car really blows at 40less HP as it feels and I keep that on and only keep premium in to keep the knock reduced as much as possible, but do you really think that may be my issue? I gotta admit I never had amazing gas mileage for a few years but now that gas is already over $4 a gallon again. I am taking it more seriously. Just to think 10 gallons of gas gets me 200 miles is absurd.
I hear a little vacuum sound when I put my head near the engine but I really can't locate it but I never had this leak before I decided to rip off half the upper manifold to fix and clean out the EGR issue these cars love to have. I have year old Michlian tires that have proper psi, I gave it a tune up 2 years ago with all plat lasers. I will do another one this summer. I changed the fuel filter from a 300zx I did 2 years ago to a maxi one this past fall.
There is only one thing that makes me think this is causing an issue and my mpg but I am not entirely sure if the knock sensor would have anything to do with it. I have had knock sensor codes in the past. Tons of them. Went to junkyards and put like 3 different ones on through out a few years span and they would go. I know, I know, I could of spent $50 bucks on a new one, but I didn't wanna spend $50 bucks on these things if the junkyard ones up to 3 kept throwing codes after a while.
So I decided to do the Resistor mod on here because the car really blows at 40less HP as it feels and I keep that on and only keep premium in to keep the knock reduced as much as possible, but do you really think that may be my issue? I gotta admit I never had amazing gas mileage for a few years but now that gas is already over $4 a gallon again. I am taking it more seriously. Just to think 10 gallons of gas gets me 200 miles is absurd.
04-01-2012, 05:08 AM
#2
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Put a new knock sensor in. It will pay for itself in 2 or 3 tanks of fuel if it's bad.
O2 sensors will cause poor gpm as well even if there is no code set.
A vacuum leak will make you run lean and should actually set a dtc code for it.
O2 sensors will cause poor gpm as well even if there is no code set.
A vacuum leak will make you run lean and should actually set a dtc code for it.
04-01-2012, 09:15 AM
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hmm, yeah I never replaced those, what is a cheap place to buy them? I really don't wanna spend like $50 a plug on an assumption tho that those are bad, but yeah I did never replace them. I have a y-pipe too.
04-01-2012, 02:48 PM
#4
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Edit: wait, were you asking about where to buy the o2 sensor or knock sensor? For the o2, there was just a thread done with the title something like "bank 1 sensor 2 will this fit" search for that, he found some o2 sensors for $30.
Last edited by 2brosgixxer; 04-01-2012 at 02:52 PM.
04-01-2012, 06:01 PM
#5
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If the link works, this is the one I bought with zero issues so far. http://item.mobileweb.ebay.com/viewi...id=24115399858
Edit: wait, were you asking about where to buy the o2 sensor or knock sensor? For the o2, there was just a thread done with the title something like "bank 1 sensor 2 will this fit" search for that, he found some o2 sensors for $30.
Edit: wait, were you asking about where to buy the o2 sensor or knock sensor? For the o2, there was just a thread done with the title something like "bank 1 sensor 2 will this fit" search for that, he found some o2 sensors for $30.
04-01-2012, 07:26 PM
#6
04-01-2012, 07:41 PM
#7
There's no sense in throwing in a KS if you've got it bypassed with a resistor already.
I don't think you have a vac leak unless you've got a fluctuating idle which you don't mention.
What other maintenance have you done? Maybe it's time for a new front left O2 sensor, maybe plugs, filter, TB/MAF/IACV cleaning etc..
I don't think you have a vac leak unless you've got a fluctuating idle which you don't mention.
What other maintenance have you done? Maybe it's time for a new front left O2 sensor, maybe plugs, filter, TB/MAF/IACV cleaning etc..
04-02-2012, 05:45 AM
#8
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There's no sense in throwing in a KS if you've got it bypassed with a resistor already.
I don't think you have a vac leak unless you've got a fluctuating idle which you don't mention.
What other maintenance have you done? Maybe it's time for a new front left O2 sensor, maybe plugs, filter, TB/MAF/IACV cleaning etc..
I don't think you have a vac leak unless you've got a fluctuating idle which you don't mention.
What other maintenance have you done? Maybe it's time for a new front left O2 sensor, maybe plugs, filter, TB/MAF/IACV cleaning etc..
04-02-2012, 08:48 AM
#10
To help locate a vacuum leak. Try spraying carberator cleaner over all the vacuum lines. If there is a leak the cleaner will get sucked into the line and your idle will fluctuate drastically. Then from there you can pin point the leak. Hope that helps.
04-02-2012, 01:26 PM
#11
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good idea. I will give that a shot... Thanks!
04-03-2012, 05:05 PM
#12
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holy ****. lol, I got did a code check and I am getting this...
2 codes for P1105 MAP sensor. pressure bar switch solenoid circuit I really forget where that is...
and 1 code for P0138 o2 sensor voltage bank 1 "Circuit high"
2 codes for P1105 MAP sensor. pressure bar switch solenoid circuit I really forget where that is...
and 1 code for P0138 o2 sensor voltage bank 1 "Circuit high"
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