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.

 

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.

 

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.

 

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.

 

o2.... I think it is pointless to replace the Knock sense I already did the resistor mod and after 3 junkyard ones failing it is probably a waste of time to chance a $50 one that could also have an issue or a chance my engine is always knocking now.

 

That's because the $17 ones on ebay are better.

 

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..

 

Did TB, Put in a new maf last spring, and IACV cleaning last year when I did the EGR valve cleaning. I should look into the o2 sensors though if you guys really think that will help. Also, The idle does dip a lot when I go into neutral right away at say a stop light. It is pretty annoying like it will dip to 300 rpm when I let it go and it will go back up to 500-600 again.

 

hey man...

a bottle of chevron techron goes a looooong way

 

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.

 

good idea. I will give that a shot... Thanks!

 

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"

 

Anyone know anything about the MAP sensor? And where can I buy a cheap O2?