Horrible gas milege.. FPS vaccuum lines backwards... ?

[dacowgod]

Well.. I have been getting horrible gas mileage in my car.... 60 miles = half tank... ?! ... anyways car seems to run ok... have af gauge and it shows lean alot...but who knows how accurate this thing is... also have dsm link have guys on the link forum looking at a few logs to see if they can help... anyways I recently had a new engine installed and mileage has been like this ever since... I got to looking at the vaccuum lines and diagrams and noticed the lines going to Fuel Pressure Solenoid are backwards..... is it possible that this causes a problem with the Fuel Pressure Regulator performing its job and causing my issues?? ... .. just an idea... i siwtched them back but am out of gas pretty much so i cant do any testing until i get some more .. I am not sure what kind of valve the FPS is to know if maybe its not allowing the vaccuum/boost to pass through it if it is hooked up wrong or if it will flow through either way regardless of direction..

Thanks for advice

 

[rich3389]

Check for boost leaks first, then check the O2 sensor.

 

[dacowgod]

i dont have any significant boost leaks... any way to check O2 sensor w/o replacing it??? I have dsmlink and can read the voltage of it .

 

[rich3389]

yea mkae sure your front O2 sensor is cycling at idle and cruising, when my O2 sensor went out it wasnt cycling at all. Make sure it jumps around up and down.

 

[dacowgod]

according to my log. the front o2 sensor would stay below .2 mostly during normal cruise or idle... most of the time it was below .1 .. .. this is very lean... i know for a fact after i switched the vaccuum lines around on my fps to where they should be the needle on my a/f gauge started bouncing all around between .25 and .75 at idle...which from what i read in the forum is how it should act...so obviously switching the lines made a huge difference... i just took a short trip up the road and during cruise it bounces around too ...so I guess i will see how mileage is now... my next question is why would i use so much gas if i was running so lean before?!

 

[fostytou]

likely your O2 sensor is bad... I don't know if that would cause that bad of gas mileage though..

Also, you can remove your FPS if you have an upgraded fuel pump... at that point it serves almost no purpose.... If the lines were, in fact, backwords that would mean you were dumping less gas at idle/low throttle and not enough gas under boost. BAD situation. (this also means that your O2 sensor should read rich. The difference may not be terribly significant depending on your setup... but either way just take it out!

If you take it out, you can use the NOs controls in DSMLink to switch from a lower boost in first gear to a higher boost in second for better launches/control/tire life

 

[dacowgod]

That sounds like a pretty cool idea for the boost... I assume that takes an electronic controller .. but it would be worth it imo.. I will bite the bullet and get a new o2 sensor... May as well i've spent so much on this car getting it where it is now back to a "reasonable" condition to even start thinking about modification..whats another 100 bucks huh