Ok guys, I really need your help big time. I know this is really long, but I will GREATLY appreciate any help you fellas are able to give me. I have a few problems, but the main one being a massive loss of mileage that I will explain below:

I’m at a severe loss of mileage here. I would go so far as to say that I’m getting no more than 10mpg, if that. This is ridiculous. It used to get 18, but then out of nowhere, it started getting worse and worse…it’s not like I even did anything to the engine, it just started getting bad. Now, when I speed up a little bit and then come down to an idle at a light or something, I smell gasoline…it’s pretty potent too. Now, I did all the obvious testing already…I checked underneath the car while it was off, running, revving, idling, and nothing was leaking. I checked the fuel lines, and all fuel lines are intact. The parts of the fuel tank that I can see are fine. Also, I am not getting a check engine light at all, and I just replaced the O2 sensor about 4 months ago. I do not think it is the EGR because of the lack of the check engine light, and the idle is still smooth. I CANNOT FIND OUT WHERE THIS GAS IS COMING FROM! But it is killing my mileage. I did a throttle body bypass mod a few months ago, but, however I never got around to plugging up the coolant inlets that were bypassed. Could this be contributing to it?

I have attached a few pictures, in hopes of maybe narrowing down the problem

-One is of some oil that has made its way up to underneath the plenum…I don’t know how or why it got there. Any ideas?




-Another one is of my fuel pressure gauge which jumps between 50-60psi continuously.




-Another one is of the passenger side valve cover and a valve that has no hose going to it…where should this hose be going to?




-I took off the AIR Diverter Valve when I installed my headers and never put it back…I figured it was useless with the lack of the AIR lines. There is now air coming out of what I detached this from (from the smog pump maybe?) Is this posing a problem?




-And last is the MAP sensor that is just loosely lying on the passenger valve cover…where should this be fastened to?




With that knowledge, does ANYONE have any idea what could be wrong? If not, could you give me what you predict could cause a loss in mileage/gas leak in order of likely-to-occur first? Please help me out here, I'm a freshman at Rutgers University in NJ, and the money that I have to spend on gas is really putting me at a loss here.


Thank you all so much
_Clark

 

60 psi is too high for fuel pressure. Is your regulator an adjustable one? Pull the vacuum line off the regulator and see if gas comes out. It should be around 45 psi with the vacuum line disconnected, less with it on with the engine idling. The thing in you valve cover is for the PCV system...don't know where the hose goes of the top of my head but you have a nice vacuum leak from it.

 

The PCV valve hose goes to the bottom side of the plenum I believe. Also, I read that the MAP sensor should be mounted horizontally otherwise it will read inaccurately. I know a few people that have had problems with inaccurate FP gauges, so I'd double check before playing around with the pressure.

 

The PCV hose on my LO3 goes to the throttle body. My MAP sensor is secured with one screw to the lip which extends from the firewall forward (where the rear of the hood meets. I'm fairly certain that the coolant passages in the throttle body do not need to be sealed when you bypass it. It should be a contained system in the throttle body, but someone else back me up here.

 

Thanks for the help so far you guys, I found a vacuum diagram and I'm going to go out tomorrow and find some hose to connect that PCV valve to the TB. I'm pretty sure I know where it's going to, but the diagram is kind of shoddy. Does anyone know EXACTLY where it goes?

Thank you, and keep it coming guys.

 

The PCV valve hose on a TPI does not go to the Throttle Body, it goes underneath the plenum.

 

The DRIVER's side PCV valve goes under the plenum...the Passenger CCV (not pcv) valve goes to the throttlebody



Thank you for your insight.

 

Also keep an eye out for "A" on that diagram. Its a tiny hose and some hard plastic piping, easy to overlook but its very important. Good lucK!