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My CO% and HC PPM at idle has failed my states emissions test twice now(both hot and cold) and both times the 2 places have said its due to open vacuum lines most likely. The problem is, two of the lines run to the back of the motor which is near inaccessible but the largest issue is the line coming off the fuel pressure regulator and another line that is coming off the manifold at the bottom right runner. My research has shown these two lines to connect with the PRC solenoid valve which usually sits under the stock airbox. About the 5th pic down or the 4th diagram seen here
http://www.mx6.com/forums/2g-mx6-genera ... e-faq.html
I understand that one is a curved neck but all other diagrams point to the same thing; the line from the FPR should go into the "side" inlet closest to the oval mitsubishi branded plastic peice and the vacuum line(which always makes a whistling when disconnectedand sucks pretty hard) should plug in the bottom where the electrical connector plugs in.
Well if i do that, the damn thing just stalls. If i remove the PRC completely, it makes no difference at all and still runs fine. If i connect the two lines without the PRC it stalls as well. If i blow or suck on the PRC it flows, but im still thinking this part may be bad since it really hasnt been in use for probably the greater portion of 3 years. I'm really at a loss, as there are no junkyard cars near me to pull one off, and the car has a great steady idle and gets fine gas mileage but my nanny state wants me to spend no less than $150 on repairs before i can get a waiver.

This tells you how to test the PRC
http://www.mx-3.com/manuals/showimg.php ... F2-119.gif

sounds like perhaps its stuck open?

I posted pics of all the vac lines and most pics show where they go to. Question is if you have another MX3, MX6 or Probe to look at you should be able to figure it out.

I posted pics of all the vac lines and most pics show where they go to. Question is if you have another MX3, MX6 or Probe to look at you should be able to figure it out.

http://images.geekazoids.net/vacuumklze_copy1.gif

I posted pics of all the vac lines and most pics show where they go to. Question is if you have another MX3, MX6 or Probe to look at you should be able to figure it out.

http://images.geekazoids.net/vacuumklze_copy1.gif
or
http://www.mx-3.com/phpBB3/viewtopic.php?f=23&t=63734

Dan posted pics of all the vac lines and most pics show where they go to. Question is if you have another MX3, MX6 or Probe to look at you should be able to figure it out.

Nd4SpdSe wrote:Dan posted pics of all the vac lines and most pics show where they go to. Question is if you have another MX3, MX6 or Probe to look at you should be able to figure it out.

Well i got a new PRC solenoid valve and it still just stalls when installed and still runs fine with the electronics plugged into it but without the vacuum lines attached.

Are you running the engine with no vacuum applied to the fuel pressure regulator (fpr)? The PRC valve only interrupts vacuum for hot restarts. But if no vacuum is applied to the fpr then you'll have higher fuel pressure at the fuel rail during idle and probably running rich at idle when emissions are tested. Forget the PRC - it is relatively unimportant. But hook up vacuum from the back left intake manifold runner (where the prc valve should be hooked up) into the top of the fpr.

Man that was like deja vu X3

davmac wrote:Are you running the engine with no vacuum applied to the fuel pressure regulator (fpr)? The PRC valve only interrupts vacuum for hot restarts. But if no vacuum is applied to the fpr then you'll have higher fuel pressure at the fuel rail during idle and probably running rich at idle when emissions are tested. Forget the PRC - it is relatively unimportant. But hook up vacuum from the back left intake manifold runner (where the prc valve should be hooked up) into the top of the fpr.

I'm gonna need clarification on that last part. None of the diagrams show anything about vacuum hoses from the back left runner going anywhere near the FPR. As stated in my original post and shown in the diagrams, the only vacuum ports/lines from the FPR connect to the PRC and then to the FRONT RIGHT intake runner where there is a ton of vacuum. coming off. If all you're saying is i need to find a suitable vacuum line to connect up to the fpr port then by all means ill give that a try.

Sorry if I'm confusing things. Left side of engine is closest to the bumper. Front of engine is timing belt and accessory belts.

The FPR needs vacuum to regulate appropriate fuel pressure. The prc valve sits between the vacuum source and the fpr. Usually the prc valve is doing nothing. Vacuum is flowing through it. The vacuum source is the intake manifold nipple at the rear of the engine left side (low on the intake runner near the distributor cap). I've got a KLG4 intake, but the KLDE was similar.

At idle vacuum is at its highest. With this vacuum applied to the fpr fuel flows through the fuel rail at a lower pressure so less fuel is pushed through the fuel injectors. Makes sense since you need less fuel at idle. With no vacuum at the fpr fuel pressure is higher than intended and more fuel is pushed through the injectors making you run rich.

The prc valve only works during hot restarts when it cuts vacuum and forces richer mix for the first minute of idle when the engine is already at operating temp.

davmac wrote:Sorry if I'm confusing things. Left side of engine is closest to the bumper. Front of engine is timing belt and accessory belts.

The FPR needs vacuum to regulate appropriate fuel pressure. The prc valve sits between the vacuum source and the fpr. Usually the prc valve is doing nothing. Vacuum is flowing through it. The vacuum source is the intake manifold nipple at the rear of the engine left side (low on the intake runner near the distributor cap). I've got a KLG4 intake, but the KLDE was similar.

At idle vacuum is at its highest. With this vacuum applied to the fpr fuel flows through the fuel rail at a lower pressure so less fuel is pushed through the fuel injectors. Makes sense since you need less fuel at idle. With no vacuum at the fpr fuel pressure is higher than intended and more fuel is pushed through the injectors making you run rich.

The prc valve only works during hot restarts when it cuts vacuum and forces richer mix for the first minute of idle when the engine is already at operating temp.

I understand what you are saying now, but when i connect the vacuum source coming off the manifold (as you stated and in the diagrams) to the FPR it just stalls/wont run. As soon as you even get the vacuum source close to the fpr it begins to sputter and die out but will immediately catch idle if you remove vacuum. I'd love nothing more than to need a Cosmo racing FPR, and it would certainly get me very close to the $150 i need to spend on it for a waiver, so any ways to diag a bad regulator?

FPR failure is usually ruptured diaphragm. If it was ruptured the vacuum hose would pull fuel into the intake and again your car would run rich. Any fuel in the vacuum hose when you remove it?

The fact that it immediately stalls makes me think something else is wrong. I'm just thinking during your testing if you saw fuel leaking from the vacuum line - or it was wet you would have noticed. I know it is a pain, but double check all your vacuum lines.

Sticking with the fuel possibilities it could also be clogged fuel filter or weak fuel pump. Maybe with vacuum on the fpr there isn't enough fuel flow to maintain idle. If possible try a used fpr to see if it makes a difference.