WTF ..... I haven't done anything to my setup lately .... was driving along enjoying the spring weather .... suddenly my car won't go above 5psi and the wideband is showing super-rich AFR at that level. Vacuum leak? Bad injector seal? (I listened with a long screwdriver and they all sound fine.) No symptoms when not in boost, although my father says he smelled fuel when I started the car.

 

raw fuel means: no spark, no combustion, less air

what did you touch?

 

Nothing! All I've done in the past few months is install Clearwater door speakers. Oddly, that ptoject worked perfectly the first time ... I should have known it was a bad omen.

(Okay, I did one other thing. Last week I brought the plu gap down from .030 to .025, in order to eliminate misfires, in order to pass OBD-II inspection. But I had no problem getting full boost after that, so I don't think it is related.)

 

Fuel pressure regulator leaking into the vacuum system?

 

Can you elaborate? I don't know anything about the fuel system. Where is this regulator gadget and where does it involve the vacuum system? Do all Miatas have one, or only certain years? (Mine's a 2004.)

 

I'll admit I am from the GM world where this was common on some models and am still learning about Miatas. If your car has a fuel pressure regulator that references the manifold pressure (which most do) then there is a possibility that the diaphram can leak fuel into the vacuum system. Look for a cap with a vacuum line attached to it on the injector rail or on the return line. Pull it off with the car running and see if fuel is coming out. The engine speed will go up or if it is a MAF based system you may throw a code, stall ect.

 

I'll take boost leak for 500, Alex.

 

I guess if it is a MAF system I can see the going rich thing with only 5 PSI. Might have a winner.

 

Like if the hose to the throttle body came off, or whatnot. MAF would read a shitload of air coming in that's being leaked. Car gets xxx fuel for that amount of air. Pig rich, low boost. Try it evan.

 

I don't know guys...my bet is on the ACLU bumper sticker, -65whp (it was distributed amongst those unfortunate enough to not have a turbo).

 

I loled.

 

I know when mine runs a bit funny...I re-load me old map and everything runs nice again

But it does sound like a boost leak.

 

Oh wait, he has the megasquirt controlling fuel and spark. I doubt the MAF has any control at all over the fuel. In that case, a blown off I/C hose won't cause the rich condition. Hmmm.

 

He took MS off to go to inspection. Keep up with it, Tim!

 

Oh. I figured he put it back on cause he was boosting around. I dunno. Maybe he should put it back on.

 

That's the plan. But first I will send it back to DIY to look for any glitches, and/or maybe I'll upgrade to MS-II. Right now I'm extremely busy with work and family stuff (my mom has cancer, so I'm going to NYC several times a week to visit her at the hospital .... luckily the bus stop is 100 feet from my house!)

 

Fixed!

Finally had time to dig into the problem today. Noticed that vacuum was less than usual at idle, so I figured. "Damn it, must be ANOTHER bad injector seal!!!" .... PITA to work on those in an MSM so instead I poked around the engine bay for a while .... and eventually noticed the throttle body elbow wasn't very tight where it meets the intake manifold.

D'oh!

Tightened. Test drove. Boost is back.

 

hmm!

 

I know, I know. I never doubted ya'll. But sometimes, for a mechanical moron like me, it helps to "discover" these things for myself.

 

I'll take "the rapists" for 500, Alex.