Wednesday, October 28, 2015

Formula vs Smog Check: 2nd Time not the charm

The saga continues...

The story so far.  My 1995 Formula failed it's emissions test.  We did some diagnostics and found out that the EGR, PCV, and Fuel Pressure regulator were all bad.  We also knew from the first test that the major problem with the car was it was running too rich.

There was also a suspicious rattling under the car which upon inspection showed a problem with the catalytic converter.  It's the original and a couple of soft taps with a rubber mallet confirmed it.
So after more diagnostics that involved chasing down vacuum leaks, replacing any crispy hoses I could find that were causing them, checking the EGR solenoid and changing the oil it was finally time to try again.

The first test a month earlier gave us readings of:

HC 1.57           .8 is the max
CO 13.77     12.0 is the max
NOx 5.99       2.0 is the max

Today's second pass at it:

HC 1.57           .8 is the max
CO 15.57     12.0 is the max
NOx 4.59       2.0 is the max

So we've taken a chunk out of our high NOx reading, done nothing for the HC but what's this?  The CO went up!  That's actually a good thing because it means we've got better fuel control.  Instead of gas leaking past the regulator it's staying in the combustion chamber.  In effect the gas is where it should be but there's too much of it!

It's also another indication (in addition to reduced NOx) that the EGR is working since it's recirculating exhaust vapor back into the combustion process.  It's taking that raw and partially burned gas and adding it back in just as the EGR system is designed to do.

The problem is that the exhaust is so rich with fuel that it adds to the CO problem.  HC stays the same because we're not adding any more raw fuel into the exhaust stream.  That any reading stayed the same across 2 tests a month apart also indicates that the catalytic converter is doing virtually nothing to help us.  It's also indicative that our rich mixture is being caused by something other than what's been fixed.

I'll cut to the chase.  We've still got an over-fueling problem and it's likely related to a leaky fuel injector.  Admittedly, all I have to back up my diagnosis is some fuel injection tools, a multi-meter and a code scanner that works with OBD1.  

And a bit of experience...

Before I changed the Fuel Pressure Regulator I'd have intermittent long starts when the car was cold.  With some of the fuel pressure bypassing the rail for places less useful it wasn't a surprise.  

What was a surprise had to do with warm starts.   I thought my fuel pressure problems were over but noticed longer starts (more cranking) after the car sat for a short period of time (15 minutes to an hour).  

That has everything to do with the fuel rail bleeding off pressure when the car was warm.  Remember that when the engine's cold the fuel pump will prime the rail but when it's warm it shouldn't need to.  So when it does it has to build up pressure again.

I also noticed that during these longer warm starts I'd sometimes see a bit of grey smoke out of the exhausts.  That told me there was un-burned fuel in the cylinders.  With the engine off the only way that can happen is if something is dripping fuel into them.

Something like a leaky fuel injector.  Which is the likely cause of my over-fueling issue.  Of course without a scan tool that can read fuel trim or at least the state of the O2 sensors it's still a guess.  

The only way to know for sure without one is to pull the injectors out of the manifold while still attached to the fuel rail.  Then turn the key on and prime them to see if they leak.  That's a story for the next installment.  Yes, I can put my fuel pressure gauge on the rail but that only tells me there's a problem on the rail not where it is.

So that's the story up to now.  I'm convinced I have a leaky injector and a bad catalytic converter even given my limited resources to diagnose the problem.

But when I got the results for the second test which I half expected to be a disappointment anyway something struck me.

Those results I showed you earlier?  They're absolutely useless for diagnosis.  All I know is that the car failed.  For all that time and trouble I have no indication what the conditions of the failure were.

In Arizona it's always been that way as I'm sure it is in other parts of the country.  But like everything else that's supposed to be "progressive" in the state Arizona's managed to turn it into a profit center.

Which is a great segue to the video below.  It's a bit of rant but for me it was a bit of an epiphany as well.  
Stay tuned!

No comments:

Post a Comment