FAILED Emissions Test...

Before you start reading, I'll warn you that this post might be kind of LONG...

Car: 1989 Olds Cutlass Supreme
Engine: 2.8L MPFI (same as 3.1L MPFI)

I'll start at the beginning.

I try keep to keep my Cutlass in tip-top shape! Mechanically and appearance-wise. I really love this car!

I've suspected a problem for about a year now...but I and my regular mechanic haven't been able to figure out what is wrong. I have KNOWN it's been running RICH for quite a while. Not rich in the sense that there's black smoke coming out the tail pipe, but rich in the sense that I had a good suspicion that I would fail my Emissions Test.

For a few months last fall I was borrowing a friends Snap-On Scanner and liked the idea of viewing various inputs that my ECM was "seeing". Everything always looked good except for my "Block Learn" figures...it was always far too low, especially at idle. So I knew that for some reason my ECM was trying to compensate for a rich running engine. After failing to for 3 months to figure out WHY, I pretty much gave up.

I continued to do my regular maintenance. Oil changes with Mobil 1 every 3 months. An entire tune-up with PCV, plugs, wires, etc. Coolant system flush and fills. Transmission services. The list goes on...

Then about two months ago, things started to get a little strange. Sometimes, for no apparent reason, the engine would all of a sudden go crazy! The idle would be jumping up and down between almost ZERO and 3000 RPMs. This would usually occur right after the engine was re-started hot. I soon realized that if I simply shut the car off and re-started it again, the problem would be gone!?

Then, just last month...three times the engine wouldn't start at all, unless I stepped on the gas and opened the throttle. As soon as I let off the gas, it would stall. But, once again, shutting off and re-starting would somehow cure the problem!?

So, with this information I started to focus in on the IAC system. This past thursday I did a complete cleaning of the entire throttle body, IAC, IAC passeges etc. I also checked the electrical aspects of the IAC and it was fine. I then re-set the ECM and did an idle-relearn.

Well, since I did this, it hasn't done the no-start or CRAZY idle thing anymore, BUT, it's still running RICH, especially at idle.

Yesterday, Before I went for my Emissions Test I decided to replace my O2 Sensor, just to be safe. Even though my old O2 Sensor was only about a year and a half old. The old O2 Sensor had a white, powdery tip, so I'm glad I changed it anyway.

I should let you know that I have a permanately installed AutoMeter Vacuum Gauge and AutoMeter Air/Fuel Gauge.

Three weeks ago I got my first ever SES Light. I checked the code and it was 45, indicating what I already knew, a RICH EXHAUST. I've gotten a few codes since then and they have all been either 44 or 45. Using my Air/Fuel Gauge, I was able to see that as I am slowing down and coming to a STOP, the O2 would stick RICH, and not move. Sometimes it would stay RICH at idle for up to 1 minute and not move.
I was hoping that changing the O2 Sensor yesterday would help, but it didn't, and it's still doing the exact same thing.

Here's my Emissions Test results:

40 km/h
HC ppm = 69(Limit), 68(Mine) = PASS
CO% = 0.38(Limit), 0.04(Mine) = PASS
NO ppm = 777(Limit), 621(Mine) = PASS

Curb Idle
HC ppm = 200(Limit), 221(Mine) = FAIL
CO% = 1.0(Limit), 0.63(Mine) = PASS

So even though I passed almost everything, the guy still said I am high in a lot of areas. He said the NO ppm at 40 km/h should be like 300, not 621. And I obviously just barely passed the HC ppm for 40 km/h as well.

Four years ago I had the Catalytic Converter replaced with one of those after-market universal types. Two years ago I replaced the EGR Valve with a brand-new one bought from a GM Dealer. I know it's not the EGR or O2 so far. I'm thinking it's ignition related...possibly a coil or something. I can sometimes detect a slight misfire at idle, especially when Hot. I can also see via my Vacuum Gauge that sometimes it will flucuate between 15" hg and 13.5" hg while idling. From what I've read, this usually indicates a spark plug gap or something...?

Does anyone have any input? Is it possible that the seldom no-start, and crazy idle is related to the RICHness and unburned fuel? Could it be a bad MAP Sensor? A bad ECM?

Feedback is appreciated!:)

THANKS:)

Rich exhaust could be a number of things.

Bad o2 sensor (maybe)
Fuel pressure regulator
high engine temp/bad sensor
Fuel injector stuck open

High NOx
bad or dying Cat
too much ign advance
high engine temps

Could be the computer is going bad, fuel reg is going bad, your Cat Convertor is going bad,
Was the car ever in an Accident?
You can go batty with a probelm like this. Pay the $75.00 and take it to Chevy, let them figure it out, then you fix it.