Breakin' [California smog test limits] 2: Electric Boogaloo.

[H-Man]

So my car [1994 Geo Prizm with 1.6L 4A-FE and 5 speed manual] failed smog like it always does. I would like some feedback on what I should do.
Background info: 270k on the body, unknown mileage on engine since engine is out of a 1995. Did timing belt a year ago, top end did not have anything wrong with it then as far as I can tell, but that was 11,000 miles ago.
Spark plugs: NGK BKR5EYA replaced 2k ago.
Cap, rotor, wires: Ebay stuff installed 27k ago.
Oxygen sensor: Replaced 20k ago after I failed the smog test in 2013. Installed a DENSO 234-1053 Oxygen Sensor.
Air filter: Replaced 5K ago.
Motor oil: Mobil 1 EP 10W30 with 5k on it. Mobil 1 claims it is good for 15k with their filter but I'll want to change it soon since I'm not able to run an automotive history check on the engine's VIN and the body's VIN, thus I don't know the actual mileage of the engine.
PCV valve: Replaced 23k ago. Cleaned out 5k ago. May still be suspect.
Steam cleaning: Never done in the ~30k I have had the car.
Thermostat: Not OEM, I don't have heat on downhill sections of my commute when I need heat (30F-40F outside).
EDIT: Thermostat has 16k on it. Replaced in in jan 2014.
Catalytic converters: Need to check both converters, I have a USB boroscope and an automotive lift. There is a rattling noise from one of the cats. I ran over a bucket earlier this year while doing 60 MPH, rear cat may have broken up even more. Never replaced.
Fuel economy: Averaging 35 MPG. Got ~34 MPG averaging 65 MPH on highway legs of a trip that was 100 miles each way.
Fuel filter: Never replaced.
Compression check: Need to do.
Injectors: Never messed with.
Intake manifold cleaned: Never, only squirted some throttle body cleaner into throttle body 23k ago.
EGR: Never cleaned.
Vacuum hoses: Never replaced.

Currently using the intake for automatic equipped models since my manual transmission intake hose cracked this spring (difference is that manual transmission one has larger resonator and resonator opening), I still have manual transmission intake and resonator in case I need to use that to pass smog. I can't seem to find a new manual transmission intake hose.
First test done with max smog allowed 13 degrees base timing:

I then drove to a parking structure and set base ignition timing to the minimum allowed value of 7 degrees and took it back to the smog station (free retests as long as you are actually trying to fix it).
Second test: Dyno printout only.


Past smog tests. Order from top to bottom: Smog test PO did in june 2012 at 1PM at 242k, done with base timing set at ~7 degrees; Passing smog test I did October 2013 at noon with 13 degrees of base timing and a new oxygen sensor. Failing smog test I did late September 2013 at noon with 13 degrees of base timing.

[2000mc]

I think I'd want to try to figure out what temp the thermostat is actually running, especially if the lack of heat at times is a new symptom since last test.

[H-Man]

Originally Posted by 2000mc

I think I'd want to try to figure out what temp the thermostat is actually running, especially if the lack of heat at times is a new symptom since last test.

EDIT: Thermostat has 16k on it. Replaced in in jan 2014.
The downhill part of my commute I'm talking about is the stretch from 1600 ft to 244 ft. About 9 miles long. Speed limit is 45 so over most of it and I'm alternating between coasting in gear with engine in fuel cut and coasting in neutral (no EOC because I can't bump start for the life of me). By the time I'm on the second downhill grade, it is closer to 50 or 60F.

[nimblemotors]

The results as I see it show very low NOx and high HC, which indicates it is running rich. If it is running cold, you'd get this result. Is the thermostat stuck open?

[H-Man]

Got the car up on a lift (friend owns a lift) and found a chunk of substrate blocking the exhaust.
Front face of rear cat with chunks of precat littering it. Has sounded that way for ages.

Blockage.


Front face of rear cat.

Not shown: Melted down precat and chunk of wayward substrate liberated from exhaust.
Think this may have been part of my problem?
I'll check compression and sensors tomorrow, it was 105F today.

[some_other_dave]

Replacing the cat should help. I would think you're still running a bit rich, as Nimblemotors said. With a new cat (s?) you stand a decent chance of getting the numbers good enough to pass. If they aren't, then suspect the thermostat.

If you can get ahold of a wide-band O2 meter, you may be able to use that to see what your mixture is like. You probably want a little bit lean for economy, but generally the best emissions are right at 14.7:1, because the catalysts work best there.

The EGR shouldn't be an issue, as the NOx numbers are OK, or at least OK-ish.

Yeah, I'd replace the cats and see if I passed.

-soD

[user removed]

No engine off coasting with engine getting so cold the heat won't work = thermostat stuck open and it could be a contributing factor to the damaged catalyst.

regards
mech

[H-Man]

Originally Posted by Old Mechanic

No engine off coasting with engine getting so cold the heat won't work = thermostat stuck open and it could be a contributing factor to the damaged catalyst.

regards
mech

I though that it was normal to lose heat on that long of a downhill grade when in DFCO half the time?

[California98Civic]

I think if I coasted down a hill that long in my car in DFCO that I would probably lose heat too. I know some much shoter hills where DFCO brings my engine temp readings down 10 and 20 degrees.

[user removed]

Originally Posted by H-Man

I though that it was normal to lose heat on that long of a downhill grade when in DFCO half the time?

You are right, I was wrong.

regards
mech