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Discussion Starter #1 (Edited)
Breakin' [California smog test limits] 2: Electric Boogaloo. (Now with maintenance)

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.
 
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Sounds like your thermostat is sticking open. That will make it run not hot enough, which will drive up your emissions, due to the computer sending more fuel because it senses that the engine isn't warmed up enough.
The temperature gauge should go to about half way and stay there to be fully warmed up, and the heater should be outputting heat at all times once the engine is warmed up.
Hopefully that's your whole problem.

Excellent thread title, BTW...
 
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Discussion Starter #3 (Edited)
Sounds like your thermostat is sticking open. That will make it run not hot enough, which will drive up your emissions, due to the computer sending more fuel because it senses that the engine isn't warmed up enough.
The temperature gauge should go to about half way and stay there to be fully warmed up, and the heater should be outputting heat at all times once the engine is warmed up.
Hopefully that's your whole problem.

Excellent thread title, BTW...
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. By the time I'm on the second downhill grade, it is closer to 50 or 60F.

EDIT: Thermostat has 16k on it. Replaced in in jan 2014.

I can read oxygen sensors and injector pulse width if that will help figure stuff out. I need to rebuild my OBD1 cable. http://toyota.kgbconsulting.ca/wiki/OBD-1_Serial_Interface

EDIT: I ordered a usb to RS232 adapter so that I can try to read sensor data without being chained to a worn out dell latitude.
 
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Out of curiosity, when you took your car for the test how was it driven before you got there? In other words, did you drive five minutes down the street to a local garage, or did you drive it open on the freeway to get to the smog test center?
 

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Discussion Starter #5
Out of curiosity, when you took your car for the test how was it driven before you got there? In other words, did you drive five minutes down the street to a local garage, or did you drive it open on the freeway to get to the smog test center?
20 miles of 35-55MPH arterial streets. Had to skip the freeway because traffic got too heavy.
 

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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.
Your new thermostat sounds faulty despite being "new". I agree with Pete.

What does the temp gauge show when you don't have heat?

Aftermarket can be hit or miss for a critical component like this.
 

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Discussion Starter #7
Your new thermostat sounds faulty despite being "new". I agree with Pete.

What does the temp gauge show when you don't have heat?

Aftermarket can be hit or miss for a critical component like this.
Varies. No heat from cold to when the needle is about 3 needle widths away from the halfway mark. Does that make sense?
 

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Well, if the T'stat is not stuck, and it's opening and closing at the proper temperatures - then your radiator is too good.

For the simplest of solutions, you could experiment with pieces of cardboard blocking airflow to the radiator - but you must keep an eye on the gauge and make sure that it never goes much if any higher than it ever did before. In any event, assuming that all else is OK, attenuating airflow through the rad on those downhill runs might help.

You could also put the car in a lower gear, and save your brakes some wear.

But if your heat is going cold, then your engine is almost certainly switching to the cold engine strategy, and injecting more fuel.

What's your temp gauge indicating when it does this?

I would assume that you've scanned for codes, if you're datalogging. And if you are datalogging, then you might as well stop paying any attention to my BS...
 

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Varies. No heat from cold to when the needle is about 3 needle widths away from the halfway mark. Does that make sense?
Weird. The three needle-widths-from-half is right about where mine always sits after warm-up, and it's definitely got good heat then.

What's the highest that the needle ever goes to?
 

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Everything looks OK except for HC. There's a criss-cross function between HC & NOx and ignition-timing. More advance will lower HC and raise NOx and vice-versa. But... it won't affect HC enough to cause the issue you're having with HC.

The CO2% is in the good range, so the cats are working OK. The O2% is low, meaning the cats are working well to convert CO to CO2 and HC to CO2+water.

Don't bother with OBD-1 scanning, you can get all the data you need the old fashion way, with vacuum gauges and voltmeters. Now, most common source of high HC emissions is... rich mixtures with too much fuel! Check the following areas as they tend to fool the ECM into injecting too much fuel:

1. IAT - measure resistance and match up to specs dictated in manual

2. ECT - measure resistance curve from freezing to boiling and match up to specs in manual

3. TPS - make angle-template and make sure its resistance matches what should be at various opening positions

4. intake-manifold vacuum... should be around 20-in.Hg with warmed up engine

5. FPR and MAP-sensor vacuum. Use vacuum-T and measure vacuum at FPR and MAP-sensor nipples. Should match exactly vacuum measured in #4

6. fuel-pressure. FPR should reduce pressure relative to manifold-vacuum. Measure fuel-pressure with vacuum hose disconnected should be ~43.5psi. Then with it connected should be around ~33.5psi. Difference should match vacuum 1:1. Manual gives acceptable range for fuel-pressure, make sure yours is at the low-end of that range otherwise you'll have too much fuel.

7. MAP-sensor output voltage curve vs. vacuum. Test at idle 20-in.Hg and, then 10, 5-in.Hg and match output to response-curve dictated by manual. A LOT of problems occur here with MAP-sensors that are clogged or failing, putting out erroneous voltage that tricks ECM into thinking you're at higher-load than actual. Thus injecting too much fuel.




Once all those tests check out and you make any repairs necessary, there are also tricks you can employ at the smog-check to ensure passing:

1. use 25% denatured-alcohol + gasoline in the tank. Alcohols carry their own oxygen-supply and gives more oxygen for combustion and for the cat to use in scrubbing HC, CO and NOx. Even with the same AFR-air fuel ratio as before, the alcohol will result in lower HC, CO & NOx. It also burns cooler than gas, and lowers NOx (which have been creeping up on your tests).

2. use 13-degree base-timing. Increasing timing will lower HC but increase NOx. You have some overhead with NOx, so it's a balancing act between HC & NOx.

3. warm-up car fully before arriving. I like to do full-throttle runs for about 15-20 seconds with my left-foot on the brake in front of the smog-station to ensure the cats are fully heated.

4. do NOT turn off car when pulling in, leave it running to ensure cats stay hot.


--------------------------------------
Finally, there are tuning-tricks that can be used to adjust/re-program the ECM's mappings. For example, you can say at 1800rpm & 15% load, reduce fuel by -20%. And at 2200rpm & 20% load, reduce fuel by -10%. That gets into dangerous areas of legality, so I won't cover those here.
 

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Discussion Starter #11
Well, if the T'stat is not stuck, and it's opening and closing at the proper temperatures - then your radiator is too good.

For the simplest of solutions, you could experiment with pieces of cardboard blocking airflow to the radiator - but you must keep an eye on the gauge and make sure that it never goes much if any higher than it ever did before. In any event, assuming that all else is OK, attenuating airflow through the rad on those downhill runs might help.

You could also put the car in a lower gear, and save your brakes some wear.

But if your heat is going cold, then your engine is almost certainly switching to the cold engine strategy, and injecting more fuel.

What's your temp gauge indicating when it does this?

I would assume that you've scanned for codes, if you're datalogging. And if you are datalogging, then you might as well stop paying any attention to my BS...
I drove it to the smog shop with a piece of corrugated plastic in the upper grill.

On that long downhill grade, on cold days in the cooler months (remember, California) my engine drops all the way back to cold mark on the gauge and it kicks up the idle speed to the cold start mode. I drove car for a period with only the outer disk of the thermostat in, the heater only performed slightly worse then compared to with the current thermostat. Can't run heater on long downhill or engine cools off. On a warm day, I can be climbing a 7% grade in 4th gear at 80 MPH (~4500 RPM) at a rather hefty throttle and I can get the engine to cool off if I blast the heater. Is that normal?

No datalogging capability at this moment (I have an OBDII dongle but car is OBD I), right now my only option is reading the oxygen sensor from the diagnostic connector by running a multimeter into the cabin. Injector pulse width is read from one of the injector pins on the ECU through this: http://ecomodder.com/wiki/index.php/MPGuino
Engine idles when warm at about .2 GPH but that is 176 cc/min for the injector flow rate.
 

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Definitely sounds like thermostat isn't working. Make sure you replace the gasket as well. But... I doubt it's contributing to the high HC issue though.
 

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My other car gets regularly bashed on the interwebs by its own enthusiasts, over its kinda lousy factory gauges. I have never seen gauge accuracy called into question here, yet I'm still kind of wanting to see a real mechanical gauge on your car, so we can be sure exactly what those temps really are, which are being indicated by the Toyota gauge in your dash.

I've never seen my temp gauge any higher than halfway - even uphill at 80 MPH with the AC on... It never appears to go much, if any, lower either, once it's warmed up.
Now when I bought the car, the gauge never probably hit the end of the first quarter of its sweep range, and the heat was very weak, and sometimes the fast idle would kick in. I bought a Fail Safe brand T'stat from McParts, and then Googled and discovered a somewhat spotty reputation associated with this particular product. I procrastinated a few months, and installed it in my car anyway. Good heat for the spring of '14 and all of '14-'15. Factory gauge always indicates the same temp. I don't doubt it will give me good heat this upcoming Winter.

These engines do have somewhat of a rep for stuck-open 'stats - but it does still beat the heck out of stuck-closed...

All of that said, don't rush out and get a new 'stat just yet. See what this thread ultimately yields.
 

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I'm almost ready to conclude that ANY gauge fluctuation after warm-up indicates a problem.

When my 'stat was stuck open, it would rise and fall in accordance with moving and being stopped. Once I replaced it, it always rides in pretty much the same spot - once it's warmed up.
 

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It's definitely a good idea to take a look at your thermostat mine has been stuck open in the past too and had all the same symptoms especially the gauge going down as you drive. Since mine is an automatic as the cold idle kicks in i can literally drive 15 mph without touching the gas lol i got the same fail safe thermostat and so far it's been fine and warming up no longer took 10 minutes
 

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Yeah, I had those symptoms with my car too. Long warm-up, wouldn't shift into top-gear for a while. Went to replace the stuck thermostat and I find it's missing! I bet some great mechanic somewhere must've thought the car would run better. hah!
 

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Discussion Starter #17
I have a multimeter that has a thermocouple that I can tape to something under the hood I think.
Going to bed now, I'll find out how much my car hates me in the morning.
It seems I can get the toyota made thermostat off of amazon for $20, if I boil the thermostat and it shows itself to be a problem, should I pull the trigger on a thermostat?
 

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LOL, whatever it is, it's likely something small, fairly cheap, and easy enough to replace.

Although another bit of study advice regarding the emissions test: Change your oil fairly soon before the test. If the engine is worn, then gasoline can get into, and taint, the oil. And if the engine burns oil, then the mixture will be slightly enriched. Just a thought...
 

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aw man that's definitely not a good mechanic smh the thermostat actually does help with cooling too since it provides some back pressure so the coolant stays in the block longer to dissapate heat... at least in my mind lol

but hopefully that fix would keep you legal here in cali
 

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Discussion Starter #20 (Edited)
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. May have been from an older precat because the front face of the precat is still intact.
Think this may have been part of my problem?
I'll check compression and sensors tomorrow, it was 105F today.
 
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