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

7K views 67 replies 8 participants last post by  H-Man 
#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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#2 ·
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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#3 · (Edited)
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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#4 ·
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?
 
#6 ·
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.
 
#8 ·
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...
 
#11 ·
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.
 
#10 · (Edited)
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.
 
#13 ·
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.
 
#14 ·
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.
 
#15 ·
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
 
#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?
 
#27 ·
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?
Yes. Absolutely. From what I understand, in today's market, official OEM-stamped and approved parts for older cars like ours can still be a crap-shoot. Can't remember if I've heard any bad about Toyota branded 'stats here, but I would definitely be less afraid of putting one in my car, than of one from the McParts store.

I saw that Autozone carried the Fail Safe 'stats, and I'd seen Sam Memmolo tout them on the old Shadetree Mechanic show, so I got one. Then I googled it and saw some bad reviews, but I installed it anyway. It's been good for a year and a half, so far.
Although, I have to say that I suspect that real Toyota OEM 'stats are designed the same way, based on my experience with my '93, and also the '90 I had before it. That car had weak heat, but I never replaced the 'stat.

And that's some impressive data gathering, on your part!
 
#18 ·
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...
 
#19 ·
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
 
#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.
 
#21 · (Edited)
My car passed CA smog just fine with most of the pre-cat crumbled away (only about 10-15% left). Your emissions results shows that the cats are working perfectly. It's already using up all free oxygen to scrub HC and NOx; cats are working optimally. Your mixture is simply too rich and there's a limit to how much conversion the cat can do.

What you need to do is reduce fuel and introduce more oxygen into your exhaust to pass the smog test.
 
#22 ·
Would the ECU be going into protective/performance enrichment with the exhaust blockage? Looks like the engine was at about 30-40% load on the second failed dyno test.

I'm going to work on the sensors tomorrow.
 
#23 · (Edited)
Not sure if the ECM has any algorithms to detect clogged exhaust; need a pressure-sensor in exhaust for that. Even then, normal exhaust pressure varies widely depending upon RPM and load. The downstream O2-sensor is used to determine catalytic malfunction. That throws a CEL if it detects that the O2-concentration coming out of the 2nd cat is too high compared to what's going into the 1st cat. We know from the smog-check that the cats are working well with minimal O2 coming out. So no CEL isn't a surprise.

The load figures at least narrows down the search, test the MAP-sensor & TPS first as those are what the ECM uses to calculate load. How did you determine load was 30-40%?? In second gear used for the 2nd test, you get about 7x torque-multiplication through the gearbox. Account for 15% loss through frictional losses and we have 7* 100-lb*ft *0.85=595-lb*ft max-torque in 2nd gear. Divide that by 107.3-lb*ft average of the 5 dyno runs and load is actually 18% of maximum. Or even less if we use the HP figures. So something is making your ECM think it's running at higher load than actual and injecting too much fuel.

So... Test the MAP & TPS 1st. Then FPR & fuel-pressure. Then the other temp sensors last as they have lower weighting in adjusting AFR. Or could be as simple as vacuum-leak in intake-manifold. I've seen quite a few instances where that throws off MAP-based cars.
 
#24 · (Edited)
I'm going off of the horsepower the dyno used and assumed the engine was at at ~1800 RPM and then compared it to max horsepower at that RPM.
http://www.toyoland.com/images/7A-FE/graphs.gif
I'm using load to mean what % of the horsepower the engine is using vs what it can produce at that RPM.
 
#26 ·
Okay, did a compression check and a shallow sensor test (I can't get to the backside of the ECU so I'll have to rig something up to test the MAP. I'm an EE major, shouldn't be an issue [famous last words].
TPS:
VC-E2: 3.42k
VTA-E2
WOT: 2.75k
67*: 2.3k
45* 1.7k
23* 1k
0* .5k
IDL-E2: within specs
Coolant temp sensor: 1300 at 35C, 480 at 67C. Will revisit when I have a gasket for it.
IAT: Meter reads it as being in spec. I'll have to check again because I didn't write down the reading.


Compression test. Written as first 3 puffs and then about where I ended the test. First time running a compression test so I may not have cranked long enough, I only cranked ~5-6 times instead of the 7 my hayes said to do.
#1 : 120, 150, 180, 205
#2 : 120, 150, 180, 205
#3 : 120, 150, 180, 205
#4 : 120, 150, 180, 210


Spark plug wires:
#1 : 3.41k
#2 : 3.08k
#3 : 2.44k
#4 : 2.15k

Rear catalyst surface temps at idle:
Front was something like 130C, outlet was 160C. Couldn't get close enough to get a better reading but the exhaust seems hotter now that it used to be so it seems like my cat may be working now that that exhaust blockage isn't making the exhaust cool down before the cat.

I have some boroscope pics on another computer, I'll post them later.
 
#28 · (Edited)
Hey, great work gathering test data!
Okay, did a compression check and a shallow sensor test (I can't get to the backside of the ECU so I'll have to rig something up to test the MAP. I'm an EE major, shouldn't be an issue [famous last words].
You can use a hook-probe on the multimeter. They're typically pointy and sharp enough that you can get to the inner-wire at the MAP-sensor itself.

The thing with allowable-ranges on multiple sensors is you should be careful of where in the ranges these are. If you have multiple-sensors that's on the rich end of the range, stacking many of these sensor-inputs may put you over the edge into a high-load area of the fuel-map. You can use a pot in voltage-divider or series circuit to adjust one or more sensors and nudge them in the other direction towards leaner mixtures... Also adjust the TPS towards lower-load values as well...

Compression test. Written as first 3 puffs and then about where I ended the test. First time running a compression test so I may not have cranked long enough, I only cranked ~5-6 times instead of the 7 my hayes said to do.
#1 : 120, 150, 180, 205
#2 : 120, 150, 180, 205
#3 : 120, 150, 180, 205
#4 : 120, 150, 180, 210
I ran into similar issue as well. The two leaky cylinders with clogged rings will allow enough blow-by of unburnt fuel into the exhaust that it will increase your HC readings on smog-test. I found doing two cycles of piston-soaking restored the low cylinders back in-line with the others:

1. remove spark-plugs
2. squirt 2-3 seconds of PB-blaster down the spark-plug hole
3. pour in 5-10cc of acetone
4. re-install spark-plugs, don't tighten, don't connect wires
5. crank 1/2 turn to slosh mixture around
6. let sit overnight
7. remove plugs and inspect cylinders, you may find low-compression cylinders have drained, others still hold some piston-soak mixture
8. re-squirt PB-blaster and acetone mixture into low cylinders
9. lightly install plugs and let sit for 5-6 hours
10. remove plugs and lay rag over holes
11. crank 2-3 times to blow out remaining mixture
12. re-install plugs, wires and start engine

After warm-up, re-do compression check. Let's see what the compression-figures are now. :)
 
#30 ·
Sorry I was reading down the columns instead of across.
You're on your way to solving this, there's a critical piece of data that will jump out like a red flag.

Yeah, you can do the piston soak on your dad's car. It brought one of my cylinders back from 85psi to 195psi. That was a while ago and I've been using full-synthetic oil to keep the burn rate and deposits down. Reduced oil-consumption too. :)
 
#31 ·
Just realized what would make a good pass through connector for testing the MAP sensor: Either N scale or HO scale rail joiners attached to a suitable pin.
Have a wire leading off of each pass through pin to a crimp style connector of the appropriate diameter to put a DMM probe into and then run the wires to the cabin for road testing if needed (may need road testing since I can't hit 12 WHP load in a garage unless I had a dyno, 12WHP is enough to move my car down a level road at 60 MPH).
 
#32 · (Edited)
Heh, heh... that's one of the old measurements of efficiency & aerodynamics, how much HP needed to move the car @ 60mph. Coastdown distance from there as well.

Hey, I just realized I've forgotten some of the old tips & tricks. Sewing needles can be used to skewer a wire to attach multimeter probes!

For quick datalogging capabilities, I hook up an old LinkECU AFM-Link box (AFM/MAF to MAP-conversion, similar to HKS-VPC). It has its own MAP-sensor to verify the car's sensor and can datalog 3 additional channels such as TPS, RPM and O2-sensor.
 
#33 · (Edited)
Do you know what the mechanical limit for the ignition advance is? I'm thinking that if my timing belt jumped a tooth (unlikely, but possible) my maximum ignition advance with TE1 shorted to E1 will not be the same as an engine that hasn't jumped time.
Did more data gathering:

MAP voltage from sensor pin to ground:
24.5" HG: 1.48 (initially read at 1.2v but then all my readings seemed to have shifted up .3v)
22.5" HG: 1.65
22" HG: 1.69
21"HG: 1.8v
engine off~ 3.56v.
Idle: needle vibrating at around 24.5" HG.
I drove around with a multi meter watching the oxygen sensor, as it cooled down outside the engine seemed to be on the rich side of .5v more and more.

I need to find somewhere that has enough vac line that I can watch the MAP from the cabin.

I am doing some looking and it looks like I should be idling at 1.2V and not 1.48. Would this be a likely culprit?
 
#34 · (Edited)
Do you know what the mechanical limit for the ignition advance is? I'm thinking that if my timing belt jumped a tooth (unlikely, but possible) my maximum ignition advance with TE1 shorted to E1 will not be the same as an engine that hasn't jumped time.
I think it would be in the +/- 17-degree range. I've advanced my distributor to the point where it was OK under cruise, but would pinging/knocking at anything above 25% extra throttle. This ended up being around 15-degrees BTDC base-timing and I had another degree or two of distributor rotation.

Ignition-timing can be compensated back to spec with distributor-rotation if timing-belt slipped. However, the valve-timing will be off. Slipping is in the retarded direction and retarded valve-timing would... increase low-end HC, lower low-end torque and increase high-end HP. That does seem to match your 1st smog-test readings with more HC in 15mph test and lower @ 25mph. Anyone know number of teeth on the cam-pulley? We can calculate the amount of valve-timing retard with a slipped belt.

Did more data gathering:

MAP voltage from sensor pin to ground:
24.5" HG: 1.48 (initially read at 1.2v but then all my readings seemed to have shifted up .3v)
22.5" HG: 1.65
22" HG: 1.69
21"HG: 1.8v
engine off~ 3.56v.
Idle: needle vibrating at around 24.5" HG.

I drove around with a multi meter watching the oxygen sensor, as it cooled down outside the engine seemed to be on the rich side of .5v more and more.

I need to find somewhere that has enough vac line that I can watch the MAP from the cabin.

I am doing some looking and it looks like I should be idling at 1.2V and not 1.48. Would this be a likely culprit?
Figuring out why all your readings increased by 0.3v might be a clue... strange... Did the reference-voltage change as well? Did you use absolute power-ground or signal-ground? Here's some calibration data from the manual:

3.96v = 112kpa, -3.6 in.Hg, 1.74 psi
3.6v = 100 kpa, 0 in.Hg, 0 psi (atmospheric)
2.4v = 60 kpa, 12 in.Hg, -5.8 psi
1.2v = 20 kpa, 24 in.Hg, -11.6 psi

Also datalog I have of warm-up cycle below. Manifold vacuum was around 20-in.Hg with leaky cylinder. MAP-sensor @ 1.5v and should be lower with more vacuum. It went up to 1.6v after warm-up and lower idle-speed (less vacuum). Didn't re-measure after I cleared sticky rings, should do that again since it's been about 1-year.



IF you've verified that vacuum at MAP-sensor is the same as in intake-manifold, then you can be sure there's no vacuum-leaks. Sounds like you've got good seal with 24.5-in.Hg at idle. Seems MAP-sensor is out of spec, reading more load than actual, causing ECM to inject too much fuel and running rich. Combined with 2-3 other variables on the rich side and that may throw you over the edge.
 
#35 ·
Not the pinging limit but how much advance (or retard, likely safer) in timing set mode does the distributor give when adjusted to either limit of its rotation?
 
#36 · (Edited)
Okay, double checked the vacuum readings and it seems that I'm still .3v high. I'm guessing that my MAP sensor is a POS.
Readings are taken by putting a sewing pin into the signal pin of the connector and the same for the ground pin on the connector.

I'm suspecting that the MAP may be erratic about readings. It initially read out at 3.4v then suddenly went to 3.56v.

I think I'll go to the scrapyard tomorrow and try to find a working sensor.

EDIT: IF the limit is 17 degrees or thereabout, that is about what I can set my timing to as max. I'll double check it, it may be closer to 20. I remember looking at another thread and it looks like that a jumped tooth will throw off camshaft timing by 7.5 degrees.
 
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