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Discussion Starter #1 (Edited)
Failed CA smog for HC emissions at idle only. here are my numbers.

IDLE at 659 rpm:
CO2 = 14.2
O2 = 1.0
HC measured 167, max is 120 = Failed
CO = 0.3, max is 1.0

at 2552 rpm:
CO2 = 14.9
O2 = 0.3
HC = 9, max is 150
CO = 0.0, max is 1.2


here's a little history I think you need to know to help....

2 years ago passed fine with a HC idle at 10. mileage 127K, and had just put on a new Raptor Racing High-flow cat, that I bought with my cat-back exhaust system purchase.

August 08, I removed and cleaned the intake plenum and runners, replcd valve stem seals, other seals, did not remove head. mileage 132K. I mention this work because at this time I took the intake apart and there was no fuel pooling in the runners, as I will describe below in July of 2009.

July 09, developed a cracked head with 137K miles:

While working to remove the head, I found my first three runners were filled with gas. I was surprised at this, as I did not experience any engine running issues, poor mileage, no error codes, and the plugs looked fine with normal deposits. I was simply removing the intake and found this...


After inspecting the plenum, it looked like the cold start injector was leaking, as I could see where it was running down the plenum and into the runners. So, as a precaution I sent out 8 injectors and 2 other cold start injetors for cleaning, drip testingm and flow matching.

After putting the new head on, and putting the engine back together with serviced injectors and tested cold start injector, I checked for leaks by bringing up fuel pressure...no leaks found.

Also, plugs, cap rotor are brand new, timing is 10 degrees BTDC, oil is new as well.


So, I could have been driving with this fuel leak, and thus a rich condition, for @ 5k miles at most between the August 08 and July 09 when the head cracked. I've researched and undersatnd that this may have led to a "pre-mature" failure of my new cat.

Smog tech measured the temp of the cat and says there is a 100 degree temp difference across the cat, so it is at a normal operating temp. I'm assuming he is correct on this. Shop wants to put on a new cat. I of course can do this myself, but the cat has at most 10K miles, of which 5k miles was during the time of fuel leak in runners.

My questions for you are:

Could this be the case that my cat has failed due to the rich condition from the pooling gas in my intake runners?
Would a cat, that has failed for the above reason, result in high HC's at idle only, but not at higher rpm's?
If the CAt has failed wouldn't the other numbers be off as well?
could it be my O2 sensor?

At the moment, the only thing I can do (without spending more money)is put on a new toyota oem O2 sensor that I've had for years as a spare and then have them "check" the emissions. My thinking is that that, the O2 sensor is only "used" during idle and not at WOT, so the sensor could be bad causing a rich condition at idle. Yes?
However, I would think I would be getting error codes or a loss in mileage, or spark plugs indicating a rich condition, which I'm not.
Other than that step, my only idea is to fork out for a new cat, put it on, and then check.

Suggestions, opinions please...

Rick
 

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Discussion Starter #3

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Discussion Starter #6
OK, You must know it all. Good luck.
Ok, then what am I incorrect about?

my intention was not put your comments down, which by your response, is what I gather has happened.

If you were not asking about the idle and what it is "set at", then perhaps please rephrase the question.


Rick
 

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When was the last time you cleaned out the EGR system?
 

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Discussion Starter #8
When was the last time you cleaned out the EGR system?
when I replaced the head in late august.
I had the Plenum hot tanked, made sure the passage through the plenum was open and also cleaned out the EGR cooler and pipe.

also, the EGR system tested and passed, vacuum was applied to valve at idle and engine almost stalled.

Rick
 

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i do not believe the cat converter will help with hc's. hc's is unburnt fuel or a rich mixture. so cat or no cat shouldnt affect that. there are ways around the hc reading as far as an inspection/smog test goes. but this is really just covering up the problem. all you need to do is create a vacuum leak in the intake system. this will get more air in to even out the mixture. i have done this a number of times with good results.
 

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Discussion Starter #10
i do not believe the cat converter will help with hc's. hc's is unburnt fuel or a rich mixture. so cat or no cat shouldnt affect that.
here's what I find with a quick search on catalytic converters:
"Since 1981, three-way catalytic converters have been used in vehicle emission control systems in North America and many other countries on roadgoing vehicles. A three-way catalytic converter has three simultaneous tasks:

1. Reduction of nitrogen oxides to nitrogen and oxygen: 2NOx → xO2 + N2
2. Oxidation of carbon monoxide to carbon dioxide: 2CO + O2 → 2CO2
3. Oxidation of unburnt hydrocarbons (HC) to carbon dioxide and water: CxH2x+2 + 2xO2 → xCO2 + 2xH2O"

Rick
 

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They didn't test you on a dyno?

I know that in some rural areas, the test is an idle only and rev test.

If it was an idle test, then the EGR system will not be in play.

Also, if the car is idling too long, the o2 sensor will stop operating in some cases.

Here are some tips to get the maximum "burn" for a smog test.

- Set idle to the highest allowable limit
- Retard timing to 8 degrees
 

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Discussion Starter #12
What do you mean by test on a "dyno"?

After the evap, emission at idle and 2500 rpm test, then they check for egr valve operation, error codes and timing for 10 BTDC. I guess it depends on the station if they see a 8 BTDC and call it OK. I can try to ask them to let it slip by if the HC numbers are better.

It failed the HC at idle and they were concerned the cat was not hot enough, so they asked me to drive on the freeway for a while. Drove back in after 20 minutes going up 2,500 elevation and back down, tech immediately tested HC's at idle and they were still too high.
 

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Lucky you to live in an area without the dyno requirement for smog test. Those were the good 'ole days :)

Gas pooling in the intake runners is not too unusual. I believe since the injectors are batch fired, there may be always some gas trickling into the runners even when the cylinder is not firing yet. Shouldn't be too much though. Have you checked for vacuum leaks? Maybe poor vacuum can throw off much of the emission stuff. How about the AFM, has it been adjusted? Might be able to lean it out a bit at the AFM (I've only richened things at the AFM, but I assume the reverse is possible). Double check your timing belt install, making sure all the cam gears, crank pulley, everything lines up at TDC. I'm not even sure if the engine will run well if off by a tooth, but nice to check everything.

If you service all your injectors including the cold start injector, I'll assume they are ok. Is your water temp sending unit ok, and car is not overheating at all? If the ecu senses the water temp is cold, it will send my gas to the injectors, again, maybe minimal, but something.

Check your coil, if spark is weak, might get poor burning of gas. Comes down to something causing too much gas, or too little air, or too little spark, resulting in the rich condition. Doesn't sound too bad, and it almost passes, so hopefully a fairly easy (and cheap) fix.

Good luck!

Don L.
 

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there is no "setting" idle speed with the 5mge engine. It is a target speed set by the ECU.
You can adjust the idle with the idle set screw in the TB, I have done it many times, for a range of different idle speeds.

How old is the O2 sensor in the car now? Pull out the one in the car now and see how it looks. You could have also killed the 02 sensor with the extra fuel coming from the leaking cold start valve.
 

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Rick my last test on the 86

HC ppm CO% NOx ppm
15 mph 34 .08 417
25 mph 24 .07 455


Not familiar with a high flow cat, but the basics come to mind, plugs, cap rotor, O2 sensor...
heck I would even change out the coil to be certain??

I would assume if too much flow the #s would be off at high mph as well as idle, cant think the thermo timing switch would cause the idle #s to be off?? seems as if the fuel is not burning at idle but AOK at higher #s hmmm???

Timing has to be spot on to perform the test.
 

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Have you checked that loop is closed using the "Idle Speed Test" in the FI section of the TSRM (think p. 59). This test is misnamed and checks for correct loop (ecu) operation.

As Don L suggested, it may be a marginally correct coolant or air temp sensor. Different airflo at diferent engine speed might cause airflo temp sensor to read differently at idle than at speed since afm body (where air temp sensor is mounted) can be hotter at idle especially if you have certain intake mods.

83CelWa
Setting idle speed by rotating "idle" screw ccw many revs, disables ecu control of idle speed and idle speed will vary as a function of atmospheric and engine operating conditions. Idle screw should be set fully cw for a correctly operating engine.
 

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Oh, I know it is bad to adjust the screw, just saying it is possible.
 

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Discussion Starter #20 (Edited)
..update..

thanks for all the replies and comments..

FYI...the plugs, rotor and cap are brand new.
Cold start time switch and coolant temp sensor check within spec.
not sure what is the "Idle Speed Test" that StanS mentioned in the TSRM. Took a look and don't see what he is referring to.
I'm not going to mess with the TB idle screw, that won't solve my problem, only mask it. The idle needs to be at the spec of @650 rpm, so adjusting this screw to raise the idle may lower the HC's, but my idle won't be in specs for the test..
...and to put other possible theories to rest, the ISCV valve I rebuilt and cleaned during the head work, so that should not be an issue here. The ISCV should go full open upon cold startup/enrichment and I'm not having any cold start idle/running issues, so that tells me the valve is opening, thus not the cause of my rich condition.

I checked my records and it shows that my air filter has ~4k miles on it. Not expecting to find it dirty, I checked it anyway and was in for a surprise when I found it was in need of changing.
So,
I replaced the air filter
put a bottle of octane booster in the full tank
set timing to approx. 8 degrees BTDC

Took it back in to the shop for a "check" only. HC idle numbers were better but dropped below 100ppm, then move above the 120ppm fail limit, then drop back down, then back up and so forth. The manager said to go ahead and test it but it failed. This time the HC idle is 138 (recall the pass limit at idle is 120ppm), so I'm better than yesterday's first test of 167ppm.

He did not charge me for this test since I went in only for a check and he gave the word to test it, so that was nice of him.

I know I can test the O2 sensor on the car, but in 5 minutes I can just put on a new one, so tonight I'm going to put in a new oem O2 sensor, and have it rechecked on Monday. I'll keep this thread updated.
Rick
 
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