Hi HT....

I know this topic if off topic.... But I'm seriously in need for answers before smog. I recently complete my 4.0 V8 swap on a SC400.... I have been a long term member of HT and will not willing to go any other forum with still couple of civic and integras on hand. I failed on 15mph with extemely high HC and CO with real low NOx and at 25mph I failed HC by just a tad.... Just wondering, if I reverse the vacuum line on a purge valve, will it give me the numbers as stated or numbers on the bottom image... I double check the line from canister to purge and seems like it was reverse. After I switch the line around, I don't have the hesitation from complete stop to acceleration and definitely runs a lot smoother..... Please help...

Recent done:

1) Complete tune up with NGK Spark Plugs, Cap and rotors, PCV, waterpump, tensioner, and timing belt. Timing is on point and ignition system is good. No fuel leak or intake leak. Don't believe it's the catalytic converter because low NOx. I'm going to clean the throttle body tomorrow and replace the air filter





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You are running rich as hell on the 15mph. Take a look at the o2 sensor(s). Also dont forget that the cats also lower HCs and converts co to co2. If i had this in my shop Id test the o2 sensors first. If those turned out fine I would drill a hole before and after the cat to see if its actually working. But to do that you need to bring it to a shop.

 

It doesn't surprise me if your cat is toast. Had a 93 Miata that had GP emissions, she took it to a test and repair station and they took off the cat and all the substrate has burn out. Replaced it and everything was normal again.

 

Right after the smog, I felt almost sure it was the Cats that was failing the smog. But NOx was low due to the amount of HC being at the Cats. Therefore, today I checked all four 02 sensors and they are working properly. I cleaned the TB and took it out on the freeway trying to run it super hot. Came home getting an intermittent misfire. Popped the hood, and found the the main spark plug wire from the coil pack pack to the distributor cap was shorting out to the head. I believe that's the problem where my L/S Bank plugs wasn't firing correctly creating that amount of HC/CO out of my tailpipe. Picked up a set of new wires today and dropped it in. No more rich smell out of the tailpipe and it runs perfectly fine. I will bring it in for smog tomorrow and hopefully this time it'll pass in flying colors.. Will keep you guys post on the update

 

After another day of failing California smog.. Anyone have any idea what else can cause this kind of reading? I almost have to believe it's the catalytic converter, but need to hear from someone else opinion.. Please help !!!!




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Anyone? Will a bad ECTS cause readings above?

 

You are still running rich. First off did you test the upstream o2 sensors with a scan tool or did you just go look at them and consider that enough of a test? Test them. Make sure they are fluctuating from 300mv to 800mv constantly. Than richen the mixture with the brake cleaner or propane and make sure that the o2 sensor stay at 800mv or above and doesn't fluctuate. Then stop the propane or brake cleaner and watch to make sure it reacts.

You are running rich and thats why your nox is so low. I can almost bet that when you repair the o2 sensor problem or running rich problem you are going to have a high nox problem because you killed the cat from running rich so long.

 

It's an obd1, therefore I cannot use scan tool. Okay, today i jack up the car and retest 02 sensors upstream. It fluctuate between .100 to .600 at idle.... At 2500rpm it will fluctuate between .200-.800..... I unplug one of the vacuum to see how's the 02 sensor will respond which it went to 50mv-100mv and when I plug it back in. It will go right back up to 800-900mv for 1-2 seconds and will fluctuate between 200mv-800mv Meaning it's reacting like it should for both upstream... Down streams stays about 500mv


Almost seems like something making my 02s to run rich. Checked fuel injectors: Reading about 13.8-14.0 ohms (Specs:13.8 ohms).. Therefore, I checked the ECTS finding out that there's no ohms across the pin. Removed the ects and found out it was crack between the plug to the unit.

Questions:

1) Even though it's obd1, shouldn't it have thrown a code for open circuit at ECTS or something

2) Since open circuit ECTS will keep system in Open Loop (Extremely rich & longer than normal injector pulse): Will it gives me the reading above?

3) On OBD1 system: How can I find out is it in closed loop system?

 

Ideally,but the ecus of that era do not use rationality, so its hit or miss.
Yes. Particularly the high CO.
The fans should cycle twice and the upper and lower radiator hoses should be hot to the touch. You can also monitor the O2 switch rate.

 

Check your PCV system for proper operation. Also, ensure your EVAP purge system is working correctly. Most engines can deal with purge at cruise, but have a harder time at idle, producing a failure, make sure it is hooked up correctly, if it is working at the wrong time, game over. See if he will run the test without the PCV, and then without EVAP, for diagnostic purposes. If it produces a pass, which I believe it will, you can figure out the cause.

Do your oxygen sensors have heaters? The second test was run at a higher engine speed, which will increase O2 sensor response time, and converter efficiency.

Check the resistance of the CTS cold and at normal operating temperature, and compare to spec. A crack is a crack, doesn't mean it doesn't work, but you should replace it if it is cracked. If your ECT was severely irrational, or defective, the ECM will produce a DTC. If you are questioning the output of any sensor, use a scan tool to looks at the PID's, there is a connector underhood.

Converter could be a problem area if it cannot scrub the emissions from the new engine, its got NOx under control and HC isn't off by much, I think you could get by without one.

I'm thinking that if you took the air filter out you may have a shot at passing XD.

 

The test cannot be run without the PCV. It is illegal here. The vehicle is not tested at idle.

This ECU does not use rationality and there is no DTC for an incorrect or "irrational" reading on this vehicle. OBD 1 ECUs only look for a signal or voltage, not necessarily the correct one.
Because the vehicle is not in fuel control it is impossible to tell if the converter is efficient or not at this point. NOx reduction may only be the result of the vehicles rich condition.It will not change anything.

 

I used to do smog in Dupage county IL, and we could run the tests without these systems, for diagnostic purposes. It is legal to pass it like that? No, of course not, be we are authorized to do it to help find the cause of the problem. You can test the vehicle at whatever RPM you want, at any speed you want, the only thing that matters is the actual test to pass the car.

What part of check resistance cold and at normal operating temperature did you not understand? I understand that some computers do not use rationality, which is why I said what I did.

True, that would have to be evaluated after whatever is wrong is fixed. I never said replace the cat, I said it could be a problem area, as I understand cold exhaust temperatures reduce NOx.

So removing the air filter, creating a vacuum leak, or an air bleed anywhere in the intake system that enables the engine to suck more air than normal will not do anything to the engine? you are dead wrong. Removing the air filter would be comparable to putting a high flow air filter in, obviously that will affect power output and thus emissions.

 

1) ECTS: So you're saying with an ECTS with no ohms or continuity may not give a code ( Hit or Miss)? I can see an improper working ECTS doesn't throw me a code for OBD1, but wouldn't and open circuit where the connector on the ects to the unit broken apart?


2) There's no fan clutch on this system because it's a hydraulic drive fan.


3) "slowcivic2k: Check your PCV system for proper operation. Also, ensure your EVAP purge system is working correctly. Most engines can deal with purge at cruise, but have a harder time at idle, producing a failure, make sure it is hooked up correctly, if it is working at the wrong time, game over. See if he will run the test without the PCV, and then without EVAP, for diagnostic purposes. If it produces a pass, which I believe it will, you can figure out the cause."

New PCV installed during swapped. EVAP have been triple check for misrouted vacuum lines. Can't run the test without PCV hooked up because "test only" and it will definitely bring up the idle rpm dramatically with that off which is great cause more oxygen.

Update: Still waiting for ECTS to arrive and hopefully once I get continuity on the ECTS. I will get better reading at the 02 sensors because when I hook the multimeter at the 02s, it'll fluctuate from 100mv-800mv at idle. During 2500rpm: 100mv-900mv fluctuating. . Please read the 02 sesnor I got above and tell me what you guys think of the reading I have been getting before replacement of the ECTS... I'll keep you guys posted once I put everything back together during the weekday

*****Also, does it really makes a big difference for the 02 heater to work for smog purpose on an OBD1 system? I figure it's there to help heating up the 02s during open loop. Once it's in closed loop driving, isn't the exhaust is hot enough to keep the 02 in closed loop? Please correct me if i'm wrong ****


Anyone have a better vacuum line schematics of the EVAP system where I can rechecked the system again on a 1993 SC400 4.0 V8.. Anything will help.. thanks

 

The heater needs to work to ensure that the O2 sensor is delivering a reliable signal, if the heater does not function the voltage output can vary, misrepresenting engine operating conditions. Most sensors must be above 500 degrees with an internal heater to produce the desired output, good or bad.

I know you cant run the "test" without it, but removing the PCV and running the test can prove that you have too much blow-by in the crankcase, causing the excessive fuel and thus your failed test. If this is a contributing factor, your HC and CO will improve, indicating you have fuel getting past the piston rings.

About the EVAP system, it would be good to verify that your fuel cap seals, and that the fuel tank vent assembly is the correct size. If you have hoses that are broken under the car, this will permit the engine to suck air into the fuel tank, and then to the engine, creating more vapor flow that can cause a failure. Most OBD1 cars do not check for tank leaks, or excessive/insufficient purge flow, but these can cause your problems.

Even though this is not my thread, please be productive with your posts. The Devils Advocate style responses are of no help to anyone. And you know who you are.

 

What you did in ILL. is irrelevant. The car is in CA and I am a Licensed Smog Tech here. Nothing you said applies here.


You specifically said the ECU will flag a code for an irrational signal. That is wrong and unproductive...


You stated that the converter had NOx under control. How can you ascertain this when the vehicle is not in fuel control and is running rich?


No. Your understanding of feedback control systems is flawed and having the OP do this will not yield any useful results and is unproductive....

 

Giving erroneous information is not productive. I will correct you when applicable, if not for your benefit, then for the benefit of others reading this thread.

 

If there is NO signal, yes it should flag a code.


It would be much better to drive the car and graph the O2's with a DSO, but given the information you posted so far I 'd venture to say the O2's are working properly. Replace the ECTs and retest.

 

Wow, he actually suggested doing something to help the OP in this thread, good job, keep it up!

 

Wish I got a DSO, it would have save me a lot of stress. Never got a fault code on this vehicle for the ECTS. I just tested it and realize no continuity. Therefore, removes ECTS and found the plug on the ects side broken from the temp unit itself. Thanks guys, I hope the unit arrive tomorrow where I can install it.... Upon installing, I will go under and get some more reading off the 02 sensor and test the heater since I thought it was there really just to put the 02 in close loop faster on start up and that's it. BUt since you guys says it keeps the 02 operate normal at all time even during driving. I will definitely check it tomorrow


This is pretty much how it looks like when I got it out but it was in once piece barely holding together. That's why I wonder shouldn't I get a code with a ECTS pretty much open complete with no continuity.



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I would check it with a multimeter like I suggested earlier, and see if the resistances cold and near 190F are within specification. If they are, you can check the entire operating range to see if it falls below or above specification. In my experience (which doesn't matter to some, but ill say it anyways) when they go bad, it is generally an exponential failure, or an open. Provided the computer sees a valid signal, it is not the cause of your problem. Obviously though it should be replaced for being broken.

 

" it is generally an exponential failure, or an open. Provided the computer sees a valid signal, it is not the cause of your problem. Obviously though it should be replaced for being broken."


So you're saying it's open, it'll provide the computer to see a valid signal? If I were to unplug an ECTS. Wouldn't the ECM will assume that the engine is still cold and dump more fuel in system?

 

I'd say at this point just replace it. You know it is broken. It may or may not be providing a valid signal. Perhaps it only works intermittently. I can tell you that a bad ECTS on this era of vehicle will def affect CO and to a lesser degree, HC.

 

Replaced ECTS..... Jacked up the car and went under check resistance for the 02 sensor heater upstreams. Both measured in spec: 5.1-6.3 ohms at 68 F. Even though the 02 measure within specification, I decided to ordered new Denso 02 sensors for upstream because it might be running lazy and I couldn't tell with a multimeter. Hopefully, I'll get a better result.

Also, I clean the EGR valve cause I realized as the HC and CO went down, the NoX went up by comparing the first and second emission Smog Report. I realize once I fixed my HC and CO. I will probably have high NoX. Therefore, I went ahead and did it.

Awaiting for new 02 Sensors arrival. While that's being shipped, I will probably I.V water through the intake system tomorrow to clean out some of the deposit to get prepare for Nox. Seafoam VS Water: I used both method numerous times before, I think water is more safe and it's a more clean method injecting natural water into the system instead of chemical. Seafoam (chemical), personal believe it eats up seals. Both methods gave me great results for both my integra gsr and EG6. Let's hope for the best

 

Not to play devil's advocate but Bosch makes horrible oxygen sensors. They are known to be bad out of the box. You really should send em back and order Denso from rockauto as they are OEM.

 

Sorry, I meant Denso 02 sensors I ordered. Hopefully it'll show up soon where I can do another smog soon to see what kind of reading i'll be getting.

NEW DENSO OEM OXYGEN SENSOR LEXUS VEHICLES 234-4211