Failing emissions and need help (sc300)

[iwannadie]

Ok, The 95 sc300 (2jzge) failed really bad the first time around.
Test 1: Results / Allowed
HC .94 / .80
CO 2.37 / 12.00
NOX 4.43 / 2.00

I had 2 new magnaflow cats welded in and re-test.
Test 2:
HC .20 / .80
CO 3.23 / 12.00
NOX 2.21 / 2.00 (ahhhh .2!)

Checked the timing and it was advanced, set timing to stock as recommended by the internet for re-test.
Test 3:
HC .32 / .80
CO .70 / 12.00
NOX 8.21 /2.00 (aaahhhh!!!)

Now my nox is going the wrong way fast. It was actually cooler and rainy outside though, I drove for an hour prior to the test, waited maybe 3 minutes at the test facility before my test, I reved the motor the whole time.

In This Graph they printed for me shows I am failing NOX bad right at the start then it gets better. Would I assume its the weather and I wasn't hot enough because of the cold/rain? Should I wait and retest when its hot out again or should I look at something as the cause?

I am thinking maybe O2 sensors Or EGR but what else? I don't want to shotgun parts at this thing, the testing fees are killing me and now it's past the registration due date also.

 

[Supracentral]

Be sure you check for vacuum leaks. It's your #1 suspect.

High NOX is a result of extremely high cylinder temps. Potential causes are really shitty low octane fuel, EGR valve stuck, lean running due to vac leaks, advanced engine timing or (rarely) cylinder hot spots -physical damage, sharp edges, etc. Also cool cats will not knock down NOX as fast as hot ones. The best bet is to choose an emissions place that is right off a highway, then do some high speed highway driving to really get the cats cooking, then pull off the exit and right in for a test..

 

[iwannadie]

Thanks for the input, I should not I use 91 octane from a quality station. I also spent the afternoon removing the EGR and cleaning it, it was very black and cruddy inside. I got it as clean as I could spraying/soaking it and using 3 cans of carb cleaner. It went from black carb cleaner draining out to clear by the time I was done at least.

I can't hear any vacuum leak but I will hook up the gauge and really focus on that next. I may just start replacing all the vacuum lines as I go as they do look like originals.

Also just to note, it's not showing any CEL codes.

---------- Post added at 05:49 PM ---------- Previous post was at 05:43 PM ----------

I forgot, is the graph helpful at all? The guy at the emissions place was a real cool old tymer and was trying to help me the best he could. He said that graph should really help narrow down the problem, was he just being hopeful?

 

[iwannadie]

On another forum(I'm sure he's reading here too ha) someone is suggesting I advance my timing back to what I had it at for test 2 and even advance it slightly more. That was the only change besides the ambient temperature. I thought advanced timing was bad for NoX though and it was standard practice to retard it back to stock. I was advanced 14* for test 2 then back to stock 10* for test 3. It's strange to me my CO went way down and NoX way up though with the timing change(or temp change).

 

[iwannadie]

I was checking for a vacuum leak and found nothing this morning. I hooked my vacuum gauge up to the brake booster nipple on the intake and it held solid and raised with the throttle, never jumped or dipped. I used a length of small diameter heater hose held to my ear and ran it along all the vacuum hoses to listen for a leak and herd nothing. I actually pulled a vacuum hose loose just to hear what it would sound like if there was a leak and it was obvious. So, I am pretty confident there is no vacuum leak, short of spraying carb cleaner or replacing all the lines.

 

[Supracentral]

short of spraying carb cleaner

Spray carb cleaner. I chased a similar problem on my Expedition a couple of months ago.. Wound up being a problem with a $0.90 rubber elbow.

 

[iwannadie]

Ok, I will do the carb cleaner then ha. I've never sprayed carb cleaner to check for leaks though, it should be obvious if the if the idle jumps I assume.

I am also going to test if the EGR is sticking closed, when I had it off to clean it was closed but I didn't think to check if it was opening.

 

[Supracentral]

Ok, I will do the carb cleaner then ha. I've never sprayed carb cleaner to check for leaks though, it should be obvious if the if the idle jumps I assume.

Yea, you'll notice it right away. Sometimes, depending on the size of the leak, it can take a while to narrow in on it.

I am also going to test if the EGR is sticking closed, when I had it off to clean it was closed but I didn't think to check if it was opening.

Good idea. Always a better solution to test rather than just throwing parts/$$$ at the problem.

 

[iwannadie]

Ok, just gone done with carb cleaner test and found nothing.

I Put on the eye protection with a fire extinguisher handy I had the ole lady sit in the car(warmed to operating temp) to watch the rpm just incase it was very subtle. I sprayed some carb cleaner into a vacuum hose to hear/feel what it causes and it was obvious to both of us.

I started with a vacuum diagram and sprayed each end of the vacuum hoses and found nothing, I sprayed in short bursts. I then started tracing each vacuum hose spraying the entire length of each hose and nothing again. I re-did that twice. I then got in close and spraying in burst trying to see if the mist would get sucked in any direction and nothing. Also spraying in large "clouds" covering bigger areas and nothing. I loosened random vacuum hoses to create a leak and it was obvious the leak was there. I am pretty sure there's no vacuum leak unless there's something I missed or should do differently? I hit every hose on the diagram and used an entire big can of carb cleaner.

To test the EGR I put a vacuum hose onto the EGR nipple and sucked on it and could hear the EGR open and close very easy/smoothly. The EGR opening also caused the idle to drop and stumble which I read is what it should do. So I know the EGR is working, next I am going to read how to test if the module is actually controlling the EGR.

I really regret not testing the EGR opening/closing Before I cleaned it now. It could have been so gunked up that it was not able to operate and now after cleaning it operates fine.

It was pretty cool using the carb cleaner though, having never done it I had visions of the engine bay bursting into flames ha.

 

[Supracentral]

I am pretty sure there's no vacuum leak unless there's something I missed or should do differently? I hit every hose on the diagram and used an entire big can of carb cleaner.

No, sounds like you did a very thorough job. I think we can eliminate a vac leak. One possibility down.

To test the EGR I put a vacuum hose onto the EGR nipple and sucked on it and could hear the EGR open and close very easy/smoothly. The EGR opening also caused the idle to drop and stumble which I read is what it should do. So I know the EGR is working, next I am going to read how to test if the module is actually controlling the EGR.

Yea, that's your next potential culprit.

It was pretty cool using the carb cleaner though, having never done it I had visions of the engine bay bursting into flames ha.

Carb cleaner is pretty safe. Don't ever try that with starting fluid. ::flame::

You're doing a good job. Thorough diagnostics will always get you to a solution cheaper, and often quicker than just randomly replacing parts.

 

[iwannadie]

Ok, I tested the EGR vacuum module and cleaned the filter it seams fine, the VSV checks out also.

I've been asking around and everyone is stumped why I had better readings with advanced timing, aside from the weather that day could throw the results by a Lot seems strange.

I am thinking of taking it for another test now that the EGR has been cleaned but I am undecided on what timing I should use for the test. Stock timing which is supposed to get the best results or advanced timing which got me the best results so far. It's supposed to be in the 90s this week, I am planning a good hour freeway (O/D off) to get it has warm as possible. The test facility is right off the freeway and has webcams so I can see if they have long lines.

 

[Supracentral]

I'd set it to stock, and try to test again. If it fails, advance and try one more time.

 

[iwannadie]

Stock it is then, fingers crossed ha.

Thanks for the input.

 

[iwannadie]

The saga continues.

I set the timing back to stock and reset the ECU figuring that would be the best way to get a clear start. I was going to drive it a few days until it hits the 90s for the big test day. Well, driving after reseting the ECU and adjusting the timing I get a CEL. Pull the code and it's an EGR system malfunction(71) of course.

I was excited about the code narrowing the problem down and I still am but now a little disappointed. I had tested so much and all seemed good now it's telling it's bad ha. The only thing I didn't test was the EGR temperature sensor. So, I pulled that out and looked up the FSM on testing it and I think it's bad but I am an electrical noob.

The FSM says the resistance should be: 69–89 k? at 50°C (112°F), 12–15 k? at 100°C (212°F), 2–4 k? at 150°C (302°F). Testing at room temperature I am getting what I think is a weird reading or sign that it's shot. I have my digital multimeter set to 20m Ohms and it reads .24. I get Zero reading under any other Ohms setting on my meter. Would that mean with the 20m Ohms setting that my Ohms are really off the scale high and showing it's a bad sensor? Or, I am reading the meter totally wrong? I figured even below the 112* F that I should get a reading close to the range shown above. I'm not sure how I should heat it to get full readings.

 

[iwannadie]

Well, scratch all that. I just tested the sensor with water(I was worried but someone said go for it). I got proper readings at 112* and at 212*. Back to square one again grr.

 

[iwannadie]

Still struggling here and found one diagnostic test that fails. This is from the FSM(shown below), and I get No rpm increase where I should get 100-300 increase. The problem is, the FSM doesn't list anything to then check as the cause, just shows that test and then goes into each individual EGR component tests(which all pass). I am guessing that is a test to see if the EGR is functioning when it should and the result I am getting is it is not functioning. Oddly the CEL has not came back on since that one time and I then reset the codes and it's been driven many times.

I've read a few people have had the vacuum passages in the throttle body become clogged and caused the EGR to not function so that is my last shot in the dark. I already cleaned the throttle body but didn't focus on the vacuum passages so I am going to rip it out and really try to get in the passages.

INSPECT SYSTEM OPERATION
(a) Using SST, connect terminals TE1 and E1 of the check
(”DIAGNOSIS”) connector.
SST 09843–18020
(b) Keep the engine at 3,500 rpm.
(c) Set the transmission shift lever to the ”N” position.
(d) Remove the SST from the check connector.
SST 09843–18020
(e) Check whether the engine rpm increases 100–300 rpm
under the following conditions:
Coolant temp.
Below 53°C (127°F) No increase
Above 55°C (131°F) Increases

 

[nightrider760]

I have a black Sc300, and I just passed emissions the very first time. All i did is use some carb cleanner, and rev it alil and let it idle for 30 min. I also changed the spark plugs, set the timming at 10btc per California Governator smog rules. And passed state test. USed the highest octane available at shell. I do recommend to drive the car like you stole it before going to the smog station. Why...because It will burn all unwanted residues.

 

[iwannadie]

Well, I'm glad you passed but I'm not sure how that helps me other than hating you for passing the first time ; p .

Just an update, the other day I was about to walk out the door to do my test and checked online to see how long of a wait. The station had a 20 minute wait so I decided to hold off. I have been posting on another forum and a couple guys posted they have had problems with the same EGR trouble code I've had. It turned out for them that it had nothing to do with the EGR and was the o2 sensors. Failing o2 sensors causing the motor to run rich with really high combustion chamber temperatures. They said these cars rarely throw trouble codes for the o2 sensors until they are totally dead and that it throws the EGR code thinking the EGR is causing the problem when the EGR is working as it should. Someone else suggested that the above test (reving the motor and pulling the jumper pin) is very difficult to see the 100-300 rpm increase on the gauge cluster, so that may be working as it should just I'm not seeing it.

So, with the hate of throwing money at the problem I am going to replace the o2 sensors. I removed them and they were completely covered in a glossy white residue, which the internet says is bad(silicone deposits). The sensors also look to be factory originals so either way replacing is a good idea I think as basic maintenance. I'm going to re-test once I get the new sensors and hope for the best.

 

[iwannadie]

Just to put this to a happy ending. I replaced the 2 o2 sensors with OE sensors from rockauto for 88 bucks. Took it for emissions and it passed with flying colors. My NoX was down to .2 now.