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Time for smog. at star station. Ugh. Car was running fine. Failed smog with slightly high hydrocarbons at 15mph. (Maybe car wasn't warm enough??) Also high Nitric Oxide at 25mph. (Engine getting too hot??) Weird and somewhat contradicting.
I had been having trouble keeping coolant in the reservoir. Thought maybe the water pump. Took my car to a friend of a friend to have him take a look. He said we should check for possible leaks in the engine because it appeared the #2 spark plug was wet and there was some water after he removed the #2 spark plug!??
I FREAKED because a year and a half ago (15K miles) I had a blown head gasket from a cracked radiator after car was hit while parked on the street. Spent over $4,000 to fix. And to date have replaced the following:
(Please forgive me for not knowing all the technical terms. But I'm going to try to explain what was done next. )
So, one at a time, each Spark plug was removed, and air was forced into the system checking for air bubbles coming out of the radiator. (hope that makes sense) nothing significant was found But we did double check the vacuum lines. And I checked the EGR vacuum modulator (which seemed to be stuck closed). Stupid boys made fun of me blowing into it (ha ha) and when they gave it back it was no longer stuck in a closed position. It was the opposite. Too easy to blow air into. Great job guys! They thought they "fixed it"
Anyway, I remembered when i failed my pre test 2 years ago the awesome Smog guy told me to go to the junkyard and pick up a new EGR solenoid modulator. Did that, popped it in and I passed no problem. So I figured maybe this one had seen better days so I placed my order for a new one.
Took my car back to the smog station before I got the new part. This time I had very high (3x the max) hydrocarbons measured at 25 mph and slightly high carbon monoxide at 25 mph, but totally passed in nitrous oxide??? Okay?
***NOTE- NO CHECK ENGINE LIGHT AT ANY TIME
Got new EGR vac mod. Put it on. Took it for smog check #3. Same results as last time.
Drove car 60 or so miles. No Problems.
Then yesterday went 1/2 mile from home to gas station. Thought I heard a weird sound. Checked under hood at station. Looked okay but when I started the car with the hood up I heard a faint intermittent snapping sound. Hmmm. Took the car straight home. (1/2 mile)
Today I double checked all vacuum lines and saw that some had been connected incorrectly. Decided to replace all vacuum lines and double check connections.
Started the car and now the "snapping" was louder and progressively more frequent. Shut off the car and jumped on here to see if you guys can help.
I want to fix it myself if possible because I have trust issues when it comes to my car. But my tools, funds, and understanding are somewhat limited. Any assistance would be greatly appreciated! I just want my car to run well and for it to pass smog!!
And for the damn meter maids to stop putting ticket after ticket on my car for expired registration!!!
All I can think of is maybe a loose ignition wire......maybe???? I'm totally guessing. Dont want to mess up my car.
Meganw1, I sympathize with you. I have the same car you have only one year newer and I have also been struggling to pass smog in time over the last few months. Most recently I had to overhaul the EGR system. If a vacuum modulator cured that and you have no CEL code 71 coming up then your EGR is probably not the culprit (although the piping can clog over time gradually-- takes a while). Seems that your EGR VSV is also in OK condition.
Replacing the vacuum lines helps and if they were incorrectly hooked up you've definitely begun to solve part of your problem. Those can definitely contribute to failing smog.
Do you have your original ECU back from Tanin yet? That should eliminate any possibility of having excess fuel as far as the computer is concerned. Injectors would be the next thing to look into but only if there are specific symptoms related to them sticking.
I've been unable to pass smog with my 1993 5-speed recently due to higher than normal HC's also. I am currently running a 1992 5-speed computer (repaired by Tanin) and I'm waiting for my 93-94 computer to come back from their repair shop. Like you I have replaced many vacuum lines. I've replaced the entire EGR system, inejctors, various sensors (TPS sensor, ECU Coolant Temp sensor among others) and I have also replaced the secondary catalytic convertor and fuel pressure regulator. These things helped the car run better overall but did not ultimately solve my high HC issue.
In my case I think a lot of factors causing to over-fueling and running excessively rich for a period of time has fouled my primary catalytic convertor so I have one of those on the way to replace the one in my car. The original cats last a long time but eventually they can go bad, especially if the engine has had running issues at one time or another.
Unless your plugs were not gapped correctly or your cap and rotor are worn (doesn't seem to be the case) then I think those are not your issue.
You even replaced your rear catalytic convertor and that has not solved your issue.
Which brings me to this question: what are your measured HC emission numbers from the last smog pre-test you had performed? For 1993 Cali-Spec 5-speeds at least (in California) the MAX allowed at 15 MPH is 82. MAX allowed at 25 MPH is 48. I am not sure if the MAX HC numbers any different for 1992 Cali-Spec 5-speed models. What were your measured HC numbers on the pre-test?
Mine were last at 161 @ 15 MPH and 55-61 at 25 MPH. Culprit in my case should be the primary cat being ineffective due to being fouled from running rich for too long. This could be part of your issue also but it's hard to tell without diagnosing it directly. I left replacing catalytic convertors as the last resort when troubleshooting my SC recently. I have been recently informed that the front catalytic convertor tends to do more work than the rear but I've never been able to confirm this one way or the other.
I understand all too well how hard it can be to do as much diagnosing work and repair possible by yourself. Most of us still need a trusted shop to help solve some problems. You'll beat this.
I can recommend a just couple of shops in the L.A. area. Feel free to PM me and I'll give you details.
Edit: Also you'll find that, unfortunately, you won't always have a CEL light when there isn't an obvious problem related to emissions (unless it's malfunctioning EGR) on SC300's. That #3 O2 sensor on your rear catalytic convertor for instance really doesn't do much of anything useful like telling us if either one or both convertors are failing or out of passing spec.
Find a good independent mechanic and let him figure it out.
- have fun
freakness, that doesn't constructively help Meganw1's situation. We've all been in a bind before as Cali SC owners at one time or another and she's obviously frustrated and just looking for informed help.
freakness, that doesn't constructively help Meganw1's situation. We've all been in a bind before as Cali SC owners at one time or another and she's obviously frustrated and just looking for informed help.
Dude,
The information is the best I can give. Not everyone is going to spend days and weeks learning and figuring out how to work on their car. That process alone can drive people crazy. A competent mechanic can tell her what the situation is, what it's going to cost, etc.
I can certainly attest that spending a few months repairing my car recently has driven me certifiably crazy-- no disagreement with you there, freakness!
There was no emotion intended from me by quoting of your post, btw. Just that she seems to be looking for help here because she's not sure the help she's had at her last mechanic (so far) has been that astute.
I've found that when emissions related problems become complex on these cars even a trusted mechanic won't always have all the answers. They will have some answers but it helps to be at least a little informed going in. Then again it really depends on what one's issue(s) turn out to be.
I agree that she still needs to take it to a decent mechanic's shop even if there is some troubleshooting imparted here.
.....
Meghanw1, my very rough guess is that, as long as the engine is running in good tune and the ECU has been reconditioned it may be related to the front cat being worn out. Your car's current symptoms seem a lot like my car's current symptoms in terms of high HC's after having replaced only the rear cat and sorted out the engine tune and EGR system.
*However*... in order to determine that for sure and justify spending money on another cat you should take the car into a shop and have an exhaust probe test performed just before the 1st cat's internal honeycomb ("substrate").
You'd need the figures from an emission manual test showing the idle, 15 mph and 25 mph HC, CO and NOx numbers at the tailpipe and then the probe test shows those same measured numbers before the exhaust gasses reach either of the catalytic convertors. Then, when comparing the two sets of measurements, there should be (generally) a 60% overall emissions reduction when you subtract the emissions dyno/tailpipe nubmers from the numbers from the probe test numbers.
Alternatively an heat sensing gun with a laser can be used to measure the input and output heat ranges before and after each catalytic convertor substrate/matrix/honeycomb without drilling into and physically probing the first catalytic convertor. This is another way of determining if one of the catalytic convertors is still operating efficiently or if it needs to be replaced. But not every shop has one of these measurement devices.
....
The "snapping" noise is a head scratcher for me. Especially since it got louder after you put the vacuum lines back to the factory diagram's spec. That definitely would be a shop visit to try to diagnose. You could post an example video on a youtube account and we can try to identify what that is but the best thing would be to take that in and have that sound diagnosed.
I did find that not all replacement vacuum hoses were created equal. The closest to factory quality I've found is the Gates #27042 5/32nd inner-diameter hose.
Chick dude, they should have performed a compression test in addition to the leak down test.
when you pull plug out and its wet, combustion isn't happening for some reason.
now a leak to the radiator could be one reason (bad headgasket)... but another one that happens is dropping a valve seat (no compressoin).
I would say bent valve but unless they shaved your cylinder head down a crazy amount last time.. it doesn't happen on these motors.
Breaking the seat is rare but it does happen, especially if you hear a snapping sound... I would lean towards a mechanical failure.
have them do a compression test, or get one of those scopes and stick it down the plug hole and have a look around.
also I saw you said you changed plugs and ignition wires.. but did you change the distributor cap and rotor. Its almost more important to do that every once in a while.
IF the rotor is worn down it will miss on some cylinders randomly until it gets really bad and it wont run anymore. also it makes a terrible sound when that starts happening.
So if you have not done that, I would start with that cause it takes like 5 minues compared to the longer checks. that would also give you a wet plug on the bad cylinder.
my gx470 made shuddering/snapping sounds, wasn't running on all 8, and when I tore it down it had dropped a valve seat on the rear passenger cylinder bank. compression test on that cylinder showed 0 psi. leak down test would have show nothing cause headgasket was fine... all the air just goes out the bad valve.
hopefully its not that, but at the very least do a compression test next time around so you will know if there is a problem with that cylinder.
btw, you can pass with flying number with no egr if everything else is working... but the egr can make you fail when it goes bad or fails.
and also a short hand way of thinking about it is Hydrocarbons is unburnt fuel, the CO is partially burnt fuel, and the NO is combustion temperature.
High hc and hich co and low nox tells me you either have an overly rich condition (like bad ecu/inejctor etc...) or you have a combustion problem in at least one cylinder (valve problem/compression or igintion).
Snapping sound could be spark ... high-tension (HT) wires discharging.
Pop the hood and take as many covers of HT off. Bring your vehicle in a garage at night time time and turn all lights off. Run the engine and see if you can spot arcing.
Not trying to be funny here or anything but, hypothetically speaking cant you just find someone to "pass it"? its not like when cops pull you over and smog it on the spot... again hypothetically speaking since someone i know might do that and is wondering how this all works
funkenstein, it's not so easy to just find someone to "pass" your car. Especially when your DMV re-registration bill requires you to not only go to a Gold Shield Smog Station... but a "STAR" Smog station (ie: this use to be called a "Test Only" smog station). They are more strict, hardly discuss anything with you and will offer no help to you if anything happens to be "off" that makes you fail the standardized smog test.
The issue that Meghanw1 is up against is that she won't be issued new tags if she doesn't have a passing smog test. I can sympathize with her because I am in the same boat at this point in time.
If you're also in CA and have an SC300 (or SC400) you're probably also being directed to a "STAR" smog station each renewal time also.
And Meghanw1, thank you for posting those smog test results. Since you have an automatic this is interesting: Your max allowed HC's at 15 MPH are slightly less allowed than 5-speeds are allowed for those years (75 for automatic, 82 HC's for manual)... BUT your 25 MPH max allowed HC's are HIGHER allowed at 15 MPH than for 5-speeds in those years (automatic is allowed 57 HC's @ 15 MPH, manuals are allowed only 48 HC's @ 15 MPH).
What is very weird is that you are failing at only one of those speeds with only a 42 RPM difference.
I don't know what this is yet. But it's cracked! Already picking up distributed cap and rotor tomorrow and a new throttle body gasket.
The broken part is behind the throttle body/ intake manifold with some kind of filter inside. Really wish I knew what this was so I can order a replacement.
05-26-16, 09:21 PM
1992 SC300 Cali-Spec smog issue
at star station. Ugh. Car was running fine. Failed smog with slightly high hydrocarbons at 15mph. (Maybe car wasn't warm enough??) Also high Nitric Oxide at 25mph. (Engine getting too hot??) Weird and somewhat contradicting. 
And I checked the EGR vacuum modulator (which seemed to be stuck closed). Stupid boys made fun of me blowing into it (ha ha) and when they gave it back it was no longer stuck in a closed position. It was the opposite. Too easy to blow air into. Great job guys! 
They thought they "fixed it" 
Decided to replace all vacuum lines and double check connections. 
