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How To Prepare For Smog Test


prix

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I really want the car to pass this on the first try, since once you're in the clutches of California's Air Quality Resource Board, if the car fails, you are forced to use their contracted mechanics for repairs, and I don't see any that specialize in Lexus, which concerns me. Plus they have you over a barrel, cost-wise. I have read some horror stories online.

Background: On the last smog check the car 'barely' bassed (there is a reason for my concern). The hydrocarbons were at 52 ppm (I think it is) and the maximum is 54. All other measurements were well within state limits.

So I am pretty sure it might fail this time. What would you do to prepare? Here is a list I have put together after doing some reading online:

MotorVac the fuel system for $250ish which includes all taxes. The service includes throttle body cleaning.

OR

I 'just' had the oil and filter changed, so that's done.

I am due for a tuneup. I think the spark plugs were last changed around 60K and I am at 94'ish K.

Throttle body has not been cleaned in several years so that is due.

I read about putting fuel cleaner in tank (not Seafoam!) and making sure I drive it and use up all the gas, then refill with premium.

The car could use a new engine air filter.

The gas cap gasket needs to be changed out (lots of pressure when I unscrew the lid to fill up with gas).

I also have flickering dash panel lights. Will this 'have' to be fixed before the smog check? What if they go 'out' when I get to the test station? Will they sitll be able to test?

I cannot do MotorVac AND all the other stuff. I have to pick and choose which of the items will be the most effective.

I guess I am leaning toward tuneup (new spark plugs), throttle body cleaning, new engine air filter, some kind of fuel cleaner in gas tank, and gas cap gasket.

Part of the reason I am leaning toward tuneup instead of MotorVac is that, intermittently, I am getting a moderately rough idle on start-up (once or twice within the last four months or so, it was really rough). Usually, it's just moderately rough and it's not every day. For instance, yesterday, on start-up it seemed a little rough, but today on start-up it was fine. The roughness goes away after a bit of driving.

Other than some battery and starter issues (which I have posted about here ad nauseum), that's pretty much all that is going on with the car.

I would really appreciate any suggestions. I am not a DIY, though would love to be. Just not set up to do that, so will have to have the work done.

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Easy. If it needs spark plugs, install new ones - the factory recommended plugs. Then take the car for a brisk drive, and use full throttle several times for extended periods. The reason is that most cars use a very rich program at full throttle, in fact most go into open loop at full throttle, as they use a rich mixture at wide open. This heats the cats to clean them, and in doing so the cats will perform better during the test.

That's really all you can do. I don't believe in the seafoam snake oil at all, or any additive other than Chevron Techron, which is approved by Bosch. But you don't even need that.

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I would also use a full synthetic oil in the engine....Make sure car is hot (warmed up) and new air filter, I am not familiar with your car but you could have bad cats or cats that are failing....You difinetly want the cylinders all to be firing so if you have bad plugs replace them with OEM plugs. Good luck, I too get a queazy stomach everytime I get a smog check in the !Removed! Air resources controlled state of California. Does that engine have an EGR valve, if so hopefully it is functioning properly....

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Our '95 LS400 is approaching 300K, all I ever do just prior to the test is change the oil and filters, oil and air fliters, FULL tank of PREMIUM fuel, drive the car HARD for 15-20 miles, not fast but holding in low gear ratios, and shut down the engine as I progress in line to the test station. Shutting down the engine in line results in a bit of engine overheating which I think is desireable.

It got new plugs, finally, at 230,000 miles along with both distributor rotors and caps.

EGR valve has been cleaned ~3 times, the MAF/IAT sensors at least once.

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I really want the car to pass this on the first try, since once you're in the clutches of California's Air Quality Resource Board, if the car fails, you are forced to use their contracted mechanics for repairs, and I don't see any that specialize in Lexus, which concerns me. Plus they have you over a barrel, cost-wise. I have read some horror stories online.

Background: On the last smog check the car 'barely' bassed (there is a reason for my concern). The hydrocarbons were at 52 ppm (I think it is) and the maximum is 54. All other measurements were well within state limits.

So I am pretty sure it might fail this time. What would you do to prepare? Here is a list I have put together after doing some reading online:

MotorVac the fuel system for $250ish which includes all taxes. The service includes throttle body cleaning.

OR

I 'just' had the oil and filter changed, so that's done.

I am due for a tuneup. I think the spark plugs were last changed around 60K and I am at 94'ish K.

Sparkplugs will typically last well beyond 100k

Throttle body has not been cleaned in several years so that is due.

Throtte body cleaning can be counter productive, it might take a long period of driving before everything "loosened" "passes".

I read about putting fuel cleaner in tank (not Seafoam!) and making sure I drive it and use up all the gas, then refill with premium.

Again, might be counter-productive for the same reasons as above.

The car could use a new engine air filter.

ALWAYS.

The gas cap gasket needs to be changed out (lots of pressure when I unscrew the lid to fill up with gas).

Air "rush" is SOP, indicates gas cap is sealing just as it should.

I also have flickering dash panel lights. Will this 'have' to be fixed before the smog check? What if they go 'out' when I get to the test station? Will they sitll be able to test?

Battery problem or more likely corrosion inside the battery connectors. Clean and burnish the battery connections and battery posts. Check the engine/chasis ground connections. Replace the battery if the flickering persists

I cannot do MotorVac AND all the other stuff. I have to pick and choose which of the items will be the most effective.

I guess I am leaning toward tuneup (new spark plugs), throttle body cleaning, new engine air filter, some kind of fuel cleaner in gas tank, and gas cap gasket.

Cleaning the MAF/IAT sensor elements and the EGR valve "core" mechanism might be a lot more productive.

Part of the reason I am leaning toward tuneup instead of MotorVac is that, intermittently, I am getting a moderately rough idle on start-up (once or twice within the last four months or so, it was really rough).

MAF/IAT sensors, EGR operation, or maybe condensed moisture overnight within a cracked distributor cap.

Usually, it's just moderately rough and it's not every day. For instance, yesterday, on start-up it seemed a little rough, but today on start-up it was fine. The roughness goes away after a bit of driving.

Other than some battery and starter issues (which I have posted about here ad nauseum), that's pretty much all that is going on with the car.

I would really appreciate any suggestions. I am not a DIY, though would love to be. Just not set up to do that, so will have to have the work done.

Hope this helps...

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I remember in the past where some smog guys would let you do a "pre-test" before the real test. You're right that once you fail, you're in trouble.

I agree with SRK on the spark plugs being the most likely thing to help. Replace with OE ones. You should be able to find them (Amazon?) for like $6-7 each. Mechanic may charge you $12-20 each (times 8, so it's $$).

It could also be the ignition wires. One way to check those is to look under the hood with the engine running in the dark. If you can see any flashes that indicates that the insulation is starting to go. But a better test would be to measure the resistance. Or just replace based on mileage. Like 90-100k, probably.

If you're getting high HC, with no CEL, somehow unburned fuel is getting through the system. So spark plugs, ignition wires are main concerns. It could also be a leaking fuel injector, not so likely (I'm guessing here).

Regarding other tips you may hear regarding "warming up" the car ... the key is to get the catalytic converters hot. When they're hot, they will be very effective at reducing HC's and NOX. So for example, you can let the car sit at idle for an hour and the engine will be up to operating temperature, BUT the cats will not be. To get those HOT, go for a good 15+ minute drive on the freeway putting down as much power as you can. It's not time, it's not RPM, it's power that heats the cats. It will be good to have an appointment so your car is checked before the cats cool down too much.

Techron might help if you've got a leaky or slightly fouled fuel injector.

The gas cap gasket sounds like it is working perfectly if you get a lot of pressure build up. No need to replace that.

The air filter will not help your smog, unless it is completely blocked.

Good luck, and let us know how it goes.

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great informaton everyone. thanks so much. i will review all (in detail) and do as much as is possible. btw, if i 'wipe' the mufflers with a cloth, they come out pitch black. would cleaning those out (as far as i can reach) make any difference? just curious whether little particles from a dirty exhaust pipe would add to the HCs. i am going to look into whether i can do a pretest....

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What is full throttle? The fastest I am comfortable going on the freeway is 70. Are you saying gear down to second and then drive fast? If so, how fast? Thanks.

Easy. If it needs spark plugs, install new ones - the factory recommended plugs. Then take the car for a brisk drive, and use full throttle several times for extended periods. The reason is that most cars use a very rich program at full throttle, in fact most go into open loop at full throttle, as they use a rich mixture at wide open. This heats the cats to clean them, and in doing so the cats will perform better during the test.

That's really all you can do. I don't believe in the seafoam snake oil at all, or any additive other than Chevron Techron, which is approved by Bosch. But you don't even need that.

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great tips, ALL. i am making a list (checking it twice) and all this will go on there. thanks.

I really want the car to pass this on the first try, since once you're in the clutches of California's Air Quality Resource Board, if the car fails, you are forced to use their contracted mechanics for repairs, and I don't see any that specialize in Lexus, which concerns me. Plus they have you over a barrel, cost-wise. I have read some horror stories online.

Background: On the last smog check the car 'barely' bassed (there is a reason for my concern). The hydrocarbons were at 52 ppm (I think it is) and the maximum is 54. All other measurements were well within state limits.

So I am pretty sure it might fail this time. What would you do to prepare? Here is a list I have put together after doing some reading online:

MotorVac the fuel system for $250ish which includes all taxes. The service includes throttle body cleaning.

OR

I 'just' had the oil and filter changed, so that's done.

I am due for a tuneup. I think the spark plugs were last changed around 60K and I am at 94'ish K.

Sparkplugs will typically last well beyond 100k

Throttle body has not been cleaned in several years so that is due.

Throtte body cleaning can be counter productive, it might take a long period of driving before everything "loosened" "passes".

I read about putting fuel cleaner in tank (not Seafoam!) and making sure I drive it and use up all the gas, then refill with premium.

Again, might be counter-productive for the same reasons as above.

The car could use a new engine air filter.

ALWAYS.

The gas cap gasket needs to be changed out (lots of pressure when I unscrew the lid to fill up with gas).

Air "rush" is SOP, indicates gas cap is sealing just as it should.

I also have flickering dash panel lights. Will this 'have' to be fixed before the smog check? What if they go 'out' when I get to the test station? Will they sitll be able to test?

Battery problem or more likely corrosion inside the battery connectors. Clean and burnish the battery connections and battery posts. Check the engine/chasis ground connections. Replace the battery if the flickering persists

I cannot do MotorVac AND all the other stuff. I have to pick and choose which of the items will be the most effective.

I guess I am leaning toward tuneup (new spark plugs), throttle body cleaning, new engine air filter, some kind of fuel cleaner in gas tank, and gas cap gasket.

Cleaning the MAF/IAT sensor elements and the EGR valve "core" mechanism might be a lot more productive.

Part of the reason I am leaning toward tuneup instead of MotorVac is that, intermittently, I am getting a moderately rough idle on start-up (once or twice within the last four months or so, it was really rough).

MAF/IAT sensors, EGR operation, or maybe condensed moisture overnight within a cracked distributor cap.

Usually, it's just moderately rough and it's not every day. For instance, yesterday, on start-up it seemed a little rough, but today on start-up it was fine. The roughness goes away after a bit of driving.

Other than some battery and starter issues (which I have posted about here ad nauseum), that's pretty much all that is going on with the car.

I would really appreciate any suggestions. I am not a DIY, though would love to be. Just not set up to do that, so will have to have the work done.

Hope this helps...

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Can you tell me what gear and at what speed you recommend? Thanks for all info.

Our '95 LS400 is approaching 300K, all I ever do just prior to the test is change the oil and filters, oil and air fliters, FULL tank of PREMIUM fuel, drive the car HARD for 15-20 miles, not fast but holding in low gear ratios, and shut down the engine as I progress in line to the test station. Shutting down the engine in line results in a bit of engine overheating which I think is desireable.

It got new plugs, finally, at 230,000 miles along with both distributor rotors and caps.

EGR valve has been cleaned ~3 times, the MAF/IAT sensors at least once.

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test results from the last smog test. this might give some clues...

15mph - rpm 995

%CO2

(measured 14.7)

%O2

(measured 0.0)

HC (PPM)

(maximum allowed 56)

(average 10)

(measured 54)

CO (%)

(max 9.32)

(ave 0.00)

(meas 0.08)

NO (PPM)

(max 477)

(ave 92)

(meas 237)

25 mph - rpm 979

%CO2

(meas 14.7)

%O2

(meas 0.0)

HC (PPM)

(max 32)

(ave 7)

(meas 23)

CO (%)

(max 0.30)

(ave 0.01)

(meas 0.04

NO (PPM)

(max 481)

(ave 100)

(meas 371)

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What is full throttle? The fastest I am comfortable going on the freeway is 70. Are you saying gear down to second and then drive fast? If so, how fast? Thanks.

No need to break the law - just get to the on-ramp, select second gear, start from a stop at full throttle and let it shift up to second. Here on the west coast in damp environments the tailpipes will spew liquid water and then steam when doing this if the car has not been driven hard. But the big thing is to pass a lot of rich, hot exhaust gases through the converter to make it work hard. It's temp goes up, and it cleans itself.

The results of your last test were good enough but NOx and HC were a bit high. That's what converters do though, through an oxidation and then reduction reaction.

Good luck.

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Its strange in IL if you have an OBDII car they don't even put a probe in your tailpipe anymore. They just look at ECU and ensure there are no emissions related codes. I guess they assume if the OBDII is happy that is as good as sticking a probe in.

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Yep but California has always led the way in the strictest emissions standards in the Unitied States....Though I will say the smog in LA is so much better (less) than when I came to this state in 1965. The windshield turned yellow with a thick film back then...The air is relativlely clear most of the time now.....

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Great. Thanks for the detail. I will do this.

The smog test is not for awhile yet, but I want plenty of time to get the little things done (maintenance or whatever) that could make the difference between pass or fail. I'll post back on what happens at the smog station.

I also found this site, which has some other tips for passing smog tests not mentioned here, like proper tire inflation and balancing.

http://www.smogtips....ssions-test.cfm

What is full throttle? The fastest I am comfortable going on the freeway is 70. Are you saying gear down to second

and then drive fast? If so, how fast? Thanks.

No need to break the law - just get to the on-ramp, select second gear, start from a stop at full throttle and let it shift up to second. Here on the west coast in damp environments the tailpipes will spew liquid water and then steam when doing this if the car has not been driven hard. But the big thing is to pass a lot of rich, hot exhaust gases through the converter to make it work hard. It's temp goes up, and it cleans itself.

The results of your last test were good enough but NOx and HC were a bit high. That's what converters do though, through an oxidation and then reduction reaction.

Good luck.

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@Lenore - About Los Angeles smog...some days you can still see the haze blanketing the city from, say, the 28th floor of one of the downtown skyscrapers, but no question that air quality has improved overall in recent years. I have no problem with having to maintain my car to pass emissions testing. Though it's a pain (and potentially expensive), it is necessary for quality of life reasons.

I created a folder on my browser toolbar where I stash websites that 'monitor' and report on subjects of interest (latest virus threats, traffic and weather conditions, the CDC, and, not least of all...air quality in greater Los Angeles). Air Quality Management District (or South Coast AQMD) is one such and it comes in handy. Today we are all green, so this is a good day for outdoor exercise and deep breathing.

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Turns out, having to pass smog has been a good thing, because it forced me to get organized, review all my records, and learn one heck of a lot about maintaining my car in future. I also see how easy it is to get ripped off. When I look back at what I paid for dealer maintenance or repairs over the years, I cringe.

I am good to go but for one more question:

The car has that flickering dash light problem (sometimes goes out altogether). I know the smog shop needs to be able to see the odometer and whether the check engine light comes on in order to do the test. I see that when I turn the key to the position where the dash lights show everything (but the car is not started). Does anyone know if the dash lights go out IN THE MIDDLE of testing, whether that would result in a "fail"?? I am located in California.

I read up on how to fix the dash lights last night...(checking the wiring harness in the trunk first, and if that isnt' the problem, remove cluster and send the circuitry board off). I am more than a tad nervous about dismantling the instrument cluster and getting it back in post-repair so that it looks exactly the same, so may need time to find someone who can do that for me.

If I thought I could go do the test now and pass it, I would. Anyone know? Tx.

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I believe the light thing is ok as long as they turn it on and see that the indicator works for check engine....I hate going to those smog places, makes my stomach nervous even on newer cars...I feel like a little black cloud is going to rain on me....I take care of mother-in-laws car and it failed 4 times in last 10 years...I had to fix it each time except this last time...She is low income and the state bought her car for recycler for $1500 so I found a 8 year newer car (Toyota Camry 1995) that passed smog with no prep....and get this the clouds opened for me it cost $1500 plus sales tax....I am so happy for her, and me because my wrenching on her car has been cut significantly.....Good luck my friend...make sure to look for coupons also for the smog checks, they can be found in local newspapers, pennysaver, etc. Every dollar counts....

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I don't drive new cars ('92 SC400, '86 MBZ 560SL, '00 MBZ 320CLK and '02 MBZ ML500) so I go thru the same angst every year in San Diego. I have it down to a standard routine for about $30 at your local parts store:

Tank of gas before taking it in: a double dose of injector cleaner (works best if you do start/stop driving giving it a chance to soak), a dose of octane booster, a dose of water absorber and a spray can of mass air sensor mesh cleaner (again, I pause for 10 minutes to let it soak with the engine off and then finish with the rest of the can).

I'll assume that you do the routine stuff: fresh synthetic oil and filter, new air filter (the high flow filters get more air in for more complete combustion. Plugs AND wires if they are needed for routine servicing (if they are due within the next 5-15K miles, you're gonna do it anyway so go ahead and do it early, it can't hurt. O2 sensors can be an issue, their response time degrades with time and use but the smog test is pretty benign so they should settle down for the steady state testing.

Tank of gas for testing: hi-test, dose of octane booster, dose of injector cleaner and make sure it is hot, hot, hot when you take it in. Just got the two older ones tested and passed with flying colors as ususal.

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Hey, great tips all. I'll use this. Curious as to why everyone says a full tank of gas going in...I was going to use EFI Injector Cleaner (it's OEM and what an indie mechanic used last time) then use up that tank of gas. Then fill it again with Chevron 92 Octane. Does that sound ok, or should I put a second bottle of EFI Cleaner in with the second fillup?

In looking at my records, I see the fuel filter was changed out three years ago (so it's due) and I know one of its functions is to block contaminants from reaching the fuel injectors. Those fuel injectors coudl be dirty. So that's why I was thinking of doing two treatments.

Is it OK to have fuel additives in the tank at time of test? Someone else said that will raise NO2 levels.

I am not comfortable touching the MAF. I read a horror story where someone sprayed it and then the RPMs were all over the map. Turns out the solvent had ruined the AFM (I think that is what they said) and they had to replace it. So I am going to leave that alone (though it looks easy enough to do). i was wondering, if it's dirty, can I blow some compressed air on it? I read it's 'sensitive', so if it ain't broke...(how I was thinking).

Thanks much.

I don't drive new cars ('92 SC400, '86 MBZ 560SL, '00 MBZ 320CLK and '02 MBZ ML500) so I go thru the same angst every year in San Diego. I have it down to a standard routine for about $30 at your local parts store:

Tank of gas before taking it in: a double dose of injector cleaner (works best if you do start/stop driving giving it a chance to soak), a dose of octane booster, a dose of water absorber and a spray can of mass air sensor mesh cleaner (again, I pause for 10 minutes to let it soak with the engine off and then finish with the rest of the can).

I'll assume that you do the routine stuff: fresh synthetic oil and filter, new air filter (the high flow filters get more air in for more complete combustion. Plugs AND wires if they are needed for routine servicing (if they are due within the next 5-15K miles, you're gonna do it anyway so go ahead and do it early, it can't hurt. O2 sensors can be an issue, their response time degrades with time and use but the smog test is pretty benign so they should settle down for the steady state testing.

Tank of gas for testing: hi-test, dose of octane booster, dose of injector cleaner and make sure it is hot, hot, hot when you take it in. Just got the two older ones tested and passed with flying colors as ususal.

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Also, I was told (years ago) by someone at a dealer that using synthetic oil in older cars might not be such a good idea, since parts are worn and the synth would make the engine work harder? What is the rationale behind using synthetic. I just had an oil change, and they used regular Valvoline 10-30 (I think).

I don't drive new cars ('92 SC400, '86 MBZ 560SL, '00 MBZ 320CLK and '02 MBZ ML500) so I go thru the same angst every year in San Diego. I have it down to a standard routine for about $30 at your local parts store:

Tank of gas before taking it in: a double dose of injector cleaner (works best if you do start/stop driving giving it a chance to soak), a dose of octane booster, a dose of water absorber and a spray can of mass air sensor mesh cleaner (again, I pause for 10 minutes to let it soak with the engine off and then finish with the rest of the can).

I'll assume that you do the routine stuff: fresh synthetic oil and filter, new air filter (the high flow filters get more air in for more complete combustion. Plugs AND wires if they are needed for routine servicing (if they are due within the next 5-15K miles, you're gonna do it anyway so go ahead and do it early, it can't hurt. O2 sensors can be an issue, their response time degrades with time and use but the smog test is pretty benign so they should settle down for the steady state testing.

Tank of gas for testing: hi-test, dose of octane booster, dose of injector cleaner and make sure it is hot, hot, hot when you take it in. Just got the two older ones tested and passed with flying colors as ususal.

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Geez...I bought a quart of oil to top it off and the guy at AutoZone looked it up on his computer and said it used 10-30W (non-synth). I just looked at an old receipt from a DEALER the last time I bought oil (I supplied it to the mechanic) and the dealer sold me 5-30. Which should I be using?? Tx.

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Cleaning the maf sensor is easy, just buy INtake and Maf sensor cleaner in the spray can....I would not use compressed air as it might break the wires....As for synthetic, my thought is use it for the smog check because of less hydrocarbons in the mix...but I may be way off. As for using it, mechanics are old fashiioned, many on this site and others have switched at high mileage and had no problems...If it bothers you dump it and switch back to dino oil after a successful smog check....either weight oil is probably fine. A high mileage oil on a high mileage engine might be a good thing...hopefully somebody will chime in.

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Three cheers for the synthetic oil, the only issue that I am aware of is that due to smaller molecule size will find it's way through areas that previously didn't leak - generally, this is a non-issue; I have converted every one of my oil users to synthetic without a problem. And, yes, the synthetic will result in lower HC readings; Castrol even makes a "senior" synthetic blend for older, high mileage cars.

As for additives in the gas (octane booster and injector cleaner), it has never been an issue. Plug wires though, with the new 100K plugs running around wear out also and break down; this is especially true if the wires are "bundled" closely and you end up with cross talk and random plug firing, I change mine every 50K just because of the almost year round heat in SoCal that jacks up the underhood temps.

Here's what my '92 SC400 blew this week:

15 MPH test: CO2 (14.7) O2 (0) HC (73 max, 2 meas) CO (0.49 max, 0.04 meas) NO (530 max, 65 meas)

25 MPH test: CO2 (14.7) O2 (0) HC (56 max, 0 meas) CO (0.39 max, 0.03 meas) NO (487 max, 127 meas)

Test conditions: Pump Hi-Test gas, 104 octane booster in tank, injector cleaner in tank, fresh synthetic oil and filter, K&N filter

The passed it with an Airbag warning light on so don't worry about the lights you mentioned, although tauted as a safety and emissions test, they are really only concerned about what comes out of the tailpipe.

The grade of oil that you need is more of a function of how you drive and the driving environment (open road vs stop & go, towing a trailer vs nothing in the trunk and one person on board, etc), a good mechanic or oil manufacturer's web site can walk you thru what is best for your car and driving needs.

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Ok, got it. I just had the oil changed and they used dino oil. I didn't know synth would give off less HC! It's 5w30 that is on the engine cap btw, so that is what they used. The 10w30 was what I bought to top off or just to have on hand, so I got the wrong weight. No biggie. It's only a quart, so I can either use it up as needed, or not. I have had synth oil in the car before, and then someone at a Lexus dealer (mechanic) said that IHO it's a waste of money. I guess not so much when you're trying to pass smog check. I know I need to clean the MAF sensor. Everyone is saying to do that. Trust me, I will be reading the directions on how to apply (twice!).

Cleaning the maf sensor is easy, just buy INtake and Maf sensor cleaner in the spray can....I would not use compressed air as it might break the wires....As for synthetic, my thought is use it for the smog check because of less hydrocarbons in the mix...but I may be way off. As for using it, mechanics are old fashiioned, many on this site and others have switched at high mileage and had no problems...If it bothers you dump it and switch back to dino oil after a successful smog check....either weight oil is probably fine. A high mileage oil on a high mileage engine might be a good thing...hopefully somebody will chime in.

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