How To Prepare For Smog Test

[prix]

Your stats look great! I bought Chevron Techron this afternoon. Based on your readings, I would say the additives are NOt an issue.

Need some clarification..how long after you put in the double dose of additive do you drive the car before going to the test station? How much time do you allow for all the loosened stuff to work its way out of the system?

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.

[prix]

There are three types of air flow sensors: Karman-Vortex, Vane Air flow meter, and a Mass Air flow meter. Can someone tell me what kind is on the LS400 1994? There is a warning label on the "CRS Mass Air Flow Sensor Cleaner" (on the can itself) that you are not supposed to use it on many LEXUS model cars (the ones with Karmen Vortex type MAFs).

[Edited to add: Yes, the LS has a Karmen Vortex sensor...maybe the RXs or SCs are different? Here's someone who ruined his AFM by using the CRC MAF Sensor cleaner anyway. He replaced it, though I wonder if he had waited a few days whether it would have dried out and been OK.]

http://www.clublexus.com/forums/ls400/336572-after-cleaning-the-throttle-body-and-maf.html

[prix]

One last bit of information, and this relates to the use of Chevron Techron. I called the 800 number for Chevron Techron directly, and spoke with a lube technician. He said the best ratio of product to gas is 1 oz. of Techron to a gallon of gas. So for a 12 oz bottle of Techron you need to mix that with 12 gallons of gas (no more than that) for the best cleaning efficiency, or 20 gallons of gas for the 20 oz. bottle. And, you don't have to wait until your tank is on 'reserve gas' or completely empty, to do this. You can add the bottle of Techron to even a quarter tank of gas, then top off with whatever amount of gas you need to add up to the required ratio. Per the owner manual, this car has a 22.5 gallon tank.

He did not recommend taking the car to the smog check station immediately after the first applicaton of Techron, as the treament could increase emissions. And depending on the ratio of Techron to gas, you may even notice the car runs a little rougher for a time as it's clearing out deposits. His recommendation was to use up the first tank of treated gas, fill it up again (no Techron this time), deplete that tank, THEN get more gas (no Techron added) and take the smog test.

I could also do two treatments with Techron, then fill up and deplete an untreated tank, etc. etc. But at that point, given the cost of gas, it would make more sense to do a $250 MotorVac treament!

For what it's worth...

[prix]

Update on Techron: In a word, wow. Seems to have muted the light knocking sound I referenced earlier, and there is also a noticeable increase in power, smoothness, and responsiveness. The car is liking this stuff.

That said, I did read (another forum, don't recall where) that it's a good idea to -- after you've gotten the benefits of it cleaning out the system -- change the oil. The gist of the comment was, used oil analysis after Techron use shows the introduction of a chemical that is not that great for your car's innards, over the long term. His recommendation was to change the oil within 500 to 1000 miles of using the additive.