Hi, newbie here from California. I bought a 93 300zx non-turbo convertible (5-spd, all stock) where the seller told me it won’t pass California smog. I was willing to make it a weekend project for me. It runs well, no hesitation, good pick up, smooth start-up. I enjoy driving it very much. 94,000 miles.
Here’s what I did before the SMOG test:
- Changed fuel filter, air filters, oil filter, and oil
- Both air filters were clogged with grime and dirt, looked as if they had been in there for 7+ years
- A bottle of fuel additive was added as instructed, ran through a tank of gas on highway speed within a month.
I ran the car hot for 45 minutes before the test. Then here’s the SMOG result (Gross polluter):
HC(PPM): @15MPH, max is 59, I got 323
@25MPH, max is 34, I got 310
CO(%): @15MPH, max is 0.34, I got 6.46
@25MPH, max is 0.32, I got 5.07
NO(PPM): @15MPH, max is 484, I got 267
@25MPH, max is 498, I got 302
Looks like I failed HC and CO.
A mechanic from a different shop checked my car for me (free) and told me my EGR and O2 sensors are good, but he can’t handle pre-1996 cars.
Pepboys did diagnostic ($162) and told me I need $2000 worth of repair (2 cats, 1 MAS, and 2 left side O2 sensors). I have a hunch Pepboys is just shooting in the dark.
I read from this forum to not replace anything that’s not broken, and definitely not parts from ebay (like MAS). I will use a MAS cleaner spray to spray clean and MAS.
Any tips on how to go about diagnosing it would be greatly appreciated! I do not know how to run diagnostic test myself, and don’t know if that would help. I read catalytic converter rarely go bad, and the only way to see if they are broken is to take them off and look through them….I don’t know.
I have tools and some experience to do minor repairs, and I would leave major tuning and major repairs to local shops.
Thanks.
-Tony
1993 z32 won't pass California SMOG
-
frapjap
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'07 Subaru Legacy - Location: South Coast Massachusetts
Re: 1993 z32 won't pass California SMOG
Howdy!
Bummer about that man. I'm really glad to not live in CA.
Given the age of your car, the cats could definitely have gone bad over time- especially if you've had high HC for a while. But you're right- start cheap before investing in cats.
Things to try first (since every retest is free, right?) in order of expenditure:
- change your coolant temp sensor and thermostat. Get the engine running at the correct temps- sometimes the CTS could be wonky and telling the ECU is 20* outside.
- spark plugs and wires
- take off the intake and spray the MAF like you suggested
- run 1 oz of Marine Stabil through a full gas tank to clean the fuel injectors
- go back to your mechanic and be sure the 02 sensors are reporting correctly, one may be on its way out.
- finally, replace the cats.
I also dug this up from another forum in regards to the 02 sensor reporting:
____________________________________________________________________________
Here's how I would troubleshoot this:
First change your engine air filter and inspect your intake hoses for any cracks or leaks. You might also clean your MAF sensor with MAF cleaner if you know what you're doing (do not touch it with anything but solvent!). Next, take your car to a mechanic with an OBD II scanner that supports live data parameters. Have them check for any stored codes or misfires, and have them confirm the car is operating in closed loop once warmed up. Next, look at the long term fuel trim (LTFT). If it is more than +/- 10%, then you might have a problem (vacuum leak or stuck injector). The CEL won't come on until its 20-25 % which is too late in my opinion. If their scan tool is good enough, also have them check the O2 sensor output to make sure your sensor is responding properly, otherwise they can do it with an oscilloscope/voltmeter. Replace if necessary.
Finally, you can test your catalytic convertor. Watch this video: http://www.youtube.com/watch?v=Qrj_ioWCk... You can skip the pressure test if necessary, but make sure you are seeing the temperature increase.
The above steps should help you find your problem. Before emissions testing again, I would fill up with a fresh tank of 87 octane, no additives. Premium gas can sometimes cause higher emissions if you catalyst is poor. It also stresses the catalyst more since it does not burn as fast as 87.
Bummer about that man. I'm really glad to not live in CA.
Given the age of your car, the cats could definitely have gone bad over time- especially if you've had high HC for a while. But you're right- start cheap before investing in cats.
Things to try first (since every retest is free, right?) in order of expenditure:
- change your coolant temp sensor and thermostat. Get the engine running at the correct temps- sometimes the CTS could be wonky and telling the ECU is 20* outside.
- spark plugs and wires
- take off the intake and spray the MAF like you suggested
- run 1 oz of Marine Stabil through a full gas tank to clean the fuel injectors
- go back to your mechanic and be sure the 02 sensors are reporting correctly, one may be on its way out.
- finally, replace the cats.
I also dug this up from another forum in regards to the 02 sensor reporting:
____________________________________________________________________________
Here's how I would troubleshoot this:
First change your engine air filter and inspect your intake hoses for any cracks or leaks. You might also clean your MAF sensor with MAF cleaner if you know what you're doing (do not touch it with anything but solvent!). Next, take your car to a mechanic with an OBD II scanner that supports live data parameters. Have them check for any stored codes or misfires, and have them confirm the car is operating in closed loop once warmed up. Next, look at the long term fuel trim (LTFT). If it is more than +/- 10%, then you might have a problem (vacuum leak or stuck injector). The CEL won't come on until its 20-25 % which is too late in my opinion. If their scan tool is good enough, also have them check the O2 sensor output to make sure your sensor is responding properly, otherwise they can do it with an oscilloscope/voltmeter. Replace if necessary.
Finally, you can test your catalytic convertor. Watch this video: http://www.youtube.com/watch?v=Qrj_ioWCk... You can skip the pressure test if necessary, but make sure you are seeing the temperature increase.
The above steps should help you find your problem. Before emissions testing again, I would fill up with a fresh tank of 87 octane, no additives. Premium gas can sometimes cause higher emissions if you catalyst is poor. It also stresses the catalyst more since it does not burn as fast as 87.