Previa Won't Pass Smog

[FanousOnTheLoose]

Hey guys! So I took my '97 SC to get smogged today and it basically passed on everything except the HC levels. Max is 31ppm and my ran 37 first test, and then 40 after it warmed up for a bit. Are there any recommendations as to how to lower the HC ppm emission level? It was also running on 87 octane, first time putting that in my engine in awhile. Anything I can do or add to help pass smog and also just help the car run better in general?

[timsrv]

There can be many reasons why you have high HC.......could be a combination of 1 or more. The 1st thing to do is read diagnostic codes as the answer may be there waiting for you. If you're overdue for a tune-up, now would be a good time to take care of these things too (might be something as simple as a dirty air filter). Tim

[FanousOnTheLoose]

Still can't pass smog! Got a master tune-up, changed plugs, distributor cap, wires etc. and changed the exhaust gasket and filled it with 89 octane gas. Did a pre-test and passed, the max is 31 HC ppm and I got 30, did the real test and I got 32 -___-

I don't know what else to do, I was gonna test again but on 91 octane. Any other reccomendations? the only problem is the HC gases.

[timsrv]

The 1st thing to do is read diagnostic codes as the answer may be there waiting for you..............

What (if any) were the diagnostic codes?

[FanousOnTheLoose]

What (if any) were the diagnostic codes?

where can I find the diagnostic codes on my result sheet?

[timsrv]

That's not something they check (your responsibility). Your Previa has a diagnostic system that records faults. You will need to check to see if there's any codes stored in your ECU. There is a little gray plastic diagnostic box under the driver's seat. You put a conductor (paper clip works good) across the terminals E1 & TE1. After that, make sure all your accessories are off and turn the key to run (don't start). Your "check engine light" on the dash will now be blinking. You decipher the blinks like Morse code. The FI section of your service manual will explain in more detail and they give you a chart to determine which codes are displaying. If you don't have a factory service manual you should get one. They come on eBay all the time for around $50 or so. I'd post the code info here, but the newest manual I have is for 93. Tim

Edit 1/8/15: Important note: The above information only applies only to the earlier vans (pre OBD II). OBD II came into play in 95 or 96. If you have OBD II, you'll need to purchase a scanner to read codes.

[pdgizwiz]

Since your van is a '97, it will have an OBD II port. I suggest that you pick up an OBD II code reader - It could be the best $100 or so you'll ever spend. Or perhaps second to a Factory Service Manual (FSM) which you can find on ebay.
Previas got the port in mid-'94, with the SC models. Prior to that the pin shorting trick that Tim suggested works. I'm not sure if you can do the pin shorting thing with a newer OBD II equipped van....

[timsrv]

Since your van is a '97, it will have an OBD II port. I suggest that you pick up an OBD II code reader - It could be the best $100 or so you'll ever spend. Or perhaps second to a Factory Service Manual (FSM) which you can find on ebay.
Previas got the port in mid-'94, with the SC models. Prior to that the pin shorting trick that Tim suggested works. I'm not sure if you can do the pin shorting thing with a newer OBD II equipped van....

:whs: Good catch PD! While writing that I wondered what year they switched to OBDII & even looked it up (although what I found said they switched to it for the 96 models). Then I glanced at his profile and saw he had a 94..........didn't read far enough to see he also had a 97, and failed to notice that in his original post :dizzy: :doh:. Thanks for catching that! I'm a bit old school for OBDII & haven't owned anything newer than 93. Wish I could be of more help. Sorry for the misinformation. Tim

[FanousOnTheLoose]

Thanks for the help guys! I did some work on the van since this post, but still having trouble with emissions. The weird thing is that I did a pre-inspection and passed that and then did the real inspection and failed :no: I was so annoyed! Anyway since this post I'v replaced the spark plugs, spark plug wires, exhaust gasket, distributor cap and rotor. Still can't pass, but I did get closer to passing (looks like luck at this point). Took it to the dealer to get a diagnostic test and they didn't even have a machine to test it! My buddies used to be a technician for toyota and he said he as all the equipment so he's gonna help me out and run diagnostics, but if not I'l probably look into what pdgizwiz was saying and just buy a scanner.
But this van is becoming a headache and I just might end up selling it and save myself the trouble later on in its life when it comes to more smog.

Do any of your vans struggle with smog? What do you guys do? Is this a significant problem with the previa?

[timsrv]

The 1st thing to do is read diagnostic codes..............

Whether OBD II or the old style, this is the 1st thing you do (you just need a scanner to check the OBD II). When you finally get around to this, I'm guessing it will tell you an o2 sensor or something is bad. Assuming there's a code stored, simply replace the part that it points to and you should be good to go. Tim

[FanousOnTheLoose]

Whether OBD II or the old style, this is the 1st thing you do (you just need a scanner to check the OBD II). When you finally get around to this, I'm guessing it will tell you an o2 sensor or something is bad. Assuming there's a code stored, simply replace the part that it points to and you should be good to go. Tim


Yeah my buddy is gonna run the diagnostic test for me and check the codes. The smog tester was also suggesting a bad sensor, but Tim could you answer my question about the previa smog in general? Is smog a problem for the previa or am I just having bad luck? I don't want to run in this problem every 2 years when I get smog.

[timsrv]

Just bad luck. No more or less problems with Previas than with any other vehicle. Actually the All-Trac Previas pass easier. This is because the smog people don't have a way to test cruise emissions (no way to disengage the 4wd so they can't use the rollers in the floor). Instead they just rev to the normal cruising RPM rather than testing under load. This typically will produce less emissions than loading the engine, so they usually pass easier.

I'm guessing that once you get your issue corrected it will pass easily. Tim

[FanousOnTheLoose]

Just bad luck. No more or less problems with Previas than with any other vehicle. Actually the All-Trac Previas pass easier. This is because the smog people don't have a way to test cruise emissions (no way to disengage the 4wd so they can't use the rollers in the floor). Instead they just rev to the normal cruising RPM rather than testing under load. This typically will produce less emissions than loading the engine, so they usually pass easier.

I'm guessing that once you get your issue corrected it will pass easily. Tim

oh really? Well that's a relief. This smog issue is making me wanna sell my previa so that I don't have to deal with this headache every 2 years. But maybe I'll look into an AWD drive one for the future. But that's awesome. I'll keep you posted once my friend runs diagnostic and checks codes for me

[FRITZ THE CAT]

My 96 regularly fails Emissions test. always involves gasket replacement etc. I invested in OBD II scanner (very new model testing 4 areas including ABS Brakes ) to find out, the scanner will not interpret or recognize the codes. This suggests later Previa's require the specific Toyota Tester ( at dealer repair places ). Is this true? Or getting an older OBDII scanner? Does the Previa have some produced early in '96 being OBDI and later half being OBDII ? That would be confusing.

Emissions failing can also come from oil leaking into the spark plugs and dist. cap. I have cylinder 1 and 4 misfiring. The dist. cap is at the lowest level under passenger seat. Oil leaks from Oil filter O ring part # 15692-76010; oil leaks from Distributor Cap O ring part # 90099-14091. This is likely the biggest oil leak affecting emission; lastly, the VALVE COVER GASKET (http://www.toyotaonlineparts.com/toyota/previa/1121376020/1996-year/le-trim/2-4l-l4-gas-engine/engine-cat/engine-scat/?part_name=valve-cover-gasket)Part Number: 11213-76020 was replaced in order to pass a past emissions test. Check these 3 areas plus new plugs / wires if they were not replaced in the past 60,000 miles.

[sited faith]

My '97 just passed CA smog, but the HC was really close. I've read that its all up to the cat. I had to replace my front one (stolen). I put in an aftermarket cat, so that may be part of my problem. Next time I'm going to run the gas low and put in a good amount of methyl hydrate (methanol). I've read that this will help you pass.

mike h
'97 DX 330k miles -- never been to the shop!

[SamPrevia]

I am a little confused. Do they still do tailpipe testing? My 97 Previa won't need an inspection sticker until several months from now. But my oldest car is a 2005 and there is no tailpipe testing in Houston. They get all their data from the OBDII port. So, if the check engine light is not on, the car would most likely pass emission.

Is it different in CA? Or does it depend on the age of the car?

FWIW: A partially stuck (open) thermostat would cause high HC reading. The engine can not get sufficiently warm, so the computer would feed a rich mixture of fuel to the cylinder. This was the actual cause for high HC and emission failure test for my 1991 Civic about 8 years ago.

[sited faith]

Sorry to reply so late to this thread, Sam. Yes, they still do tailpipe testing in CA, on rollers depending on age.

My coolant temp runs in the 190s to low 200s (Scanguage) so I don't think the high HCs are due to running cool.

mike H.