[Tutman]

The check engine light came on my 95 Previa (98000 miles) and it started idling high once engine was warmed up.
I took it to my mechanic who put it on the diagnostic computer and said it showed "lean mixture".
He cleaned the mass airflow sensor and the light went out. On the way home, the light came back on. After 2 hours of searching and tweeking, he said he "thinks" it's the Idle Adjustment Valve becuase when the engine is revved, it the rpm's do not come back down all the way. He put a carb jet in one of the vacume hoses (to restrict air flow) and it fixed the idle high and rev problem, but the check engine light is still on and it idles uneven in nutral when warm, but idles fine when in gear.
He said it was only a temp fix until I can afford a IAV.
Ever since then, the idle has gotten progressively lower when started cold, but only until the engine warms up. Now it won't idle when started cold without giving gas peddal until it warms up a bit.
He's not 100% sure about exactly what part it needs and I don't have the $$$ to start buying parts that won't solve the problem.
Any help is greatly appreciated!

 

[awtomakina]

02 sensor. IAC RARELY FAILS . RARELY.

 

[Tutman]

02 sensor. IAC RARELY FAILS . RARELY.

Thank you for the reply. I'm getting conflicting advice on this..however,
how will I know which o2 sensor to replace? Pre-catalyic converter, or post?

 

[awtomakina]

the IAC unit is not something you replace. it just something you clean. its located under the throttle body assembly ( visible from the bottom when looking up ) easy to service, just remove it, buy some carbon cleaner / brake clean. not too corrosive cleaner u can get. dont' use metal tools when cleaning the IAC VALVE. heres what u do

grab a hard toothpick. and flatten one end. and keep the point on the other. use the point to scrape the tight areas and use the dull edge to scrape the valve face(surface). DO NOT USE METAL TOOLS you'll SCORE it and fuK it up. this is something you can do. very easy, i made a TOPIC about CLEANING IAC on this forum. look for it. more info there.

try replacing the FRONT O2 sensor. the back sensor is just a reference for the cat converter.

i will be honest with you, not many mechanics knows a PREVIA. even in the TOYOTA DEALERSHIP not many techs, knows how to work on these cars. because these previas are WORKHORSES. THEY RARELY FUCK up. when maintained properly. so they rarely end up in a garage, specially a dealership . next to the oil change , brakes, and suspension parts. thats really much it.

i have a 91 toyota previa with 450 000 km on the ORIGINAL ALTERNATOR - I NEVER KEEP THE BATTERY DRAINED. AND I NEVER BOOST THE CAR - BOOSTING CARS CAN STRAIN YOUR ALTERNATOR -

get back if u need to know anytihng else. hopefully i can help you, having 4 previas. i think i gotten to know these vehicles very well.

 

[junoflydog]

awtomakina,

this is a previous post that you made. very good description.


http://www.toyotanation.com/forum/showthread.php?t=257130

 

[awtomakina]

what can i say, i can be very graphic. i was gonna add photos but thats just too HARDCORE might turn these guys on. hahaha.

glad you understood my description : this is the purpose of this site. help each other out.:welcome::clap:

awtomakina,

this is a previous post that you made. very good description.


http://www.toyotanation.com/forum/showthread.php?t=257130

 

[Tutman]

HUGE thank you awtomakina!!!!!!!

 

[awtomakina]

i am guessing that fixed the problem?


you're very welcome :welcome:: anything else comes up with your pre-teen van let me know. i'll be around.

HUGE thank you awtomakina!!!!!!!

 

[Tutman]

UPDATE:
I found my supercharger was leaking fluid, so I purchased a used one off a '95 Previa with 125,000mi from a salvage yard in SoCal for 200.00 + 80.00 shipping Hawaii. The supercharger included the throttle body. (after some negotiating)
My mechanic quoted me 4.5 hours to change out the supercharger as per his mechanics job-time book. He is not firmiliar with the Previa and it wound up talking him MUCH longer than that, but still only charged for 4.5 hours + the cost of a new gasket kit for something er other. Total cost for install = 495.00.
He cleaned the AICV that came on the perlacement throttle body while cleaning the replacement throttle body and installed it with the replacement supercharger.
Problem solved!! Check engine light is off and it runs like a top! Only 97,000 mile on it, so I should get years of driving out this baby-egg!
I also changed the supercharger oil to Castrol Syntec 5 w50 synthetic.

 

[Franksi]

95 Previa Hi NOx HC Issue

i am guessing that fixed the problem?
you're very welcome :welcome:: anything else comes up with your pre-teen van let me know. i'll be around.

Awtomakina,

I just bought a 95 Previa w/197K miles on it for $800 from a friend that took really good care of it; extra clean inside/out as well as mechanical, no knocks, noises, leaks, etc. He bought it used w/135K mi, drove it ~6K mi/yr for the last 10 yrs, had it serviced regularly at a local Toyota Dealership. He didn't need 3 vehicles when his son left for Bethel and I needed an inexpensive and reliable vehicle - I am on a very limited income (which is why he sold it to me for so little).

Anyway, on a CA smog pre-test it reported hi NOx (902 vs 508 limit) and hi HC (62 vs 62 limit). The CO is (.17 vs .45 limit) and the CO2 is (14.7), O2 is (.3). When cold it idles fast for ~2 minutes then idles down properly. No other noticeable aberrant behavior that I can determine.

I Google'd lots of stuff on the various forums/sites for hours and it appears the symptom points to an EGR system, or O2, timing, or catalytic issue (likely in that order driven by the cost of replacement/repair). Tomorrow I'd like to begin working toward getting the vehicle to pass smog and complete the DMV transfer of ownership.

With your extensive personal experience over the decades/vehicles where do you recommend I start w/o throwing in too much time or $s in order to get the NOx and HC numbers down?

Anything you could choose to share would be greatly appreciated, since I have my 10-day transfer of ownership countdown timer started as of yesterday 6/28/12.

Regards,
Frank

 

[awtomakina]

sorry i wasn't able to help you out in time; but in your case i would've replaced the catalytic converter; hopefully everything went well and you got your problems fixed; next time...keep eggin