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Discussion Starter #1
I had 2 dead o2 sensors. Van ran great 26+mpg, no hesitation. Replaced bank 1 and 2 o2. Van began having little hesitation on Acceleration and throws p0174 after about an hour of driving. I can’t find any vacuum leaks and the van runs ok just not perfect I see a slight rpm fluctuation at idle. If the plugs are bad, would the Cel show a misfire code? Any ideas are appreciated. Thanks mike
 

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Update. Went around retighten air snorkel and lines. I ran the throttle to stop point and seems like the throttle needs some force to get to low idle. Gunk in throttle body? I’ll clean it soon. Weird thing is, gave two new codes, P2198, p2240. Which may mean my 13 buck cheapo o2 has failed.
 

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Discussion Starter #3
This is cool also. When I was wiggling the throttle, the LTFT bank 2 started coming down. “Green line”. iAC and throttle needs a cleaning?
A732A563-F909-4459-B9A0-087FF2B78107.png
 

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These vans have been pretty finicky about their oxygen or A/F sensors. Consider using Denso sensors--see the denso aftermarket site for the right part number.

The IAC valve gets sticky on the 2001-2003 vans especially, but this usually causes a stall after starting, not a code; the van in these cases can only be kept running by pressing the gas pedal. If you haven't cleaned the IAC, try that. A good cleaner is SeaFoam Deep Creep, or TriFlow lubricant has been used by others, or use whatever you have for a throttle body. Easiest first thing to try is to take the hoses off the throttle bode and squirt cleaner into the IAC's "hole" on the right side.
 

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Discussion Starter #5
I did have the IAC gunk up alot in my last Previa and it stalled fast just like you say. I ended up leaving my wife a big wrench to bang on it if it did it when I was not around . THE Sienna starts real well. The new Bank 2 O2 that is acting up on the Sienna was onsale for $13 bucks. I complained to the vendor and they are sending me a new one some day. Not here yet. The $22 buck O2 in bank 1 seems to work fine. I've owned a 85 Toyovan, 2 Previa's and this Sienna. I see Denso o2's for sale from $20 to 44$. not too high.
 

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Discussion Starter #7
Hey PJ. I sprayed out the throttle today . Not too dirty . Below it was a soliniod thingy. 2. Phillips screws. It was stuck. I goes left or right. Maybe idle control? Sprayed it . Engine idles 1100 now but runs smoother. Crazy
 

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Discussion Starter #8
My fuel trim scan looks better. The longterm fuel trims are closer to zero. Short term is around 15% to 20%. It seems high but is much better than earlier chart. You were correct about th IAC PJ. No CEL after 40 miles! Fingers crossed
E8798D77-C62D-49C6-A546-3DDB8E6F7860.png
 

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Discussion Starter #10
Back to the drawing board. Got the P0174 P081 and a code that says Bank 01 is stuck on rich. ugh
 

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Discussion Starter #11
Cleaned out Pcv today. Not much improvement. Still pulled a lean code. I have 290k on this car. Is the fuel filter in the tank a real filter or a mesh bag? Could it be clogged? When I drag race the engine, the cel and codes appear.
 

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Hoping others might chime in here, but I'd wonder about that A/F sensor. It could be the injector.

Are you sure about the code P0174 as being Bank 1 rich? See attached from the 2001 repair manual.
 

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Discussion Starter #14
I think it said ltft stuck on rich. I cleared the Cel and It seemed to operate ok. Here is the trim graph. Crazy. I’m waiting for a replacement o2. If it was easy to swap with bank 1, That would settle it. I recall getting that o2 in was no fun at all. I will pull the wacky o2 out and see if it looks odd. I checked my parts order and both o2 have a number that is a Denso part number.
42EE83C0-2B80-4DA7-B6D2-EAAF78077793.png
 

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Discussion Starter #16
I started over, Looking for air leaks again. Pulled maf, sprayed it again, noticed I missed the little elements down the tube last time. Really inspected the rubber snorkel to the throttle body. Re Sprayed Throttle and Iac real welll. Put it all back tight. Replaced o2 sensor I switched. Drove and got Cel lean in bank 2. arrrrrhg
 

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Discussion Starter #17
I started looking a MAF. If Maf is giving freaky air rates. Then the injectors will give more fuel and the the o2 will say go lean to fix rich condition. This is Either giant vacuum leak before maf or electrical issues. Most all the time mafs either work or don’t. This Chart shows the My maf going super high during a drive around block.
C60BE9D9-58D5-43E3-BC75-C4E0D407B46B.png
 

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Discussion Starter #18
I caved in and replaced the MAFs. The fuel trims look like they changed. The long term trims are tracking together. The short term trims are staying together. I’m not convinced it’s fixed. I want to ohm check the old maf to the new one. To see if there is a difference.
 

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Discussion Starter #19
I caved in and replaced the MAFs. The fuel trims look like they changed. The long term trims are tracking together. The short term trims are staying together. I’m not convinced it’s fixed. I want to ohm check the old maf to the new one. To see if there is a difference.
F994981D-C4B7-43BB-9A5C-7687E3D76648.png
 

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Discussion Starter #20
I drive a couple days andtoday I get p0171 and p0174 codes Right after I start up this morning.
 
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