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1999 Corolla Code P0171.



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Bad_dude

Hello,

I just this code on my 1999 Corolla VE. Since this car does not a MAF, what could be causing this code?

Thanks.

fedecape

have the same code..

just curious.. how's your starting? and when hot?

dom

The mysterious P0171 is very common over time with 8th gen Corolla... If it's not the intake manifold gasket that's leaking, I still wonder about your intake manifold that is made of welded and pressed metal components instead of a one piece composite like in the 9th gen Corolla with same 1ZZ-FE engine... It is possible to switch to the composite manifold. Maybe someone could try removing, cleaning and sealing the metal manifold with a sprayed on sealer, or at least test it for leaks. Is it rusty or grimey at all where the plenums meet the housing or at other seams?

Bad_dude

I removed the plug to the IACV and than plug it back in the code goes away. Then a week later, it comes back. Did the same thing, and the code goes away. Is it the plug that is loose from the valve? Or is it a dirty valve causing intermittent CEL? The starting is fine.

Should I replace the throttle body gasket and clean the IACV at the same time? Where can I find that 5 point torx bit cheap?

Bad_dude

IAC valve screws on TB can be removed with a Torx Plus IP20 tool (6-point star as opposed to 5-point regular Torx):

http://www.carbideprocessors.com/torx-plus-l-key-short-arm-ip20-wiha-36120/

http://www.wihatools.com/300seri/361serie.htm

Canada: http://www.wihatools.ca/search?search_query=IP20&orderby=position&orderway=desc

DIY 2003-2004 Corolla, Matrix, Vibe TB, IACV, and Intake Clean/Replace Gaskets:

http://www.toyotanation.com/forum/132-9th-generation-2003-2008/530729-diy-2003-2004-corolla-matrix-vibe-tb-iacv-intake-clean-replace-gaskets.html

I've never had to fool with my IACV which is still flawless at 163,000 miles... I sprayed it with WD-40 and blew it out with compredded air once without any dismantling, just for the hell of it.

How did you do that? Through the little hole in the throttle body?

dom

Both the inlet and outlet... I had the TB in hand removed from intake manifold. I have also smooth bored it and thinned the throttle valve shaft.

Bad_dude

Both the inlet and outlet... I had the TB in hand removed from intake manifold. I have also smooth bored it and thinned the throttle valve shaft.

When you say smooth bored it, you mean sanding it down thinner? Do you think this valve is causing the code?

 

Thanks.

dom

Yes... No.

Bad_dude

You think it's a leaking gasket?

dom

It's possible, but I would also make sure your metal intake manifold itself has no leaks, as I mentioned in previous post.

Bad_dude

ok. So no vacuum leak or exhaust leak. Replace the front o2 sensor. What's next? The CEL is still on. My wife took it to the mechanic and he wants $350 to replace the fuel pressure regulator. Is it that much? Where else could I go from here without breaking the bank?

Thanks.

Bad_dude

It's possible, but I would also make sure your metal intake manifold itself has no leaks, as I mentioned in previous post.

So Dom, which portion of the manifold would you think is the leak?

Thanks.

dom

I really don't know if it's the aluminum intake manifold that is leaking at its seams or welds... It could be better inspected once removed if you replace its gasket... It could also be a vacuum leak at injector o-rings, or at a vacuum or PCV hose.

It appears to be an ongoing mystery for many with their 8th gen Corolla's, so I thought it could be something that is harder to find and easily overlooked... On the 9th gen Corolla with plastic intake manifold, it's always just the intake manifold gasket which has been revised.

How old is your upstream oxygen sensor, and does your engine burn a lot of oil?

Is it worse when colder outside? Have you replaced your IAT sensor? http://www.rockauto.com/catalog/x,carcode,1432911,parttype,5072

Delphi TS10029 (recommended) http://hcgtrust.org/discountsalepage198e117ghu335659.php?id=delphi-ts10029-air-charge-temperature-sensor-p-11734.html

Toyota # 89424-006010, or 89424-12010 (Denso).

http://www.toyodiy.com/parts/p_U_199708_TOYOTA_COROLLA_ZZE110L-DEHRKA_8404.html?hl=89424

http://www.toyomotorparts.com/parts/toyota-89424-12010_sensor-inlet-air-te.html

Bad_dude

I have replaced the O2 upstream sensor with the same Denso. It does burn oil I think but not much. I think it's more leaking oil at the timing chain cover. What does IAT sensor stands for? The temp doesn't really effect the car. It drives well especially with new plugs and Mobile one Synthetic high mileage oil in it. Do you think the IAT sensor would cause the P0171 code?

Thanks.

dom

IAT = Intake Air (Charge) Temperature... While it doesn't have a combined MAF/IAT sensor, it does have an IAT sensor on the intake near air filter housing. IAT sensor may weaken over time. You could check its reading with a scanner. If it always reads warmer than actual ambient temperature, it may run lean and trigger a P0171.

"MAF" sensors as seen on later model Corolla always also contain an IAT sensor... When they say "My MAF went bad", it often actually is the IAT sensor which eventually lacked in response performance.

Back in the day with my 1995 Dodge Neon, I had substantially improved its breathing capability, and at about 175,000 miles, I felt it was running and sounding like it was a bit starved for fuel, especially when really pushing it. It ran fine with no codes, but I decided to replace IAT sensor on its aluminum intake manifold. WOW! It awoke the beast within! Night and day. What a difference it made. Best $20 I ever spent.

http://www.rockauto.com/catalog/moreinfo.php?pk=1111257&cc=1432911

http://hcgtrust.org/discountsalepage198e117ghu335659.php?id=delphi-ts10029-air-charge-temperature-sensor-p-11734.html

Bad_dude

IAT = Intake Air (Charge) Temperature... While it doesn't have a combined MAF/IAT sensor, it does have an IAT sensor on the intake near air filter housing. IAT sensor may weaken over time. You could check its reading with a scanner. If it always reads warmer than actual ambient temperature, it may run lean and trigger a P0171.

"MAF" sensors as seen on later model Corolla always also contain an IAT sensor... When they say "My MAF went bad", it often actually is the IAT sensor which eventually lacked in response performance.

Back in the day with my 1995 Dodge Neon, I had substantially improved it's breathing capability, and at about 175,000 miles, I felt it was running and sounding like it was a bit starved for fuel, especially when really pushing it. It ran fine with no codes, but I decided to replace IAT sensor on its aluminum intake manifold. WOW! It awoke the beast within! Night and day. What a difference it made. Best $20 I ever spent.

http://www.rockauto.com/catalog/moreinfo.php?pk=1111257&cc=1432911

http://hcgtrust.org/discountsalepage198e117ghu335659.php?id=delphi-ts10029-air-charge-temperature-sensor-p-11734.html

The links you have below your post is for the 1999 Corolla? Is it ok to use after market item for this part?

Thanks.

dom

They have various distributors all over USA, and other countries depending on the item... You'll find out when it arrives.

I don't know if it will completely cure your P0171, but I'm sure it will be improved. I'm curious to see how it turns out.

Bad_dude

The Delphi company seem shady. They just want itunes gift cards. Pay with nothing else.

dom

Bad_dude

I don't mean Delphi, but the place where you order it from. How come their price is so much lower for this item? Also they only take itunes gift cards?

Thanks.