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2000 Corolla
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Discussion Starter #1
Hey guys so I have experienced a P0171 code for years. It comes and goes as it pleases. Over time I have replaced many part's and tried many possible fixes (Both o2 sensors, pcv valve, gas cap, cleaned the MAF sensor, fuel injector cleaner, etc. Also replaced the rusted out Fuel fill neck which kept the code away for a solid 5 months. My real reason for this post is because I have noticed Engine shaking/vibration at Idle. Now this only happens once the engine is warm. So if my engine is Misfiring once warm could it be related to the P0171 lean condition?Also important to note I never seem to get any Misfire code. I have never replaced Spark plugs either...
 

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2000 Corolla
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Discussion Starter #2
Another thing I should mention is Idle Surge after start up. Car also wants to die unless I let it idle for a minute before driving...
 

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2002 corolla ce
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Did u use aftermarket parts or genuine Toyota denso? Are your plugs the ones listed under your hood or just what the shop sold you?

Your vibes at idle is likely a mount that is bad. You need 2 people to check them but just do a break stand and watch for movement. Best done by a pro but the repair can be simple. Your car automatic?
 

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Porsche
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The surging idle is primary clue. ECU is trying to adjust IAC to compensate for leak, but results in a roller-coaster ride of catch-up and missing back & forth.

You’re right about other clue, it gets shaky and can even stall when warmed up due to lean mixtures. Extra air is getting sucked in along intake-tract somewhere after MAF, thus is not measured by MAF. Therefore, ECU doesn’t inject extra fuel to match what’s sucked in by vacuum leak leading to lean mixtures. It’s better when cold because ECU properly detects cold-start and engages cold-start cycle with extra fuel (+6 to 25% more depending upon actual ambient temp).

There is absolutely nothing that you can do with scanner that will find vacuum leak (other than confirming leak exists by low MAF readings and positive fuel-trims; don’t kill the messenger, it’s working fine). Absolutely zero parts you can replace that will fix this. Have to do good ol' fashion troubleshooting like smart mechanics have been doing for 100-years.
 

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Porsche
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All this reliance on electronics makes people soft and not capable of critical thinking and logic. They just want answers and be told what to do. When apocalypse comes, those who can't set traps for rabbit or kill with your bare hands are gonna starve to death! Zombies are gonna getcha even though they're slower than molasses! Come see our newest game in Orlando: http://nomadicvr.com

Now, i'm going to show you some survival skillz. Put down the xbox, or tablet or whatever gizmo is your temple of Truth and get hands-on dirty and touch your car physically and mechanically. Touch it, feel it vibrate, learn how it sounds when it's healthy and when it's sick. Pull and yank on hoses to see if idle note changes. Squirting with propane, carb-cleaner, water or even strategic aiming of pee can help, but you need to have some prior experience to recognize the subtle change in idle tone. And you need to know where to squirt.

Here's a sure-fire 100% way to find vacuum leaks with positive visual confirmation.

1. Plug your exhaust with banana, potatoe, cork, wet-rag or whatever gives 100% blockage

2. Make a plug fitting that replaces MAF on intake hose with compressor quick-fitting


3. Install your plug into intake hose which normally connects to outlet of MAF


4. Then set compressor to 3-5psi and connect to fitting

5. Squirt soapy water at every connection point from intake hose all the way to intake valves. Every seam, every joint, every clamp, etc. Pay particular attention to intake-manifold to head mating surface. Also injector tips.

In this case ironically, I had leak at external idle-valve. There's O-rings and seal inside case of idle-valve that needs replacing.


And another leak at throttle-body/TPS. There's O-rings on both sides of butterfly shaft that needs refreshing.


Also leak by dipstick tube. Looks like someone previously replaced O-ring with one that's too big. New correct O-ring with some sealant takes care of that!


Bubbles stay around leaks and gives you time to find them. Squirting propane isn't nearly as effective because you need to squirt at ALL leaks simultaneously for enough to get into engine to affect idle note. And you can't see propane and see exactly where it was sucked in. Bubbles are easier!!! :hi:
 

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2000 Corolla
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Discussion Starter #10 (Edited)
The surging idle is primary clue. ECU is trying to adjust IAC to compensate for leak, but results in a roller-coaster ride of catch-up and missing back & forth.

You’re right about other clue, it gets shaky and can even stall when warmed up due to lean mixtures. Extra air is getting sucked in along intake-tract somewhere after MAF, thus is not measured by MAF. Therefore, ECU doesn’t inject extra fuel to match what’s sucked in by vacuum leak leading to lean mixtures. It’s better when cold because ECU properly detects cold-start and engages cold-start cycle with extra fuel (+6 to 25% more depending upon actual ambient temp).

There is absolutely nothing that you can do with scanner that will find vacuum leak (other than confirming leak exists by low MAF readings and positive fuel-trims; don’t kill the messenger, it’s working fine). Absolutely zero parts you can replace that will fix this. Have to do good ol' fashion troubleshooting like smart mechanics have been doing for 100-years.



Wow that makes perfect sense. Thank you so much the the reply and your time. I think I might try the Carb cleaner trick. Which areas I should check/spray for leaks? It's hard to tell what I'm looking at Vacuum line wise....I remember reading that Intake manifold gaskets going bad are common on our Cars?
 

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Porsche
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Wow that makes perfect sense. Thank you so much the the reply and your time. I think I might try the Carb cleaner trick. Which areas I should check/spray for leaks? It's hard to tell what I'm looking at Vacuum line wise....I remember reading that Intake manifold gaskets going bad are common on our Cars?
Every seam, every joint, every clamp, etc. Pay particular attention to intake-manifold to head mating surface. Also injector tips.
You're most welcome. Yup, squirt everywhere intake-air flows. From MAF all way to intake-valves. Every joint where hoses has an end with clamp should be squirted 360-degrees all way around. Squirt along body of every hose. Each intake-runner may have leak, so squirt all 360-degrees around every runner where it touches head.

Bubbles would be easier and take less time! Good luck! :hi:
 

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2002 Corolla CE
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Did you fix your P0171 code?

I recently fixed mine. I replaced the intake manifold gasket, throttle body gasket, valve cover gasket, vacuum hoses, PCV valve, and MAF sensor, but my high fuel trims still weren't correcting!

Most everything I read talked about the P0171 lean condition being caused by some sort of vacuum leak somewhere in the intake. I guess that's pretty common, but lean can also mean a lack of fuel, not just an excess of air.

The last thing I did, which immediately fixed my problem, was get my fuel injectors cleaned at RC Fuel Injection. My injectors came back looking and performing like new and immediately fixed my lean code.

I know you mentioned using some sort of fuel system cleaner, but that's nothing compared to getting them professionally cleaned and flow tested to spec. It was a hundred bucks for the cleaning and I got a data sheet with the flow test results.

Hope this helps!
 

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Porsche
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I've also had good luck with http://mrinjector.us for injector cleaning. They'll give you a before and after flow-report so you can see how much cleaning helped.

Of course, you should confirm or deny you have vacuum-leak or not by measuring intake-manifold vacuum.
 

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2000 Corolla
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Discussion Starter #15
Did you fix your P0171 code?

I recently fixed mine. I replaced the intake manifold gasket, throttle body gasket, valve cover gasket, vacuum hoses, PCV valve, and MAF sensor, but my high fuel trims still weren't correcting!

Most everything I read talked about the P0171 lean condition being caused by some sort of vacuum leak somewhere in the intake. I guess that's pretty common, but lean can also mean a lack of fuel, not just an excess of air.

The last thing I did, which immediately fixed my problem, was get my fuel injectors cleaned at RC Fuel Injection. My injectors came back looking and performing like new and immediately fixed my lean code.

I know you mentioned using some sort of fuel system cleaner, but that's nothing compared to getting them professionally cleaned and flow tested to spec. It was a hundred bucks for the cleaning and I got a data sheet with the flow test results.

Hope this helps!

Hey bud. No not yet. I have always done my own fluid changes and repairs for my six years of ownership. Looking for a vacuum leak though makes me feel like a NOOB. I feel like I'm just staring at my car lol. I am scared to spray carb cleaner. As well as worried about messing with hoses. I am embarrassed to admit this, but I think my Corolla has had this problem for years. I love my car so much and it hurts me to know it is running lean. Maybe I should try Fuel injector cleaner again since you had good luck.
 

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All this reliance on electronics makes people soft and not capable of critical thinking and logic. They just want answers and be told what to do. When apocalypse comes, those who can't set traps for rabbit or kill with your bare hands are gonna starve to death! Zombies are gonna getcha even though they're slower than molasses! Come see our newest game in Orlando: http://nomadicvr.com

Now, i'm going to show you some survival skillz. Put down the xbox, or tablet or whatever gizmo is your temple of Truth and get hands-on dirty and touch your car physically and mechanically. Touch it, feel it vibrate, learn how it sounds when it's healthy and when it's sick. Pull and yank on hoses to see if idle note changes. Squirting with propane, carb-cleaner, water or even strategic aiming of pee can help, but you need to have some prior experience to recognize the subtle change in idle tone. And you need to know where to squirt.

Here's a sure-fire 100% way to find vacuum leaks with positive visual confirmation.

1. Plug your exhaust with banana, potatoe, cork, wet-rag or whatever gives 100% blockage

2. Make a plug fitting that replaces MAF on intake hose with compressor quick-fitting


3. Install your plug into intake hose which normally connects to outlet of MAF


4. Then set compressor to 3-5psi and connect to fitting

5. Squirt soapy water at every connection point from intake hose all the way to intake valves. Every seam, every joint, every clamp, etc. Pay particular attention to intake-manifold to head mating surface. Also injector tips.

In this case ironically, I had leak at external idle-valve. There's O-rings and seal inside case of idle-valve that needs replacing.


And another leak at throttle-body/TPS. There's O-rings on both sides of butterfly shaft that needs refreshing.


Also leak by dipstick tube. Looks like someone previously replaced O-ring with one that's too big. New correct O-ring with some sealant takes care of that!


Bubbles stay around leaks and gives you time to find them. Squirting propane isn't nearly as effective because you need to squirt at ALL leaks simultaneously for enough to get into engine to affect idle note. And you can't see propane and see exactly where it was sucked in. Bubbles are easier!!! :hi:

After 60,000 hours on the job that ended 20 years ago in 12 months, I seldom learn much new. Sadly my memory is going slowly at 68, but this is one of the best ideas I have ever read. Soap bubbles and compressed air!!!!
I absolutely love it.
 

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Did you fix your P0171 code?

I recently fixed mine. I replaced the intake manifold gasket, throttle body gasket, valve cover gasket, vacuum hoses, PCV valve, and MAF sensor, but my high fuel trims still weren't correcting!

Most everything I read talked about the P0171 lean condition being caused by some sort of vacuum leak somewhere in the intake. I guess that's pretty common, but lean can also mean a lack of fuel, not just an excess of air.

The last thing I did, which immediately fixed my problem, was get my fuel injectors cleaned at RC Fuel Injection. My injectors came back looking and performing like new and immediately fixed my lean code.

I know you mentioned using some sort of fuel system cleaner, but that's nothing compared to getting them professionally cleaned and flow tested to spec. It was a hundred bucks for the cleaning and I got a data sheet with the flow test results.

Hope this helps!
Now we go to another top post ever. Have your injectors professionally cleaned. The only way you can inspect the spray patterns is to remove them and use an injector activator-cleaner to visually see the improvement.

In the meantime and before you get to deep in either of these especially important processes, try a simple bottle of techron and see if you get a noticeable improvement. IT ELIMINATES THE POTENTIALLY FRUSTRATING CONSEQUENCES OF MESSING WITH SOMETHING THAT MAY COME BACK TO BITE YOU IN THE ARSE.

I am not that familiar with Toyota specific vacuum leak issues, but the method described here is fabulous and it requires practically 0 risk, as does the bottle of techron. I pulled my plugs today on my Echo at 167k miles, and they look perfect. I have run several bottles of the injector cleaner over the close to 20k miles I have driven my car.
It runs like a blueprinted brand new engine, which is what you would expect at 167k miles. I have a spare engine with injectors that I might send to a professional cleaner to keep on hand just in case.

My recommendation try a bottle of techron, either injector cleaner or fuel system cleaner. If you see a measurable improvement get a 6 pack from costco and add it for another 10 k miles. This assumes you are NOT fighting a vacuum leak in which case you need to do the soapy water test.

There is a strategic method to diagnosing driveability issues and lean and random misfire codes to a successful repair without wasting money. I never believed standing in front of any car with a "parts shotgun" throwing money at a problem when you have a brain that can save a lot.
 

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The thing with injectors is How do you visually inspect the quality of atomization. The cpu controls the duration of the solenoid in the injector itself, but NOTHING controls the spray pattern. We used to do diesels at a Mercedes dealership with a simple hand operated pump that would produce 2500 psi. The Benz diesel injectors needed 1800 psi for good atomization. When they got old the springs in the injectors got a little weak and their break off pressure dropped to 1400 psi and fuel atomization went to crap. Shimming the springs up brought the pressures back and everything was fine, or you could replace the springs and get to the same place.

Think of what an injector has to do and in what environment it has to do that. After 100k miles they start loosing the proper spray pattern and eventually it tripps a CEL, when the cpu can no longer balance them through pressure alone. Get the pattern balanced and they are operating as new again. A fuel injector can cycle 1500 times a minute at 3k rpm, multiply that by 167,000X1500 cycles in my Echo. Thats 250 million cycles. Think they might get a little out of sorts spray pattern wise?

If you remove the injectors and reinstall them for cleaning make sure you replace the seals and clean everything to operating room standards. With the vacuum leak test weapon you have the ability to really check your work as well as find out first if a vacuum leak is there to begin with.

Great thread.
 

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Hey bud. No not yet. I have always done my own fluid changes and repairs for my six years of ownership. Looking for a vacuum leak though makes me feel like a NOOB. I feel like I'm just staring at my car lol. I am scared to spray carb cleaner. As well as worried about messing with hoses. I am embarrassed to admit this, but I think my Corolla has had this problem for years. I love my car so much and it hurts me to know it is running lean. Maybe I should try Fuel injector cleaner again since you had good luck.
From your description it sounds like a vacuum leak.
This is my favorite p0171 diagnosis video. Starts at 11:30. Scannerdanner is very thorough and uses basic tools and water instead of carb cleaner.

[ame]https://youtu.be/pv9R2IEG4mU?t=690[/ame]
 

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Haha, I'm the same way. For the longest time I was trying to figure out how to detect a vacuum leak. I was also afraid of spraying carb cleaner.

Like me, you might not even have a vacuum leak. Do you have a scan tool? I researched how to look at the fuel trims to determine if there was a vacuum leak.
Basically, start your car and get live data up on a scan tool, and look at the short term fuel trim and long term fuel trim both at idle and at a load like at 1500 or 2500 rpm.
If you have a vacuum leak, you'll have high positive fuel trim numbers (I had +15 to +35) at idle and then they'll correct themselves at higher rpm (go down to regular numbers within +/- 10) since there is less of a vacuum when the throttle plate opens up.
In my case, my fuel trims didn't lower/correct themselves when I was at a higher rpm so according to my research that indicated there wasn't a vacuum leak, but rather a fuel delivery issue.
I think I'm explaining this properly, if not, someone more knowledgable can chime in.

I thought it could be an issue with my fuel pump or fuel injectors and it ended up being my injectors. The pre-cleaning flow test showed that 2 of the injectors were dripping, 1 was kinda okay, and the other was restricted.
 
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