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It chokes and sputters when applying gas. We changed the…

It chokes and sputters...

It chokes and sputters when applying gas. We changed the catalytic converters when running rough and had codes. Then it ran ok- then threw codes again -changed gas cap followed with spark plug change and cleaned the emaf. The plugs and EMAF made everything worse, it barely runs now. 2011

Mechanic's Assistant: Have you metered out the ignition system?

No what is that?

Mechanic's Assistant: What is the model of your '11 Toyota?

Tundra

Mechanic's Assistant: Are you fixing your Tundra yourself? What have you tried so far?

Mechanic did the converters. plugs and gas cap and EMAF clean was me. I also unplugged th emaf while running to verify it being good or bad. when unplugged the engine stopped. So the EMAF is good

Mechanic's Assistant: Anything else you want the mechanic to know before I connect you?

The codes are po171, and 173

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Answered in 7 minutes by:
3/27/2018
Amedee
Amedee, Toyota Technician
Category: Toyota
Satisfied Customers: 27,623
Experience: ASE certified tech advanced level specialist. Wisconsin certified emissions state inspector
Verified

Hello and welcome!

My name is ***** ***** I can assist you with your question.

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The most common cause of this condition is a faulty mass air flow sensor, low fuel pressure or faulty oxygen sensors.

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I am glad I can help! My goal is to give you the best experience possible! I hope I have earned a 5-star rating! Please remember to rate my service by selecting the 5 stars at the top of the screen before you leave today. If you need more assistance, please use the reply box and let me know.

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Customer reply replied 26 days ago
Great. I think I am recalling the codes correctly. 1st The engine light was flashing and it starting running kind of rough when stopped - had 2 catalytic converters replaced. It ran good yet mechanic warned may need to change plugs if lights came back on. Ran code and it indicated bad gas cap. Replaced that. Not much difference. So then changed the plugs/.
Customer reply replied 26 days ago
the mass air flow- I cleaned and all got worse. I thought maybe it was faulty, did the check by pulling it it while running and it stops running. Assuming that trick showed the mass air flow to be working?

While it can work at times, it is not an accurate way to check the mass air flow sensor.

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Customer reply replied 26 days ago
What is the most accurate way? Is it possible I could have ruined it by cleaning it? Will a mass airflow from a 07 fit on an 11? I could just try it if so.

If the connector fits and they are the same part number, yes it will work

The most accurate way to check the mass air flow sensor is by using a voltmeter or a scanner reading the grams per second under live data.

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Customer reply replied 26 days ago
Do I need to clear the codes before I replace the flow sensor? Will the bad codes 'confuse' the computer even if the part is working?
Customer reply replied 26 days ago
How bout the oil pressure and fautly oxygen? how to confirm either of those?

You dont need to clear the codes, but it would be a good idea. No, it wont confuse the computer if you dont clear them.

You mean the fuel pressure? This is tested using a fuel pressure gauge at the fuel rail.

The oxygen sensor is best checked using a scanner watching the live data.

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Customer reply replied 26 days ago
Ok so if changing the MAF out does not do it for me, sounds like I need to get it into our mechanic- If I can get it to putter along will it cause more damage to drive it with low fuel or oxygen?

Driving the vehicle when it is running that bad is not a good idea. It wont cause further damage to the engine but it could damage the converter in the exhaust system which can be an expensive repair.

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Customer reply replied 26 days ago
when they changed out the converters there were 4. two pre and two 'Post'. The guy removed all four and replaced with 2 universal converters, saying this would work as well or better. Any way that could be issue
?

Universal oxygen sensors should not be used at all in my opinion.

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Customer reply replied 26 days ago
I was talking about catalytic converters. The O2 sensors were not replaced or removed.

Got it! I still would not recommend using universal converters at all. However, no, they will not cause this condition provided they are not plugged up.

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Customer reply replied 26 days ago
Saturday afternoon and only guy in town to work on it caused the acceptance of universal. I suppose there is possibility the new converters already fouled? maybe from plug change or???
Customer reply replied 26 days ago
I will change out the mAF tomorrow- hope that does the trick. Thanks for the ideas. Nothing more to do tonight.
Customer reply replied 26 days ago
Maybe 50 miles on the new converters - it completely when south with the plug change and the air sensor clean. It has to be one of those.

I agree. But keep in mind, everything should be checked before anything is replaced. In addition, this web site is for general information only and is not intended to be used for a full blown diagnoses on your vehicle.

This is a starting point. My goal is to give you the best experience possible! I hope I have earned a 5-star rating! Please remember to rate my service by selecting the 5 stars at the top of the screen before you leave today. If you need more assistance, please use the reply box and let me know.

Amedee
Amedee, Toyota Technician
Category: Toyota
Satisfied Customers: 27,623
Experience: ASE certified tech advanced level specialist. Wisconsin certified emissions state inspector
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