P0171 on 01 Echo with 19.5+ LTFT from 2 MAFs - Page 2 - Toyota Nation Forum : Toyota Car and Truck Forums
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post #16 of 69 Old 03-01-2017, 09:25 PM Thread Starter
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In preparation for doing the fuel injector o rings, I removed the valve cover. It was brittle and there was a slight crack in one section between the 3rd and 4th ignition coils, the section of gasket where the center most bolts screw the valve cover into the head. I will replace the valve cover gasket when I do the injector rings which are still in the mail.

If I can't get this thing fixed by those methods them I'm taking her to a pro.
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post #17 of 69 Old 03-01-2017, 09:53 PM Thread Starter
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Here is where the valve cover gasket was cracked
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post #18 of 69 Old 03-03-2017, 03:23 PM Thread Starter
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I took the fuel injectors off and ran carb cleaner through them while under pressure and activated with current from a battery. I then backflushed them the same way. All four injectors held pressure when they were not activated by the current and at the end of cleaning had a uniform wide "V" spray pattern than seemed effective at atomizing the carb cleaner. The lower plastic rings were a bit cracked and not very flexible. They didn't seem to be too terribly clogged or displaying a poor spray pattern before cleaning. I will be installing a new valve cover gasket, throttle body gasket, and new fuel injector rings this evening and will report back.

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post #19 of 69 Old 03-04-2017, 01:24 AM Thread Starter
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I replaced the fuel injector o-rings, valve cover gasket, throttle body gasket, spark plugs, O2 sensor, MAF, and I still have a 19.5+ LTFT after resetting the computer. The good news is I'm not getting that astronomically high LTFT anymore (35%)

I have tried for the life of me to find a vacuum leak on this car. The gaskets I replaced were worn and hard and my STFT numbers are back to a normal level. I can't find any vacuum leaks in the hoses or pipes but some of them are fairly rigid from heat and time. The car is not setting a code but doesn't a LTFT that high mean it is running lean?

I don't mind using a bit more fuel if the engine is safe and it will pass emissions.

Should I replace the vacuum lines?
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post #20 of 69 Old 03-04-2017, 09:31 AM
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19.5 is just under the 20% threshold for being too high for most cars, I would not be happy seeing 20% on either of my cars. You can use carb cleaner or propane gas (unlit torch without the torch tip) to help find the leak, look for O2 sensor voltage to go high when the extra fuel is taken into the engine. Are there any exhaust leaks? An exhaust leak can set an O2 sensor to read lean and push the trims high too.
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post #21 of 69 Old 03-04-2017, 12:24 PM Thread Starter
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Well lads, here's an update. My LTFT is back to sky high 34% at idle BUT the STFT are in the normal range when driving at highway speeds. Can I safely assume that I have a vacuum leak based on these symptoms and everything I have done and replaced?

I have ordered replacement vacuum lines and clamps, OEM Toyota parts.

I have not checked for an exhaust leak, yet. I will pull the mid pipe and replace the gasket after I do the vacuum lines.

I also have not checked my fuel pressure. So far we have been through 2 OEM MAFs, one a known good unit from another car that runs well, and one aftermarket MAF. The MAF -!: FT numbers never change between them.

My STFT is high at idle and falls with RPMs

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post #22 of 69 Old 03-04-2017, 12:30 PM
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It sure sounds like a vacuum leak since trims are normal at higher engine speeds, more air enters the engine but the vacuum leak stays the same size so it's 'masked', or diluted if you will.

http://www.autoserviceprofessional.c...for-you?Page=1
Good article on this subject. 3 pages long but maybe you'll find some ideas.
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post #23 of 69 Old 03-04-2017, 06:03 PM Thread Starter
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Introducing propane to the intake duct causes STFT to drop down and for bank 1 sensor 1 O2 sensor to spike in voltage, showing it is richening up.
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post #24 of 69 Old 03-04-2017, 06:10 PM
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So there is an actual lean condition going on and the O2 is responding correctly, good. Now point the propane anywhere there could be air entering the engine that's not gone through the MAF.
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post #25 of 69 Old 03-04-2017, 07:04 PM Thread Starter
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I have not had any success with the propane in making the fuel trim change when pointing it at the intake components to identify a leak. Only when I introduce propane to the intake tube does the fuel trim change. However, I did just bathed the throttle body assembly in carb cleaner and I got a little blip of a reduction in short term fuel trim *but* the intake pipe joint is directly under that point and it is possible it got sucked into the intake pipe before the MAF and I might have tricked myself into thinking there is a vacuum leak there. I will continue to investigate.

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post #26 of 69 Old 03-04-2017, 07:10 PM
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Making some progress hopefully, if need be use some plastic pipe to extend the air inlet farther away from where you're spraying to prevent false positives. Look at O2 sensor voltage, it should read faster than stft.
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post #27 of 69 Old 03-05-2017, 12:27 AM Thread Starter
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I took apart the throttle body assembly and cleaned it out with. There was lots of crud in the IAC. This resulted in no change to my LTFT.

I then took the mid pipe off and re-aligned it with the header. My LTFT is now down in the 15.6-18.8 range at idle instead of the astronomical 34 I was getting earlier today.

I'm getting really frustrated with this car.
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post #28 of 69 Old 03-05-2017, 08:35 AM
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So it sounds like there IS some kind of exhaust leak? Moving exhaust around shouldn't have affected the trims if it was properly sealed before and is properly sealed now. For fun put some seafoam into the engine and let it set a couple hours, then start it and watch the exhaust system for leaks near the engine.
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post #29 of 69 Old 03-05-2017, 12:56 PM Thread Starter
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The car squeaked by in passing an emissions test but my LTFT is still 18+ so I will investigate further. For now, the CEL is off and I have no codes and the onboard emissions monitors all passed.
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post #30 of 69 Old 03-05-2017, 05:33 PM Thread Starter
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The exhaust header to mid pipe collection flange is leaking as evidenced by soapy water sudsing up with a shop vac introducing positive pressure from the tailpipe. I don't know if the exhaust manifold gasket is leaking itself but I'm going to take it off anyway. I don't want to miss anything.
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