P0172 after fuel injectors. - Toyota 4Runner Forum

Bucket81 · 12-12-2020, 05:43 PM

So I ended up with a bad fuel injector. I replaced them all with rebuilt injectors. Once I got everything back to gather, I ended up with a P0172 code and breaking up above 3500-4000 RPM. So I cleaned the MAF, I was going to replace the fuel filter, but it looks like my mechanic did that when he did a motor swap not too long ago. I also built a smoke machine to look for vacuum leaks but can't find any. The next thing would be O2 sensors, but I don't see it because this started right after I did the injectors at first start. I think it has to be something in the fuel system. I did not do the regulator....

gamefreakgc · 12-15-2020, 11:47 PM

P0172 is a very uncommon code, it means the engine is too rich. Did you buy your injectors off Ebay or something? If the only thing you did was change injectors and it's getting too much fuel, that points to only one issue, the fuel injectors.

19963.4lsr5 · 12-16-2020, 09:57 AM

Put the old ones back in and see if it goes away.

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Bucket81 · 12-16-2020, 11:40 AM

Quote:

Originally Posted by gamefreakgc

P0172 is a very uncommon code, it means the engine is too rich. Did you buy your injectors off Ebay or something? If the only thing you did was change injectors and it's getting too much fuel, that points to only one issue, the fuel injectors.

I got them off Amazon. They are rebuilt but had good reviews. I also pulled the valve covers and did the gaskets. I could pull it apart this weekend and put the old ones back in. Do you think I should replace the fuel regulator while I'm at it?

LittleCaesar · 12-16-2020, 01:29 PM

I would not replace the regulator as of yet. They rarely if ever go bad on a 5vz.

Probably a bad injector is causing the rich lean condition but before tearing back into it, check to make sure all vacuum hoses were correctly connected after you put everything together.

gamefreakgc · 12-16-2020, 01:51 PM

Quote:

Originally Posted by LittleCaesar

I would not replace the regulator as of yet. They rarely if ever go bad on a 5vz.

Probably a bad injector is causing the rich lean condition but before tearing back into it, check to make sure all vacuum hoses were correctly connected after you put everything together.

Would it at all be possible that a vacuum leak would cause a rich code? Normally it causes a P0171 lean code due to unmetered air entering the engine and not burning off. Unless maybe there's a leak causing a lack of air entering the engine?

gamefreakgc · 12-16-2020, 01:53 PM

Quote:

Originally Posted by Bucket81

I got them off Amazon. They are rebuilt but had good reviews. I also pulled the valve covers and did the gaskets. I could pull it apart this weekend and put the old ones back in. Do you think I should replace the fuel regulator while I'm at it?

If you know you had a bad injector in your old set, putting the old ones will bring back the original issue you were trying to fix though right?

Most injectors on the market now for our engines are reman'd DENSO injectors. Even from the most reputable sources people get a bad one now and then.

19963.4lsr5 · 12-16-2020, 02:36 PM

He may have gotten a higher flowing set of injectors.

The MAF and Bank 1 sensor 1 O2 sensor control the show.

Vacuum leaks and bad MAF in my experience always gave a lean code not the rich code.

What was bad about the injector that caused you to replace the whole set?

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LittleCaesar · 12-16-2020, 03:51 PM

Quote:

Originally Posted by gamefreakgc

Would it at all be possible that a vacuum leak would cause a rich code? Normally it causes a P0171 lean code due to unmetered air entering the engine and not burning off. Unless maybe there's a leak causing a lack of air entering the engine?

Once or twice I have seen the po172 code be tripped due to a vacuum leak. But my guess would be a bad injector out of the box.

Bucket81 · 12-18-2020, 01:17 PM

Quote:

Originally Posted by LittleCaesar

Once or twice I have seen the po172 code be tripped due to a vacuum leak. But my guess would be a bad injector out of the box.

I'm I put new valve cover gaskets on as well. I'm wondering if I over tightened them causing a vacuum leak. but probably not...

I'm not going to rule anything out at this point. I'm going to take it apart this weekend and put the old injectors back in and see if I have any missing vac lines. Really wish I would have marked the bad injector.....

Bucket81 · 12-19-2020, 05:04 PM

Quote:

Originally Posted by LittleCaesar

Once or twice I have seen the po172 code be tripped due to a vacuum leak. But my guess would be a bad injector out of the box.

Well I put the old injectors bad in. It runs worse breakers up at around 3k. I haven't been able to get it to through a code yet.

The odd thing is it doesn't seam to be miss firing. And I really expected that.

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LittleCaesar · 12-19-2020, 08:54 PM

Quote:

Originally Posted by Bucket81

Well I put the old injectors bad in. It runs worse breakers up at around 3k. I haven't been able to get it to through a code yet.

The odd thing is it doesn't seam to be miss firing. And I really expected that.

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My next two questions will be if you have access to a scan tool that gives live data? It may be a lazy or non working 02 sensor.

The po172 is still there correct?

Bucket81 · 12-19-2020, 10:46 PM

Quote:

Originally Posted by LittleCaesar

My next two questions will be if you have access to a scan tool that gives live data? It may be a lazy or non working 02 sensor.

The po172 is still there correct?

No code has come back. I can't get the CEL to come on agian. But I'm sure it will, I'll run it a bit tomorrow.

My scanner might give me live data. It has bluetooth and an app but never used it. What data do you want to see? I also might be able to get the Torque app to work, will that give you what I need?

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LittleCaesar · 12-20-2020, 08:50 AM

Quote:

Originally Posted by Bucket81

No code has come back. I can't get the CEL to come on agian. But I'm sure it will, I'll run it a bit tomorrow.

My scanner might give me live data. It has bluetooth and an app but never used it. What data do you want to see? I also might be able to get the Torque app to work, will that give you what I need?

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You should see if the scanner’s hardware can perform a 02 sensor test. Also look at long and short term fuel trim values when the engine is cold and when it warms up.

Bucket81 · 12-20-2020, 02:19 PM

Quote:

Originally Posted by LittleCaesar

You should see if the scanner’s hardware can perform a 02 sensor test. Also look at long and short term fuel trim values when the engine is cold and when it warms up.

Is this a bad down stream O2? And I can customize these if other data is needed.

O2 readings - YouTube

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