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2002 Chevy Tahoe. It runs and idles fine until hard

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acceleration, or going up a...
2002 Chevy Tahoe. It runs and idles fine until hard acceleration, or going up a hill. Removed the cats, and o2 sensors because the guy I got from told me they were clogged. That didn't make a difference. It is still stalling from stepping on it hard. There was a code for flex fuel sensor, but I cleared it. I've driven for around 50 miles since clearing the code. The check engine light is back on, but that p0179 code is not showing. There are codes for o2 sensors and cats.
Submitted: 7 months ago.Category: Chevy
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Answered in 34 minutes by:
11/12/2017
Chevy Mechanic: Mike, Auto Mechanic replied 7 months ago
Mike
Mike, Auto Mechanic
Category: Chevy
Satisfied Customers: 490
Experience: Lead Tech at Solis Auto Repair
Verified

Hello, my name is***** will be helping you out! I have over thirteen year of experience in the automotive industry for numerous different makes & models. I enjoy doing what I do, it is my life.

The first step we can attempt if you like is diagnose the code you just showed me, it could possibly be the issue you are experiencing as well.

It is a fuel related sensor, so it could be causing a stall or buck type of issue I just can not guarantee you that is the problem, but its highly possible it will be your problem.

If the problem continues after our diagnoses, then we will then have to have a fuel pressure

Is this thing a flex fuel? Can I have VIN if possible to make sure I am looking at my diagrams and trouble codes procedures accurately?

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Customer reply replied 7 months ago
The vin number has the Z on the 8th place. I can see the flex sensor. I did a fuel pressure test. I plugged the gauge, and turned the key to on then off. While on it was going to a line below 50 and immediately dropping to 20 psi once key was off. I'm just not sure if it could be the fuel pump.
Chevy Mechanic: Mike, Auto Mechanic replied 7 months ago

Ok so you did a fuel pressure test? Showed 50, then dropped to 20 correct? Yes this is a flex fuel then.

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Chevy Mechanic: Mike, Auto Mechanic replied 7 months ago

Can you also give me the short fuel trim along with the long term fuel trim data readings from your datastream please. Let me know if you do not understand this question :).

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Customer reply replied 7 months ago
That is correct I did the fuel pressure test using a gauge from AutoZone and got 50 with key on and 20 immediately after turning the key off. I don't have such fuel data.
Chevy Mechanic: Mike, Auto Mechanic replied 7 months ago

ok so you do not have a scan tool on freeze frame data it shows no fuel trim?

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Chevy Mechanic: Mike, Auto Mechanic replied 7 months ago

What about start up after shutting off, is everything seeming normal? Or does it have a longer crank or something abnormal it is doing other then what you have already stated?

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Customer reply replied 7 months ago
I don't have a scan tool. I got the cat and o2 sensors from AutoZone. A friend of mine let me use the scanning tool but he took it back. Also while running I unplugged the flex fuel sensor, and it had no effect at all. I also tested the wire voltage and the wiring showed the right voltage of 12 volts.
Chevy Mechanic: Mike, Auto Mechanic replied 7 months ago

You did not complete the full test procedure just by checking 12 volts, so you have a voltmeter that way we can run other test I will provide you?

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Customer reply replied 7 months ago
It turns right on just fine. No hesitation whatsoever. As soon as you press hard on the gas , it stalls while sputtering. Then I have to wait for a few to start because it does not start right away once it stalls.
Chevy Mechanic: Mike, Auto Mechanic replied 7 months ago

You are also going to have to get your buddy's scan tool again so we can run a 3rd test as well. Scan tool first is always the best way to start this procedure to test the fuel sensor

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Customer reply replied 7 months ago
I've been trying to get the scanning tool from him but he has not been available for a few days. I know I did not complete the full diagnostics by getting 12 volts. Yes I have a voltage meter.
Customer reply replied 7 months ago
I've read a lot about this issue and other people with the same truck have said that with the bad sensor it only affected gas mpg. They said nothing about stalling at hard acceleration or going up hills. That is why I was leaning towards fuel pump but not sure, hence why I'm seeking advice.
Chevy Mechanic: Mike, Auto Mechanic replied 7 months ago

No problem, we will run other tests without it in the mean time, just understand it makes this job of checking a lot more time consuming than it should be.

If we had the scan tool all we needed to do is see data stream of how many Hz or frequency it was showing, it should indicate 50 Hz if you are running on pure gas and 150 Hz if you are running on pure ethanol. If the readings are off in the data stream, the sensor is bad.

First, I want you to test your ground, if ground is good then check continuity on the computer wire (see attachment) if that is good, then our wires are all good.

Second, if all wires are good, then we can remove the sensor and see if there is any restriction visually when we put key on, (you will know it is restricted when you see it)

THIRD, would be looking at the data stream and will immediately tell you bad or good.

It is a fuel related sensor, it will affect the fuel system if the sensor is glitching out, it will make the ECM freak out and not accurately do its job either in the fuel air ratio bc of the Hz it reads, so yes it will affect your fuel system :).

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Chevy Mechanic: Mike, Auto Mechanic replied 7 months ago

And based on the fuel readings, we can not say fuel pump is good or bad yet, fuel pump is still a possibility.

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Chevy Mechanic: Mike, Auto Mechanic replied 7 months ago

Let me know if any of it makes no sense, maybe we can talk on the phone or describe it better here :).

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Customer reply replied 7 months ago
I will try using the scanning tool which will be easier for me.
Chevy Mechanic: Mike, Auto Mechanic replied 7 months ago

Sounds good, but you still have to check for that fuel restriction on the sensor AFTER seeing the Hz off in the data stream. If there is fuel restriction or slow fuel running through the line, then the reading will be wrong always. Likely though, the sensor is bad.

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Chevy Mechanic: Mike, Auto Mechanic replied 7 months ago

If you have time, please leave me a rating, it gives me credit for the answer and would mean so much to me :). It was my pleasure helping and we can still continue after rating, I will still be here for you.

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