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AMEDEE
AMEDEE, CHEVY TECHNICIAN
Category: Chevy
Satisfied Customers: 24412
Experience:  ASE certified tech ADVANCED LEVEL SPECIALIST. Wisconsin certified emissions state inspector
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Chevrolet Tahoe 4x4: I start my vehicle in the morning. If

Customer Question

I start my vehicle in the morning. If I don't give it gas. It idles down and dies out. If I give it a little gas for a few seconds it idles. But it's really rough. If I just get in and start it and put it into drive and take off it drives like Crap. It's hard to explain. You give it gas, it bogs down and dies out. I have to let it warm up for like 15 minutes then it drives really good. You can definitely smell that it is burning rich. Fuel mileage is terrible. I get about 150 miles to the 25 gallon tank. We just put a new engine in. Didn't do it before we put it in. Almost all the sensors are new. New fuel injectors. New egr valve. New fuel pressure regulator.
Submitted: 6 months ago.
Category: Chevy
Expert:  AMEDEE replied 6 months ago.

Hello and welcome! My name siCustomerand I can assist you with your question. Can I start by getting your VIN? Thank you!

Customer: replied 6 months ago.
1GNEK13K4SJ369919
Expert:  AMEDEE replied 6 months ago.

Hello and good morning! Sorry for the delay! Thank you for the VIN. Before we dive into this, we you checked the fuel pressure when this happens?

Customer: replied 6 months ago.
I have not. What is the best way to do that?
Expert:  AMEDEE replied 6 months ago.
Hook up a fuel pressure tester to the fuel rail and take a reading when this problem occurs.
Expert:  AMEDEE replied 6 months ago.
The reason I say this is because you may simply have a bad fuel pump. This is very common on these vehicles. If memory serves me correct you have a low pressure but high volume fuel pump. The fuel pressure may actually even check out good, however it may not have enough volume to supply the engine with one cold. One thing you can do is pinch off the fuel return line and check the fuel pressure to ensure the deadhead fuel pressure is within spec. This is the best way to check the fuel pump. I can get you the specs a little later today when I get home from my computer.
Customer: replied 6 months ago.
This is a 95. There is no fuel rail...
Expert:  AMEDEE replied 6 months ago.
Hook the fuel gauge between the fuel pressure line and the throttle body.
Customer: replied 6 months ago.
What should the pressure be?
Customer: replied 6 months ago.
Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Expert:  AMEDEE replied 6 months ago.

The fuel pressure should be between 9 and 13 psi. Keep in mind, that I have even seen it where the pressure is within specs but the volume is low that is why you need to pinch off the fuel return line to check the deadhead fuel pressure. It should quickly increase past 15 PSI and it should stay 15 PSI under a load. If fuel pressure will not increase, check the fuel filter and check power/ground to the fuel pump and replace the fuel pump as needed.

Customer: replied 6 months ago.
I took it to a local mechanic today. PSI was at 15 and the flow was steady. But as soon as you turn the key off pressure goes to 0. Shouldn't it stay pressured for 30 minutes or so?
Expert:  AMEDEE replied 6 months ago.

No, this system is not supposed to hold pressure with the key off.

Customer: replied 6 months ago.
Okay. What next?
Expert:  AMEDEE replied 6 months ago.

See if the engine runs better on alternative fuel when this happens.

Customer: replied 6 months ago.
Like what?
Expert:  AMEDEE replied 6 months ago.

starting fluid

Customer: replied 6 months ago.
Okay. Will try that in the morning.
Expert:  AMEDEE replied 6 months ago.

Didn't you pay your mechanic to diagnose it?

Expert:  AMEDEE replied 6 months ago.

If so, what was his diagnoses?

Customer: replied 6 months ago.
No. I just asked him to test my pressure.
Expert:  AMEDEE replied 6 months ago.

Did he charge you to do this?

Customer: replied 6 months ago.
Nope
Expert:  AMEDEE replied 6 months ago.

Thats very nice of him. Did you watch him do this test?

Customer: replied 6 months ago.
No. Dropped off and went to work.
Expert:  AMEDEE replied 6 months ago.

Got it

Customer: replied 6 months ago.
Do you have any possible ideas?
Expert:  AMEDEE replied 6 months ago.

YES, I have lots. BUt you need to run the test so we can narrow it down.

Customer: replied 6 months ago.
How do i spray it? Continously or just spurts?
Expert:  AMEDEE replied 6 months ago.

Spray a small amount continuously

Customer: replied 6 months ago.
It helped pick engine idle up to about 700. Got in put in the drive and drove about 10 yards. But it still bogs down really bad when you put throttle to it.
Customer: replied 6 months ago.
It didn't do this before we put the new engine in.
Customer: replied 6 months ago.
Before we put the new motor in, everytime it would rain or be really humid out, it ran like crap. Misfiring, stuttering, pushing out black smoke and dumping way to much fuel. Haven't had that problem since the new one tho.
Customer: replied 6 months ago.
Still with me?
Expert:  AMEDEE replied 6 months ago.

Hello! So did adding starting fluid to the intake help?

Customer: replied 6 months ago.
I sent you messages this morning around 7.
Expert:  AMEDEE replied 6 months ago.

I got that reply. I am looking for a yes or no answer.

Customer: replied 6 months ago.
It picked up idle a little. Still ran like crap. Let idle for 10 minutes ran fine like everyday.
Expert:  AMEDEE replied 6 months ago.

I still think its the fuel pump.

Customer: replied 6 months ago.
Think? What other things can I do to see? I am not going to buy a $250 fuel pump if I am not 100% sure that is the problem.
Expert:  AMEDEE replied 6 months ago.

I agree. I would not either if I were you. Have you mechanic take a video of this fuel pressure gauge showing the correct specs WHEN this happens and send it to me. I will be waiting.

Customer: replied 6 months ago.
Here is the video you requested.
Customer: replied 6 months ago.
It would take let me post the video. Do you have an email I can it to you with?
Customer: replied 6 months ago.
Wouldn't let me post
Customer: replied 6 months ago.
Took a minute to build pressure to 12 psi.
Expert:  AMEDEE replied 6 months ago.

Hello! I was not able to open the file. Are you able to post it to youtube and send me the link?

Customer: replied 6 months ago.
https://youtu.be/miIauVoAMtE
Expert:  AMEDEE replied 6 months ago.

Thank you for the Video. Looks to me like you have a bad/weak fuel pump. :)

Customer: replied 6 months ago.
Are there any other tests I can do to confirm this? Why would it run just fine the rest of the day? It sat for 2 days sttaught. Through a pressure gauge on it about 6 of clock last night. Started just fine and psi was right at 12 psi with no problems. Then this morning is when the video is from. As soon as it reached 12 psi. I let it sit an hour and tried it again and it was right at 12 psi no problme.
Expert:  AMEDEE replied 6 months ago.

This is what the fuel pump does when it starts to go bad.

Customer: replied 6 months ago.
Are there any other tests I can do to confirm this?
Expert:  AMEDEE replied 6 months ago.

YES, you can clamp off the return line and watch the dead head pressure like I mentioned earlier. However, you would have to perform this test WHEN the problem occurs (when the engine is first started when cold) or you can use a lab scope to watch the pattern

Customer: replied 6 months ago.
Where do you clamp it off at?
Expert:  AMEDEE replied 6 months ago.

There should be a rubber part of the return line from the throttle body that you can clamp it off.

Customer: replied 6 months ago.
Nope. Two metal fuel lines.
Expert:  AMEDEE replied 6 months ago.

Ok, then you wont be able to run this test.

Customer: replied 6 months ago.
What then?
Expert:  AMEDEE replied 6 months ago.

Replace the fuel pump

Customer: replied 6 months ago.
I am replacing the pump tomorrow afternoon.
Expert:  AMEDEE replied 6 months ago.

Sounds good!

Customer: replied 6 months ago.
I hooked a live data stream software to my OBD today. I was wondering if you could send me a diagram of what is normal for everything.
Expert:  AMEDEE replied 6 months ago.

I dont access to that information at the moment

Customer: replied 6 months ago.
Got the fuel pump put in yesterday. Started it this morning. Seems like it runs a little bit better. But it's still not running right. It still bogs down randomly when accelerating. Doesn't matter if it's slow or a quick acceleration. It still bogs down for like 2 seconds and picks right back up. Then it will big down again.
Expert:  AMEDEE replied 6 months ago.

Ok, excellent! Thanks for the update. Please run the same tests/steps we have been talking about and take another video for me so I can see what is going on. Thank you

Customer: replied 6 months ago.
How many 02 sensors are in a 95 Tahoe? Just one on the cat? Could the tps or iac have any responsibility for these problem? How could I test to see? When I was driving it yesterday day. I was in reverse and put it into drive and tried to take off quickly. It stalled the engine and backfired. And them earlier last week I went through a small mud hole, slowEd down right before I went through then went almost full throttle and it stalled out and back fired. And it seems like it reacts slow to respond when accelerating from a stop sign.
Expert:  AMEDEE replied 6 months ago.

Hello! The TPS can do this but not the IAC.

It should only have one oxygen sensor before the cat.

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