Help Any Ideas???

Its a 1999 tahoe. today it was warm out and truck started actin up after 1 1/2 hours of driving.. at first it hesitated on accelartion but if you gave it gas graudaly it would get up to speed fine. if you kicked it down it would hesitate and rpms wouldnt go past 3000 rpms.. from a dead stop same thing about 2500 rpms and would hesitate.. in park it acts normal.were do i start? no ses light and it has 130k on it tranny fluid looks clean!! PLEASE HELP!!


ok just went out and pressed on accelerator in park and it spits and spudders threw intake when steped on rpms only go to 2300 or so.. it idels fine THANKS PLEASE HELP

Got fuel pressure?
What engine?
Hard to start cold.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak.
Post back fuel pressure readings.

it is a 350
engine OFF key ON 37-38 psi
in park engine on 51 psi accelarate in park 60 psi
accelarate while driving 60 psi
pinch what?
now that the truck cooled down its running normal again???

also for like the past month it seemed the truck would turn over a little bit longer than normal b4 it would start

Pinch off the rubber part of the return line only.
Between engine and frame you will find the rubber part of fuel lines.

Your fuel pressure is low.
If pinching off or blocking off the return line does not raise pressure to 75-85 lbs of pressure.
Check the direct pressure where the fuel pump line goes into the back of fuel filter.
If you do not have full pressure of around 75 lbs there you fuel pump is bad.

thanks for the help!

i left preassure tester on it over night it went down to 10 psi
key on engine off went up to 60 psi (cold motor)
ideled at 52 psi

im a try to pinch line and ill post back in a little bit

Fuel pressure is low.
A cold start requires 64-65 lbs of fuel pressure to squirt the injectors good.
Do not leave home without good pressure.
Check the full fuel pump pressure .
If it is not 75-85 lbs and the fuel pump is getting good 12-13 volts and good ground.
It is time for a new fuel pump.
If it has good full direct pressure have a look at your fuel pressure regulator.

ok i pinched off return line first time i got 74 psi, second time i got 70 psi and third time it was 71 psi..

the snap on fuel preassure tester i borrowed dosnt have a fitting to test line going in to fuel filter..

ok i pinched off return line first time i got 74 psi, second time i got 70 psi and third time it was 71 psi..

the snap on fuel preassure tester i borrowed dosnt have a fitting to test line going in to fuel filter..

Your fuel pump is putting out good pressure then.
Better check fuel pressure regulator for holding or regulating the right pressure or leaking off.
MT

how do i do that?

it is a 350
engine OFF key ON 37-38 psi
in park engine on 51 psi accelarate in park 60 psi
accelarate while driving 60 psi
pinch what?
now that the truck cooled down its running normal again???

also for like the past month it seemed the truck would turn over a little bit longer than normal b4 it would start

On this test it may also be a weak fuel pump.
I would jumper the fuel pump and let it run for a hr or so and recheck pressure with fuel line pinched off.
It could have a bad fuel regulator and a bad fuel pump that loses pressure after it runs for a hr and gets hot and weak.
Good luck and let us know how it goes.
MT

how do you jump fuel pump? cant i just let it run normaly?

im a start it and run engine for a hour.. ill post back as soon as i can

ok i let it idel for 40 min and drove it for 30 more min..
and the readings stay the same 50 psi driving 60psi when i step on it

it is running normal it is also 25 degrees cooler outside todat than yesterday..

50-60 is not normal.
Go back up to post 2 and read it.

so should i change pump or regulator? were is regulatror located?
I APPRECIATE THE FEED BACK!!!! THANKS MT

That is for you to test and figure out.
All I can tell you is your fuel pressure is low.
Proper testing.
Go threw the test.
They will tell you what is what.
Fuel pressure regulator controls the pressure but you need pressure to control.
Is the fuel pump putting out full pressure all the time hot or cold?
Have you also checked for good 12 volt power and ground to fuel pump?

From what you have told us so far it may be both regulator and fuel pump.
But makes always make sure .
Like Have you also checked for good 12 volt power and ground to fuel pump?


If fuel lines runs into the top of the engine you will find the fuel pressure regulator in there.

Run a search on how to.

do i have to take down fuel tank to check power supply?

Can you see or get to the fuel pump wiring plug in going into the fuel pump?

im a check its raining out and no garage so it may be later today...
i was told 900 for shop to do fuel pump..is fuel pump swap simular to a swap on 97 astro van? THANKS man im getting frustrated with this truck!

i just found a shop to change it for $501.00

Good luck on it.
But I would have the fuel pressure retested after the fuel pump is replaced.
As said before your fuel pressure regulator may be bad to.
Let us know how it goes.
MT

when i crimped off return line i used plyers, today i put a needle nose vice grips on it and pressure went up to 80 psi...

i also turned key on engine off and put a needle vice grips on both rubber lines, the in and retun and then turned key off, to see if pressure held and it started dropping after about two min ..
so would that mean it is regulator leaking?

i also talked to previous owner whom was a mechanic and he said he replaced fuel pump 19 months ago with a oem from his dealer ship. if that matters

If your pump is pumping 80 lbs of fuel pressure and and the fuel pressure at the test port is low with engine running check or replace the fuel pressure regulator.

The fuel pressure regulator regulates fuel pressure as long it has pressure to regulate.
80 lbs of pump pressure and low running fuel pressure spells bad fuel pressure regulator to me.
Good luck
MT

thanks.. do you think went i pinched off both rubber hoses with key on. and it leaked down said any thing or could fuel leaked threw injector?


what all is needed to change the fuel pressure regulator? gaskets etc..

anyone?

Fire up the old search engine for how to on fuel pressure regulator.
Or try one of these.
http://www.alldata.com/products/diy/index.html
Good luck
MT

had fpr changed today it runs the same so far except the ses light cam on at first 40 miles so im a scan it and see why, it wasnt on before it was changed.... ill post pressure as well

had fpr changed today it runs the same so far except the ses light cam on at first 40 miles so im a scan it and see why, it wasnt on before it was changed.... ill post pressure as well

Did it help fuel pressure?

fuel pressure is at 62 key on engine off and at 53 engine on. and when off it holds fuel pressure..

now it is throwing up stream o2 sensor codes right and left.. i changed right one like 2 weeks ago so i dont know if its a stored code or what or if comp has to re calibrate its self

What code no.?
Your fuel pressure is still low.
Low fuel will cause 02 sensor codes.
You need to fix the low fuel pressure first thing.
MT

Dude I hope you find out what is causing this. I have the exact same situation going on with my 97 Tahoe. I am hesitant to start changing things just because of the issues your running into. I have a P0300 code right now which doesn't tell you anything other then a mutiple miss-fires. Yeah, I know that but I have a stupid computer tell me that. I am going to put the pressure tester on it and change the fuel filter and see what's happening. I will keep you posted on what I find with my truck.... Keep at it.

i belive codes are p0171 and p0174.. going to bring it back to dealer again.they tried to tell me that psi is in spec. :nono:

Take this with you and show them.
Hard to start cold.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak.
Post back fuel pressure readings.


Also tips on going to the dealer.
Ask for a good factory trained tech not the grease monkey or wash boy.

Tip on going to the dealer
Ask that only a factory certified gasoline engine performance specialist work on your car.
Not all dealerships are concerned with how repairs are dispatched, and not all dealership techs bother to take advantage of the training offered by factory (the vast majority of which is paid training). If the dealer is uncooperative, ask for your money back and call around for a dealer that will accommodate you.

Good Luck MT

Dude I hope you find out what is causing this. I have the exact same situation going on with my 97 Tahoe. I am hesitant to start changing things just because of the issues your running into. I have a P0300 code right now which doesn't tell you anything other then a mutiple miss-fires. Yeah, I know that but I have a stupid computer tell me that. I am going to put the pressure tester on it and change the fuel filter and see what's happening. I will keep you posted on what I find with my truck.... Keep at it.

01TahoeJunk
If you have a miss fire code you need to work on that end first.
If you need help on it start a new thread/post and someone will help you.
MT

MT-2500 i wish i would of read your post before i went to dealer... they read and cleared codes they returned again now.. i talked to tech who installed fpr and he said it was leaking..and trying to tell me that 52 psi is in spec and is realy trying to convince me...also he said there was a diafram up side down it was were the aluminum fuel lines go in to intake, from when lower intake was changed i guess.. i couldnt see..he said he corrected it... im just frustrated that the ses light is now on.. and they want another 168.00 to diagnos it..and told me dont worry about light unless its flashing..