99 Tahoe 5.7L vibrates and looses power

[dzzyd1970]

Lester, on my tahoe can you advise where the Schroeder access valve will be located for pressure check? Also, where is a good place to pick up a good fuel pressure check tool? I will start with the pressure test first as you advised.... much thanks!

 

[lesterl]

Schrader port should be on a fuel line towards the back of the engine IIRC (it will look like a tire vavle)......

 

[Beeker702]

I've been having random misfire but not always throws a code. But this has been happening ever since I had to change it over multi-port injection and changed the intake gasket. But I think mine is more a distributor problem then anything and I'm changing that out in a few hours or tomorrow so I hope that fixes my problems.
But I did drive it thru the hills in tennisee with my truck fully loaded with the cruise on and didn't have a single problem

 

[thedriza]

i'd be willing to bet my life you have a bad injector. I have the same issues going on. the blinking cel is when a misfire is present if you don't get it fixed it will smoke your cat.

 

[dzzyd1970]

Thanks guys.. Im limiting the driving.. in fact im not driving at all as of today. This Weekend I will be doing the Fuel Pressure test and report my findings.....

 

[lesterl]

Fuel pressure leakdown test.....

 

[dzzyd1970]

Hi Lester, I did the pressure leakdown test. at idle the gauge was at a steady 54/55psi. increased idle a few times and it went above 60/65. 2) turned engine off and then timed how long gauge dropped pressure if at all.. It only dropped 2-3 PSI in 10-15 min... So I figured it was pretty good? Not sure if I did the test correct but the instuctions seemed basic. I didnt see any leaks around the schrader valve. But I did find something intresting.... Look at the pictures I attached. I decided to probe around checking the vacuum lines and came across what appears to be a long vacuum "pre-bent" line that has some metal tape on the end. the tape and the connection looked bad so I removed it at low in behold the dang hose was severely damaged somehow well before I ever owed the rig. The bottom pic you can see how big the "gash" is... Someone had taped it.... Looks like it was burned.. Anyway.. This Vacuum line appears to be going near the top or the side of the intake.. I really dont know what this is called but I would like to replace it. Let me know what you think and whether this could be causing my misfires?? Much thanks!

 

[lesterl]

Wow, big gash, Looks like an emissions line to me.....

 

[dzzyd1970]

ok, so do you think this might be causing some of my issues? Also, what about the leak down test I did? Are you satisfied with the results I gave you? After I posted the results I went back out today and did another test.. The PSI didnt drop already anything.. It might of just been my eyes.. So, Can I rule out bad injectors or bad fuel regulater? Whats my next step? I will be going to the dealer with this evap part in my hand hoping they have one.. not sure what the hell it is.. Thanks....

 

[lesterl]

My Bad, sorry havent slept a whole lot lately.

Leakdown test... sounds ok. Fuel pressure while Idle seems a tad low, is it hard to start? Could be fine since when you revved it the pressure came up good....

Definitley look into that line....... At least find out what it is for shure....... Did you get a big sucking sound with the crack exposed?

 

[dzzyd1970]

Idle has always been a little low.. running at 500 rpms.. not sure if thats spec or not. I havent bought a Chilton or haynes book. It starts rights up every time great. never had an issue.. Unfortunately I pulled the emmisions line before I couldn test it. Im buying a new one today. I will do that and see how she runs... thanks!

 

[lesterl]

600 - 650 in gear idling IIRC.... you shure your tach is right? Scantool could tell you what it actually is.

 

[dzzyd1970]

so, dealer discontinued the evap line. so I had to fix myself. super easy.. cost me 1.50 with some vacuum hose.. Put it back together.. Will take it for a test drive in a couple days.. been busy.. Im not sure it fixed anything. Do you have any other suggestions what I should do? Should I change the Rotor? cap? anything else? What about a Vacuum leak around the Intake manifold? How do I test for that? Cause I do remember smelling gas when I was on the freeway a couple weeks ago. Right as I was going up hill around 50mph and then it started vibrated and I started smelling gas..

 

[Beeker702]

That hose will make you smell gas. To test for leak around the manifold start it up and spray starter fluid and if the idle changes then you have a leak some where

 

[dzzyd1970]

Beeker, I will try that hopefully this weekend.. I guess I go around the outer edge of the manifold? Never done that before.. Not too familiar with that.. but will try to do some research before the weekend... thxs

 

[lesterl]

Go near the valvecover to manifold area, lines, throttle body, fuel injector pod seal area, etc.