2003 Chevrolet Tahoe Fuel and/or ignition

Tiny
PATRICKHANES
  • MEMBER
  • 2003 CHEVROLET TAHOE
  • 232,294 MILES
Got a 03 Tahoe w/4.8L, running a little rough misses upon warm up not real bad just a slight miss. Pulled a spark plug on the left bank and it was carbon fouled, so I pulled the rest of the plugs. All the plugs on the left bank are carbon fouled (rich) but all the plugs are normal on the right bank. Fuel pressure regulator doesn't control the amount of fuel in relation to the left or right bank, it controls the overall fuel pressure, correct? Now this is a Vortec engine could the piping in the manifold be damaged on one side and not the other? What I mean by piping is the spider legs that com off the injector or are there 2 injectors one for each side? I think I may have just answered my own question.
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Wednesday, September 18th, 2013 AT 1:26 PM

5 Replies

Tiny
SATURNTECH9
  • EXPERT
That engine doesn't use a spider for the fuel injectors it has externally mounted on the fuel rails. What I would check is see if the vacuum nipple on the fuel pressure regulator is leaking fuel in the vacuum line that's hooked to it?Also if the pressure regulator is holding vacuum?
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Wednesday, September 18th, 2013 AT 1:54 PM
Tiny
PATRICKHANES
  • MEMBER
Your right it's MFI, I've checked the fuel pressure as well as the fuel pressure reg. I've noticed thar when it first starts up it runs good but once warmed up it runs rough with black smoke and water out the exhaust. No water in the oil though. That indicates a head gasket leak across a water and exhaust or cracked block? The thing that really is confusing to me is the fouled plugs on only the left bank. Also compression is good.
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Sunday, October 6th, 2013 AT 11:52 AM
Tiny
SATURNTECH9
  • EXPERT
Have you looked for fuel leaking into the vacuum line to the pressure regulator? Also if the fuel pressure regulator holds vacuum? Also you can rent a engine block tester to check for a bad head gasket.
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Sunday, October 6th, 2013 AT 1:08 PM
Tiny
PATRICKHANES
  • MEMBER
Checked the regulator but how could the regulator control the amount of fuel to only one side of the engine? Wouldn't it show up in all cylinders after running for any length of time? Going to do a block test tomorrow. Pulled a plug on the right bank and it looked white. The other thing that is confusing is there are no DTCs, should have an O2 sensor code or something.
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Monday, October 7th, 2013 AT 12:02 AM
Tiny
SATURNTECH9
  • EXPERT
If the vacuum source to the fuel pressure regulator pulls fuel to left back that would explain how it would only make the left bank plugs look richer. So sound like it could be just bad enough to just make a slight miss and make the plugs look. Darker. Let's check that out. Also wouldn't hurt to look for a vacuum leak. Is the miss only at idle?
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Monday, October 7th, 2013 AT 7:28 AM

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