2002 GMC 2500HD 6.0L

[Roberts2500HD]

So I bought a truck 02 GMC Sierra 2500HD and it had a bad manifold leak ( common on the 6.0L ) Sluggish on take off & blinking engine light at 2000rpm . Bad smell coming from exhaust when idling and driving 
 

Codes : P0174 , P0300 

 

Next Day 

 

NEW : 

Manifolds + Gaskets 

EGR Valve & Tubes+Bracket

Plug , Wires 

Intake Gasket / Cleaned Injectors 

Fuel Filter 

 

Wanted To check plugs after a day of doing that . Bank 1 plugs ( all 4 ) was burnt/corroded . They was black not oil black . Did research on it .. most people said  it’s your 02 sensor 

 

Then I changed the 02 on that side and it gained little more power .. but still missed fire above 2000rpm 

 

Called GM 8/3/2020 . Then say 8 out of 10 it’s then cam sensor 

 

Changed Cam Sensor 

 

and it sound smother and has even more power 

 

but still miss fires at 2000 rpm or more . 
 

please help with what it could be I’m exhausted with it 

 

should I do a CASE relearn? 

 

[davester]

would have suggested doing the knock sensors & wiring harness  when you did the intake manifolds, as you need to remove the intake manifold to do them...

 

all the exhaust manifold bolts are present?

[Roberts2500HD]

1 hour ago, davester said:

would have suggested doing the knock sensors & wiring harness  when you did the intake manifolds, as you need to remove the intake manifold to do them...

 

all the exhaust manifold bolts are present?

Well driver side I haven’t replaced due to it wasn’t leaking no where near as bad as the passenger. But 3 bolts hold the manifold on driver side . But it doesn’t really have a leak 

Edited August 4, 2020 by Roberts2500HD

[CamGTP]

You need to figure out what cylinders are misfiring. Then look into why those cylinders are.

 

Also check fuel pressure to make sure it's within spec at idle and under load.

[riverbanks]

Try that new 02 on pass. side,or old one if you still have it

[Roberts2500HD]

4 hours ago, CamGTP said:

You need to figure out what cylinders are misfiring. Then look into why those cylinders are.

 

Also check fuel pressure to make sure it's within spec at idle and under load.

I can’t seem to get the truck to throw a code for a cylinder.. it’s just saying random misfire P0300 .. and when pulling plugs only drive side looks bad . I’m going to do a pressure test soon when I find a place to do it . No local stores have one for sale . 

[Roberts2500HD]

2 hours ago, riverbanks said:

Try that new 02 on pass. side,or old one if you still have it

I put new sensor on drive side cause the only code for 02 sensor was Bank 1 Sensor 1 

[davester]

Missing exhaust manifold bolts can result in air being drawn into the exhaust, making the O2 sensor think the engine is running lean, and put more fuel in (which is bad for fuel economy and the cat's).

[riverbanks]

You mentioned p0174,bank 2 lean,what if that 02 is bad?a double whammy with bank 1 exhaust manifold leaking, should get improvement with new 02 on pass side,seeing how you have that side buttoned up, surprising that you don't have a rich code for bank 1

[Roberts2500HD]

2 hours ago, riverbanks said:

You mentioned p0174,bank 2 lean,what if that 02 is bad?a double whammy with bank 1 exhaust manifold leaking, should get improvement with new 02 on pass side,seeing how you have that side buttoned up, surprising that you don't have a rich code for bank 1

Just did Fuel compression test : with truck key turned over but not started about 53 psi , with the truck started it dropped down to about 48psi . With engine in park and rev’d to 2500 it went down to about 43 or 45 psi 

[CamGTP]

That's pretty low for fuel pressure. It should stay above 50psi and increase in pressure to around 58psi under heavy load.

[Roberts2500HD]

1 hour ago, CamGTP said:

That's pretty low for fuel pressure. It should stay above 50psi and increase in pressure to around 58psi under heavy load.

Under heavy load ( in park with it rev’d to 3k rpm it’s at 43psi . So I’m guessing with a new pump it should stop the random missfires above 2k rpm .. probably why it’s missing cause it isn’t getting enough gas 

[CamGTP]

Yeah it's a possible weak fuel pump or bad fuel pressure regulator on the fuel rail.

[davester]

or a plugged fuel filter (inside the frame rail under the driver's seat).

[Rebel Rouser]

And the verdict is???