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-   -   need help fixing a truck (http://www.njfboa.org/forums/showthread.php?t=40336)

chrisfrom nj 01-15-2009 02:53 PM

need help fixing a truck
 
my uncle just bought a 98 chevy 1500 4x4 the motor runs like crap the number 5 and 7 cylinders are dead we did a compression check all 8 cyl are good now when you start the truck it smells like gass and pops alot i just ran 2 bottles of seafoam in it to try to clear it it still pops and dies out and still no power what do you think the prob is

BigRocsFirebird 01-15-2009 03:00 PM

5 and 7 dead as in not fireing? no spark?

ZeroCool8891 01-15-2009 03:34 PM

hes there is spark and fuel, the timeing and fireing order are rite, and the cap, rotor, plugs and wires are all new too.

chrisfrom nj 01-15-2009 03:39 PM

everything is new the timeing is right

Jersyboyy 01-15-2009 03:59 PM

Sound oddly familiar to my motor that had two blown pistons...compression checked out but it ran piss poor. Pop them heads off one more gan' maybe check the cam too(wiped lobes)?

chrisfrom nj 01-15-2009 04:23 PM

i had the valve covers off the everything works

BigRocsFirebird 01-15-2009 04:33 PM

is it getting fuel

crazyblazer87 01-15-2009 04:35 PM

how did you check for fuel? maybe you can move injectors around and see if the misfire moves with injectors

SRGN 01-15-2009 07:56 PM

98, should be just a regular vortec. A few common failures on that. The injector assembly(poppets go bad or regulator leaks). Intake gasket failure causing a vacuum leak into the lifter valley. Pull off the oil cap while it's running and see if it changes RPM, if it does there is most likely a lower intake gasket leak. The simplest one is a bad distributor cap/rotor, they tend to crossfire badly on a vortec when they fail.

chrisfrom nj 01-15-2009 09:55 PM

Quote:

Originally Posted by BigRocsFirebird (Post 534476)
is it getting fuel

its getting fuel

Quote:

Originally Posted by crazyblazer87 (Post 534479)
how did you check for fuel? maybe you can move injectors around and see if the misfire moves with injectors

i checked for fuel on the fuel rail with a fuel pressure gauge

Quote:

Originally Posted by SRGN (Post 534616)
98, should be just a regular vortec. A few common failures on that. The injector assembly(poppets go bad or regulator leaks). Intake gasket failure causing a vacuum leak into the lifter valley. Pull off the oil cap while it's running and see if it changes RPM, if it does there is most likely a lower intake gasket leak. The simplest one is a bad distributor cap/rotor, they tend to crossfire badly on a vortec when they fail.

im going to check that tomorrow thanks alot

HardcoreZ28 01-15-2009 10:38 PM

fuel pressure gauge won't tell you if a poppet has gone bad. What do the plugs look like from those two cylinders? That may be your best indication. Also as stated an internal vac leak will cause it to misfire or run bad.

Tru2Chevy 01-17-2009 06:31 PM

Yea, just because it's got fuel pressure at the rail doesn't mean that the two cylinders you mentioned are getting fuel.

- Justin

91chevywt 01-17-2009 10:53 PM

what do the plugs look like in the dead cylinders? if theyre wet after running, spark problem. If theyre dry after running, fuel problem.

NJ Torque 01-18-2009 01:08 AM

Quote:

Originally Posted by SRGN (Post 534616)
98, should be just a regular vortec. A few common failures on that. The injector assembly(poppets go bad or regulator leaks). Intake gasket failure causing a vacuum leak into the lifter valley. Pull off the oil cap while it's running and see if it changes RPM, if it does there is most likely a lower intake gasket leak. The simplest one is a bad distributor cap/rotor, they tend to crossfire badly on a vortec when they fail.


Yup. Happened on both out 98 and 96... Got a whole new "spider" injector assy.


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