TahoeMatt

Starting getting this rough idle and a cylinder 6 misfire code....

I switched out the plug wires, cap, rotor and plugs....

Still have the same problem...

New Cylinder 6 plug was pulled and it's def not firing right... there was corrosion on the plug.....

Checked compression and it was fine / 115.

Not sure what to do next.... ?

Any input is greatly appreciated.

Thank you.

tech2

115 seems a little low...check another cylinder to compare. Its best to compare compression numbers relative to other cylinders.

A vacuum guage reading would be a test i'd do to check the valve train.

MDTAHOE

115 sounds a little low but still could be ok.Check another cylinder to make sure the problem is not you gauge and complete the equation below. However if the problem is with the fuel injector the cylinder could be washed causing low numbers. . Add 3-4 caps full of motor oil into the cylinder through the spark plug hole, disconnect the fuel injection plug in the center of the intake bump the engine around a few times (at least 2 revolutions) by taping the key then crank it like you were staring it. Now recheck the compression. If the number goes up and or is close to the same as the other cylinders you most likely have a fuel injector problem which is very common (the system was updated). If the number is low then you may have an internal engine problem.



The minimum compression in any one cylinder should not be less than 70 percent of the highest cylinder. No cylinder should read less than 690 kPa (100 psi). For example, if the highest pressure in any one cylinder is 1035 kPa (150 psi), the lowest allowable pressure for any other cylinder would be 725 kPa (105 psi). (1035 x 70% = 725) (150 x 70% = 105).

TahoeMatt

my tahoe is carburated not fuel injected....

was hoping it might be something electrical...ecm maybe...
what do you think boss ?

MDTAHOE

Your post says it is a 1999 which does not have a carb. What year is it? It has to be fuel injected if it setting a code for a cylinder misfire. OBD II vehicles are the only one capable of setting a misfire code. All OBD II vehicles are fuel injected.

TahoeMatt

here's a link to what my engine looks like...
1999 Chevrolet Tahoe 4x4 Used Parts - Stock #9F6051

i know it's a 99 and as far as i can tell that looks like a carb when i pop the breather tube that runs to the filter off..

if i'm wrong i'd like to know it that's for sure.

thanx man.

( i thought the obd2 was initiated in 1996...or 98 or something.)

please inform when you get some time please.

73shark

Not sure but it looks like a throttle body injection setup to me. OBD II started in '96.

MDTAHOE

It is 100% fuel injected. The Fuel injectors are inside the upper intake. Unfortunately I think you need to take it to a shop for repair as you need to have some knowledge of what is going on under the hood. Most GM cars after 1988 were fuel injected.By 1990 almost all cars were fuel injected. Some 1994 vehicles were OBD II by 1996 all were OBD II. I will help you the best I can but if you want it fixed the least expensive way in the soonest possible time you really should consider a professional.

TahoeMatt

Thanks for the input.... thinking it's gonna be a valve issue but sure hope not. Don't want to have to pull that sucker apart and take it the shop.

Any other input is greatly appreciated.

TahoeMatt

Thanx for the heads up. You think that no#6 injector could be fried ?