hi,
I have a Yukon 6.0 V8 2000 SLT, it has 158000 miles on the clock.
I wont start when cold without the throttle, it will start without the throttle when warm.
I get a random p0300 code now and again, and on tickover it just doesnt run sweet. It is also running on LPG with a muti point LPG injector system.
When driven it sounds sweet and pulls hard but on tickover it runs a little lumpy. when i disconnect all the coil packs one at a time the engine changes note apart from cylinder 4. I have swapped the plugs, leads, and coil pack from cylinder 4 with other cylinders and the fault still stays on cylinder 4. The plug and piston is wet in a morning when i used my camera down inside the cylinder all the other pistons are dry. The plug sparks ok on a tester on cylinder 4 so leads coil and plug is ok.
The fault is the same whether on LPG or Petrol so that rules out the injectors.
I get some blueish smoke on startup when cold in a morning and after about 2 minutes of driving it disappears.
I suspected that the valve on cylinder 4 might have got stuck or maybe the spring is week.
I did a compression test and they all came back from (dry) 130 to 145 psi when warm, (130 dry) 150 psi (wet) on cylinder 4 with a tablespoon of oil on a wet test on cylinder 4, the oil is very clean on the dipstick there is no breathing through the dipstick or oil filler and the coolant is red and normal.
Is there anything else I can try before i either take the head off and replace the valves or even worse find that the rings on cylinder 4 are shot.
It has a massive service history so I am a bit baffled with it.
I am in the UK so its hard to find anyone who knows there stuff on the big V8's.
I have a Yukon 6.0 V8 2000 SLT, it has 158000 miles on the clock.
I wont start when cold without the throttle, it will start without the throttle when warm.
I get a random p0300 code now and again, and on tickover it just doesnt run sweet. It is also running on LPG with a muti point LPG injector system.
When driven it sounds sweet and pulls hard but on tickover it runs a little lumpy. when i disconnect all the coil packs one at a time the engine changes note apart from cylinder 4. I have swapped the plugs, leads, and coil pack from cylinder 4 with other cylinders and the fault still stays on cylinder 4. The plug and piston is wet in a morning when i used my camera down inside the cylinder all the other pistons are dry. The plug sparks ok on a tester on cylinder 4 so leads coil and plug is ok.
The fault is the same whether on LPG or Petrol so that rules out the injectors.
I get some blueish smoke on startup when cold in a morning and after about 2 minutes of driving it disappears.
I suspected that the valve on cylinder 4 might have got stuck or maybe the spring is week.
I did a compression test and they all came back from (dry) 130 to 145 psi when warm, (130 dry) 150 psi (wet) on cylinder 4 with a tablespoon of oil on a wet test on cylinder 4, the oil is very clean on the dipstick there is no breathing through the dipstick or oil filler and the coolant is red and normal.
Is there anything else I can try before i either take the head off and replace the valves or even worse find that the rings on cylinder 4 are shot.
It has a massive service history so I am a bit baffled with it.
I am in the UK so its hard to find anyone who knows there stuff on the big V8's.
