Mechanics

CAN HYDRAULIC ROLLER LIFTERS RE-PRIME WITHOUT TAKING THEM OUT?

2006 GMC Envoy • 108,000 miles

I have a 2006 envoy denali with the 5.3L. It has a misfire on cylinder #1 and iv changed the oil since it was losing oil pressure, changed spark plugs and wires and even replaced the coil pack for the cylinder and it still has a misfire. Could a lifter have lost its prime and causing the misfire and if so do the hydraulic roller lifters re-prime themselves with the engine running?
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Gearhead90
July 23, 2012.



Check fuel pressure first as that will cause a misfire as well. Then check for a vacuum leak. Lifters will reprime themselves as long as there is oil pressure. If the lifter collapsed it would make a very loud ticking noise then go away after a few seconds

Hmac300
Jul 23, 2012.
How do it check the fuel pressure? The motor has a ticking noise but it is getting quiiter.

Tiny
Gearhead90
Jul 23, 2012.
You will probably need an adapter to tap into the fuel rail. Most auto parts stores have them to rent. If you are lucky there will be a tap on the fuel rail where you can check it. It should be55-62 psi at idleor with key on andengine not running

Hmac300
Jul 23, 2012.
Ok now if the fuel pressure is not in the PSI range what would be the next step?

Tiny
Gearhead90
Jul 23, 2012.
Replace the fuel pump or filter.

Hmac300
Jul 23, 2012.
Ok fuel pressure is at 56PSI so that is good. Any other ideas what could be causing the miss?

Tiny
Gearhead90
Jul 23, 2012.
Check compression and vacuum leak spray choke cleaner for a vacuum leak around intake area also look for vacuum hoses off or holes in them. What is the correct code you are getting.

Hmac300
Jul 23, 2012.
Ok the code that is coming up on my code reader is P0301 and all it says is cylinder #1 misfire.

Tiny
Gearhead90
Jul 23, 2012.
I used a broomstick and put it by cylinder 1 and I could hear some ticking. Its starts fine but after it runs for about 30 sec it bogs down and then you can really tell its missing

Tiny
Gearhead90
Jul 23, 2012.
Broom sticks aren't that reliable. If you have changed plugs, wires and coil then do what I said in last answer

Hmac300
Jul 23, 2012.