Not running so smooth...
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Joined: Sep 2014
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Not running so smooth... My 4.8L Gen III has 280,000 miles on it. On my last oil change there was a small amount of water in my oil and I noticed the oil pressure was running low -around 40psi. The motor later shut down and the check oil pressure warning light appeared. I had the heads machined and replaced the oil pump. After reassembly I got the multiple cylinder misfire warning and the motor ran like it was miss-timed. My understanding is that the sensors will work them selves into the right timing. It has smoothed out as if the timing has found itself, but it runs like it's unbalanced -wobbly. The multi cylinder misfire warning has not returned since I cleared it. It also has a tap increasing with the RMPs. On inspection it seems to be coming from the passenger side head. I ran the motor with no valve cover on the passenger side and no oil is running thru the push rods and the oil pressure is still around 40 psi. I did not remove the lifters or disassemble the bottom half of the motor. I know I have a lot of miles on this motor but I would really like it if someone could give me some tips on what to next on fixing this. I have not replaced the cam or crank sensors and the motor has sat for a few months since I primed the new pump. Any help besides "buy a new block" or "swap to a bigger motor" would be appreciated.
TECH Resident
Joined: Aug 2005
Posts: 980
Likes: 2
Could you run something down the passages to make sure it's not clogged anywhere? I'm sure after 300k miles you have some build up somewhere, but that seems unlikely to cause your misfire problem unless you have a stuck lifter?
Last edited by maroonls1z; Sep 16, 2014 at 06:44 AM.
i agree with maroonls1Z, i may attempt runing some type of ummm i forget what its called atm but you drain some oil and put in 1 quart and run it for a hour or 50 miles and its suposed to clean the oil passage ways. something like that and that may help if you have build up. and if you had a stuck lifter i think the noise would be much more prominent. oh its called sea foam! let us know what you do and the outcome!!
