Bentley

Just got my engine, not installed yet

Just got my engine, not installed yet. Read through this post from beginning. It may answer some of your questions.

I was a little fooled at first with weather temp.. In my case the lifter 'bearing' was shot. Like any bearing, I am sure that the fail is sporatic at first until it fails completely. Maybe in cold weather it contracts - Idk? If the cam is still good, you are fortunate. FYI - if you replace lifters, do all of them, and replace the VLOM.

Mileage/kms ?? You are describing my (old) engine exactly. On a scan, the oil pressure spikes BEFORE the misfire. This seems to indicate non-electrical, that is a mechanical defect. You can read my thread for details, but I replaced many parts - including oil pump - as I thought it might be the relief valve in the pump being faulty. In the end, it was a bad lifter, which ruined the cam, and quite possibly hurt the valve. Considering the high mileage on my truck, I just received my new engine. For me, the rebuild option did not make sense. Lots of info on low oil pressure but not on high oil pressure. My theory: The bad lifter is causing the computer to increase oil, or at least leak oil. This influx of oil works on the back end of the pump to offset the relief valve, thus causing high oil pressure. Just a theory, not looking for arguments.

HawaiianRR: I think you've convinced me not to swap motors right away. Keep me updated on how it goes. Thx.

HawaiianRR: Can you tell me how you inspected your cam?

HawaiianRR: Brilliant! OK, you may have convinced me to do this job. At least I may pull out the lifter(s) and inspect.

HawaiianRR: Ughh. Curious what your plan is. I told my wife to post on fb that I keep forgetting to take the keys out of my truck. Perhaps someone will jump on the opportunity to drive the truck into the lake. (lol)

HawaiianRR: Ughh. Curious what your plan is. I told my wife to post on fb that I keep forgetting to take the keys out of my truck. Perhaps someone will jump on the opportunity to drive the truck into the lake. (lol)

HawaiianRR: What is the mileage on your truck?

HawaiianRR: This has been a relatively complicated problem. Please read thread to see what I have done. Presently, there is vacuum pressure problem on cylinder 8 and misfire, which is now spreading to 7 etc. My guess is there is some kind of back pressure into the oil pump which is nullifying the pressure relief valve. If I were crazy, I would bring it into GM and they would now replace lifters and rods, but then I would not know if the Cam is scored. So then replace the Cam, but then I don't know if the Cam bearings are shot (leaky). [I am guessing that the oil is leaking through the bearings causing the back pressure...] Of course, after spending thousands, I still would not have addressed the heads and valves.... My solution: I have ordered an engine. So far I have been waiting about 2 months. When the engine comes and is installed, I will immediately add a catch can and possibly nullify the AFM electronically. CONCLUSION: I will never buy a truck newer than 2007 again. The fella replacing my engine said he has a lineup of GMs, Fords, and Dodges waiting for engines. The cause is all the emission control crap, direct injection etc.

asilverblazer: Nope

Petermackenzie: Curious: Start engine cold and let idle. Watch the Oil Pressure. If same as mine, you should be able to hear the oil pump solenoid click, then the oil pressure will spike. ?? Also: Rough idle after spike Just a long shot: Unrelated events for me: Have you changed thermostat and/or temp sensor recently?

asilverblazer: Yeah, so when cold there is a spike that happens about a minute after idle. This sets off the engine light blinking, and immediately causes misfire. I will shut engine off and restart. Repeat above, until engine warms up. As the engine heats, the oil thins and the spike stays low enough to not trigger the engine light blinking. After warmup, the pressure is about 1 - 2 o'clock at about 2500 rpm (275 kpa is 12 o'clock which I think is normal)

asilverblazer: I kind of agree, except that the pressure spike is far above spec. The spike in oil pressure triggers the engine light. The misfire triggers the engine light 'flashing'. As well, after warming up, the oil pressure is higher than normal. All of that said, the truck has 260k (km) and it would not surprise me that the lifters are weak. PS: I think my scan tool can turn the solenoid off, but I am not competent enough with it yet.