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High Oil Pressure / Misfire

Bentley

By Bentley
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Bentley Enthusiast

Bentley

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newdude: Well that gets rid of one possibility.

 

Can't figure it out. I start the truck and about 15 seconds later I hear a click and the oil pressure spikes.

Now, after the spike, I hear a buzzing in the engine.

About ready to look for a cliff.

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silveradosid
silveradosid

you need to have a balance test done or even better have some one who knows how to scope the engine. i have seen on gm v8's that miss fire on cylinder 8 was caused because cylinder 1 fires before 8 an

HawaiianRR
HawaiianRR

Pulled the head off and took out the broken lifter. Camshaft lobe is not damaged. I plan to put 8 new gm lifters and guides. Replace the 1 bent pushrod. Change the filter in the VLOM because it’s easy

Bentley Enthusiast

Bentley

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newdude (or anyone):

So there must be a relief valve for the LT engine, am I correct. 

Where is it located if not in the oil pan? or how does the system deal with excess oil pressure?

 

 

  • 2 months later...
Davis 84 New Member

Davis 84

Posted
Posted

2015 5.3. mine is giving me same symptoms but I doesn't just do it at startup. Sometimes it's fine on a 100 mile drive then will start missing traction control popps on and oil pressure goes from 40 to 55pai. I will keep driving and in a while it all goes back to normal like you say, like a switch 

Bentley Enthusiast

Bentley

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Davis84: My scanner shows this order of events:

1) everything normal at startup

2) oil pump high pressure solenoid shuts (off I think) - this creates the high pressure

3) misfire immediately after

 

Apparently there is a pressure relief valve in the oil pump. (LT engines) So I am just about finished: new oil pump, new vvt solenoid, fixed oil pan leak etc. New motor mount. The job was massive (for me).

 

I will have it running (hopefully) by next week. I am guessing that the pressure relief valve was stuck closed. So when the 2 stage pump kicks into high pressure mode, then the relief valve does no do its job.

 

PS: check something out on your truck. The pump kicks in to high pressure at around 3500 rpm. See if that is when your oil pressure spikes. 

 

Davis 84 New Member

Davis 84

Posted
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I will do. But I was running at hiway speed under 2000 rpms when it last occurred. I think it is an ecm problem. Man please let me know how yours works out. Good luck 

  • 2 weeks later...
Davis 84 New Member

Davis 84

Posted
Posted

Not yet. Put new wires on mine and had a frayed wire on #8. 166600 miles, now instead of a #8 misfire gotta random misfire, gonna put new plugs in this week. I won't remember to post the outcome so if you would. Make a post to this thread and I will let you know how it works out. 

Bentley Enthusiast

Bentley

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Kbrock3397: Well, problem not solved. This is what I have done so far:

- Walnut blast to intake

- new VLOM

- new plugs, wires, injectors

------------ First project no change

 

Then:

(I had an oil leak so some of this I had to do anyway)

- re/re oil pan

- new oil pump (thought that the relief valve might be stuck)

- new VVT solenoid

- new wires / and some sensors

------------------ Second project (massive) no change

 

I am bringing it in to GM this week to get diagnosis.

Engine does not tick or sound funny, just the same misfire AFTER spike in oil pressure.

 

I have researched this up my ying yang. Lots of problems with low oil pressure, but nothing related to my issue.

We will see what GM says - unless someone has a better idea...

Davis 84 New Member

Davis 84

Posted
Posted

Dang I hate that, right now I have already replaced my spark plug wires and a coil on number eight and Monday we are going to replace all the spark plugs. I will let you know how it turns out

Bentley Enthusiast

Bentley

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asilverblazer: Possibly, but the main culprit is the spike in oil. The misfire is secondary to that (according to my scanner)

asilverblazer Senior Enthusiast

asilverblazer

Posted
Posted (edited)
14 hours ago, Bentley said:

asilverblazer: Possibly, but the main culprit is the spike in oil. The misfire is secondary to that (according to my scanner)

Wonder what level of scan tool would be able to take over control of (or at least monitor) the oil pump solenoid... turn it off and see if the miss fire clears up. 

 

The only way oil pressure could affect engine performance would be through the DFM lifters.

 

Maybe the oil pump and pressure are as intended (no codes) and the lifter is the problem. 

 

In other words, so what if the oil pressure spikes - none of the other cylinders have a problem with it. 

Edited by asilverblazer
Bentley Enthusiast

Bentley

Posted
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Posted (edited)

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.

Edited by Bentley
Correction
asilverblazer Senior Enthusiast

asilverblazer

Posted
Posted
On 4/16/2024 at 11:38 AM, Bentley said:

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.

I guess I missed where the oil pressure spike is setting the engine light. What code specific to that is there?

 

What is "higher than normal"?

Bentley Enthusiast

Bentley

Posted
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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)

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