Engine Knocking.

So, Here's the story a few weeks ago, I went camping, On my way home, I started hearing engine knock and had loss of power. Looked at my temp and it was running HOT. Not in the red, but hot. Immediatly pulled off, let it cool and tried again. started knock and started getting hot. Pulled off. Added some water (it was low) got back on the road once cooled, no knock, everything was normal. Once home, the next day started examining why I had low water. Infamous Quick Connect Heater Line on the manifold. Wiggled the line and it snapped. Left threads in the intake. After days of fixing that, It's time for a test drive. Everything is working. Drove around maybe 10-15 miles car up to temp, running normal. good to go. Later on driving It starts idling rough, Pop it in neutral. All is good. Pop it in drive and try to go, engine starts knocking again(under acceleration). Since then, Everytime I drive it's making loud knocking sounds(under acceleration). If I pop it in neutral and rev, no knock. If I drive then let off no knock.

Reminds me of a timing issue. If its to retarded (i think) Like it's trying to have the power, can't make it and just knocking/rattling.

Only thing that gets me is the rough idle (only in gear) and the fact it doesn't knock when i rev the engine in neautral (well a SLIGHT knock at first but that's it)

99 Suburban 2x4
5.7 (K&N Filter)
Lifted with 33's
107,000 (106 and some change) Miles

Pulled the code.

P0102 - MAF Which has been unplugged
P0300 - Random Misfire
P0300 P

I'm going to do the tuneup tonight and see what the next step brings.

Thoughts on a leaking headgasket causing the random mis-fire? From what I understand 99 Burbs aren't smart enought to know WHICH cylinder is actually mis-firing?

Oil appears to be fine and no white smoke.

Is it possible, Initially I didn't drive it long enough, Therefore the thermostat didn't open allowing water to enter the cooling chambers? Once i didn't, My problems started.

based off my theory that there's a small head gasket leak fouling my plug.

Is it possible, Initially I didn't drive it long enough, Therefore the thermostat didn't open allowing water to enter the cooling chambers? Once i didn't, My problems started.

based off my theory that there's a small head gasket leak fouling my plug.

the p0300 will throw with an engine knock. since the engine did over heat the heads will get hurt. could have distorted the heads with low coolant. adding coolant to an over heated engine is another very tricky deal also.


why is the MAF disconnected ?

did you bleed the air out of the engine/run engine with the coolant cap off rev engine to 2000rpm a few times until at the normal operating temp. this will get most all the air out.

remove all plugs mark where they came out . look for very clean white plug out of the litter. if all light brown your good with the heads/gasket.

if it is still knocking this could be lifter/piston issues. add 6 OZ of marvel mystery oil to the crankcase engine oil. see if the noise lessens or goes away. carbon can loosen up with overheating and create these issues.

lastly the oil pressures must be correct. if the oil pressures are jumping around this would mean you damaged the crankshaft bearings. if so junk it.

My MAF is disconnected, becuase years ago I was having significant power loss. I searched everywhere trying to figure out why, I eventually just disconnected it and now I have power! Just have left it at that since. Unless I need to smog, then I plug it back it (to shut the light off)

I did run it until normal operating temp with the cap off and front and rear heaters on. Coolant has always sat about 2 inchese below the top of the radiator. Even after I replaced it, No idea why.

The oil pressure, Is a bit low, roughly 12 psi at IDLE (when warm) and up to about 50ish when Driving. However when the engine is cold idle pressure is always around 40.

Also, Not sure how reliable the temperature guage is, But If my engine EVER got to the red, I immidiately shut my car off, Even if in the middle of the intersection. First time I added water the engine was cool (cool enough to open the radiator cap) and I added warm water (from the back of my car, camping water) second time was at a gas station(engine was cool enough to open again, however water was a bit colder)

As for everything else I'm going to check them tonight if I have time, otherwise I will have to do it this weekend!

Thank you for your input!
Will defintely keep you updated.

the MAF measures the air flow to the engine. the O2 sensors measure the exhaust mixture. these together are sent to the computer to properly control injectors for the correct fuel/air mixture.

the MAF disconnected is going to create a rough running engine. I did this before on my 5.3L 2000 sillverado ran bad.

could be the MAF is dirty or damaged. I clean my MAF every 20,ooomi with CRC MAF cleaner. this is safe for the electronic /plastic parts. carb cleaners etc will kill the MAF.

your oil pressures indicate your bearings are worn.

your engine should have 40-55psi oil pressures when hot at all times.

when cold the pressure should be 70-80psi.

this would be with 5-30wt regular engine oil. with these pressures being low/ engine worn I would guess that your using the cheap stuff/non synthetic. would not be surprised if your using a 10-40wt oil. your mileage you should not have low oil pressures. you may be going too long on the oil changes. 3500mi with reg engine oil.

these engines go over 200,ooomi with not having this low pressure if properly maintained using regular engine oil.

check fuel pressure . ignition on eng off 60-66psi. should hold pressure .

engine running you need 57psi.

I did run it until normal operating temp with the cap off and front and rear heaters on. Coolant has always sat about 2 inchese below the top of the radiator. Even after I replaced it, No idea why.

As for everything else I'm going to check them tonight if I have time, otherwise I will have to do it this weekend!

Thank you for your input!
Will defintely keep you updated.

explain that you have a radiator cap ? so the cap is on the radiator ?

what about the plastic tank ? you have one ? if not this is weird.

Would not be surprised if I ran 10w40? a bit patronizing, no?
I run 5w30 Mobil No Synthetic. Always have.

It's a lifted Burban, Running 33's and I used to tow, alot. Tranny was rebuilt about 85k. Intake gaskert changed twice.

I have a radiator cap. Initially when I let it warm up i left the cap off and heater running, then added water as needed. No plastic other then overflow.

Would not be surprised if I ran 10w40? a bit patronizing, no?
I run 5w30 Mobil No Synthetic. Always have.

It's a lifted Burban, Running 33's and I used to tow, alot. Tranny was rebuilt about 85k. Intake gaskert changed twice.

I have a radiator cap. Initially when I let it warm up i left the cap off and heater running, then added water as needed. No plastic other then overflow.

using 10-40wt does more engine wear. GM banned this viscosity back in the 1980's.
so i guess then your most likely going too long on your oil changes.as this engine has oil pressure issues.


I know regular oil of the proper viscosity with the 3500/4000mi oil change you can get well over 200,ooomi with not having low oil pressures and engine wear.

coolant system , well then the radiator coolant system must not be OEM design. should have a plastic coolant res. with the pressure cap on that, not the radiator.this is so that the radiator is always 100% full. the plastic pressure tank is where the over flow is located. the tank is filled to the full cold mark when the engine is cold.

so if you loose just a small amount of coolant with this gone the radiator will have air in it. this is not good.

also you have no idea when your low on coolant !

When I got my oil changed last time, He said I had an oil leak. Tried selling me a steam cleaning and some service where they put dye in the oil and check where the leak is. Could an oil leak cause the low pressure at idle? It doesn't leak to where there is oil on my floor, Just a little messy around the oil filter and under the engine..

Also, and FYI, This is a 99 OLD STYLE,
Therefore I have a radiator with a pressure cap, Then a line running to a plastic overflow.

here is a screenshot of my similar setup. Aside from theintake and Crazy Electrical setup.

here is a screenshot of my similar setup. Aside from theintake and Crazy Electrical setup.

that is quite a setup. dual alternators. dual battery.

the over flow tank on the firewall also quite different.

well the over tank should keep the coolant level at 100% in the radiator. you add to the tank not the radiator.

oil leaks will not cause a low pressure. also steam cleaning should be avoided. steam cleaning is good when you prep for a engine overhaul.

also small leaks at this age are quite normal.

So, Just got finished diggin in... Plugs seems to be semi-worn.
However I noticed on Wire 2 there was a big ol gash in it. So i replaced it almost 100% sure that was my prob, Nope.. Didn't fix it.. What a let down.

One thing I noticed was my valvecover got ALOT hotter above like 6 and 8. Not sure if this has anything to do with it.. But, The ticking/knocing is def coming from bank 2 (passenger side?).

Compression check to follow.

So, Bad news for me.. Did my compression check just now.. 4/6 0 PSI, All the Rest a solid 150. So, My head gasket is toast. However, My coolant and Oil are still fine... *shrugs*

Now, My next question. The fix is cheap but alot of work. I feel like if i'm that far in there, I should just do a complete overhaul Just pull the motor, change my bearings and anything else that may need to be done. Anyone have any imput/thoughts on this idea?

Or should I just fix what's broken and get out?

So, Bad news for me.. Did my compression check just now.. 4/6 0 PSI, All the Rest a solid 150. So, My head gasket is toast. However, My coolant and Oil are still fine... *shrugs*

Now, My next question. The fix is cheap but alot of work. I feel like if i'm that far in there, I should just do a complete overhaul Just pull the motor, change my bearings and anything else that may need to be done. Anyone have any imput/thoughts on this idea?

Or should I just fix what's broken and get out?

I would have the both heads checked for distortions. then install and run it.

107,000mi you have on this is not much.

over heating most always will cause this to occur.

when the temp gauge starts climbing what is that temp ????not too accurate.

I've attached some screenshots... Totally a headgasket... Nice...

However, any recommendation on cleaning my block? I have a parts washed i'm going to clean up the heads with, but as for the block.. I'm thinking scrape and clean then vacumm out the cylinders? Any sugesstions?

Everything is back together and running.. I still got a Check engine light on.. Need to read the code later..

However, Have my MAF plugged in again and i have loss of power.. I 'm thinking about just pulling it again and seeing if it make a difference like before.. If so.. I'll prolly spend the 150 on a new one..

What are chances the timing is causing loss of power? Engine revs with SLIGHT hesitation at first.

Check engine code was my Cam/Crank shaft positioning sensor. Following an artice I found online, I got it roughly back to 0 ±2 and no light anymore!

However still lacked in power... I just unplugged the MAF sensor and got all my power/fuel economy back. Going to follow another procedure I found to test my MAF sensor.