Knocking Sound?

My wife owns a '95 Riviera that was overheated and blew a head gasket. After repairs the car has a loud solid tap. Can anyone assist me identify what this is?

Is the engine supercharged?

Yes the engine is supercharged

Hey guys i don't know if you remember me But i fist posted around November (i think) whether to buy a 96 or not well i did. haven't had a chance to work on it till last week. If you remember the car was sitting for three plus years need basic work .so heres what i did
-Change Oil / filter
-New plugs Al605
-Clean Maf
-seafoam treatment gas, and vac lines (no oil yet)
-Gutted air Box
- A/C Bypass pulley (Due to Bad Compressor)
-New Rear brake lines
So after i did all that the car was running great.(200 + miles) excellent pull no slipping in trans, all around good feel(SES light on though).So this Morning i was going to meet a friend and show of the riv, started her up knock knock sound coming from engine proceeded to leave the drive way gave it gas total loss of power till around 45% throttle still not what i was accustomed to .Turned around and parked it had to take the e250 work van what a pig. any sugestions on what could be going on. Also one more thing after my oil change i would get the check oil level light on for approx, 30 sec to 1 min the it would go out. im thinking just a bad sensor but who knows.
I dont have a scanner yet.
thanks for any thoughts
mike

You have checked the oil again, and it's still full?

My oil light goes out in about 2-3 secs after an oil change on startup, but I also fill the filter about 2/3 full of oil before I screw it on.

Doesn't sound good

That happened to me a while back, and then it never happened again. i pulled over, let her cool down a bit, and drove off. I wasn't able to start it for a while, and when it ran it made some pretty nasty noises.

whit2285 wrote:

...........Also one more thing after my oil change i would get the check oil level light on for approx, 30 sec to 1 min the it would go out. .....

Is that what the lighted indicator says on the dash? Can't say I've noticed what wording is on there. However, I believe that oil light being on indicates low oil pressure, not low oil level. Low oil pressure can mean you are not getting oiling where you need it... not good. My manual shows the oil light label as "engine oil pressure".

Ok, I see we have both indicators, for oil pressure and check oil level.

Ya oil level is fine

i almost think it might be something with the valves, the oil light doesn't happen all the time and i guess its for only 10 to 20 secs

Mike, you say you never saw the light before you changed the oil?

sorry, I meant the oil pressure light. I've never seen my oil level low light. Didn't know I had one...

Derek, the low oil level light should be on for 2-4 seconds when you start the car. I don't notice it either. Manual says during operation, it will turn on if you are a quart low. I'd assume that means a qt below the add mark, not a qt below the full line.

no , i never saw the light stay on for more than a few sec. but i really never had the car running for long either. do u think it has any thing to do with changing to synthetic oil. just checked oil level again it is actually just above the cross hairs by a smidge. Does it work high and low. Once again its only on start up
Any thoughts on my new knocking noise?
Im going to get a scanner today see what it says

does the light ever come on when you stop and are idling at a light?

No never comes on then, just initial start up and not all the time .thats why i think it might be a bad sensor but i dont know.
Got the auto tap 3.1 loading it now, see what i get. i'll let you guys know.

alright scanned today got a few codes but for some reasons i couldn't stay connected
1. P0102-Mass air flow low frequency
2.P0341-Camshaft Position sensor A circuit
3. P1573-PCM/EBTCM Serial data circuit

any thoughts

There is a dash light check on startup, are you sure that's not what you are seeing?

Did you say it was knocking? Is it still knocking?

Did these all come on at the same time?

Have you checked your spark plugs/wires? A bad misfire could cause these to come on together... If the engine has dropped a cylinder or two you would be getting the cam position code because the drivetrain would be shaking so much. You can get also throw a MAF or O2 sensor code for a couple of misfiring cylinders.

What's it running like? Any symptoms?

I posted last night that i got a new knock but not sure what it is? bought a scanner today auto tap, but it wont stay connected to do live readings not sure why either. i guess i have to figure that out

Oh, okay. Aaron can you merge his threads so we know what's going on?

FYI It's very confusing for us if you start a new thread for the issue we were discussing in a different thread...

AutoTap is a great scanner, I never had any problems with it doing live scanning. Did you get the enhanced GM parameters?

You had the low oil light situation and knocking, right? Now I'm thinking much more that it's a wiring/plugs issue.

I cracked a plug on one install on the rears (that ummm challenging angle to get your arm in there with a socket etc...). Ran only okay at idle, but you couldn't put any load on the engine or it would buck like crazy.

Triple check your spark plugs and wires.

I notice in the other thread you didn't mention wires, just plugs. Old wires can disintegrate upon removal sometimes. How old are the wires?

wires are probably original , the engine really dosnt buck its just a persistent clicking/ knocking noise. dumb question the obd2 connection , is it the one behind the little sliding door under the dash