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Old 05-17-2016, 05:45 PM   #1
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Default cold start spark knock

Hey guys,
97 olds 88, 103k miles

I am noticing a spark knock, engine is cold, i live 2 blocks from the interstate ramp..

I start it up, everything is fine

drive the 2 blocks to enter the interstate ramp, while accelerating, I'm noticing spark knock

nothing major, but it'* there, if I accelerate harder, it will spark knock louder

I'm guessing its burning lean, since, if I accelerate more, opening the airflow, and thus spark knock

normal? or something going on?

once at hwy speeds, no spark knock or after engine warms up, i never hear it again

just in mornings going up ramp

I did blow out a coolant elbow a few months ago, puked out all the antifreeze, threw the serp belt... i ran it a mile...to get off the interstate...it was warm, but never pegged the temp gage

replaced with steal elbow, installed new idler tensenior, , fresh antifreeze..and all is well, thats been 5k miles ago

i've replaced
radiator
hoses
belt
intakes upper/lower, plentum
plugs/wires denso tt iridium
oil sending unit ....leaking
motor mt dogbone underneath
shocks/struts
headlight assy'*
vac tee'*
brakes/calipers,rotors/drums.cyl'*
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Old 05-17-2016, 09:59 PM   #2
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It may be a good thing to check the fuel pressure regulator, as they were a known problem area in that era, or even a full pressure test would be in order too.
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Old 05-18-2016, 12:02 AM   #3
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sorry, I forgot to put fuel pressure regulator as replaced....about a year ago... it'* on the fuel rail, and was letting fuel leak into vac lines..replaced

no access to pressure tedt equpt
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Old 05-18-2016, 02:53 AM   #4
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Try your local auto parts store, Autozone or Advance Auto may rent the pressure tester tool.
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Old 05-18-2016, 08:12 PM   #5
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what is the pressure suppose to be?


also, wouldn't this effect other operating temps? across the range....trigger check engine light?

as i said, this is rare, usually dont hear SK anywhere..just the rare occasion cold, getting onto interstate
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Old 05-19-2016, 12:31 AM   #6
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Around 48-55 psi.

I am not sure it is actually spark knock that you are hearing, if you are only hearing it when the motor is cold, and it is fine once it warms up, then I'd be thinking more like an issue with the valves (possible valve clatter), or the injectors clicking.
You could rule out the injectors if you had a mechanics stethoscope.
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Old 05-19-2016, 11:46 AM   #7
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yes, only when it'* cold, just after start up, when entering freeway, and only if your accelerating hard..not normal acceleration as usual, could be just the valves clattering....but also sounds like detionation knock..could be either

if its valve clatter...whats causing that?..just being cold, slow to move?
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Old 05-19-2016, 03:43 PM   #8
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Could be low oil pressure, maybe there is too much valve lash.
I'd try to check the oil pressure, if it is a bit low the oil pumps pick up screen, or the oil filter could be partially clogged.

You use the regular weight oil that your motor calls for right?

Try to rule out oil pressure as a problem first, then if it is not that move on to checking valve lash, which will require you to remove the valve covers, and measure each valves lash with a feeler gauge..


One thing to consider since the noise is gone as soon as the motor warms up, the piston to cylinder clearance may have increased a little over time, which would be normal, and if that is the case I'd not worry much.
Just try to let it warm up a little before you drive it, and if it is still making the noise go easy on it till it stops..
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Old 05-19-2016, 11:31 PM   #9
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I dont think it'* much to worry about either, it is rare, i'm just "in tune" with the motor,

i was worried when I ran the car without coolant a few months ago..to get it off the interstate..i'm sure a few things got a little hot..but as thats about 5-6 k miles ago, and everything seems ok

it run/drives perfectly, out of the hundreds of cold starts..i've only heard this claddery sound maybe 3 times...for a few seconds...and i was pushing on the pedal...going up interstate ramp...

I've read these engines are good for 300k+ miles..so time will tell

thanks guys
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Old 05-20-2016, 01:33 AM   #10
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Maybe a lifter that takes a bit to pump up? Something maybe clogging a passage or somesuch?

L36'* aren't known for detonation or spark knock issues. Or lifter issues for that matter. In a past life we had a few 2000ish L36 Impala 9C1'* with a couple hundred thousand miles of hard service, and no unbecoming sounds (except for tired starters).

Trying to fix it would probably make it worse. If you can use a regimen of being nice to it then you're probably good for a good long time.
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