Ongoing Pinging Issue w/ 84 GM 2.8L V6 - was it designed to run on 87 or 89 octane?

My '84 Pontiac w/ V6 has always pinged for 20 some years. The timing appears to be dead on to factory spec. A recent
major tuneup didn't help any. It has 144k mi - While it's in a Pontiac I think it's essentially a Chevy engine.

Today I tried mid-grade gas (89 vs 87 octane) and there was no pinging.

Qs:

Wasn't this engine designed to run on 87 octane? Or is my memory in error and '89 is the way to go.

Should I consider setting the timing a little conservatively compared to factory?

Could the knock sensor have been bad all these years? How can I test it?

Are there any other areas I should check that might affect timing/knock? The distributor doesn't have a vac advance and
is controlled electronically.

Thanks

I should add I'm near sea level and gas here typically comes in 87, 89 and 91 for regular, mid and premium grades
respectively.



On Sun, 25 Jun 2006 02:44:44 -0500, LoadHawg > wrote:

>
>My '84 Pontiac w/ V6 has always pinged for 20 some years. The timing appears to be dead on to factory spec. A recent
>major tuneup didn't help any. It has 144k mi - While it's in a Pontiac I think it's essentially a Chevy engine.
>
>Today I tried mid-grade gas (89 vs 87 octane) and there was no pinging.
>
>Qs:
>
>Wasn't this engine designed to run on 87 octane? Or is my memory in error and '89 is the way to go.
>
>Should I consider setting the timing a little conservatively compared to factory?
>
>Could the knock sensor have been bad all these years? How can I test it?
>
>Are there any other areas I should check that might affect timing/knock? The distributor doesn't have a vac advance and
>is controlled electronically.
>
>Thanks

I would give 'er the gun, ie.: put in pedal to the metal,
occasionally, in 2ND (or 'L') gear.

repete as neccessary,...,...

if no improvement after a feww weeks,

i would try to SLOWLY drip distilled WATER into intake with motor
running btween 1 & 2 RPM × min. POOR MAN'S STEAM CLEAN valve seats &
PISTON DOMES.

but you aren't me.

I would give 'er the gun, ie.: put in pedal to the metal,
occasionally, in 2ND (or 'L') gear.

repete as neccessary,...,...

if no improvement after a feww weeks,

i would try to SLOWLY drip distilled WATER into intake with motor
running btween 1 & 2 RPM × min. POOR MAN'S STEAM CLEAN valve seats &
PISTON DOMES.

but you aren't me.

LoadHawg wrote:
>
> My '84 Pontiac w/ V6 has always pinged for 20 some years. The timing appears to be dead on to factory spec. A recent
> major tuneup didn't help any. It has 144k mi - While it's in a Pontiac I think it's essentially a Chevy engine.
>

Well if it has been the same for 20 years - Why worry about it now?
Eventually the compression will drop and the pinging will stop. With
good maintenance and luck that might be another 10 years down the road.


> Today I tried mid-grade gas (89 vs 87 octane) and there was no pinging.
>

The issue is not really the pinging since a small amount of pinging is
obviously doing no harm. What you should look at is your gas mileage.
It's quite possible you will get slightly better mileage with the 89
octane. It may be enough better that it will be as cheap or even cheaper
to run it on 89 octane. Or you may find that the best mileage is when
you switch back and forth between 89 and 87 every other fill-up. It may
also vary with the seasons.
OTOH, retarding the timing will get rid of the pinging but may cost you
more in fuel consumption. But that is easy to check also. It has been my
observation that engines that get the best mileage (all else being
equal) will last the longest.

-jim


> Qs:
>
> Wasn't this engine designed to run on 87 octane? Or is my memory in error and '89 is the way to go.
>
> Should I consider setting the timing a little conservatively compared to factory?
>
> Could the knock sensor have been bad all these years? How can I test it?
>
> Are there any other areas I should check that might affect timing/knock? The distributor doesn't have a vac advance and
> is controlled electronically.
>
> Thanks

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Maybe your engine was designed to run on gasoline? Lots of stations mix
in alcohol or ethanol which can make some old engines ping like buggers
and lose power and gas mileage.

By going up to a higher octane, you might be altering the flash point
enough to overcome the added junk.

I know my 86 Jeep engine pings and goes on with regular and an alcohol
or other 'ol' mix and the gas mileage drops dramatically. So does top
end power.

If I up the octane, both my power and mileage come way up.

I also have had my engines apart and know there is no carbon buildup in
them.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
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LoadHawg wrote:
>
> My '84 Pontiac w/ V6 has always pinged for 20 some years. The timing appears to be dead on to factory spec. A recent
> major tuneup didn't help any. It has 144k mi - While it's in a Pontiac I think it's essentially a Chevy engine.
>
> Today I tried mid-grade gas (89 vs 87 octane) and there was no pinging.
>
> Qs:
>
> Wasn't this engine designed to run on 87 octane? Or is my memory in error and '89 is the way to go.
>
> Should I consider setting the timing a little conservatively compared to factory?
>
> Could the knock sensor have been bad all these years? How can I test it?
>
> Are there any other areas I should check that might affect timing/knock? The distributor doesn't have a vac advance and
> is controlled electronically.
>
> Thanks

Possible the egr valve is not working or the passages carboned up?
"LoadHawg" > wrote in message
...
>
> My '84 Pontiac w/ V6 has always pinged for 20 some years. The timing
> appears to be dead on to factory spec. A recent
> major tuneup didn't help any. It has 144k mi - While it's in a Pontiac I
> think it's essentially a Chevy engine.
>
> Today I tried mid-grade gas (89 vs 87 octane) and there was no pinging.
>
> Qs:
>
> Wasn't this engine designed to run on 87 octane? Or is my memory in error
> and '89 is the way to go.
>
> Should I consider setting the timing a little conservatively compared to
> factory?
>
> Could the knock sensor have been bad all these years? How can I test it?
>
> Are there any other areas I should check that might affect timing/knock?
> The distributor doesn't have a vac advance and
> is controlled electronically.
>
> Thanks
>



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Thanks

I've run water through it to clean it once or twice as well as some
seafoam. At this point I don't think it's carbon - it has done this
since the car was purchased (2 yrs old and about 10K mi at the time.

Every day I have to floor it once all the way up to 70+mph to get onto
one particular fast moving road lacking a merge lane.

The pinging has gotten somewhat worse in the last year - very
noticeable at slower cruise speeds and light accelleration, hills etc.
Driving through my neighborhood holding to about 35 and it clatters
pretty bad - you can 'feel' it not just hear it. Everything I know
about pinging from predetonation indicates it's not good for the car
despite the mileage accumulated in this case.

Stepping up to the mid grade 89 octane helped very nicely.

How do I accurately test the knock sensor? I'm thinking that 'should'
allow me to run whatever grade of gas if it is functioning properly...?

As I said, you don't have a knock sensor if it's an '84, like you
posrted....


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