97 Pathfinder Spark Knock (Pinging)

[A1218]

I’m experiencing some engine pinging anywhere between 1300rpm and 2500rpm. Especially good if uphill or when the engine is under more load with the A/C on.

Everything has been maintained on it recently. New injectors, intake gaskets, IACV, TPS, MAF, Nissan plugs, new ngk leads, injector rail to intake seals, knock sensor, coolant hoses, new coolant.

I did replace the distributor last year, again Nissan original part purchased. That I had my Nissan mechanic install. However he didn’t use a timing light. He just marked it up with the old one and then put the new one it. But I did really experience pinging much until now.

I’m not sure if it’s the gas. I’ve been fulling for a while at a Mobil station with 87 octane. So I’m my last fill up I decided to 89 octane at a shell station. It was half tank I filled up on top of the previous gas. Still pinging so far.

Should I wait a couple more fill ups with the 89? Try and octane booster? Or do I need the timing to be reset?

[VStar650CL]

With a "by ear" timing setting, the ECM may not have enough latitude to correct a knock situation. Get it timed right with a light. If you're a "grandpa" driver it's also possible you have a carbon-buildup issue. Carbon on the piston crowns artificially increases compression and can induce knock in an engine that didn't used to do so.

[A1218]

With a "by ear" timing setting, the ECM may not have enough latitude to correct a knock situation. Get it timed right with a light. If you're a "grandpa" driver it's also possible you have a carbon-buildup issue. Carbon on the piston crowns artificially increases compression and can induce knock in an engine that didn't used to do so.

Gotcha, will try the timing light. Never used one before but I’ll see. Any recommendations? I know it should be 15 degree +/- 2 degrees.

It honestly gets a lot of city driving. I live in Queens, NYC. highway here and there but even then not that long on it. So carbon could be a possibility. I try to give it some spirited driving on the occasional longer trips.

[VStar650CL]

Warm it up fully, have an assistant hold the RPM's between 3~4K, and put a teaspoon of any type transmission fluid down the brake booster hose. Bam, no more carbon.

[A1218]

Warm it up fully, have an assistant hold the RPM's between 3~4K, and put a teaspoon of any type transmission fluid down the brake booster hose. Bam, no more carbon.

Is that a safe option? Just wondering, it won’t damage anything?

Doesn’t carbon in certain areas of an older engine help seal things better?

[VStar650CL]

Yes to Q1, no to Q2. We probably de-carbon 5~10 cars a week that way, the only small risk is that big chunks on a severely-carboned engine can hit a spark plug and bend the electrode shut. The ATF pretty much "explodes" whatever carbon is present by means of thermal differential, not much different from tossing an ice cube in boiling water. It doesn't melt, it cracks. To Q2, dirt can hold seals together on an old car, but carbon isn't dirt. No amount of carbon thicker than a hair is healthy on pistons or valves.

[A1218]

Yes to Q1, no to Q2. We probably de-carbon 5~10 cars a week that way, the only small risk is that big chunks on a severely-carboned engine can hit a spark plug and bend the electrode shut. The ATF pretty much "explodes" whatever carbon is present by means of thermal differential, not much different from tossing an ice cube in boiling water. It doesn't melt, it cracks. To Q2, dirt can hold seals together on an old car, but carbon isn't dirt. No amount of carbon thicker than a hair is healthy on pistons or valves.

Alright, I’ll give that a try if adjusting the timing doesn’t work. I ordered a timing light to adjust it this weekend to 15 degrees if it’s not timed right.

[A1218]

With a "by ear" timing setting, the ECM may not have enough latitude to correct a knock situation. Get it timed right with a light. If you're a "grandpa" driver it's also possible you have a carbon-buildup issue. Carbon on the piston crowns artificially increases compression and can induce knock in an engine that didn't used to do so.

So I checked the timing and it is slightly under the 15 degree mark. But it would still be within spec because it’s 15 degree +/- 2. Should I adjust it to exactly 15 degrees?

However, more advancement in timing would mean more pinging? The pinging is very light and appears mostly on hotter days up a hill and especially when the a/c is on.

[VStar650CL]

However, more advancement in timing would mean more pinging? The pinging is very light and appears mostly on hotter days up a hill and especially when the a/c is on.

Correct, more advance will only exacerbate it. I'd leave it alone. Since the problem is heat- and load-related, I'd pull a couple of plugs and see if the cylinders are running on the hot side (white-ish electrode). If so you might have an EGR issue or something causing lean fuel.

[A1218]

Correct, more advance will only exacerbate it. I'd leave it alone. Since the problem is heat- and load-related, I'd pull a couple of plugs and see if the cylinders are running on the hot side (white-ish electrode). If so you might have an EGR issue or something causing lean fuel.
[/quote]

Gotcha, will leave that alone.

I’m doing a maintenance today. Oil, filter, air filter, transmission fluid, and fuel filter. I’ll see if it’s better and will also check plugs.