Knock Control Spike to .83. A/C compressor?

[cryptolime]

Just noticed my knock control spiked to .83 earlier today. I've had it spike in the past but not this severe.

Usually happen on the freeway when I'm in 6th gear cruising with A/C on low load (I'm thinking maybe the ECU is getting false knock from the A/C compressor or clutch?) but only to .63 at the most.


Anyways, I always use 93 octane. New OEM plugs 5k miles ago (and no new knock spike events after)gapped correctly and installed with a torque wrench.

I did recently fill up at the Harris Teeter gas station (usually go to Exxon) but it was like $1.30 off normal price so couldn't pass it up.

I'm hoping it's just a tank of bad fuel. Anyone else have similar knock control spikes?

Seems mine always spikes when I'm in 6th gear on the highway, especially in Sport mode. Guess I got to be light on the pedal to not lug it.

Just changed my oil when I got home so I'm going to take it for a spin later today and see how it does. Will update when I'm back.

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[cryptolime]

I was able to get it down to .49 after taking it for a drive last night. But, today, I saw it spike in real time to .73 in about 3 seconds. Again, cruising in 6th gear, 70 MPH, Sport mode, on the freeway.

Wasn't using A/C this time so guess I can rule out the A/C compressor.

I'm trying to run this tank of fuel down as much as possible and I'm going to refuel at Exxon (best fuel I've found in the area) tomorrow.

I did put about 4 gallons of fuel in from Harris Teeter last week and my Tacoma would sometimes run sluggishly after filling up there a few years ago. I'm wondering if they have moisture issues in their tanks. Guess we'll find out if that's the issue tomorrow. Anyway, hoping that's all it is!

 

[AZCWTypeR]

I've read most states don't test octane. A few years ago a sample of metro Detroit stations found 25% were selling regular fuel as premium.

 

[cryptolime]

I've read most states don't test octane. A few years ago a sample of metro Detroit stations found 25% were selling regular fuel as premium.

sure feels like it. about to head to work and going to fill up on the way. will update tonight.

 

[cryptolime]

filled up at Exxon and knock control only spiked to .54 under the same conditions. I think Harris Teeter has bad fuel; at least at that particular location.

 

[cryptolime]

so, i'm still getting knock control spikes. I'm not really seeing or feeling any misfires. What else causes knock control to spike up?

could it be from a dirty air filter? injectors? valves out of adjustment? carbon buildup?

 

[AZCWTypeR]

Pull the spark plugs. They should all have been snug and also look the same. If okay, reinstall and torque.
If not consistent, may indicate injector issues or other problems.

 

[cryptolime]

Pull the spark plugs. They should all have been snug and also look the same. If okay, reinstall and torque.
If not consistent, may indicate injector issues or other problems.

new plugs were installed with a torque wrench a month ago. I might try another bottle of fuel injector cleaner.

is there a way to see if i have injector issues with datalogging? maybe monitoring injector pressures?

 

[AZCWTypeR]

Did you replace the plugs due to this, or did the issue crop up after changing plugs?

Hopefully you installed NGK plugs. A Big 3 engineer tells me newer ND plugs have a high failure rate, spiking warranty claims for them.

I run Shell V power nitro+ premium gas, which hasn't needed additional cleaner. Shell also cleaned the gunk off my motorcycle intake valves due to previously running non Top Tier fuel.

 

[cryptolime]

I had this issue before replacing plugs. I used OEM NGK plugs. Going to pick up a bottle of Redline SI-1 later today to see if it helps.

 

[cryptolime]

A few days ago I added a bottle of Redline SI-1 to a full tank of 93. I also replaced the air filter with a WIX I had, and I'm not getting any more spikes.

Had 15k miles on the air filter but it was pretty dirty.