SOLVED: Engine knock without check engine light - 2017 V6

[SirLoin]

I have a 2017 V6 automatic with 45K miles that suddenly has a noticeable engine knock (never had the typewriter click common in GTs). It has all of the symptoms of a bad engine knock sensor, according to YouTube (knocking, sudden loss of power, bad gas mileage) EXCEPT the check engine light has not come on in the 3 days since I noticed the knock.

The knocking doesn't happen at all RPMs. It's there at idle and very loud during deceleration, but intermittent during acceleration. I'll be honest, I let it go at least 2-3,000 miles past the oil change light this last time. However, I changed the oil yesterday, drove it 60 miles roundtrip to work, and it made no difference in the knocking. I'm also using regular 87 gas.

I've read about the false knock issues. I have everything stock except for a muffler delete (which I don't recommend on a V6) and it's a convertible, but I think the chances are pretty low that this is being caused by a false knock somewhere else.

From what I can tell, the knock sensor isn't exactly easy to change out. The shop said it would cost $110 just to diagnose. I'm wondering if I should bring a new knock sensor with me, so they can change it quickly if that's the issue.

Has anyone else had this issue with a V6? Does the V6 have more than one knock sensor? Is there anything else that it could be?


***UPDATE*** The dealership is replacing the "short block." That's all the service advisor was able to tell me.

***UPDATE*** Finally got the car back after 2 weeks. The paperwork says "wrist pin binding" on cylinder 6. I drove it 30 miles to work and so far she's purring like a kitten.

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[Deleted member 35644]

A knock sensor isn't involved if you're hearing it during deceleration. Spark knock can't exist where there is no fuel. Focus on mechanical parts of the engine and try to localize the noise. It could be anywhere in your rotating assembly, valvetrain, etc.

 

[cmxPPL219]

A knock sensor isn't involved if you're hearing it during deceleration. Spark knock can't exist where there is no fuel. Focus on mechanical parts of the engine and try to localize the noise. It could be anywhere in your rotating assembly, valvetrain, etc.

Largely agree, except depending on the speed at which OP begins to decelerate, injectors may still be spraying fuel.

Deceleration Fuel Shut Off/Cut-off (DFSO/DFCO) strategies kick in and shut off the injectors only at a certain vehicle speed at deceleration (say 15mph for example, not sure what Ford has programmed specifically for this car.)

OP, it's worth getting it diagnosed professionally, if you're unsure, because this *could* be many things, and *could* be a major issue.

Also OP, it may be wishful thinking/long shot, but what fuel do you use? Top-tier? Try to run a tank of top-tier gas 91 octane, and see what happens.

 

[SirLoin]

Appreciate the ideas. I've only ever used regular octane gas, as Ford claims there's really no benefit for using premium in the V6, although I know there are many who disagree. I'll try a tank of premium and see if it helps.

In the meantime, I just realized that it's still under the powertrain warranty, which covers "all internal lubricated parts." I might take it over to the dealer to have a look.

I still haven't gotten over the $150 charge for them to tell me the massive oil leak was because I didn't tighten the oil filter enough.

 

[cmxPPL219]

Even if there's no technical benefit from using 91 vs 87 on car designed for 87, that assumes all best case scenarios.

For example, my bro's vehicle was misfiring and running rough, and we changed the spark plugs and coil only a year and half prior. So I asked him, where do you fill your gas, etc., and he revealed that he sometimes goes to budget stations and 87 is what the car requires.

So I told him next tank, go to Shell, or any other top-tier, and run 91. Higher octane fuel is not only higher octane, but they have higher levels of detergents, etc. And depending on who is the source of the fuel, it *can* be higher quality than the same octane at a noname gas station. So, he did that, and halfway through the tank, car started to run fine, and has run fine since. And, you can run 91 every other 2 or 3 tanks if budget allows.

Bad batches of gas, low quality gas - sometimes, it can be as simple as that. If only it were always that simple

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