Bad fuel economy, knocking like crazy in first gear at WOT?

Truck: 2007 TRD Off Road V6 6MT

Mods: 265 65R16 tires instead of 265 60R16. Literally nothing else beyond that.

Problems: Knocks like crazy in first gear from 4,000-5,200RPM at WOT. Getting like 12-14MPG, on premium gasoline, and it gets like 10MPG with regular. If I floor it in second gear, no knocking at all? It's really weird.

I have tried: New spark plugs, both copper and iridium (ran like crap on Copper, runs better on Iridium, running NGK brand plugs). Had a local dealer do a top end fuel cleaner treatment, the canister type that you hook into the fuel rail, and that really helped, but it gradually went back to how it was before. I cleaned the throttle body, changed out the air filter, and even seafoamed it. There's no MIL, and I don't have a laptop for logging, and unless I can get some free software, I'm not really looking at logging anything anyway, it's a damn truck, not a sports car, and I'm not paying $2,000 to a SnapOn truck to get a scan tool that does logging.

Last thing, before anyone screams this in the comments: I only get fuel from a local Shell station. I never ever run discount gas, and I never will.

 

Have you owned it since new or, or did you just buy it? Since you've owned it, did it always do this or start recently? How many miles?

Factory tires should be 245/75/16 or 265/70/16. Yours are smaller than factory.

I can't imagine why you'd need 4000-5000 rpm. Torque peaks at around 3500 rpm.

Fuel shouldn't matter. My 07 was bought new and now has 240,000 miles on it. Runs like new on the cheapest gas I can find. I've used premium some in the past. Fuel mileage never changed, but there was a little more power when towing.

It sounds like you need to take it to a qualified mechanic who can scan it to determine the actual problem instead of throwing parts at it.

 

It's got 286,000 miles. I've had it for a bit over two years, it wasn't doing this when I first got it. I noticed a problem when I was accelerating up a hill and I let the RPM go up while at part throttle, it was completely cutting out.

You're right, it's a 265 75R16 on it, flashback to my Subaru days, I think. o.x

Because I live in a place where it is actually fun to push it in the mountains, and puttering around at 2,000 RPM all day, every day is just asking for carbon buildup problems. It's also really bad for the VVT-i if you never actuate it all the way.

That's irrelevant; my truck has severe power loss and knocks enough on regular that I'm worried about actual engine damage, and I know that if the cylinder walls get damaged, it's new block time, and I don't want to deal with that.

It's $135/hour to take a vehicle to a mechanic around here. It's $135 for diagnosis, and they charge a freaking ton for anything, and that's if I go to the Toyota dealer. There's a Toyota master tech at my local Subaru dealer, and I actually take my truck there, since they know what they're doing, and only charge for actual labor.

Hmmm I should check the VVT-i screens. Then, I'm not sure where to go after that.

Edit: I forgot that I have also cleaned out the MAF sensor, since I'm using a K&N filter, and I've had issues in the past on my WRX and Baja Turbo with MAF sensors getting oil from the K&N filters on them, but that doesn't seem to be the issue here at all.

 

Seems most likely that you need a new fuel pump/filter. Filter is highly saturated, and the pump is aged.

The URD upgrade kit is cheap, and offers a changeable fuel filter.

RockAuto has options. There is also OEM.

 

Mine knocks if I use regular gas so I use premium. I don’t want to hear it, it’s my money to waste. I recall reading here a sentence something like, designed to run on regular gas. If it knocks you can use higher octane.

Im suspecting carbon buildup. Mine gets driven mostly on the weekends and short trips. What helps is if I know I’m going on the freeway, I’ll use Jectron. Towards the end of the drive, hammer the throttle. After that, idle is smoother and mpg gets a little better for a little while.

$54 Liqui Moly Jectron Gasoline Fuel Injection Cleaner- 6pk

https://www.amazon.com/gp/product/B00LPW3E2I?smid=A2O8ZUA9Q2NA0

 

Odd, I’ve heard most have the opposite results. They weren’t Amazon counterfeits? Mine were. They were correctly gapped? Something else I always do is make sure the ground electrode is centered. I did 8 plugs last week, 5 needed to be centered. Then, I don’t know if it’s necessary but I always do it, a reset of sorts. Either disconnect the battery or use my OBD tool and hit erase codes. Then it runs different while it relearns.

This is why I’m thinking you have carbon buildup. My understanding is the carbon sitting on the pistons increases compression higher than what it’s designed to be.

 

I have this problem once per year: when the gas stations are filling up with the summer blend: ping-ping-ping... Proof: Fill up the next time with next higher octane or shoot the whole money clip and fill up with Shell/Mobil/BP/Chevron 93: Problem gone. Next tank after that: 87 octane whatever-brand and let the engine ECU deal with it. It's October now and the problem will go away soon.

It's a game/ conspirancy. Alcohol boost equals: ping. The ECU will deal with it best it can. Push things and fill with "no-name" gas from the local donuts place in town: "knock-knock". ECU diags determine: "cheap a** owner" and throw you under the bus: Engine throws-up and launches a piston.

Who can really blame it? YMMV

 

I really like the replaceable filter, that will be very likely the way I go on this. Thanks.

Should I worry about the screens on the injectors? Or is that just not worth it to check? Man, I really don't like playing with injectors.

I got my spark plugs local at an O'Reillys. I think the copper plugs were Autolite, I literally only bought them because nobody in town had anything else, that was during the worst part of the pandemic, and I swapped them out with NGK's. The truck had NGK's when I bought it. NGK's were pre-gapped, I double checked the gap on them all to be sure.

Carbon buildup makes sense but... Not right after I seafoamed the engine. I also do actually punch it from time to time, and I'm consuming no oil at all. I've got 5 1/3 quarts after 5,000 miles, I run Royal Purple oil.

See, here's the problem, it started in the middle of summer. We've switched over to winter blend, but I live in a state that runs E-10 year round, so unless I run ethanol free premium, there's no way around it. Let me be clear: E-10 premium is $3.30ish a gallon, and E-0 premium is $5.00ish a gallon right now.

 

would be nice to see fuel pressure and fuel trim numbers in this situation

 

When I get a chance, I'll toss my fuel pressure gauge on it, though that requires me to find it, first.