kdogy313

truck using excessive fuel and rattle\knocks around 2800 rpm. brand new o2 sensor any ideas?

justin_4runner

how many miles on motor? last tune up? fuel filter? timing belt? just somethings that come to mind of hand..

85toyman

iTrader: (2)

Time for a rebuild. Oil consumption not a good sign unless you have it dripping of the block from gasket leaks. Rattle and knocks. Sounds like main bearing in the bottom end.

kdogy313

Top end rebuilt totally about 7,000 miles ago. new water pump, timing belt and idler pully. Don't think it is a main bearing as it only does it on startup and between 3500 and 4000 rpm. Sounds like a lean condition which is causing preignition and louder valves. Have a whistle at higher rpm which I think is a vacum leak causing afr to change outside of what the computer can correct. Big issue is fuel consumption. Getting about 13mpg. Have not changed fuel filter. Will check for vacum leak 2morro. Thanks for your help

85toyman

iTrader: (2)

Definetly low on the mileage side of things. I would bet you should be in the 16-18 range, with a slush box. If you have any kind of intake mods, then a whistling sounds in the higher RPM range is not out of the question. Mine did that and I didn't like it, so I removed the aftermarket intake and put a K an N filter in with the silencer delete mod. Sounds much better, less restrictive than stock. As for the knock on start up, I have had that in the past and it ended up being a bad bearing on the bottom end. Did you do anything with the bottom end when the top end was rebuilt? The only reason I say this as the bearing on the bottom end has wear and as the truck sits the lubrication can draw away and lack of it during initial start up can cause a knocking sound, then as you reach higher RPM's the load on the crank is higher causing the sound to come back. I just would not rule that out.

However a video of the sound for us to listen to will stop speculation as a knock to some one might sound completly different to another who may have heard that same sound before and know exactly what it is your having problems with.

sam333

Knocking and pinging ( detonation ) wont just show up at start up( mostly when hot and under load). Piston slap( worn pistons /rings/ cylinders) is most common on a cold engine.

85toyman

iTrader: (2)

X2, I am definetly thinking a bottom end problem.

kdogy313

nothing was done to the lower end becase i had great compression and no noise b4 the head gasket blew. checked vacum today and it was great. 24 at idle and came right back down after acceleration to about 24. Certainly not ruling out bottom end totally. wondering about egr valve now too. shop teacher at school thought it sounded like predetonation. It is hard to hear unless you are in gear driving. It is loudest when you have been running somewhat hard in third gear at 3500-4000 rpm and right as you back off the throttle a little it rattles/pings/knocks. LOL! sounds more top end vavle rattle than anything else. worked on a 22re the other day with real similar noise and by adjusting the valves to specs it got a lot better almost gone. Valves ar not so easy on a 3vze and they were set to factory specs about 7000 miles ago. Thanks for the advice.

modlite

I had the same thing, knocked at start up, and around 2800 rpm. It was the rod bearings in the bottom end.