Simple4012

Well....here we go. I will give all the details i can and answer what i can before it is asked.

05 scion tc. Original owner. 322,000 miles (yes, 322,000). No mods at all. Replaced all 4 coil packs and plugs about 6 months ago. Old ones were arcing.

Symptoms....severe hesitation with anything more than 20% throttle. Audible clack-clack from under hood that IS NOT rpm dependent. Meaning at an idle it is not heard, acceleration it is heard, cruising it is not heard. Very weird. Gas mileage has not been affected at all. I drive with my cruise control on and it drives normal, until a hill comes and it hesitates.

Check engine lights?? Yup. Misfire 1-2-3, cylinder lean, cat converter code.

Starts up fine. Idles perfect. Cruises perfect. Loud clack clack from under hood.

It is not a spun bearing. The oil is perfect and i have put about 500 miles on it since it started.

My guesses are....
1 valves are so far out of spec and need to be adjusted.
2..bad camshaft timing gear
3..stretched chain/faulty tensioner
4..bent valve(highly highly unlikely. I never ever beat on it and havent missed any gears)

Tommorow afternoon i will be taking off the valve cover and checking the clearances...any guesses before i proceed??

Anything is much appreciated!

sciontc_mich

yes you're on the right line of thinking. The maintenance guide says if there is noise, to check and adjust the valve clearances. Yep, just found it, under 120k, it says to "inspect the valve clearances". You made it almost triple the mileage before it made noise, not bad. So start there, that's probably the issue.

Simple4012

Yea prob im just not looking foward to taking out the cams and measuring and yada yada yada lol... Jyst wanna make sure i explore all the avenues.

Thanks for the comments!

MrBurrito

iTrader: (2)

i kind of want to know how you put on all that mileage

Simple4012

Yeaa i dont blame ya lol

Simple4012

After checking the clearances im very confident it is the tensioner/chain. I think the tensioner broke and the belt has slack so it has either skipped a tooth or is so loose its doing whatever it wants. Should be fun/cheap to replace. Boooooooooo..

Btw...car still drives and iv put 1000 miles on it since this started...stupid? Sure. But how cool is that? Lol

Supra12big

iTrader: (1)

What kinda things have u had to replace with all those miles??? Super props to ya! Let me guess it still drives like day one huh? Btw are u hard on the car ever?

Murphys_Law

iTrader: (3)

props on the miles

Simple4012

Thanks guys.

No the car doesnt drive like it did on day 1 but it has never let me down. And no i never beat on it.

Replaced a broken clutch at 252k. Few sets of front hub bearings also

Simple4012

Iv decided it would be smartest for me to get a used head and do that as well as the chain/tensioner...i will let you guys know how it goes

egobuster1

yeah i was gonna say if your gonna go through pulling the motor or how ever you plan on getting into the chain and tensior you might wanna get some work done to the motor if your planning on keeping the car

Simple4012

Yea well labor wise its about the same so it makes sense to do it this way. My bottom end is fine so hopefully this will take care of my issues.