jht3

so my 3.0L V6, 3vze, has been running poorly with a noticable drop in power and a misfire. it also failed emissions for Hydro Carbons, but JUST barely. i really haven't driven this truck in a year. today i dug in to figure out WTF is going on.

started by running the engine and selectively pulling each plug wire off at a time. cylinder 6 is the problem. when i pulled that wire off there was no change like there was on the other 5. i can see a nice spark arcing from the #6 boot to motor, so it's not a spark problem.

with the #6 spark plug removed it is a bit sooty looking as compared to the #2 and #4 that are more white sooty colored. i think i can also smell raw fuel on the #6 plug so i don't think fuel delivery is a problem.

so i hooked up my compression gauge and with the ignitor disconnected and WOT i saw 185psi on #2 and #4, but only 60psi on #6. did it three more time with the same result. bingo.

i also noticed that my distributor is damn near maxed out to set proper timing, so i pulled the upper timing cover off to take a look. at TDC, it appears that the timing belt is one tooth too far clockwise on both cams. with the cams lined up, the crank was indicating over 15* BTDC, so that's a problem. since i've never had this engine open this far, here are some pics to look at

TDC:


Pass cam:


Drivers cam:


Both:



where should i go from here?

pull the timing belt off the cams and rotate them both back a tooth? could it be this keeping a valve open leading to low compression? do i only have to remove the tensioner in order to get enough slack for this? i assume i can just slip the belt off both cams, rotate them back a tooth, and slip it back on?

pull a valve cover to check valve clearance? maybe #6 is super tight?

leakdown test? burnt valve? bad piston?

i consider myself pretty handy, but this is all a first for me. i'm also doing this all so far in the parking garage where i live; not the ideal location. i've owned this truck since '99 when it had 34k and it's now at 158k. i should get rid of it since i have 3 other newer vehicles, but if i can get it running again easily it's worth it to me to keep it.

oldblue

i don't like or trust using a balancer marking to check valve timing. i would go ahead and tear the rest of it down and make sure the crank cog pulley is lined up with its mark on the front cover and then check your cam pullies. even if the timing is off, this wouldn't cause one cylinder to have low compression. it is possible, however, that you have more than one problem. as for the #6 cylinder, i would say most likely cause would be a valve issue, possibly a head gasket issue. if you have a vacuum gauge, hook it up to a manifold vacuum port ( the line off the brake booster works good) and check the manifold vacuum at idle. if its a valve issue, the needle with fluctuate rapidly somewhere between 17ish-20ish hg.

jht3

i do have a vacuum gauge. the booster line seems a bit big if my memory is correct, i don't think it will hook up nicely to my gauge but i'll give it a shot.

i do believe i have more than one issue going on. i'm not blowing any smoke out the exhaust, and my emissions test was VERY clean for both CO and NO. my local dealer is the last one to go in there a few years ago when a timing pulley went bad, and years before before that when the head gasket went.

oldblue

the closer you get to the source of manifold vacuum (the intake manifold itself) the more accurate your readings will be. often time though, its easier to just yank the booster line off and shove a vacuum gauge on there for quick reference. i would start with this test, as it's very easy and very quick.

ToyoTech559

i would tear it down to reset timing. im sure once remove some more stuff, you might find something that caused it to jump. maybe time to just replace the belt

TNRabbit

Cam gears are definitely off.

As stated, probably a valve issue on the #6 cylinder.

jht3

yea, that's part of the plan. belt isn't that old yet. but what's the recommended order of operations since i also have a suspected burnt valve? redo the timing belt, put it all back together, and THEN recheck compression and/or leakdown?

i don't currently have the tools to pull the crank wheel off, or wrench to hold the cam gears so that is something i'll have to address.

ToyoTech559

hmm, since we know timing is off. i would start with correct what we know than go from there

oldblue

you could just re-set the timing, and without putting anything back on fire it up and see how it runs (poorly i assume with the low compression on #6). it won't hurt anything to let it run for a minute or so with nothing hooked up. it looks like you have a hydraulic tensioner, so you will need to put the fan bracket and tensioner assembly back on to hold tension on the belt though.

jht3

ok, so i've read up on this job (timing belt) and do i really need to pull the crank nut off? since i have an auto tranny, is there a trick to re-torqueing it? in manual cars i can put it in high gear and have someone stand on the brakes while i torque it/put it on really ˟˟˟˟˟ tight.

also, short of having the SST, what can be substituted to get the cam gears off? just normal wrenches? the FSM talks about taking tension off the spring w/ the special tools

and finally, since i have a hydraulic tensioner, i assume i need a press to reset it before installation? that's what my FSM says.


anyways, to pass emissions my plan is to button it all back up and disconnect the #6 fuel injector. this SHOULD lower my HC count w/o throwing a CEL? thoughts? after getting legal, i'll then tear it all back down, fix the timing, and replace the possibly burnt valve. need to get it legal to avoid my HOA...grrr

oldblue

air tools are the best route. the crank pulley has to come off to check the crank sproket timing. you can buy a generic cam pulley holder and use that to remove the cam pulley bolts. if you're gonna be doing work yourself at home, might as well invest in a decent air compressor, air tools, and mechanic tools. its what men do.

ToyoTech559

for the crank pulley. i use a chain wrench to hold pulley and a long breaker bar to remove the nut. after that, i use a trick. a small hammer and i tap the top of the pulley and pull on the under side of the pulley with my hand. most of the time it will start to slide out. if no than a crank puller will be needed. once crank pulley is off, reset crank timing to ZERO. never done a 3VZE t belt that had a hydraulic tensioner, without looking at it. i would remove the idler pulley inbetween the two cam gears, take belt off, that will let then tension fully release, now you can remove the tensioner and compress it according to book on a bench. nows a good time to chain water pump if within budget, if not. reset cam timing to zero/marked lines by using a 14mm or 17mm on the cam bolt. now you should be ready to reinstall everything
if the belt is still fairly new, use the marks that are still on it. if not make new ones but make sure its correct.

no need for air tools for the budget repair. this job isnt too hard but i have done a million t belts but it wasnt till last year that i did the 1st 3VZE t belt lol and it was on mine

jht3

well didn't get my truck through emissions today. got hung up replacing my muffler. couple years ago some d-bag stole the cat, so i welded in a universal cat. well that made swapping a muffler on a little more difficult than just unbolting it. argh.

thanks for the tip on the chain wrench.

as for the tensioner, a friend said that on many cars he's worked on he is able to pin the tensioner in its compressed state while still installed on the car. don't know if this is possible on the 3vze. avoids the need for a press/vice/etc though.

ToyoTech559

yea you can. its another trick but usually need to use a pry bar on the belt and compress the very little bit it needs to get the pin in. i never done it on the 3VZE but i have on similar toyota v6 tho.

as far as leaving an injector off before smog. the noticeable misfire and cel will show soon

Hellvision251

Did your problem every get resolved. I have the same problem with my number 3 cylinder, Only 30 psi comp. I believe one of my intake valves is stuck open, but i have yet to confirm. Any input on what was wrong with your rig would be awesome thanks!

Fj40highroller

Did you ever figure out the issue?

Thanks