"Vehicle needs valve clearance adjustment/Throttle and fuel system cleaning"

wouldn't the OP's truck be throwing a CEL if the valves were out of spec? i'm thinking that anything out of tolerance would cause a "bad" fuel air mixture and throw an emmisions code?

 

You guys are all wrong on the adjustment part.
There is a Toyota special tool that allows you to push the valve cup down to remove and replace the shim.

BUT -
DO NOT EVER ADJUST THEM! They are ONLY adjusted if you are rebuilding the heads. EVEN THEN, most of the time they are very close and only a few need replacing. I've done well over 200 head jobs on these things, and over 100 engine jobs.

 

The valve clearance check is not a "dealer recommendation". It is in the service schedule. It must be in there for a reason.

From what I read on another forum thread here, it is not the shims or buckets that wear necessarily. It's the value seats and valves that themselves wear over time. The wear does not cause the valve train to become noisier as seems to be the common thinking here but in fact quieter because the clear decreases. Decreased clearances on the exhaust valve (which wear quicker than intake) can lead to valves and seats burning. This is the danger.

I am no Toyota mechanic for certain but this is my understanding for studying it the best I can. So it seems to me at some point in the engine's life, adjustment will be required. I wonder when folks have the vehicles serviced how many techs are actually checking the clearances as they are suppose to? I never trust them to do what they are actually supposed to.

The other thread I referred to above is this one: http://www.tacomaworld.com/forum/2nd-gen-tacomas/83310-valve-adjustment-2.html

As far as the nissan's VQ40, there is no mention of valve clearance checks in the maintenance manual. Maybe your right on it having the same shim under bucket design but I can find that. My Isuzu is a 3.2L SOHC, 24-valve V6 and it has automatic valve lash adjusters. So did the 3.5L DOHC Isuzu engine. I'll have to dig some more on the VQ40DE. Maybe someone can point me to a manual, diagram or other trusted source?

Man I love reading tacomaworld!

 

Yeah...I see that now. So, while the consequences can be as bad as those deriving from ignoring service to a belt-driven cam system, I do start to wonder....

This engine (I assume with this valve train design) has been sold in Tacoma's for 5 years; the entire Toyota line of bigger vehicles (including Lexus') for even longer.

How many do we think have had valves clearance's checked in their service life, much less adjusted? Putting it in perspective: at 60K miles warranty is expired so most people, the majority of whom never even read the recommended service manual, have stopped going to the 'stealership' for service where they will 'remind' you of this item.

Is there a raging storm of controversy among 80K mile V6 Camry owners with burned valves? How many 200K mile owners have ever done this? Has anyone heard of ANY serious engine damage from burned valves on this engine. If so: how many miles and what was the service history, if known?

Just trying to guage the risk of ignoring this and going about my business.


Do you know if the VQ40 is similar valve train to the VQ30? I have a 2k1 Maxima service manual with that engine...and the car!

I also (had) a 94 Rodeo with the 3.2L V6...what a beast! The lifters were intermittently noisy from varnish build-up on the oiling ports, but the engine was great otherwise. I finally had to get rid of it because of mounting little things going bad: electricals like starter, headlight and blinker switch, power windows, power steering pump. All going in quick succession at 13 years and 140K; I lost confidence taking it on long trips. That car and an Acura I had told me that the problem with cars is rarely the drive-train nowadays: it's the accessories that make me give up and trade!

 

Well I AM a former MASTER TOYOTA TECHNICIAN so I DO know what to do.

 

Here's the deal. If the valve seats wear, the clearance between the cam lobe and valve bucket decreases. This wear is minimal compared to the wear on the cam and buckets.
Think about it. Which has more friction? (On a properly running engine) valves don't slam shut. The cam rotates constantly and rub on the buckets. As the buckets wear, the clearance increases and the valves lo longer close as slow, they close earlier and slam shut. Noisy, tap, tap.
I have disassembled worn, noisy engines. The buckets are gouged where the cam rides on them.
I'm no toyota mechanic, just a regular mechanic. I work on engines as small as lawn equipment and as large as ship diesels. I'm not here to flame, just educate. There's a lot of speculation out there. My info is not.

 

Damn, learn something everyday. I assumed that the 4.0 had hydraulic valve lifters.

Is that why the 4.0 owners are always bitching about the ticking noise. Don't ever plan to get one anyway since my first gen will last me for a long time.

 

I checked my service manual on my 2001 Maxima with a VQ30 engine. It has what I take to be 'shim on bucket' design. At least, the lifter (which I assume is a 'bucket lifter') is under the shim with the cam lobe acting directly on the shim. Don't know if the VQ40 is same but Nissan has kept a lot of similarity in the internals of the VQ ever since inception so they may have.

At any rate: this engine now has 105000 Mobil 1 miles at 10K intervals and valves are as quiet as day I bought it and no chain noise either. Couldn't be more pleased...I only hope the rest of the accessories hold up 1/2 as well (haven't so far: have needed alternator and O2 sensors at considerable expense).

 

I wouldnt do shit unless you had a problem...bottom line....The engines are noisey...IT IS A TRUCK....not a ROLLS ROYCE

 

I have religiously shifted before or at 2k for 38k miles...what are the negative effects from doing so?

 

The adjustment requires alot of work. They are not hydraulic self adjusters and yes it requires shims to set the valves.

I don't understand why they don't make the adjusters like the other vehicles on the road. I have done valve adjustments on everything from old Chevy trucks to new(last production year) CAT ACERT C15's and all of them use the same system of rockers with adjusters that have a jam nut and set screw to set the valve lash. Why the heck did Toyota over complicate themselves.

 

Lol... if this scared you reconsider that Frontier now hahahahahahhaaha. Read up on the G35 oil starvation issues on the VQ35DE (same motor the frontiers run just a different tune). Also if you think the Tacoma's motor is noisy wait until you fire up that VQ engine, or worse yet the 3000GT DOHC TT motors... LOL. It's just a bit of normal mechanical noise, nothing to worry about.

The chances of this engine going out of spec for valve adjustment before 250k is laughably small. As Paul said, he was a master tech for Toyota and almost never saw it. Even when I put almost 30k per YEAR on my truck, 250k "possible unlikely maintenance" isn't even on my mind at this point. The truck will be long paid off and if need to perform some extensive maintenance like that (presuming the rest of the truck holds up like the auto transmission, rear diff, front diff, and the other 200 systems on it) then I'll call that an excellent run that beats most other manufactures by far.

 

OP- The bucket design is a pain in the neck if you don't know what you are doing. I had some idiots do some head work and totally messed mine up. Had to take them to another guy. Not a head to experiment with. I really wouldnt worry about a valve adjustment unless your engine is sounding like a tractor and clean your fuel system yourself like eveyone else said. Save some coin. lol

 

The valve train in piston engines have always been a performance bottleneck, inertia in valve train components limits engine speed/performance, by eliminating rocker arms you remove a major 'inertia' issue..
Many Manufacturers (& racers) use the shim & bucket design (Volkswagen/Audi/Porsche), & all designs that I have seen permit the use of a tool that wedges under the cam & depresses the bucket/valve enough so that shims may be replaced (ie-other then valve cover removal, no engine dis-assembly is necessary).
IMO, shim & bucket engines are more efficient then rocker-arm type engines due to the reduction in engine mechanical inertia ..

 

I don't think anyone's disputing the value of the shim/bucket lifter approach (even though in a truck engine that red-lines at 5500RPM and perfectly comfortable operating 90% of the time below 2000RPM I have to ask "WTF??")

What you describe, a shim over bucket, is true (my Maxima VQ30 has this design). But this engine is a 'bucket over shim', you HAVE to remove the lifter to get to the shim which looks to be nestled in the 'bucket' against the valve stem cap(**), removing the lifters means removing all 4 cams, at great expense! THAT is where the griping comes from.

What I've read says the advantage of bucket on shim is the shim is well contained and can't get 'spat out', apparently a common problem at high RPM operation with SonB designs; to which my response is a double "WTF??"

AT LEAST this seems to be a VERY durable design and in spite of Toyota's recommendation to check clearance it's just not likely to be a problem in the service life of the truck.

**looking at service manual again...it may not really have a shim...it kinda reads like the entire lifter is chosen for desired thickness to obtain required lash. Either way, cam has to come out.

 

You most likely need the fignut on the malibar adjusted as well as the catastrophic converter. The dealer is feeding you a load of beans. My mother in law went in for an oil change and they told her she needed brakes and she called me. They never took the wheels off of the vehicle. They must have xray vision. If it is running fine leave it alone and do the regular maintenance and find a good Toyota mechanic that does not work at the dealer.

 

Are you sure the bucket is over the shim? I havn't seen that design before. I havn't worked in a Toyota dealership for 10 years, so I could be missing somthing. BUT - I'ver NEVER seen the bucket over the shim.

AND- Like I said before, JUST LEAVE THE THING ALONE~ DO NOT ADJUST THEM> Many techs will just make them worse.
Paul

 

I've never been under the valve cover of my V6...and hope I never have to...so I can only relate what I see in the V6 service manual. To tell you truth, it may not even have a shim exactly since the words describe replacing the entire lifter with one of the correct thickness to obtain the desired lash.

And I totally agree that unless you have extreme high confidence in the mechanic, don't let them touch this. Taking 4 cams out and getting them all back in perfectly: it just scares the willies out of me thinking about the ham-fisted wack jobs I've been seen doing most of the work in dealers' shops.

 

Inertia happens at all engine speeds. If some engine parts that produce inertia can be removed, then the 'work' or energy required to overcome that inertia effect can be put to better use, like moving the vehicle. This is called 'efficiency', & even tho you think it doesn't matter, it does, as every little bit helps...

hope this helps you understand why it done this way...