moroza

2000 5VZE with 325k, has been monkeyed-with by previous owners but was running, not great but ok, until we just finished putting it back together after a valve adjustment. Eight valves were too tight, two loose. It took a while to put back together because of delays in sourcing replacement shims. Now it won't idle at all, will run with half throttle or more, but very poorly and with backfires. I'm not familiar with the 3.4, had this one down for too long so I can't remember everything, and am getting conflicting info on where vacuum lines are supposed to go, particularly the one on the very front of the intake manifold facing forward - most photos show there being a blank casting nub where mine has a medium-sized vacuum port. Between that and the previous owner's handiwork - loose fasteners everywhere, garbage bag over the vacuum port on the intake silencer, and more - I suspect something's not hooked up right and causing a massive intake leak, but hard as I look, I can't find what. I have neither a code reader nor a smoke machine, and the trick of jumping TE1 and E1 in the diagnostic port doesn't work.

So while I look for a smoke machine... can anyone tell me what the deal is with this front vacuum port, and where it's supposed to go?

75w90mantraN

Here are a couple old shots of mine....the top of the intake manifold has two ports that are capped off, but unfortunately, are obstructed from view.

You could have an auto parts store pull the codes if your engine light is on.

moroza

Yup, you've got the port I was wondering about, connected to a vacuum hose with a damper (?) that ends up at either the charcoal canister or some vacuum switching manifold behind the battery. What are the two that are capped off and not visible? I've got two smaller caps on top of the throttle body - visible in your photo - and one on the larger intake silencer, but that's it I think.

It doesn't drive enough to make it to a parts store. And anyway it had codes before and I'd expect any new ones to be the bleeding obvious: a lot of misfires.

Jomoka

Perhaps you have some of the driver's side spark plug wires mixed up?

I replaced the valve cover gaskets a couple of months ago, and noticed when I was putting it back together that the spark plug wire numbering scheme is NOT intuitive at all. I think perhaps it makes more sense when a V6 is installed sideways in a FWD car.

moroza

Yes, it's confusing, but I traced the high-voltage plug wires twice, according to two references, and they were correct. The lengths of the ignition coil 12V wires are such that it's about impossible to cross them, as well. But I don't think ignition is the problem; I've crossed plug wires on 4-bangers before and they ran poorly, but they did run. This one needs ~50% throttle to even stay turning over, and it does so with a lot of shaking and banging. It's not running on fewer cylinders to my ears; there's a systematic problem like an intake leak.

Just came back from removing, carefully inspecting, and reassembling the intake manifold and driver's side valvecover. Doublechecked cam timing including the driver's side exhaust cam... timing is spot on, problem persists. I'm completely stumped.

75w90mantraN

See if you can borrow a friends scan tool. Or invest in one. It makes the misfire hunt much easier.

Could check injectors, crank/cam sensors, plugs (if not replaced yet), MAF, PCV valve...

Can't remember if you said, but how's the smoke test coming along?

moroza

Borrowed a scan tool, checked manifold vacuum, and checked compression. The latter got interesting. I checked the compression in April right before this truck was bought, using the same tester as just now. All six measured around 150-160. Now there's this:

Passenger-side cylinders all tested the same: first stroke ~120psi, second ~140, third ~150, and so on with diminishing gains until they all hit about 160 after perhaps 6-8 pumps. Weak but ok, and the pattern of buildup is normal in my experience.

Driver-side cylinders all tested the same: first stroke usually 15psi, occasionally 60, and nothing on subsequent strokes. I've never seen this before, where there's no further compression on further compression strokes. Adding oil to the cylinders didn't make a difference.

The headgaskets were replaced by the previous owner. Some other things that the PO worked on were finger-loose, so I suspect the head bolts weren't torqued correctly. Why they suddenly let loose on only one cylinder bank remains a mystery. At this time I have both driver's side camshafts removed. I need to go out and get a 12-point 1/2"-drive socket to check the head bolts; that's where I'm at now. Thoughts? Does the 5VZ have the same problem as the 7M, where the factory lists wrong torque specs?

75w90mantraN

Torque specs should be reasonably reliable off any legit Toyota forum, including here, and on the net. Haynes manual is mostly correct.

With that much mileage and past ownership, I guess anything is possible for what's causing your issues. Seems like many things are amiss with what you're finding. I would think if no codes, it could be things like loose crank bolt, broken teeth, or whatever component not tied in with electrical monitoring and code setting, but with the turning of the crankshaft/camshafts.

What basic maintenance have you crossed off the to do list?

That's quite a find with loose head bolts likely messing up your compression readings. Makes me think whatever parts were touched by the previous owners may not have been reinstalled correctly. So perhaps getting some specifics from the most recent seller could point you in a possible direction.

vital22re

iTrader: (2)

It sounds like you've possibly adjusted the valves too tightly and they are hanging open.

Malcolm99

^^This sounds likely, and I find it surprising that the only imperial bolt on the 5vz-fe is a head bolt, everything is metric and you don't want to be using anything else IMO. At this point, not knowing or trusting the PO's handywork, I would consider a known good set of factory heads. I would also completely eliminate any possibility of any intake leak as the vehicle just won't run properly.