141bpm

Hi everyone,
I'm a seasoned mechanic and have just picked up an awesome 1992 Mini-camper with Toyota pickup chassis. It has the 3.0L 3VZE motor with 73,000mi on the clock. I'm new to this motor and I'm still learning its quirks. This thing has been very well cared for overall, all maintenance records. Including head gasket recall work done by Toyota years ago. It drives great, but has a rough or stumbling idle that is driving me nuts. All the vitals look good, replaced the plugs that looked worn, but all showed a healthy off white, normal deposits for old plugs. Found a small vacuum leak or two and that helped a little bit. New O2 sensor, seemed to help quite a bit with smoothing out the idle, but it's still a bit shaky. Also, the best idle vacuum I can get out of it is 15-16, and there is a strange "spitting" sound coming out of the intake (see link of video). When I first bought it, I assumed the noise was a idler pulley getting noisy, because it sounds very similar. And this is a motorhome, so it's sits more than a DD.

So my questions are: 1)WTH is that noise in the intake? Is that normal for these things? Sounds like a leak, or partially clogged idle circuit? But I can't confirm either of those... 2) Is that vacuum (avg 15-16in/hg,fairly steady) normal for an otherwise low mile and seemingly healthy motor? 3) If I pull the crankcase breather hose on the drivers side near the throttle body, that connects from the main intake hose to valve cover, it will stall. That tells me that this thing is very reliant on accurate crankcase pressure for (PCV valve?) for a proper tune?

Other info: Vacuum otherwise seems to respond normally when snapping throttle, passed recent emission test with no problems, when running codes I get the constant blink that means all is well right? Motor is bone stock and completely intact. There is a slight exhaust leak at the passenger side manifold making a slight tick, will get to that later. Probably when I do the upcoming valve adjust and timing belt replacement. But I don't think the exhaust leak is enough to cause emission regulation problems. New cap and rotor, plugs, o2 sensor. Timing at 10degrees, premium fuel and some sea foam in the tank. PO furnished all service records, and seemed to very on top maintenance.

Starts and drives great, but the rough idle shake at stop lights is making me nuts. Also, being a motorhome, I want to make sure it's in top condition before a trip.

And the video...

141bpm

No ideas?

ycats

I have the same problem with my '93 3vze, but without the intake noise. I've only had it a couple of months, and ironically, the motor runs great and has been well maintained by the PO. It just has that "shake". New NGK V plugs, cap and rotor. Plug wires might be a little old. I thought it might be the motor mounts, but I ruled that out by jacking it up a little by the oil pan to get the weight off of the mounts. Didn't change anything.

141bpm

ycats - interesting. Sounds very similar. My next thought for mine was that the EGR valve may not be seating properly allowing exhaust gas to recirculate at idle, which it shouldn't be. Need to get the gaskets first at least before I take it off to test valve seat. If that doesn't make a change, I'm going to pull the intake when I do a timing belt, valve cover gasket, and PCV valve replacement. Maybe I'll find a vacuum leak under the upper intake plenum. OR, it could also be a PCV valve issue....
Just drove it from Vegas to Phoenix and back without any problems or change. Ran fine, and 16.5mpg for a 21 Winnebago ain't bad. But this idle is still making me crazy. Will post any updates...

ycats

That would be great if you could post updates! I'm an amateur mechanic at best, but I also am going to tackle the valve cover gaskets pretty soon. I've got everything that I need to do it, except time.

141bpm

I'm really surprised that no one has listened/watched that video and not at least have more questions. Is that intake noise normal?
I'm still trying to get the time to get the intake off and inspected, etc. Hopefully this week!

saladbarkido

I have the same problem, BPM. Low VAC, Rough Idle, Intake noise.

On a cold morning start, the engine idles about 1200 rpm with about 14 inHg of vacuum. About a minute later it warms up but instead of a steady drop in idle it kind of "switches" to a lower idle, to about 1000 rpm, which is something I noticed did not happen before. Once it is fully warmed up, it idles about 800 rpm with 16 inHg of vacuum. It is rough idle too. I'll try to post a vid.

Another thing I noticed was that I had to SCREW IN the idle valve on the throttle body. I've seen pictured of other 3vzes' throttle bodies that have the idle valve screw out almost flush with the surface of the hole. This leaves me to believe its a Vacuum leak somewhere.

saladbarkido

Also I forgot to mention that when I start the truck about 30 minutes after having been driving for a while the Park idle drops to around 600 rpm and a lower VAC of about 14 inHg.

141bpm

So I have an update, but still no resolution:
Tonight I went after my current suspect, the throttle body. I thought maybe the IAC (idle air circuit) was clogged and not metering air properly. Because it kind of sounds like that could have been the source of the "noise". It wouldn't make sense really for it to affect the vacuum or idle smoothness, but I figured it was a starting place. Plus, with the throttle body off, I could correctly calibrate the TPS and learn more about how this 3VZE works. Took the throttle body off, cleaned it thoroughly and inspected. Not that dirty, and looked pretty clean except for the inside of the cold idle valve. There was some heavy, sticky, dark junk in there probably old solidified oil vapor coming in through the valve. Probably not unusual for the age, etc. DO NOT take apart the valve without somehow taking note of the setting of the valve seat. This controls cold engine idle speed and is adjustable, but I have not found any reference for setting it. And really can only be adjusted with the throttle body off, which make the adjustment a process of trial and error. There is a plate near the TPS with 4 philips screws, behind that is a valve that works off of engine coolant flow to control warm up idle. Works much like a coolant thermostat, but controls idle air volume. ANYWAY, cleaned, inspected, and calibrated throttle body and TPS, new gasket. NO change.
On to the next suspect, the EGR valve. My thought here was that if the EGR was not sealing in the closed position (got some gunk in it), it would leak exhaust gasses into intake at idle, causing a rough idle. The EGR should only pass exhaust when the ECM says so. Usually at cruising speeds, not idle, WOT, or under considerable load. Took the EGR out and blocked all connections for test. You can do several very effective tests of the EGR very easily without removal, but the leak I described requires taking it out to bench test. Seemed like it may be leaking more than spec. This is where I thought I had a breakthrough. Started engine with EGR removed and capped off lines. Vacuum went up to 19 and so did idle speed, which was a good sign. Backed the idle screw out to bring idle back in line and the vacuum stayed around 19. Also, the closing of the idle screw to bring the idle back down seem to quiet the intake noise a bit. Made sense at first, if someone opened that screw up to compensate for rough/low idle it may have opened the screw too far introducing that noise?? At first I thought BINGO... but no dice. What had happened was that in the order I had done the work, I forgot to reconnect the TPS harness. This somehow brought up my vacuum and idle speed. Somehow, the ECM, when it no longer sees the TPS, it makes some kind of change that gave me the higher vacuum. Had nothing to do with the EGR it seems. Now I need EGR gaskets...
SO... this is where I called it a night. But, with the TPS removed it does some interesting things, the vacuum goes from 16-19 very certainly and idle speed goes up maybe 200rpm. Never seen this engine pull that kind of vacuum at idle. Now, what is the ECM doing to make that change??? Raising/lowering fuel mixture? Changing timing?
Removing system components (or disconnecting the TPS) can send the ECM into "open loop", which means it gives up reading the sensors and just throws default values at everything to get you home. The sensors are what the ECM uses to fine tune the engine as you drive.
With the TPS removed (which I tested according to the service manual, and then some), the ECM goes into open loop. And it seemingly runs better. Is this because I have another bad sensor and in closed loop it's throwing everything off? Making it run better on default open loop settings??? Coolant temp sensor???
Stay Tuned......

vasinvictor

iTrader: (3)

Sorry I've never read your thread before now. That noise in your intake is absolutely your PAIR valve. It goes from the rear passenger side of the motor to your intake via a large diameter hose. It's right beside the EGR valve. At a certain RPM it will gurgle, but that RPM should be above idle, like 1,200rpm and up. It's allowing exhaust has to be piped back into your intake and that's why you're getting a rough idle. It's some kind of emmissions function and after mine broke, I removed it with no ill effect long term. I used to know more about it, but I haven't owned a 3vz for a few years now and I have a bad memory :-)

vasinvictor

iTrader: (3)

Oh, and there's a good chance your exhaust leak is coming from the PAIR valve too. There's a vacuum fitting on the PAIR valve that you can pull and plug with a golf tee or whatever. See if that makes the noise go away and also cleans up your idle. Then feel around the tube that connects to the exhaust manifold and see if that is the source of your exhaust leak.

141bpm

Outstanding info! I read up on the PAIR valve, but passed over it. Thanks Drew, I'm on it....

scope103

It doesn't sound like the PAIR valve to me, but you don't need to take my word for it. Just put your finger on the metal cover; if you can feel it vibrating in time with your noise, look further.

PAIR issues are often described as "buzzing" on the passenger side. The thin metal cover of the PAIR is held on with four 5mm screws, and after 20 years they can back out allowing the cover to "buzz." Tighten (or replace if they're gone) the four screws to fix it.

vasinvictor

iTrader: (3)

I could be mistaken. Scope has given me doubts about my statements. Check out that egr real good too. Pull vacuum line off of it and plug I and see if that changes anything

141bpm

Another update with no resolution. Still no answer for intake noise, low vacuum and rough idle.
Checked EGR inside and out. Ran engine removed from engine, and installed. No change. Even compared the valve seal to a new unit.
TPS was measured tested. Reinstalled with settings from manual with the TB off the intake to get it just right. No change.
Volume Air flow meter measures at 300ohm per bench test, spec is 200-600ohm. Checks good.
NO troubles codes.
Gave a good visual inspection to the PAIR valve, seems to be intact. Nothing loose or leaking, no rattles at the reed valve cover. Screws are secure, and no leaks in hoses. No engine change while pinching related hoses.

Still runs and drives great, except the idle. Idle speed is consistent. Vacuum is stable, but low at a MAX of 16.

Previously, I noted that if I remove the TPS connector, the idle goes up, vacuum goes up. Then I can bring the idle back down with the air screw and it maintains near 19 vac. This is because the ECM kicks timing waaay up with the TPS unplugged. Replace connector, idle goes back to "normal".
I also noticed in this process, that with the jumper in the DIAG port, the timing is set to 10 deg on the nose. Remove the jumper and the timing now ECM controlled, drops to around 8.5 deg at idle. Not sure if this means anything, but it's an observation.

Did they ever make a device for ODB I that can read active info from the ECM/sensors??

Anyway, I can't find a fault anywhere on this engine so far. But it continues to idle like crap and drive me nuts. And to further describe the idle, it's not so bad that it's barely running, but it's shaky enough that you can feel it when slowly coming to a stop. You can feel the shake of the idle in the vehicle through the drive train just as you come to a slow stop.

skypilot

iTrader: (1)

here's my 2cents. Go get a gallon of Lucas brand injector cleaner and start really using at every fill up. for some reason these engines are picky about spark plugs. Get the factory brand and heat range for that vehicle. Block the EGR valve with an aluminum plate from a beer can to eliminate that from the intake. If all else fails, pull the top intake and pull all 6 injectors and send them to witchhunter. Get six new injector bowls and o-rings. I bet one of the bowls is broken and leaking air around the VAFM. And of course the pass side is a scooch to do.

vasinvictor

iTrader: (3)

Have you done a compression test?

Possible valves have stretched and you need yours valves adjusted. It's actually a 60k maintenance to check/adjust valves. The use a shim over bucket style.

vasinvictor

iTrader: (3)

On that intake noise, pull the large diameter hoses off the air breather box. The ones the cross horizontally across the front of the motor. See if 1 of the hoses has that sound coming out of it. Try putting a longer hose on the pair valve or egr vacuum nipple and manually activating it with your mouth and see if engine speed changes.

Just babbling now but a partially clogged cat would show a lower vacuum reading.

141bpm

Thanks guys.
On the injector note, I haven't tested them or REALLY looked for a leak around the injectors yet. Mostly because half of them are hidden However, thats what I'm down to now, the harder stuff. Pull the upper intake, inspect gaskets, PCV (which checks out in that it passes air out, and seals in the other direction), fuel injectors, and anything else I can't see with the upper intake in place. I can say that a smoke test didn't reveal any leaks at all, except for one small one that I fixed and it wasn't big enough to make any change in performance. That leak was on a vac signal hose near the VSV. Found that right away and it didn't make any change.
I have not done a compression test because I haven't suspected a 70k mile engine that burns clean and responds properly on vac gauge to a throttle snap, etc to have a compression problem. It is a relevant test, but it's one I've saved for last considering other checks show no problem. Guess its time to include it just to CYA.
EGR is not causing any of the problems. It checks out fine, and motor runs exactly the same with it physically removed, as installed.
Also, the cats being clogged would show up on throttle blips on the vac gauge as well I would suspect. However, now is a good time to use that Harbor Fright inspection camera! I could remove the o2 sensor and fish the camera into the hole to see the cats up close. But again, I'll eat my hat if they're bad. But I'd do it happily at this point!

saladbarkido

same here, but I found a significant vacuum leak at the #1 cylinder Fuel injector. I sprayed some carb cleaner on the very seat of the injector and sure enough it sucked it right in and idle stumbled, but did not die. I fixed it but it wasn't the major problem. Although I'm getting about 17 inHg of vacuum on parked idle, drops to 15 inHg when in any drive gear. FYI i have the exact same symptoms as you 141bpm.