'92 V6 - bad sound and now bad compression/no start

Hi all, first post here...
a couple of days ago my daughter was getting ready to go to work. She started her '92 V6 4Runner (unknown mileage as odometer has been broken for a long time). It started normally (it isn't the strongest engine in the world but has been totally reliable since she bought the truck 9 months ago) and after idling for maybe 1 1/2 minutes it made a sound she described as if something metal was dropped and the engine stalled. It would not restart. I checked, it seems to crank normally and there was spark and tailpipe smells like gasoline but not even a hint of firing.

I did a compression test and got these numbers:
#1 130
#2 40
#3 120
#4 30
#5 130
#6 42

That would tend to make me think maybe somehow the cam timing on the driver's side bank got messed up but the thing that is totally confusing me is when I went to check the oil the end of the dipstick is bent and I am pretty sure that wasn't the case last time I changed the oil a couple of months ago. What could have messed up compression on one bank and bent the bottom of the dipstick? Whatever it may be, I am guessing it is time to rebuild or maybe better yet, does anyone make a kit to drop in the 3.4 V6? In any case, she needs a vehicle and this doesn't sound like a quick fix so looks like time to buy a 'beater' car until I can get the 4Runner back in action.

I have a fair bit of mechanical experience but the only automotive engines I have ever rebuilt were 1960s Ford V8s.

Thanks for any insight you may be able to share.

PS - I have never owned a Toyota in my life and never worked on one until my daughter bought this '92 4Runner. All I have done to it so far is replace the CV shafts and add manual hubs (plus general maintenance like brakes, etc.) but I gotta' say that I am pretty impressed with how this thing is built. I have a lot of 4x4ing experience and I think that with either limited slip diffs or lockers this thing would be almost unstoppable, although sadly I haven't taken it off-road yet.

 

The bent dipstick is normal. The bend ensures the dipstick can only be inserted one way. On 3VZ-Es, it's almost ALWAYS the driver's side head gasket that gives out as it runs hotter than the passenger's side because of the silly exhaust crossover design. Since cylinder numbers 2, 4 and 6 are low, it'd be a logical thing to check. And conveniently, the distributor runs off the driver's side camshaft so that's a shortcut to check for correct engine timing. As for the odometer, it might be leaking capacitors on the speedometer circuit board, corroding it. Most can be repaired.

 

Welcome

 

Thanks for the info about the dipstick! That is a relief.

My timing light is broken but I am going to get a replacement and check ignition timing (to see if possibly the timing belt/driver's side cam could have jumped a tooth - does that ever happen on these engines?) The odd thing to me is how to explain the sound of dropping metal she heard when the engine went from running normally to not running at all. In my experience, leaking head gaskets cause symptoms like poor running, loss of coolant, etc. but the problems tend to come on more slowly and never cause a sound like dropping a hammer into a metal bucket (I didn't hear it myself, unfortunately).

I'm thinking next steps are get timing light, check ign. timing. If if is radically off then suspect timing belt or cam problem. Maybe pull drivers side valve/cam cover. I wonder how many hours a timing belt job tends to take for this engine in a 4Runner.

Thanks again!

 

Fortunately, a timing belt job for this engine is very well-documented on forums and YouTube. The time depends on "while yer in there" stuff like cam and crank seals, belt idler, etc. (and stuck fasteners, of course). Keep us posted.

 

I'm no big expert, but I don't believe your timing belt could have "jumped" unless it is severely damaged, i.e., degraded. It would have impacted the compression ratio on both sides. And I don't believe your problem has anything to do with ignition timing. My guess is that you might have a broken camshaft. As a first step, I would try to remove the driver's side rocker cover (no small feat) and I think you will see (my memory is hazy) most of the camshaft in relationship to the valves. If you can then spin the engine, preferably by hand, you will (should) see the movement of the cam in relation to the valve lifters.

In the event that you need to replace the camshaft or decide to replace the timing belt, here is my post mortem on the timing belt job on a '95 4 Runner for the little that it may be worth. I removed the air plenum from the drivers side and flipped it up about 60 degrees towards the passenger side so as to keep all of the vacuum tubes on the passenger side more or less connected. Otherwise, here is what I had to say in my notes:

Post Mortem – Not for the Faint Hearted

I think I purchased the car in 2020 with about 136,000 miles. But with no known service history and now 160,070 miles, I decided that I needed to replace the timing belt. For the most part, I tried to follow the procedure described in the service manual at pages EG2-33 through EG2-49.

The car had come with the AISIN Water Pump – Timing Belt Replacement Kit, Kit TKT-014 which included the following components: a new AISIN water pump with gasket and a gasket for the thermostat; the new timing belt by Mitsubishi; a new hydraulic tensioner; a new tensioner bearing; and a new idler bearing. Not included in the kit, but also installed were a new air plenum gasket, new PVC valve, new crankshaft bolt and three new belts for alternator, air conditioner and power steering. Also installed was new antifreeze coolant.

I consider myself a reasonably competent shade tree mechanic with a reasonable compliment of hand tools and an impact gun, but the job was pretty tough and I needed to buy a few tools along the way at Harbor Freight. I needed one of those bent screwdriver prybars to remove the fan. I was going to make one from an old screwdriver, but for $7.00 I bought one at Harbor Freight instead. Once the fan was off, the removal of the belts and peripheral components was tedious, but fairly straight forward. But a very healthy variety of wrenches and sockets and the 3/4", 1/2", 3/8" and 1/4" rachets with 3" and 6" extensions and a breaker bar was more or less mandatory. Some 16 inch reach wrenches would have come in very handy!

I was never able to pull a single spark plug wire, so I worked against engine compression when rotating the engine.

Do not go too far with disassembly until you have a real (i.e., feasible) plan on removing the crankshaft bolt. The crankshaft bolt is torqued to 180 foot pounds and unbeknownst to me, comes with green thread locker. My 350 ft lb impact gun was no match for the crank bolt! My breaker bar was no match for the crank bolt! A gorilla might be strong enough and available in some cases, but no circus was coming to my town for the foreseeable future!

So, it you opt to use the starter to break the crankshaft bolt, do that to loosen the bolt as early as possible in the process. By the time I was forced to consider using the starter to break the crankshaft bolt loose, I had already removed the timing belt and feared the consequences.

To remove the nuts holding the camshafts, I was able to fashion a tool to hold the camshaft sprockets steady while using the impact gun to loosen the nuts. Not too difficult, as those nuts are torqued to 70 ft lbs.

But I was never able to fashion a tool sufficiently strong to hold the crankshaft steady while I tried to muscle it off. Ultimately, I came up with the following approach that might be used by other overly optimistic, hapless, wannabe mechanics finding themselves stymied mid job.

The crankshaft pulley is held by the crankshaft bolt. But attached to the crankshaft pully by four small bolts is the power steering pulley. I had removed the power steering pulley. After a lot of failure by trial and error by other means, I had a short piece of chain that I wrapped around the frame as tightly as I could and bolted it together to be held there. I then took the loose end and bolted that to the crankshaft pulley using a bolt hole for the power steering pulley with one longer bolt and some washers. When trying to loosen the crankshaft bolt, I attached on top. When tightening at the "end of the job" I attached on the bottom.

All very well and good, but with about 20 degrees of play when force applied. But even with the crankshaft pulley chained to the frame, I was unable to remove the crank bolt. I feared that my 32" breaker bar was going to snap. I tried a big ratchet with a 3/4" drive, but that didn't work. Ultimately, I got a three foot piece of 1.5" pipe onto the big ratchet. I padded the car pretty heavily in case (a) the chain broke; (b) the bolt holding it to the crank pully broke; or (c) the ratchet broke; but ultimately with an ungodly amount of strain on the chain - and my back! - the crank bolt broke loose.

During reassembly, I had a bit of a problem in that my torque wrench only goes to 150 ft lbs. I torqued the bolt to the 150 ft lbs. Then, I swapped back to the 3/4" ratchet and turned the bolt another 15 or 20 degrees. In both cases, I used the pipe.

Another time consuming conundrum involved setting up the timing belt on the crankshaft timing gear that sits within/under the crankshaft pulley. On page EG2-42 of the service manual, step 3(c) says "align the installation mark on the timing belt with the dot mark on the crankshaft timing pulley." That dot is so small that it is virtually impossible to see unless you know what it looks like and where to look. When the timing gear is installed on the shaft, the dot is at the very bottom (the 6:00 o'clock position) of the gear. The crankshaft mark on the belt is supposed to be aligned with this tiny dot. But once I figured that out and found the elusive dot, the rest of the timing belt installation was little trouble.

The final puzzle had to do with the engine coolant. I had drained at least two gallons of coolant from the radiator and engine and it was pretty decrepit stuff. I flushed the radiator and I also removed and flushed the radiator overflow canister. When refilling the radiator, however, it only took about two quarts. I was very nervous about starting the car and running it without sufficient coolant in the block. I puzzled over this for quite some time, but could not come up with a solution for "burping" of bleeding the air out of the system. Ultimately, I started the car and monitored the radiator and hose temperatures with an infrared sensor as well as the gauge. Several times, when it seemed to get too hot, I shut it off. Eventually I discovered that air was bleeding off into the overflow canister, and then as the radiator cooled, fluid in the canister was drawn back into the radiator. So I filled the overflow canister maybe 4 times until I had refilled the system with the two gallons originally drained.

Otherwise the job is done. The car runs. I think the job should take a Toyota mechanic 5 hours. It took me six days!


A few months later, I went back in to check the valve clearances. Again, from my notes:

All of the exhaust valve clearances were tight, especially #6 exhaust which had no measurable clearance.

The clearance specs are as follows:

Intake: 0.18mm – 0.28mm / 0.007” – 0.011”
Exhaust: 0.22mm – 0.32mm / 0.009” – 0.013”

#1 Intake – initial clearance .007” – final clearance 0.007” No change
#1 Exhaust –initial clearance 0.003” – final clearance 0.011” (0.279mm)
removed 2.6mm shim, installed 2.4mm shim

#2 Intake - initial clearance .006” – final clearance 0.008”
removed ???, installed 0.1073” shim
#2 Exhaust –initial clearance 0.008” – final clearance 0.012” (0.30mm)
removed 2.6mm shim, installed 2.5mm shim

#3 Intake - initial clearance .007” – final clearance 0.007” No change
#3 Exhaust –initial clearance 0.005” – final clearance 0.010”
removed 2.71mm (0.108”) shim, installed 2.56mm (0.102”) shim

#4 Intake - initial clearance .007” – final clearance 0.007” No change
#4 Exhaust –initial clearance 0.007” – final clearance 0.011”
removed 2.6mm shim, installed 2.5mm shim

#5 Intake - initial clearance .008” – final clearance 0.008” No change
#5 Exhaust –initial clearance 0.008” – final clearance 0.015”(.038mm)
removed 2.65mm (0.014”) shim, installed 2.55mm shim

#6 Intake - initial clearance .006” – final clearance ??? Within Spec, probably 0.008”
removed ??? shim, installed 2.85mm shim
#6 Exhaust –initial clearance 0.000” – final clearance 0.012” **
removed 2.5mm (0.014”) shim, installed 2.3mm shim

** after installation of the 2.3mm shim in #6 Exhaust, the clearance measured only.0015” (.04mm). I planned to install a 2.2mm shim, but after running the engine, the clearance measured 0.12” and was in spec. I assume that the shim was not properly inserted / set in the valve lifter, but dropped into proper position once the engine was started.

After the valve clearance work, the car would start, then immediately die. Eventually, I got it to run at 2,000 – 3,000 rpm, very erratically. Not drivable! When I was unable to resolve, I decided to remove the plenum and go back to the valves to see if I could find any errors in my work. While tearing the engine back down, I discovered 1) that I had failed to attach one of the water coolant hoses to the underside of the throttle body, causing a substantial coolant leak and 2) that I had failed to remove all of the old plenum gasket as well as the fact that the new plenum gasket had suffered two tears. I believe that plenum gasket was leaking and that this is what caused the erratic idle and engine speed.

Once I had everything apart for the second time, I planned to change the #6 Exhaust shim from the 2.3mm shim that I had installed to a 2.2mm shim. I calculated that this would give a clearance of 0.14mm versus the minimum 0.22mm required, but I was pleasantly surprised to find that the #6 Exhaust in fact had adequate clearance. I measured repeatedly and concluded that the original shim had been misaligned and had dropped into proper position once I was able to start the engine. I did replace the shim for the #6 Intake to bring that valve clearance into spec. At present, the only valve out of spec is the #5 Exhaust which has a 0.15” (0.38mm) clearance instead of the maximum 0.13” (0.32mm) clearance specified.

 

Hi blueosprey90,

Thanks for the detailed response. The info you shared will be helpful. I did get a replacement timing light over the weekend so hopefully this evening I'll get a chance to look at ignition timing (to confirm no issue with anything "upstream" of distributor). By upstream I mean if the ignition timing is good then I am going to assume that the timing belt and sprockets are all still working normally and that at least the front section of the drivers side cam is spinning normally. Pulling the valve cover seems like a logical plan. Looks like my daughter may have found 1999 4Runner in great shape. Hopefully that'll work out as a temporary replacement vehicle as I don't have a huge amount of time to devote to fixing the '92 4Runner quickly, and she needs transportation.

 

Welcome from Wisconsin! Hopefully you get this sorted out.