This morning i went to go crank my '99 4runner. i turned the key and the engine turned over a few times with violent shaking for 2 seconds then it stalled, and blew out a cloud of white smoke from the tailpipe. I tried it again but this time the engine did not respond at all, the starter motor was the only sound, also blowing out more white smoke. I tried it a third time, same thing. It's a daily driver but the truck was sitting for 3 weeks while i was out of town, before that it was fine. I've never seen any smoke ever. It has 6000 miles since the last oil change, i was about to change it. I use full synthetic and change it every 6000 miles. I checked the oil dip stick, it is full. It has 202k miles on the 3.4. I'm in eastern NC so it's not super cold. I use toyota red coolant, changed it 6 months ago along with spark plugs, pcv valve and other general maintenance.

I don't know anything about diagnosing engine problems. Can someone point me in the right direction? Is the engine gone forever or is there hope? Any theories or ideas? I always try to fix my truck when I can but this is above my skill set. Thanks.

Unbolt the upper timing cover and see if your timing belt and other timing components are still intact.

Any coolant in the oil?

If you remove the clutch inspection plate are any teeth broken on the starter or flywheel? I'm assuming that since it continued to blow white smoke that the starter and flywheel are fine and turning the engine over.

How do the spark plugs look when removed? Do you have any way to take a peek inside the cylinders? (Borescope/endoscope)

Any check engine codes?

If you spray starter fluid in the intake will it start and run briefly?

Sorry, I'm just throwing out ideas, I don't really know what it is.

Mine did the same thing one time. I still don't know what the problem was. Maybe there was or is a slow coolant/water leak into the cylinder and you possibly hydro locked it. When mine did this, it smelled up the garage awful when it fired back up. I thought it was dead but its still ticking right along. Sorry, no help but I know exactly what you are talking about.

White smoke is coolant in the combustion chamber. The most common reason is a leaking head gasket. I would suggest pulling all the plugs first and looking to see which cylinder might be the problem. This will also keep you from hydro locking the engine unit you figure out where the water is coming from

Sounds like you may have a blown head gasket and your engine may be hydro locked.

Pull the plugs as already suggested.

How is your coolant level? Have you been losing any? Head gaskets generally don't all of sudden fail completely, it's usually gradual. Since your truck sat for several weeks, it may have leaked a bunch of coolant into one (or more) of the cylinders and hydro locked it.

Have you noticed any rough starts after the trucks been sitting overnight in the past?

If you have a leak down tester, you could do that next while you are pulling the plugs. That will tell you for sure whether or not you have a blown HG.

Sorry, but the initial diagnosis doesn't look good (fingers crossed anyways). Who knows, maybe it's some other thing???

Thanks for your help, Ill be able to check the plugs tomorrow. I forgot to mention, the timing belt and water pump was replaced 6 months ago after overheating a few times from a busted water pump seal. I've heard that overheating can lead to head gasket failure. If this is true I'm assuming my head gasket has most likely failed. I don't have the time or skill to do this repair so I'm planning to let a shop deal with it. Anyone know any good mechanics in Raleigh?

Thanks so much for the help, I believe the coolant level has gradually dropped so unfortunately you may be right. We will know for sure when i pull the plugs tomorrow.

Sounds like a broken timing belt to me.

im leaning towards head gasket. Do report back when you figure it out. GL

I'm the farthest thing from an expert, and the posters above are likely more on the right track than I am, but that behavior is almost exactly the same behavior I experienced when my fuel pump went out. Similar mileage too, I was maybe at 208-210k or so.

Best of luck.

based on this and your original description, I would say a blown head gasket is high on the list of suspects.

Aww bummer, if your truck was drinking coolant then it might be the case and your head gasket failed because of the overheat. However, these engines are pretty stout so you might catch a break and nothing on the bottom end might be damaged. When you pull the plugs out, get a long breaker bar and turn the engine over one complete revolution by hand (360 rotation clockwise) via the crank pulley bolt. Watch for anything bubbling out of the spark plug holes and listen for any abnormal noises. That will give you a clue as to what might have went wrong and if there's hope to revive it.

check for codes pending or stored if you have access to an obd-II scanner.

Pop the plugs out and shine a good led light down there. Look for wetness. It is hard to miss.

I am going through this now. Mine would run/start terrible and worse the longer it sits. I could see wetness in the top of the piston in cyl 3. I also had coolant loss and a smoke show.

My HG failed on cylinder #3. I also had a slow coolant loss I couldn't find and the rough start up in the mornings.

Eventually I got the massive white smoke show and decided to do a leak down test. Once I pressurized the #3 cylinder, bubbles came out of my radiator.

I had a good working engine on hand so I swapped engines instead of trying to rebuild the old one (had 214k miles on it).

For the last couple months I've been losing coolant on the new/used motor and it's had me worried. Could I really have the insanely bad luck to blow another HG on one of these engines even though the donor engine was meticulously maintained (bought it off a member on here)?

Thankfully, I found my leak. The heater hose that goes from the heater core to the heater control valve sprung a leak. It would only leak occasionally after the truck had been running for awhile and was really warmed up. What made me a little less concerned was I could smell coolant under the hood but I couldn't find the leak.

When the HG blew on the original engine, I never smelled any coolant.

Good luck to the OP!