This thread says it all: 3rd Gen 4Runner Buyer's Guide

As a long term owner I've unfortunately, personally experienced a rod failure at 237K km (due, I believe, to lack of maintenance from before I owned it), and I then performed a JDM swap in my driveway. The only other issue I experienced with this truck was a rear axle seal failure.

All the years I've been a member, I've read of a few other rods failures, some head gasket failures, 2 of which on disassembly, were identified to be head failures---- a valve stem and a crack, if I remember right. Recently, I've read of a few flex plate failures--- which aren't really engine related.....
Considering how many thousands of these engines exist in 4R's, Tacoma's, T100's, Hiace's etc, and how few failures we hear of, it's truly amazing! The bottom line is, there really isn't one specific root failure with this engine.

You may well be correct, however, the truck had been neglected for 18 years and never once went back to the dealer for anything. Records I have from the PO indicate that oil changes were infrequent at best and non-existent most of the time. 10k or more was not uncommon between oil changes. When changes were done, the cheapest oil and filters were used.

At approx 360k when I got the truck, it still had original PCV, wrong plugs and crappy flea-market looking wires that looked as if they were installed during the Bush administration. Shit man, I found dead maggot husks under the back seat! Cleanliness and maintenance were the last priority for this truck. If the passenger LBJ hadn't failed catastrophically — the previous owner would probably still be rolling around on 4 bald mismatched tires with date codes ranging between 9 years and 11 years old.

While I suppose the Oil Fairy could have been secretly working on keeping the engine shinny inside, I've seen no outward indication of anything other than neglect, so I assume the worst based on what I know and what I've seen.

Still love this damn truck though.

I worked on these at the dealer when they were under warranty.. I've owned at least 8 since then, and worked on hundreds. This is still about the best engine I've ever come across. A select few crack heads. Headgaskets going away are rare. I'd venture to bet that majority of blown headgaskets are due to improper surface cleaning practices during the X01 campaign to replace headgaskets at the dealer due to the factory having installed them on the wrong sides. Factory sealed engines that have never been overheated seem to never blow the headgaskets. The later 3.4s used an MLS headgasket, which I always switch to if I'm resurfacing both the block and the heads, but they don't play nice with used deck surfaces...the earlier composite head gaskets are more forgiving to surface imperfections but are nowhere near as robust.

If the engines have been well taken care of, I'd bet 95% or better will run to well over 350K miles without more than timing belts. At about the 200-220K mile mark, I start seeing oil leaks...oil pan, VC gaskets. I just yanked a 245K mile engine and the rear main seal was dry...which was a pleasant surprise.

Don't try and outsmart the Toyota engineers...use a name brand conventional 5W-30 oil, regardless of mileage, change it at 4000-5000 mile intervals and they'll about go forever. Synthetic may make you feel better but won't improve longevity and will just cost you more money. Use the oil these engines were designed for. Use good Wix or OE oil filters.

These are relatively low output engines for a 4 cam 3.4L, so it's real tough to hurt 'em. Because of this simple fact, people lose their minds when something major goes wrong well after 200, 300, or even 400K miles. Most other engines would have been replaced once or twice by that point. Toyota has conditioned their owners to expect nothing less. When I went to work for GM dealers, I was shocked to see customers not surprised to spend $1000-$2000 fixing their 4 or 5 year old car...they'd clearly never owned a Toyota. I haven't spend that much on maintaining my 96 4runner between 2008 and now, and it just clicked over 245K. I replaced the engine with a good used because it blew a headgasket...head had been off once in about 2000 for the X01 campaign and again a bit over a year ago for a cracked head...I was skeptical about the condition of the deck so opted for a complete engine due to time restraints.

This. That baffle gets oil on it that doesn't cycle well, so it cruds up over time.

Mine looks exactly the same, but is clean as a whistle beneath.

Sweet! One less nail in the coffin!

Love the annual fuel cost on that window sticker.....

I have a 99 4runner with 350000 miles on the original engine and the only problem I'm having is when I get up to 70mph is that the CEL comes on and its a miss in cylinder 5 and 2. It only happens at highway speeds and once I get below 70 it stops and the light won't stay on. Not sure if anyone else has had this problem if so please any info to fix the problem would be great.

Also I already replaced the TPS, coils plugs wires, injectors, and the fuel pump.

Have you ever done a valve adjustment? It may be time. Aren't 5 and 2 on the same coil?


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Yes. Pairs are always separated by 3. 1-4, 2-5, 3-6. So I would start by swapping coil on #5 with one of the others and see what happens. If the miss follows the coil, swap out the coil.

You can check for the Strawberry Milkshake by disconnecting the transmission cooler line on the bottom of the radiator (there are two, use the low pressure one on the driver side), have an assistant start the vehicle and take a sample. These engines are also known to leak oil from the valve covers; an involved job, but not impossible. Also, go with DENSO plugs with two prongs/double platinum (something about the way the spark is delivered or something like that, I forget why). Other than that; they are powerful, easy to fix, parts are plentiful and reasonably priced

A much easier way to tell if you've got the milkshake is to remove the radiator cap and shine a light. Another tell-tale is to feel the radiator hose. The transmission oil once mixed with the coolant softens the hose. Yet another easy way is to simply look in the coolant overfill.

I live in the Northeast, so the leaky valve covers have the added benefit of rust proofing. Couldn't care less about those gaskets.

Or check the fluid on the transmission dipstick

I would love to hear from those who have the 90 series Prado. I am about to purchase one 3400 V6 GX with 280000km. I’ll share pics when I can figure out how to do this

My water pump made it to about the 200k mile mark before developing the slightest seal problem forcing me to top off every 3 weeks until I could get i replaced - I was impressed. I am steadfast on annual coolant changeouts, and when I do that I ONLY use distilled water for mixing antifreeze [using Toyota spec].