SkidmoreAJ

I have a '98 4Runner w/ 133k miles on the 3.4L engine. Never a problem with it until about 2 months ago when it started knocking loudly, but the knocking went away w/in 30 minutes. Two weeks later while driving at about 35 mph, the spark plug in the #3 cylinder blew right out of the head. I took it to an engine shop and was told that the 3.4L motor is known to have major problems with detonation (news to me). Possible causes being: (1) sticky/leaky fuel injector; (2) carbon buildup; (3) problem within the ECM system (i.e., faulty sensor(s)). I went ahead and had the motor completely rebuilt to factory specs and balanced. I replaced the #3 fuel injector, cleaned all carbon out of the intake plenum (carbon in combustion chamber removed when heads rebuilt), and had Toyota run a full diagnostics on the ECM - nothing bad was found. With only 800 miles on the fresh engine, I was accelerating onto the freeway (not pushing it hard) and all hell broke loose (literally). With oil pouring out of the bottom, I now had a hole in the side of the block and an outward puncture on the bottom of the oil pan. We're pulling the motor this weekend to do a "post-mortem", and assess whether lightning (detonation) struck twice. Has anyone ever heard of, or dealt with, this "denotation" problem? Any suggestions??

rimpainter.com

Only detonation problems here are with the Supercharged rigs, and that is at low RPM's.

It appears to me that you have something very unique going on. The bottom end is very strong on the 5VZ.

The second "explosion" on your motor could have been unrelated to the first problem. Let us know what you find out.

oly884

When the motor was rebuild, did you trust the people doing it? Sometimes people have been known to cut corners.

96LtdYota

ok when an engine knocks, does is also kinda studder for like .5 second... mine has been doing this thing when i accelerate hard onto the freeway from 30mph where it will do 5-10 quick "shudders" and i can feel it and hear it through variations in pitch in the deckplate. It stops as soon as i release the gas, or after i reach about 40 mph
i hope its nothing bad

rimpainter.com

Have you checked your plugs lately? How about your plug wires?

SLC Punk

Wow there is something major going wrong there. I have only heard on one 3.4L engine blowing out and that was in a 96 Supercharged 4Runner tha was running BOSH Platunum +4 plugs (known for running hot). He used to post on 4x4wire.com and was from SLC, Ut.

SkidmoreAJ

Thank you all for the replies. I pulled the motor and oil pan over the weekend. What a mess. I've never seen a bottom-end of a motor so totally obliterated. It looks like the #6 rod let go, hit the side of the block (punching a 2" hole), broke into multiple pieces which then worked their way down the crank between the other rods - all while the crank was still spinning. The top-end was fine. No obvious signs of detonation. At this point, I'm thinking that the reply from oly884 might be the problem. Although I checked out the shop in advance of letting them rebuild the motor, I'm starting to have my doubts. Thanks again for all your replys.

rimpainter.com

Got a digital camera?

Sorry to hear about this. Go after that shop!

Pretacopower

About a month ago, when my mass airflow sensor went bad, my engine knocked pretty bad while accelerating on the freeway. Only when I accelerated though, when I let off the gas it stopped. Only did it for about 10 minutes and has never happened since...I figured it was either my bad MAF or a bad tank of gas.
btw I've since replaced my MAF.

jonwilly

I know it has been years on this thread but i have only hear of 2 5vzs ever died that way. From what others said my 4Runner use to do that 4 years ago now it sputters all the way to 4000 and after that its golden but up to 4000 it runs lean and knocks and pings

I would make a post some where else but it wont let me and I have used search. So yeah my ecu resets it self, it has now power, bank 2 lean code, time to time it will pull slow then lose rpm the pull more the lose rpm up to 3800 then sputter and slow down. Other times it runs like it has no tune in the engine. I am just lost on whats wrong with it and makes me a little worried about a rebuild.

vital22re

iTrader: (2)

somewhat common problems with the 3.4 5vz
flex plate on auto 4runners
spark plugs coming loose and blowing out the head
early 96 motors had hg issues( resovled)
detonation with forced induction
Radiators-strawberry milkshakes
every so often the bottoms do fall apart.

These are issues I've seen and delt with personally when I worked in a shop.

FogRunner

Check the fuel system pressure coming from the fuel pump. Also check the fuel pressure regulator and see if the vacuum lines are leaking and that the regulator is working properly at idle (with vacuum) and at heavy load (without vacuum).

If the regulator doesn't increase the pressure when it should then the injectors are not going to give the amount of fuel needed and will result in a lean condition.

The computer times the injector pulse length with the assumption of a certain amount of pressure at the injector but if that pressure is lower less fuel will enter the cylinder and cause the lean condition.


FOG