Help Diagnose Engine Knock

[Badbob]

I just bought a 93 T4R for my daughter. Got a good price, $1500. Clean, no rust, body and interior in good shape. 3VZE, auto, 4x4, AC, power steering.

It has an engine knock! Not the ticking injector but a true knock. I've read through old threads and got a sense of the possible issues: sticky valve, bad camshaft, crankshaft, main bearing. Bad rod, lifter, rocker, and so on.

I'm starting a thread to get help diagnosing the problem by figuring out what steps to take. Can you give me a hand?

Here is what I know/done so far:

1) check engine light is NOT on
2) 173k miles
3) knock is worse when cold, gets much quieter as the engine warms up (a good 15 minutes.
4) oil pressure gauge normal
5) heat gauge normal
6) done-put Seafoam in fuel --helping to run soother and more power
7) put Seafoam in oil--helped quite the knock but has not gone away
8) knock is present at all RPMs--but quiets when deaccelerating like going down a hill and letting off the gas.
9) resent oil change--oil looks clean.
10) did notice cracked vacume hose going to the PS pump.

I got a stethoscope so I'll try to pinpoint the knock location and post my findings

What should I test next?

Compression? Remove sparkplug wires one at a time to see if the knock goes away? Remove belts to see if the knock is from AC compressor, etc.

Thanks in advance for the help.

Badbob

 

[Overbear]

it could be a sticky valve. There is a old trick to fix this, BUT...be warned don't do this at home on the street.

On VW motors that had a problem with a lifter sticking, we use to pour a little ATF fluid into the carb as we revved teh piss out of the motor. Keep revving it, its going to create a cloud of white smoke that will block a road...however it works almost every time to free said lifter

Now, what I suspect is you have a valve thats sticking in the guides, this should clear that too. Just know, ive ONLY done this on a VW air cooled, no clue what it will do to a toy motor.

 

[Badbob]

it could be a sticky valve. There is a old trick to fix this, BUT...be warned don't do this at home on the street.

On VW motors that had a problem with a lifter sticking, we use to pour a little ATF fluid into the carb as we revved teh piss out of the motor. Keep revving it, its going to create a cloud of white smoke that will block a road...however it works almost every time to free said lifter

Now, what I suspect is you have a valve thats sticking in the guides, this should clear that too. Just know, ive ONLY done this on a VW air cooled, no clue what it will do to a toy motor.

This probably is the same thing as putting SEAFOAM in the vacuum system, eg. the white smoke. I have not done that--mainly cuz I don't which vacuum hose to pour it into.

Not sure how one would get the ATF into the fuel injectors.

Anybody have more details on this type of action?

Thanks,

Badbob

 

[Overbear]

This probably is the same thing as putting SEAFOAM in the vacuum system, eg. the white smoke. I have not done that--mainly cuz I don't which vacuum hose to pour it into.

Not sure how one would get the ATF into the fuel injectors.

Anybody have more details on this type of action?

Thanks,

Badbob

Not the fuel injectors into the intake, you want the seafoam/atf to run across the valves not spray into the cyl directly.

To use seafoam, pull the vacuum line that attaches to the intake just aft of the throttle body, stick it into the seafoam, start it up and rev the piss out of it, dont let the RPM drop below 2000.

 

[Bad_Vision]

you use the brake booster vacuum line to pour seafoam in in.
i would not recommend using the atf. i have used it before on old engines but never a fuel injected one.
you should start by ordering a rebuild kit
lowrangeoffroad.com has them fairly cheap.

 

[Badbob]

you use the brake booster vacuum line to pour seafoam in in.
i would not recommend using the atf. i have used it before on old engines but never a fuel injected one.
you should start by ordering a rebuild kit
lowrangeoffroad.com has them fairly cheap.

Mentally, I can't go there. I've never rebuilt a motor before. I want to diagnosis this first using some simple techniques like checking compression etc and then go from there.

I probably would just buy a rebuilt motor unless I could get some help.

Thx Badbob

 

[Bad_Vision]

well if you live near me ill help.

 

[4runnerBrett]

I recently bought a 94 with a rod knock. Luckily previous owner parked it as soon as he heard it and it sat for a year. I bought it and pulled the front diff and out and all the other stuff in the way pulled the oil pan off and found it had a spun bearing. I used a plasti gauge and there was so much play with the stock bearing. I ended up putting a undersized bearing in and it helped alot. Cost me like 100 bucks in parts and stuff. Still knocks alittle but has been running strong for 2 -3 months. Also you can try putting really thick oil in like lucas oil and thats suppose to help. 50/ 50 mix with regular oil.

 

[SUBTEGRAL]

collapsed piston perhaps?
Hope for this because it's not a big deal and doesn't mean
the engine is going to blow any time soon.

With engine idling, pull one spark plug wire from the distributor cap
and then listen.. one wire at a time ..
If the sound is gone with one particular wire pulled from distributor,
then you've located which cylinder it's in.
Careful, you could have a shocking experience.

 

[Badbob]

Status Update

Ok, we spent the day working on the car.

Did a more thorough visual inspection. Found two rotted vacuum hoses. 1) small hose leaving charcoal canister; 2) medium hose entering the PS pump.

I found a small amount of oil and coolant leaking between the tranny and rear motor. I'm not sure where the coolant is coming from, that is more of a concern for me--any ideas? Heater coil hose, perhaps?

PS pump has a few minor leaks.

We put 1/2 pint in of SeaFoam in the vacuum system. Seems to run smoother but we still have the knock.

Went around the engine with stethoscope. I could not detect any different sounds. However, I was idling it in the garage. When we put it in drive the knock is more pronounce.

Key--the knock gets quieter the more I drive it.

Then we disconnected each spark plug wire and found the knock went away when we disconnected cylinder #2! :guitar3:

We then ran a compression test. Here are the results:

#1=140psi
#2=120psi
#3=135psi
#4=130psi
#5=130psi
#6=130psi

Do you think #2 is low because of a valve problem?

What do you think the next step should be?

Thanks,

Badbob

 

[SUBTEGRAL]

by the way,
a collapsed piston is only really heard during initial throttle up.
... if that makes any sense ...
I don't claim to be an all powerful wizard as others are.

 

[Badbob]

in terms of compression I forgot to adjust for altitude. I'm at 7000'

The min factory psi for the 3vze is 142psi. If I apply a conversion factor of .8106 for being at 7000' feet above sea level, I get a new factory min of 115psi.

My vehicle is within specs.

However, either way i think the head needs to come off.

thanks

Badbob

 

[Bad_Vision]

ok #2 is lower then the rest on compression
#2 also is the knock when their is no detonation in the cylinder your knock goes away.
put a new spark plug in that cylinder even if they look new remember they come off a assembly line and could be faulty.
if that doesnt fix the issue check to contacts for the number 2 cylinder on the dizzy.
if thats all good then you may have a bad valve or valve seal. a bent valve will knock but without hearing it and feeling it i cant say for sure if its top or bottom.

if you take a metal rod and place one end of it to the engine and the other near your ear you can locate the knock.
place the rod on the block first right on the #2 cylinder were you think the rod will be sitting wile the engines running and then place it on the head were the #2 cylinder is you will be able to tell with certainty if the knock is in the head or block.

 

[Badbob]

ok #2 is lower then the rest on compression
#2 also is the knock when their is no detonation in the cylinder your knock goes away.
put a new spark plug in that cylinder even if they look new remember they come off a assembly line and could be faulty.
if that doesnt fix the issue check to contacts for the number 2 cylinder on the dizzy.
if thats all good then you may have a bad valve or valve seal. a bent valve will knock but without hearing it and feeling it i cant say for sure if its top or bottom.

if you take a metal rod and place one end of it to the engine and the other near your ear you can locate the knock.
place the rod on the block first right on the #2 cylinder were you think the rod will be sitting wile the engines running and then place it on the head were the #2 cylinder is you will be able to tell with certainty if the knock is in the head or block.

BV, we put new plugs in when we did the compression test. We check the ohms of the wires as well. The knock persisted.

I did the hearing test and could not really hear anything. However my son said he could hear the knock at #2 in the head.

I pulled the dizzy (distributor?) and it looks nearly new, no wear, no corrosion. What kind of test did you have in mind?

So, I think your right, a bent or burnt valve at #2. We'll pulled the head this weekend and have a look. I'll first check the valve adjustments. We need to inspect the timing belt since this T4R has 173k.

Thanks for helping process this. I'm not sure what a burnt or bent valve looks like but I guess I'll find out.

Badbob

 

[Bad_Vision]

youll know when you see it whats wrong!
good luck with the pull! may all your bolts come out nice and easy

 

[Ekimrm]

I have the same exact issue. I am wondering if the valve spring has broken or collapsed? Mine sounds more like a valve rattling because it is loose. Like the spring isn't holding it tight like no pressure.

 

[Bad_Vision]

you may need to adjust your valves they may just be loose and in need of proper adjustment.

 

[Badbob]

you may need to adjust your valves they may just be loose and in need of proper adjustment.

But even that sounds like a core with the special tool and all the shims and so on.

I think I'll check the valve adjustments first and see if anything is majorly out before I pull the head. however, I would hate to do the adjustment and put it all back together only to find it didn't fix it. My instinct is to just pull the head and look.

Any thoughts?

Badbob

 

[Ekimrm]

I have the same problem. I am waiting on your finding to help determine what I do. I think it is out of adjustment or spring is broke. I bet out of adjustment.

 

[Ekimrm]

Badbob. Other than the ticking noise how is your 4runner running?