1998 RZJ95 rough idle help (1 Viewer)

[1998prado]

Need help!!
My rzj95 has been idling increasingly rough over the last 2ish months, I’ve been trying to track down what it is with no luck so far.
I’ve replaced:
PCV valve and grommet
Exhaust header and gaskets

My best guess now is maybe my valves need adjusting?

Yesterday I finally noticed that there appears to be a leak on the exhaust side of the engine. Wet and dirty on the block and header a little and on the timing chain cover. No dripping, no milky oil, no loss of coolant. But wondering if the issues are related??
I’ll attach photos, any help would be super appreciated!
Thanks

 

[1998prado]

Also forgot to add that my dist cap, plugs and wires are all new

 

[1998prado]

Going to update this in case it’s helpful for anyone later on. My next step on this list of things to check/fix was a valve adjustment. Upon checking my clearances I saw that ALL my exhaust clearances were very tight .004-6 too tight on most. So naturally I got my new shims ordered and replaced them all, checked new clearances and every valve is now in the center or slightly loose side of the spec. I turned my truck on and it sounded pretty much the same, the sound was just a little quieter. After considering my findings on the tight valves and all the oil build up on the side of my block I’ve determined that my tight valves have led to a blown head gasket, just beneath my exhaust manifold. I haven’t been running the truck, the oil doesn’t look milky and I’d like to keep it that way. For anyone else with this motor, your warning sign to do a valve adjustment is a slightly rougher sounding idle when it idles low. That what I ignored before going on a big camping trip. Don’t do what I did. Save yourself the head ache!!

 

[Eurasiaoverland]

.. After considering my findings on the tight valves and all the oil build up on the side of my block I’ve determined that my tight valves have led to a blown head gasket, just beneath my exhaust manifold...

How do you conclude that?

Shrinking valve clearances indicate valve seat recession. If the valve seat and margins are bad, compression will likely be bad. No connection at all to a blow head gasket.

Rough idle could be a vacuum leak or a faulty IACV, faulty charcoal tank valve (if it has one) or fuel issue, and probably more things I am not thinking about.

 

[1998prado]

How do you conclude that?

Shrinking valve clearances indicate valve seat recession. If the valve seat and margins are bad, compression will likely be bad. No connection at all to a blow head gasket.

Rough idle could be a vacuum leak or a faulty IACV, faulty charcoal tank valve (if it has one) or fuel issue, and probably more things I am not thinking about.

My understanding was the tight exhaust clearances could have resulted in too much pressure inside the cylinder, causing the gasket to blow. Also noticing the new build up of dirty oil on the side of my block right at the head gasket, and the sound coming from the same area. Admittedly I am still very novice in the world of engines so my understanding of this may be flawed. I’m open to looking into other potential fixes, replacing the gasket isn’t exactly easy for me to do at home.

 

[Eurasiaoverland]

My understanding was the tight exhaust clearances could have resulted in too much pressure inside the cylinder

How?

I think it would be a good idea to read/watch some very basic information on internal combustion engines. Recession of valves would cause very tiny (negligible) decreases in cylinder pressure and would not have any connection to a blow head gasket.

Blown head gaskets are diagnosed by low cylinder compression, mixing of oil and coolant, combustion gases in the coolant system. Not by a simple oil leak.

I strongly recommend that you do not dismantle your engine without getting a proper diagnosis, and without supervision from someone who knows what they are doing.

 

[1998prado]

How?

I think it would be a good idea to read/watch some very basic information on internal combustion engines. Recession of valves would cause very tiny (negligible) decreases in cylinder pressure and would not have any connection to a blow head gasket.

Blown head gaskets are diagnosed by low cylinder compression, mixing of oil and coolant, combustion gases in the coolant system. Not by a simple oil leak.

I strongly recommend that you do not dismantle your engine without getting a proper diagnosis, and without supervision from someone who knows what they are doing.

This seems like quality advise thank you, I’ll start by doing a compression test.

 

[1998prado]

This seems like quality advise thank you, I’ll start by doing a compression test.

I’ve also been trying to find someone to help me diagnose this issue, but the shops in my area have, mostly, not been willing to dig into this truck because its imported. I’m on the eastern shore of Maryland and theres not a lot of options without traveling 100 miles.

 

[Eurasiaoverland]

I’ve also been trying to find someone to help me diagnose this issue, but the shops in my area have, mostly, not been willing to dig into this truck because its imported. I’m on the eastern shore of Maryland and theres not a lot of options without traveling 100 miles.

That's annoying, maybe you can come from the angle that it's identical to the engine in the RZN185 3rd Gen 4Runner.

 

[1998prado]

That's annoying, maybe you can come from the angle that it's identical to the engine in the RZN185 3rd Gen 4Runner.

Trust me I have tried, stated it ad nauseam, but some shops just aren't willing. Adding to that I’m not loaded so I’d like to do as much work myself as possible. Saves me money and helps me learn.

 

[1998prado]

It may also be pertinent to note that there’s been a few times that when the truck was put into reverse, the RPMs dropped very low and actually killed it.

 

[Eurasiaoverland]

Trust me I have tried, stated it ad nauseam, but some shops just aren't willing. Adding to that I’m not loaded so I’d like to do as much work myself as possible. Saves me money and helps me learn.

Sounds very frustrating. The 3RZ is a fairly simple engine to start working on, make sure to get the downloadable pdf workshop manual for the engine (I think I got it from T4R.org).

The philopsophy of fault finding is ruling things out - and you start with the simplest rather than the worst-case scenario. Forget about the oil leak for now (unless it is really pouring out) as it is unlikely to be related to the idle problems and is certainly not the cause of them.

It may also be pertinent to note that there’s been a few times that when the truck was put into reverse, the RPMs dropped very low and actually killed it.

What you are calling a rough idle might be a low-idle based on this (though I have no knowledge of auto transmissions) and the simplest and most likely culprit for this is a vacuum leak. Check the vacuum hoses going from the engine to the reservoir, to the transfer and/or axle shift solenoids, and to the steering pump (basically all of them). Pull them off one by one and plug the upstream end with a finger and see if the idle bumps up.

I would recommend joining one of the 4Runner forums as they have far more knowledge of the 3RZ than you will find here.

 

[Mudder]

https://forum.ih8mud.com/resources/1996-2002-toyota-4-runner-factor-service-manual.244/

This is for the US Spec 4Runner but it may be helpful with troubleshooting steps if you don’t have a FSM already.

I’ve been working on a 3rz with a rough idle and just used a smoke machine and found some vacuum leaks I have to deal with. The injector cups are known for causing vacuum leaks eventually and the hoses can cause them if they haven’t been replaced. You can buy bulk hose from Toyota to replace a good majority of the EGR and vacuum lines.

This is the one I’m using

https://www.amazon.com/gp/aw/d/B08QV6RGVS?psc=1&ref=ppx_pop_mob_b_asin_title

 

[1998prado]

Sounds very frustrating. The 3RZ is a fairly simple engine to start working on, make sure to get the downloadable pdf workshop manual for the engine (I think I got it from T4R.org).

The philopsophy of fault finding is ruling things out - and you start with the simplest rather than the worst-case scenario. Forget about the oil leak for now (unless it is really pouring out) as it is unlikely to be related to the idle problems and is certainly not the cause of them.



What you are calling a rough idle might be a low-idle based on this (though I have no knowledge of auto transmissions) and the simplest and most likely culprit for this is a vacuum leak. Check the vacuum hoses going from the engine to the reservoir, to the transfer and/or axle shift solenoids, and to the steering pump (basically all of them). Pull them off one by one and plug the upstream end with a finger and see if the idle bumps up.

I would recommend joining one of the 4Runner forums as they have far more knowledge of the 3RZ than you will find here.

Ok, I’ve replaced a few vacuum hoses in my ownership, but I’ll look ever them all, thank you for your help!! Thought I was never gonna get a reply on this thread lol

 

[1998prado]

https://forum.ih8mud.com/resources/1996-2002-toyota-4-runner-factor-service-manual.244/

This is for the US Spec 4Runner but it may be helpful with troubleshooting steps if you don’t have a FSM already.

I’ve been working on a 3rz with a rough idle and just used a smoke machine and found some vacuum leaks I have to deal with. The injector cups are known for causing vacuum leaks eventually and the hoses can cause them if they haven’t been replaced. You can buy bulk hose from Toyota to replace a good majority of the EGR and vacuum lines.

This is the one I’m using

https://www.amazon.com/gp/aw/d/B08QV6RGVS?psc=1&ref=ppx_pop_mob_b_asin_title

I’ll follow these leads! Sounds like vacuum hoses could be the simple issue, thanks a lot man. Also I have a FSM for a t100 3rz, and a Haynes manual for the same truck

 

[1998prado]

Had a moment to inspect the lines and noticed this hose dangling behind the throttle body I put it back on where it goes. The lines are a bit crusty so I do think I’ll be replacing them all too

 

[1998prado]

Update time:
I’ve now replaced most of the vacuum lines with no change. I decided it was time to try a compression test so I bought a tester and here are the results
Cylinder 1: 195psi
Cylinder 2: 80psi (110 after adding oil)
Cylinder 3: 95psi (110 after adding oil)
Cylinder 4: 200psi
Very obviously there’s a problem with cylinders two and three, I did the adding oil test which leads me to think the issue was either with the piston rings or the cylinder itself. I’m going to attempt to do what I can to clean out the inside of the cylinders just in case a carbon deposit is keeping my piston rings stuck.

 

[Eurasiaoverland]

OK, well that's progress. Simple fixes ruled out.

Your exhaust valve clearances being tight suggests some burning of the valve seat and/or valve margin, which will in time reduce compression (as the valves don't seal). However, having two adjacent cylinders with low compression can also indicate a blown head gasket (between the two cylinders). Rings could also be worn, but we already have strong suggestions of valvetrain problems, and possible cylinder head gasket leak.

If you are confident of the accuracy of your result (you might want to double check it with a leak-down test), then the engine needs rebuilding.

 

[1998prado]

OK, well that's progress. Simple fixes ruled out.

Your exhaust valve clearances being tight suggests some burning of the valve seat and/or valve margin, which will in time reduce compression (as the valves don't seal). However, having two adjacent cylinders with low compression can also indicate a blown head gasket (between the two cylinders). Rings could also be worn, but we already have strong suggestions of valvetrain problems, and possible cylinder head gasket leak.

If you are confident of the accuracy of your result (you might want to double check it with a leak-down test), then the engine needs rebuilding.

unpleasant findings, engine only has 230km on it

 

[Eurasiaoverland]

Must have been neglected. I bought a JDM 3RZ-FE which had about 250k kms on, had been badly neglected, dropped a valve or two, repaired by idiots who got so much junk in the engine that all bearing surfaces were scratched. I decided to do a full rebuild, with oversized pistons, new balance shafts, ground the crank, new head and valves. Not cheap but the resuts were worth it.

Before condemning yours, make sure you repeat the measurements, all plugs should be out so the engine can spin over as freely as possible.

But assuming the numbers posted are correct, sorry to hear that.