Should I rebuild my engine, or buy a new one?

Hey guys, this is my first post. Recently my 99 2.7L Tacoma started throwing miss fire codes. So I went ahead and did a compression test. All cylinders were right around 185 psi, except for cylinder 2 which tested around 85 psi. There was also on the threads of my plugs. After talking to some people and doing some research i believe there is something wrong with piston rings in that cylinder or something wrong with the cylinder itself. Any thoughts on what could be wrong? Also should I bother taking the whole thing apart and taking it to a machine shop, and go from there? or should i just buy a new engine, or a remanufactured one? If so what are my best options for a new engine, or remanufactured one? Ohh and my truck has about 135k miles on it. Thanks!

 

If three cyls were at 185 psi that is really good. Most have dropped much more by now, it sounds like it could be a bad valve or a maybe a valve not seating properly (research stuck valves). It wouldn't make much sense if only one cylinder had shot rings, generally they all wear evenly and by the sound of it the rest of your cyls are in outstanding condition.

The 3RZ 2.7L is notorious for needing valve adjustments throughout its life to remain in check. It is much cheaper to have the valve clearances checked before going and replacing rings or the whole motor.

If you want to save even more money, before having your valve clearances checked go have a leakdown test performed on your motor. A leakdown test is similar to a compression check but it will instead tell you where you are loosing pressure. For example if you have a stuck intake valve you'll hear pressure escaping through the intake manifold when they use the tester.

Good luck, and keep us in the loop. Don't give up hope on your motor just yet. Feel free to ask more questions if you have any.

Welcome to TW!

 

What he's saying is correct.^^^ You can have a pretty accurate test done to tell you what's wrong.

 

i have a 99 prerunner 2.7. i have never had my valves adjusted. do you guys recommend i get this done? ive never had any tests like you guys mentioned done to it either. what do you guys recommend at 230k? car seems to run fine other than i do hear the valves taping here and there but nothing serious like loud knocking. thanks

 

First post.. Mostly a lurker

Pour some oil in the cylinder and redo you compression test.. Compression increases that means its in your rings.. If the compression stays the same its in the valves or head..

If you determine the issue to be in the head, it can possibly be carbon build up on your valves, you can try suck water through a vacuum line to clean it out.. make sure you control the rate.

 

It certainly cannot hurt to have them adjusted properly. On the 3RZ 2.7L there is a tendency for the exhaust valves to tighten up as the valve shims wear. Over time this can cause cracks in the cylinder head. Tapping isn't necessarily a bad thing, these engines are loud by design (having chain driven heads). If it is running good then I wouldn't worry about the tapping, I would just have the valves adjusted, many people suggest having the valves adjusted anywhere from 100,000-150,000 miles. By those numbers you may be a bit overdue.

If you do decide to have the valves adjusted I would suggest you find someone who is very comfortable with Toyotas or is a Toyota certified mechanic as these "shim over bucket" valve trains are finicky and require the mechanic to do a bit of work to get the measurements correct to order the right shims.

 

Great advice on the leak down test. I always do them on my customers engines when we have one with low compression. It allows you to know where you are loosing your compression.

 

Thanks for the fast responses everyone. Im going to try the wet compression test today. I also bought a leak down tester about a week ago, but had trouble getting it work correctly. I think it could be that I was not correctly getting that cylinder to top dead center. Any tips on getting a piston to TDC?

 

Also forgot to add that there is some oil on my plugs, and it does not look to be in good shape. Just replaced all plugs a month ago.

 

What part of the spark plug has oil on it? The top or the electrode?

 

Wow that low of miles and engine trouble? I have heard with Toyotas all you have to do is maintain it properly and change tires when need them

 

Yeah, I always maintain my stuff but I've only owned this for 6k miles. The only "wet" oil I see on them is on the threads. I did a leak down test again today, and cylinder 2 would not even build up pressure, but the others did. And when I put my ear over my oil cap hole I could hear some bubbling/gurgling noises in there. I also did a wet compression test on cylinder #2 by pouring 2 cap fulls of oil into that cylinder and it didnt have any affect on the results. So does that eliminate the possibility of bad piston rings? From the little I know its may just be a valve problem...but does that explain the oil on the threads of my plugs?

 

Here's a little info from a site informing how to read compression results.

Interpreting the readings.

Normal: Compression builds up quickly and evenly to the specified compression for each cylinder.

Piston Rings Leaking: Compression is low on the first stroke. Compression builds up with the following strokes but does not reach normal. Compression improves considerably when you add oil.

Valves Leaking: Compression is low on the first stroke. Compression usually does not build up on the following strokes. Compression does not improve much when you ad oil.

If two adjacent cylinders have lower than normal compression and injecting oil into the cylinders does not increase the compression, the cause may be the head gasket leaking between the cylinders.

 

As for the oil on the spark plugs, you probably have a worn seal around the spark plug hole. On these motors I don't know if it's individual seals or if it's a larger gasket.

 

This is most likely what you need to stop the oil leak in the spark plug holes.

 

Just so you know the 3rz and 2rz seem to have a lot of blowby by nature. Mine sounds like another exhaust when I take off the oil cap while it is running.

 

Where can i find this set of gaskets? Whats the set called?