Toyota 4 Cylinder Turbo Low Compression

B

Bobster99

Joined
Jan 6, 2024
Messages
8
I am new to this forum (Today) and I could use some advise.

I have a 91 Mr2 Turbo with an honest 70,000 miles that hasn't seen a full tank of gas run through it in 20 years. It has been sitting in my garage gathering dust since 2003 and maybe saw 100 miles of use every few years. The engine should be pretty clean inside. Even though I rarely drove the car, I did change the oil ever couple of years before I took it out and put some miles on it.

Recently I decided to clean it up and put some miles on it and discovered that the #4 cylinder has almost no compression. I did a leak down test and it points to bad rings. I have thought about getting it rebuilt but I can't find a shop down here that I trust and I don't know if I am motivated enough to pull the engine out myself and take it to a machine shop to get it done.

The thing is, I just find it hard to believe that the rings are shot. The car really does have 70k miles on it, I bought it back in the mid 90's with 60K on it and just never used it. I looked in the cylinder with a bore scope and everything looks perfect. There was some carbon on top of the piston but the cylinder walls looked perfect. I have heard that Toyota's of this vintage had weak ring lands but the people who were saying that were running 2-3 times the factory amount of boost trying to get 600 Hp out of a 4 cylinder. Besides, I would think that if I had a bad ring, there would be some evidence of this damage on the cylinder wall.

Like I said, I am new to this site and never thought to ask the experts here until now. Late last year I soaked all of the cylinders in Marvel Mystery Oil for several days but I suspect that was an exercise in futility since likely most of the oil probably ran past the rings in cylinder 4 pretty quickly and I just ended up with some pricey Marvel Mystery Oil mixed in with the oil in the oil pan.

After I did that I did change the oil and take it out for a 75 mile drive to a get an estimate on an engine rebuild from a shop up north. When the estimate went from $5K to 10K very quickly, well, they didn't get my business. The car actually drove really well for a 4 cylinder that is pretty much down a cylinder but sadly the drive didn't seem to free anything up.

Maybe I am just dreaming since I don't really want to pull the engine but I am wondering if something might free up the rings and bring back my compression. I have read about soaking the cylinders in ATF and Acetone and I actually bought some to try this but I figure I should ask the experts before before I literally recycle a gallon or so of ATF and Acetone and still end up in the same place.

Any suggestions... other than quit being a wimp and pull the darn engine and have it rebuilt... :p
 
Its just after Christmas and I want a miracle..., shouldn't I get a miracle? :unsure:

Thanks for the response
 
spasm3 said:
This! AFT does not belong in an engine.

I would pull a valve cover and look at the valve train, just to make sure the springs look good on cylinder 4.
Click to expand...
I will, I had the valve cover off a while back but never thought to look.

Thanks for the idea.
 
spasm3 said:
This! AFT does not belong in an engine.

I would pull a valve cover and look at the valve train, just to make sure the springs look good on cylinder 4.
Click to expand...

Valve train gets a vote here. Very common for a valve to corrode to the guide after long period of disuse.

This is another example of engines needing regular exercise.

Z

PS: this engine very unlikely to need a complete overhaul.
 
How did you perform the leak down test? The test can be done "dry" and then "wet" by squirting some oil in the cylinder. If the wet test shows an improvement then it points to the rings. If no improvement then it points to the valves.
I lean to the valves on that cylinder being the problem. I don't see that low a mileage causing stuck rings.
 
zray1 said:
PS: this engine very unlikely to need a complete overhaul.
Click to expand...
I like your optimism!

I just noticed that Berryman B-12 Chemtool has less than 3% Acetone so at least the Acetone wasn't a bad idea.
I think that they suggested ATF was just because they wanted some sort of oil to combine the Acetone with.
 
oldcodger said:
How did you perform the leak down test? The test can be done "dry" and then "wet" by squirting some oil in the cylinder. If the wet test shows an improvement then it points to the rings. If no improvement then it points to the valves.
I lean to the valves on that cylinder being the problem. I don't see that low a mileage causing stuck rings.
Click to expand...
I did both wet and dry and that is why I was leaning towards rings.

My only hope, see miracle comment above, is that maybe the sitting caused stuff to harden up and freeze a ring.
 
As others have said, a stuck intake or exhaust valve. Pull the #4 spark plug and hook up an air compressor. Listening to the exhaust pipe and intake will quickly tell you which one is leaking. Remove the valve cover and lightly tap the offending valve (if it's cam-in-block or push rod style) may break it loose and save you a lot of work.
 
If you’re sure it’s rings - and it sounds like you are - I’d venture to guess it’s ”just” a stuck ring (or two). And unfortunately that can be a challenge. I’d ask myself, am I going to damage the cylinder wall be driving in? Because actually driving it might help, with your piston soaks, multiple heat cycles, more soaks, etc. Then again, maybe not.

Like others said, check that valve train. Depending on the lifters it could be a bleed down situation where the lifter is not functioning. It could be a stuck valve in a guide (whoever said that, that’s a great thought). It’s Easy to pull that valve cover off of a four cylinder and take a look, I’d start there. Hell, I’d pull the head and try moving that piston around in its bore while it soaks! Couldn’t hurt if you’re thinking a full rebuild is on the way (which I’m not sure it is).
 
Bobster99 said:
I did both wet and dry and that is why I was leaning towards rings.

My only hope, see miracle comment above, is that maybe the sitting caused stuff to harden up and freeze a ring.
Click to expand...
When you do a leak down, try to listen or feel for where the air is coming out. Bad rings will cause air to come out of the dipstick tube. With valves it will be either the intake or exhaust manifold.

The issue is probably related to corrosion. Normally a cylinder will be sitting with open intake or exhaust valves and that cylinder will corrode if there's enough moisture. I'd try the B12 piston soak. An Italian tuneup afterwards might help unstick things as well, but don't overdo it since you could have a lot of bore wear if the rings are stuck.
 
Have a read through this one.

So we're all buying Toyotas now 🤔

I won this 2009 xB on eBay, I'm gonna go pick it up Friday 281k, warned of grinding brakes and having to add oil 🛢️ Bring on the piston soak 😈 I got a few cans of on sale B12 chemtool, and a can of Kroil, might let it soak for multiple days It's an auto, coming from it's first and only...
bobistheoilguy.com

Define "almost no compression" and what were the other 3.
 
Oh Man!! The Mister 2 turbo. What a fantastic little car. If this were my car I'd pull the valve cover and check the valve clearance on the no. 4 valves. I think you got some carbon stuck between the valve and valve seat. With the lack of use and the short duration run times when it was used I can guarantee those combustion chambers are ugly.

considering that ancient, filthy fuel that's contaminating the system, I'm surprised it even runs.
 
Jetronic said:
because it's a 2-seater roadster, hardly spacious enough to go grocery shopping with... so a good weather only, for fun car.
Click to expand...

my 1978 Triumph Spitfire, similar to this one pictured below:

2 seater roadster, check.

Hardly spacious, check.

Good weather only, uh, no check.

I took my (daily driver) Spitfire on a circuitous 6,000+ mile trip up from the south western USA to the Dakota’s. Then over to British Columbia. Down the west coast to Tijuana. Then all over the Grand Canyon and back to Oklahoma. All of this with my girlfriend / navigator / companion keeping things even more interesting.

There’s no car to small for adventure.

Z
IMG_8575.jpeg
 
Jetronic said:
because it's a 2-seater roadster, hardly spacious enough to go grocery shopping with... so a good weather only, for fun car.
Click to expand...
That is part of it but mainly it was that life just got in the way. I was in the car business 20 years ago now and I bet I have had at least 10 Mr2's spread across the first two generations. This was always a 3rd or 4th car and when I bought a SC430 back in 2008, having a quiet car with a retractable hardtop just pushed the MR2 and the Allante farther back in the garage.
 
FowVay said:
considering that ancient, filthy fuel that's contaminating the system, I'm surprised it even runs.
Click to expand...
You would think that it would cause a bigger problem but surprisingly it hasn't. I have been putting in ethanol free fuel in the cars that don't get driven regularly for some time now. The cars are kind of grumpy when they are first started they seem to get over it rather quickly.
 
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