I dont agree about worn piston being his issue, with only 6-7 psi gain from adding oil, that is very small. I agree he has another issue entirely. He is expected to have SOME blow by with that many miles, but with the oil only jumping it up that little.

Mark

 

I tried the gauge on my S2 and it showed 210psi and that's dead on where it should be.

It's more than a "little" laggy. Off boost there is absolutely no power. Compared to my S2, my S2 would be the equivalent of a top fuel dragster. Theres no hesitation...it just won't go. It idles well and starts right up but it takes about 3-4 seconds to rev to 3500 rpm. Once the turbo spools up, it's fine.

I had my hopes set for it to be the head, but I think it's just a matter of a worn out motor. I took a chance on a high mileage car, I lost.

 

I'll try a leakdown test again but I can't imagine anything else giving a consistent result across all 4 cylinders except for the rings. Of course...I am a novice mechanic!

 

Alright, acceptance is creeping in but I don't give up easy.
The alusil bores and rings are TOUGH cookies.

 

Woooooh, I'm with tool on this one. Compression tests are not very good diagnostic tools. They're good for finding an issue but not good for telling you what it is. I typically don't pay attention to the # but the consistency across all the cylinders.

There are too many things that affect the readings on a compression tester such as ...throttle opening, engine temperature, carbon build-up, gauge calibration, spark plug seal, battery voltage, starter speed, number of revolutions, wet - dry, etc.

A leak down is where you need to start. My craftsman CT gives me 120 across the board and I have less then 2% leak down on all the cylinders. I find it highly unlikely you have 4 worn compression rings (although I did just pull apart a friends motor that had 3 broken ones).

Here's the gauge I use... http://www.tavia.com/cat8.html

 

Here is the leak down tester I bought from paragon.
http://www.paragon-products.com/product_p/lr_73010.htm

I had a hard time the first time I tried it, 95% loss and so forth. Not sure if it was me, the gauge or the engine. However, the cylinder head was in bad shape so maybe it will be easier this time?

 

95% loss means you have a 1" hole in the top of the piston or you probably weren't at TDC and had a valve completely open. To find TDC, I use a screwdriver in the plug hole and slowly rotate the motor until the handle crowns. Do #'s 1&4 first then rotate the motor 180 degrees and do 2&3.

 

Good call on not honing the alusil bores. Ive never had to do the job and Im unfamiliar with how to re-bore with alusil motors.

As the others have mentioned, run your leakdown test again, there is no way you could be reading 95%. Your bores did look good in the picture and if you measure them out and they are still in spec you might try running just new rings and replacing rod/main bearings while you are there, rather than buying an oversize piston set. I dont think you lost with that car at all! You own the best car of the 80's!

 

If you got a 10psi rise across all 4 when adding oil to the bores then they are fine. You have 225k miles, expect SOME ring wear. If you saw a 20-40psi rise then open your wallet.

You are on track chasing the 10"Hg vacuum reading at idle. When the car is slow to rev, does it sound like it is missing or stumbling?

 

What about vacume leaks, have pressure tested the intake system for vacume leaks? Those bores look good and compression is fairly even, check for vacume leaks.

 

Very likely, too.

Clint - most mportant thing for you to remember....do NOT seek advice from wrench only familar wth NA engines.
Careful with that.
Big difference in number of possible faults - some are simple.

 

I suspect that you have a problem with your turbo/ boost control. You have ruled out head problems (which you did have some problems) having those corrected you should have seen some improvement. Common sense would suggest that if the bores are good and the compression numbers are consistent across the cylinders the valves are good and the engine is not smoking excessively that the pistons/rings/valves are good enough that your problems shouldn’t be related to low compression( which you compression numbers confirm) A turbo car will have much lower compression numbers than an S2. Look somewhere else.

 

I didn't have a chance to do the leak down test today because work was fantastic!

Looking over the replies, here is some more food for thought...

1. Vacuum only reading 10hg.
- I have replaced all of the vacuum lines under the hood. Venturi delete and have even bypassed the idle control valve. I hear a hiss under the passenger side dash and I am ASSUMING is part of the HVAC system. The vacuum is so low that the fresh air flaps are open at idle and will close as the engine is revving down. Weird. I have pressurized the system (after the turbo) with a compressor and I cannot find any leaks except the one under the dash which I can't see or reach. Boost gauge is connected to the KLR line under the hood by the fuel rail.

2. Exhaust leaks-
I have replaced a missing head stud, missing wastegate seal ring, two sealing rings where the headers meet the crossover(still leaking) and I know the downpipe is leaking at the crossover. I think the crossover is cracked as well. I do have a new DP wastegate on. Assuming I can get it running right, I will put on an entirely new 3" exhaust system.

3. There is no smoke of any kind at idle or full throttle. There is some condensation that comes out of the exhaust when I first start up but clears up after a couple minutes.

4. There is some oil, about a teaspoon worth in the intercooler pipes. The AOS seals are shot but I don't want to replace them until I replace the turbo which is waiting to see if I can get the car running right. See a trend here?lol

5. When you stab the throttle while sitting in the driveway it will rev fine based on how fast my S2 will rev being higher compression. If you drive it and stab the throttle, the best way I can describe it is, take off using only a 1/4 of your throttle and that's what it feels like. Stumble? not really, there's no jerking like it's missing or anything. Hesitation? well, it does go when I press the throttle, just very slowly until the turbo spools up.

As for advice, it all comes from Rennlist!

Thanks again everyone!

 

They are all slow off boost, you can not compare it to your S2. These cars do not have power off boost and low rpm. Higher Rpms meaning 2000 and some on up it should move ok off boost, off the line they are pathetic. I am just trying to help, hope this does. Mine and every other turbo I have driven (eccept one with an exhaust and maf) are like this. I have driven quite a few turbos. The S2 is much quicker from a dead stop to lets say 20mph.

 

NOW WE ARE GETTNG SOMEWHERE!

Your KLR line is dsconnected at the KLR(or more likely at the tee since you didn't zip-tie it), HOWEVER, since it is in series with the boost guage, you will recieve an ARTFICIALLY low vacuum reading and a conversely low boost reading.
When you fix the signal line leak, you should show the actual vacuum of 18 IN/HG, or so.