I have a 2000 Civic Si B16a2. Brought it to the shop for a Catalytic Converter engine Light. The Cat that is on there is only 8000 miles old. I wanted them to try some tests to see why. During Initial testing they came up with compression across the cylinders in the 40 to 60 PSI range(should probably be around 200 with my higher compression pistons in). The Leak Down test passed they said... The whole engine was rebuilt about 10000 miles ago and all the internals top and bottom were replaced and fitted/installed by the machine shop. They are checking the timing but I just looked at the timing marks and they were perfectly lined up at #1 TDC. They are doing a valve adjustment as well before digging too deep. Any ideas on where my compression is going???

Thanks in advance

 

A leakdown test would have shown 'where' the air was going...idk how you could have bad compression and pass a leakdown.

Also, why are they doing compression/leakdown tests for a bad cat? You should find another shop.

 

This^

They bumbled the compression test, and now they are likely charging you for unnecessary work.

Does the cat code return after resetting the ECU? If so, immediately fire the shop, take your car home, do a full ignition system tune up, install new cat, and go from there.

 

This. While we're at it, what CR pistons do you have installed, and is your car properly tuned, or are you running a stock ECU or basemap?

 

Did you have the cat fitted while you broke the engine in? did you use break in oil?

All the extra stuff in break in oil will destroy cats.

 

That has to be one of the silliest things I've heard in a while.

 

Are you also thinking that they didn't spin the starter enough?

 

secondary o2 can throw a false flag for a bad cat. i'd start the actual diagnosis there, as far as that's concerned. as to the compression- go drop $15 on a tester and do it yourself. very, very, very easy.

 

That was my first thought that they messed up the test, so i will get it home and check it myself, i just didn't know if this was a common issue but didn't make sense to me.

I wanted them to do a leakdown to mainly see if i have a headgasket leak because i am blowing some white smoke and thought that could have contributed to the cat going bad.

The Cat was installed around 2000 miles after rebuild. No i did not use different oil for the restart...

I will update once i get the car back and test it myself. Thanks for all the advice

 

Please do a proper compression test before anything else.
If you only had 60-90 psi in all cylinders, your car wouldn't had made it to the shop on its own power.

Have you had any coolant loss?

 

That is why it is weird, the car runs very well and pulls as well as ever. I have noticed coolant drop in the overflow but i do not drive it daily only once in awhile so it is not much at all.

 

Slight coolant loss in the overflow tank isn't uncommon and doesn't prove a head gasket failure. Smoke could be from unburnt fuel, could be from slight oil consumption or even slight antifreeze consumption.

Leak down test makes me think that its not oil or coolant, and probably fuel since your engine is aftermarket. Seems normal. That also could contribute to cat destruction, but you may want to try replacing the secondary o2 sensor..

You may also want to shim the o2 sensor..

You may also want to bring your car thru emissions testing

 

Yeah that would probably be a good idea checking the emissions to see what is getting burned, probably check the coolant tank as well to see if any combustion gases are in there as well to tell for sure if coolant is or is not getting burnt during the cycle.

What do you mean by shim the o2 Sensor? Never heard of that before?

 

It allows you to bypass the secondary o2 sensor while keeping them installed and semi finctional. They're strickly for off road use only vehicles, like racecars and stuff like that.

 

Get an actual emissions test done though, not that obd2 crap. A tail pipe emissions or "sniffer", "**** probe" test will actually give you accurate results as to how clean your burn is.

it works even better on a dyno.

 

Understood. Thank you for all your help. I will keep this up to date if i find anything else out on my own.

 

Well I got it home finally, after they did a valve adjustment and replaced my oil seals behind the cam gears, they told me i had 130 psi in cylinder 1 and 150 in the other 3. I got it home and did my own test and was 180-185 across all 4. Never Going there again...WOW! They also had it running checking for leaks and it died and they figured out the ignition coil was not sparking. They removed it and saw that it was all corroded and rusty. Any ideas how this could happen? It has been garage kept for the last 2 years and the coil was replaced around 2 years ago as well. Will drive it more and see if the engine code comes back for the cat bc as of right now i have no codes...

 

Glad you got your compression straightened out.

As far as the rust, how is the moisture in the garage?

 

They didn't even perform the compression check properly...

 

None to speak of really, i have other bare metal parts such as the ac fan bracket that i wire wheeled about a year ago and that is pretty much still clean...the old coil looks bent as well...see pictures

 

Sorry for the big pictures...

 

It's fine, the forum resizes them to make them reasonable. Still waiting for answers on multiple previous questions, though. If you want solutions, you're expected to answer all questions.

 

Manswers!!!

 

They could have done the compression test on a cold motor with only 3 turn overs. The results are okay with 130,150,150,150. The compression is right in range with one another.

How many cranks did you do for each cylinder? Was the engine warm? There is usually a decent difference between a 4 or 5 crank method and maximum pressure test (9+ cranks per cylinder). The biggest thing to be looking out for is a major difference between cylinders regardless if it's a cold or warm test, especially when doing the 4-5 crank type test.

As for the coil, the dizzy gets a fair amount of warmth to it so moisture can condense in it pretty easily. I would suspect the dizzy cap seal wasn't seated properly allowing excess air flow into the warm dizzy.

I didn't see the questions you missed answering that NAR mentioned or I would have repeated them hear. You might want to re-read your thread and see what has been missed. Vital help could be missed otherwise.

 

By shimming the O2 I believe he means a spark plug anti fouler. Backs the O2 out. Good to do sometimes if you need a sticker and can't afford a expensive repair