Need help! Weird problem with engine, low comp in one cyl? Stuck oil ring?

[Accord-R]

This question is for my Father's 98 with the 3.2, Normally Aspirated, with I/H/E (no cats). I'm asking in this forum as this is the most technical of all the forums here and this problem is related to the short block.

My Acura dealer just called and said that one of the cylinders compression was down to 80 in one of the cylinders (all others were fine). I have been getting some misfire codes, but had been thinking it was due to no cats. After they called, they said they would do a leak down on it. But before they did that they flushed the cylinder and they said the compression came back up to normal (on par with all the others). They said that the "oil ring" had gotten stuck. Now from what I know if a ring got loose or stuck, it's not repairable. Does this sound like a possibility? We thought maybe one of the valves were bent, but if this is true, what could cause this?

The car has never been misshifted and has not been on the track in over a year and a half. One thing that does seem off is it takes about a half hour of driving for the car to warm up in cold weather.

 

[Briank]

If you have long warm up times things can get gumed up because of the less then perfect combustion. I would get the thermostat and oil changed and then run it for a couple of weeks and then recheck.

 

[Accord-R]

That could cause the rings to get stuck? I thought if the rings were unseated it was almost as bad as blowing out your rings?

 

[Briank]

There is no room for the ring to come out of its grove but it may stick in the grove and loose contact with the cylinder wall and leak compression.

 

[Daedalus]

Did they test the engine warm or cold? Has the car been giving off dark smoke? I didn't think a stuck oil control ring would affect compression.

 

[Doc308]

I have seen compression figures fluctuate wildly in Ferraris for a variety of reasons, including carbon buildup on the valves. One mechanic told me that he did a compression test on a 512 Boxer and it looked like a near-dead engine, reading near 0 on every cylinder. After a spitited drive for a few miles it got blown out and then read w/i normal limits on every cylinder. So, it is possible to do a clean up of a cylinder and get different readings. It is oimportant to do such a test on a hot engine and, for more accuracy as to motor integrity, follow-up leak-down testing should be done. Good luck!

 

[Accord-R]

Thanks for all the responses. We think it is a combination of carbon build up and the ring being "stuck" like posted by BrianK. The dealer thinks it was carbon build up from the car running too rich from the lack of cats. Anyways they cleaned it up and the compression on all cylinders is back in the 160 range (I think he said 160, but it is all around the same number). The cats have also been reinstalled and they tested the warm up and said that is back to normal. Also the car has never blown smoke and still runs like a champ (dealer says it is the fastest non-supercharged NSX they have ever driven). Anyways we are going to pick it up now and see how it runs.

Thanks for all the help.

 

[rbirling]

Did they say why running without cats would cause a rich condition? I'm curious. Thanks.

 

[drew]

Me thinks your dealer is not very smart or has the paper work switched up. The "everything is fine now" is not comforting at all.

No cats, if anything, should probably make the car run leaner a bit, unless you are using your own engine management.

Now I can see is that you had a long term misfire that failed to ignite the fuel-air mixture. This unburnt mixture washed off the oil on the cylinder ("wash") and scrape away at the cylinder wall, resulting in low compression. It would also make the engine appear that it was running rich.

160 PSI? 80PSI? You should call back and verify. My memory states that it should be ~190-200 PSI. What was the results of their leak down?

Isn't the oil ring on the bottom, how does the oil ring effect compression? What did they flush the cylinder with???

You should do you own compression test, it is not that difficult. And/Or seek a second opinion.

Good Luck

Drew
/Dealer Professional: means they do it for a living, does not mean they know what they are doing.

 

[Accord-R]

Me thinks your dealer is not very smart or has the paper work switched up. The "everything is fine now" is not comforting at all.

No cats, if anything, should probably make the car run leaner a bit, unless you are using your own engine management.

Now I can see is that you had a long term misfire that failed to ignite the fuel-air mixture. This unburnt mixture washed off the oil on the cylinder ("wash") and scrape away at the cylinder wall, resulting in low compression. It would also make the engine appear that it was running rich.

160 PSI? 80PSI? You should call back and verify. My memory states that it should be ~190-200 PSI. What was the results of their leak down?

Isn't the oil ring on the bottom, how does the oil ring effect compression? What did they flush the cylinder with???

You should do you own compression test, it is not that difficult. And/Or seek a second opinion.

Good Luck

Drew
/Dealer Professional: means they do it for a living, does not mean they know what they are doing.

The dealer is pretty good as the guy working on the car was trained when the NSX first came out an has worked on them since plus the service manager buils race cars as a hobby. Normally I wouldn't trust anything the dealer is saying, but they have been good for the last 8 years with the car.

We'll see how it runs with the cats on, it would take a maximum of 200miles before the CEL would come on, sometimes as little as 50milles...so we'll see if we get any more misfire codes. Then maybe do another test after it appears to have the CEL gone.

But yea, the cats running making the car run rich could have been from the O2 simulator...maybe. Also without the cats the car would take a half hour to get to warm, so I'm thinking the motor running cold for so long would have some effect on it.

This car is also a "freak" an we suspect something is different in it as the former owner was Honda and they used this car for the magazine tests and it is noticeably faster than another in the same configuration.

I'll have my Father chime in later on it as he can explain it better since it is his car!