Misfiring or something else?

So today I finally had some time to do the compression test again.

I drove the car for a bit and started about 15 minutes later (coolant temp was 88 Celsius when I parked).

This time I did the procedure as follows, which I believe made for a more consistent test:

1. Warmed up the car (as per above)
2. took out all spark plugs
3. placed tester in Cylinder
4. turned on the car
5. Went back out to watch the gauge
6. Waited for ICE to start running
7. Let it turn over for the 5-6 seconds or so until it errored out and more or less stopped
8. turned off car.

The first round I did a dry compression test (without the oil squirt as recommended) and on every cylinder, pressure would go up to around 100 to 105 (gauge is really annoying - only has numbers at 30,60,90,120 and so on, so have to watch it like a hawk to get a semi-accurate reading) and then would settle down to around 96 as engine stopped turning over . I did not see any difference at all between cylinders, it was like deja-vu as I went from cylinder to cylinder.

Then I squirted some oil in cyl 1 and redid test with a result of 110.
Cyl 2 resulted in 130
Cyl 3 resulted in 130, and as I pressed the needle to reset gauge and release pressure, the hose popped off with a pop off of the part that goes into cylinder spark plug location, resulting in my spending the next 1.5 hours coaxing it out. As mentioned previously, the hose was turning around the base part that goes into the cylinder, make me have a hard time tightening the tester and I guess now I've learned my lesson - NEVER use a compression tester that has the hose turning or loose.
I obviously skipped cyl 4.

At this point, it seems that I do have some wear on the piston rings. However, besides the strange noise and slight vibration, the car seems to be driving ok. Certainly would be fine if it drove this way another 100k miles.

It should be noted that I did not find any oil on any of the spark plugs this time.

So,

1. What can I do to prolong the time until the engine dies?
2. Acc to this guy
   changing the spark plug may help the engine run better for some time.
3. Will high mileage oil help? Any other additive?
4. How many more miles can I expect to get at this point?

 

Can you elaborate? What if my car (not the prius, but one of the newer cars) calls for 0w-20 which I believe is fully synthetic? And what do they do wrong during oil changes? Fact is, I'm not going to do my own oil changes, and having history of maintenance at place like the dealer seemed to me as a good idea, especially when I'm selling the car (I do realize you're not my target customer). I'd like to avoid making the same mistake again since it seems I'll need a new car in the near future - what do you recommend I do to make sure a car I would like to buy is a good choice?

 

I did not hear any rattling sound when spinning for the compression test. It was more like a train/steam engine sound - "chugg chugg" which makes sense as the compression moves air. The rattling/gurgling sound only happens when I put the car into drive and the ICE is on - even if I hold the brake and rev the engine, it only makes sound when in Drive. Driving on battery only I hear no sounds. Leaving the car to idle only causes vibration sounds and a sound in the first half second the engine starts. For some reason I feel it has some exhaust component to it, and a mechanic I went to (not knowledgeable with the prius) seemed to guess that first too. Likewise, the dry compression test was perfectly consistent across cylinders - the engine may be worn, but it seems to be a very even wear and therefore I have a hard time concluding that the worn piston rings are the sole cause of my current issue. Loss of power and efficiency yes... but to have some strange sound suddenly that didn't exist for the past 50k miles is hard for me to attribute to the engine wear.

I just added a quart of mobil 1 super high mileage to it - I checked the dipstick right after and it is now showing a tiny bit above the second dot - hopefully I didn't overfill, but if I understood correctly reading various threads here, oil level on the dipstick is about 1 quart per 1/4 of the way between the two dots. Meaning, oil should should 3.5/4 of the way up between the two dots. So even though it was showing about halfway before I added oil, after 1 quart it is past the second dot...

Considering my issues with the compression tester I would interpret my test results "with a grain of salt", which leads me to believe that even though I do have some piston ring wear, I question how bad it really is - yes I know the engine will die eventually, but I could still be looking at many more miles of good enough driving - especially at the 50 mph speed I typically don't exceed in my city.

The questions I have are

1. What can I do to prevent the CAT from being ruined and at least make it until the next smog inspection this December (NJ state)? Any way I can test the condition of the CAT?
2. Are additives like "Restore" are a good idea to help with that?
3. Any tests I can run with the Torque app that may yield helpful info?

I do plan on getting a replacement car in the next 6 months, and will therefore sell this one. I obviously don't want to mislead any buyers, but considering the low price I will probably obtain, the idea would be that I am selling a "runs & drives" car that will work for an unknown length of time, which is exactly what I did when I purchased this car in the first place - and I've had it nearly 3 years. Nevertheless I would like to sell it in as smooth running condition as possible - I don't want to sell a "car with issues" I want to sell a car that is old, and yes, most likely worn - make your own conclusions and do your own tests.

That is why I still have an interest in trying to eliminate this weird sound (obviously if it can be done cost effectively) as it will probably have a significant effect on its market value (or even how many people may be interested). This is even more true if I can pinpoint the issue to something other than the engine wear.

I will try to take a good look at the intake manifold, but I welcome any other suggestions.

Thanks!

 

Just an update on this - for the past 6 months car was driving without the heavy misfire & shake that I had occur at some point. Over the past few days:

1) we had a snowstorm 6 days ago (here in NJ) and got about 1.5 feet.
2) I tried to get car out during the storm, and had to turn off traction control
3) I did find plenty of snow in the engine bay
4) 2 days ago, when getting in car to drive home car started to misfire. codes 300,301,302,303. Since then I have tried to get as much snow out of engine bay as possible, and at this point, car starts to misfire as soon as it warms up.

In other words, first thing in the morning the car is fine for the first 10 minutes or so. Once its warmed up (and likewise on drive home when its not so cold as in morning), it misfires. Mostly getting 303 code.

To update on previous discussion of oil consumption - I would say about a quart is consumed per 5000 miles, which, if I understand correctly is not so terrible for a 275k miles car.

Assuming low compression is the issue - would it make sense that once oil warms up it doesn't seal the compression chamber as well and then starts to misfire? My understanding is that hotter engine = expanded metal = better compression. But if there is a problem, maybe it would be the opposite...?

Regardless, I question the conclusion that compression is the issue, as the misfires are mostly at low rpm, at higher rpm its either not a problem or a lot less noticeable.

Is there something that would perform worse when warm and better when cold? I am led to believe that fuel injectors would work better, not worse when warm, so I would assume that would be the wrong issue, but maybe I don't understand the process fully.

I am also wondering what could be exacerbated by snow or moisture getting into the engine, as these misfires have been greatly increased right after the snow (I've had no codes in the past 6 months).

Obvious things I will still check - moisture or fluids by the spark plugs - if there is moisture in coil it could be misfiring, and its a known issue that coils aren't sealed well in this car. Likewise if I have coolant leaking into engine... However, I again don't understand why this would get worse after the car was warmed up...

Anyone have any insight or direction with some of these new clues?

Much appreciate the help!

 

Just an update - I just took out the coils to see if they're wet - #3 had a bit of black wet stuff on it - did not smell like oil. I wiped everything off and put it back (and broke the bolt holding it down... 2nd bolt I've broken on the coils...). I turned car back on and it was heavily misfiring (codes for #1 & 3). But when I bring the rpm to 1500, no misfires - only misfiring under 1500 rpm.

I decided to take a quick look at the MAF through the air filter hole and even though I cleaned the MAF sensor 20k miles ago, I see it has some grey stuff on it instead of being that shiny dark red color. Is it reasonable that the MAF sensor could be the source of all my woes?

Also, just to clarify, after watching someone else do a compression test - he seemed to read the # on the guage based on the highest the guage read at any point during the test vs where the pressure settled at. which way is correct?

Thanks!

 

Here are the pictures: I don't see any carbon tracking, but maybe I didn't understand exactly...

 

So you're saying the new ones with only 20k miles on them need to be replaced? what is causing the tremendous heat? Is there a cooling system problem I'm not aware of?