Intermittent CEL

I drove a hybrid prius for the second time ever this past Sunday and drove a whole 22 miles on open roads. (This is the genesis for me driving one is in this thread here under genII main forum and a video of my first drive is in post #28).

This is earmarked to be the parts car, but I believe is actually in better shape than the principal car. Regardless, I'm trying to ensure the motor will be suitable for swapping into main car when needed prior to me pulling it out so I'm tinkering/driving it this next week.
The engine has a misfire, and I suspect that is the reason for the flashing orange check engine light. But what I'm not used to is that the light goes off and doesn't stay illuminated. The light comes on and flashes when any significant demand is placed on the engine-- when I nurse the throttle pedal, I can hear the engine running (I think) and there's no miss. But when I give it throttle the engine starts to miss and the CEL starts to flash. When I slow back down, the engine stops missing and the light goes off.

1) Can anyone shed light on how/why the CEL flashes but then turns off?

The only background I have on this car (2008 at 225K miles) is it was taken out of service with the following writeup:
P0300 Random misfire, 0301 Misfire #1, P0302 Misfire #2 and P0101 Mass Air Flow Stored in ECM. Intermittently car only runs on 2 cyls. Suspect problem with intake due to the fact there is a recall for newer vehicles with the same condition. #1 spark plug continually getting wet with oil. Possible valve guides or ring issue allowing oil in to combustion chamber. To correct engine replacement or rebuild will be necessary.

2) what is this maf recall and might that issue apply to this 2008?
Truthfully, I only need the car to function for ~ 400 miles on a racetrack. I realize this this sort of "hack job" isn't what PC-ers are about, so forgive me if I offend. But maybe just embrace this as an opportunity for me and these Prii to be your guinea pigs for the greater good of better Prii and Prius owners everywhere.

I've been reading about the pcv valve replacement and MAF sensor cleaning. I'm considering venting the pcv line into a catch can or into the exhaust stream (to reintroduce a vacuum to the crankcase) and plugging the opening in the throttle body so there's no chance the throttle body is sucking in crankcase oil that's fouling the plugs.

3) Aside from rings and guides (which I understand how those work and wear), is there any other path for the engine to suck oil into the induction system?

Thanks for reading.

 

Thanks to the helpful members and their posts here on PriusChat, I was able to replace the spark plugs, remove the throttle body and clean it, and clean the MAF sensor and reinstall all of it before lunch today.

Cylinder 1 plug was horrendous:


The rest were normal. I believe they were all replaced just 5K miles ago (car has 226K)

Unfortunately, it didn't resolve my misfire. Going to try swapping coils out as well as injectors.

I also have a inspection camera I'm going to put down in the spark plug hole on #1 and see what may be visible. I suspect there may be metal deposits on that plug which means something inside that cylinder is melting.


I also realized there is absolutely no good reason to remove the cowl simply to replace the spark plugs.



Regarding throttle body removal-- I found it easy to just clamp off the coolant lines with some needle nose vice grips and/or stuff a bolt into the line to minimize any coolant loss.

My throttle body was about as ugly as the spark plug on #1.




Inside of the intake was some puddled fuel or oil.
http://hubgarage.s3.amazonaws.com/photos/6135230/IMG_3817_detail.jpg[/img

I cleaned it out with TB cleaner and a paper towel on some hemostats. Yes, that was a white paper towel
[img]http://hubgarage.s3.amazonaws.com/photos/6135294/IMG_3834_detail.jpg

All cleaned up good as new


As soon as I can get pics/video of inside the cylinder, I'll post that up, too. and some compression test numbers when I figure out how to get engine crankover.

 

(yes, I'm talking to myself here. But will continue to post in the event that it may help others or, at least, entertain a few of you).

Today I did some more digging. But first, I'll post that I (think) I learned that the difference between a flashing CEL vs a solid CEL is that that a flashing one means it's bad and it shouldn't be driven, and a solid check engine light isn't as bad??

I got my mini vci in the mail, bought a cheapo $50 laptop of craigslist, and plugged it in today and am still (and will be for about 100 years) what this thing can do. Suffice to say I found this page:


And I believe it was cleared yesterday when a kind board member came over with his snapon reader and told me, "Yes, Cyl 1 and 2 misfire". And that was AFTER replacing the plugs.

Today I went and pulled 2 coils and injectors off of the 340K mile car. Problem is, that car has misfire issues, too, so I was at risk of using worse parts to replace bad parts. I decided to pull the plugs to see which cylinders might have been running the best (and have the least likelihood of being the ones that were misfiring on it). And... WOW, it was pretty obvious that cyl 1 in that car was / is a problem cylinder:



If you can't tell, there's broken insulator porcelain there.

Cyl 2 looked bad in that one, too, so I scavenged the coils and injectors from 4&5


I swapped in the coils for 1&2 but didn't replace the injectors and went for a spin. I got the flashing CEL again, but there was certainly air in the fuel rail from me puling out some injectors so that could have contributed to the initial rough-running. When I returned it seemed the idle was pretty smooth (comparatively) but the lights were still on. I looked at the software and it again said misfires in cyl 1 and 2. (sigh).

I'll try the injectors next.

 

Thought I'd post a follow-up after some (professional) diagnostic testing this weekend. A fellow PC member (and now team-mate, I think!-- I'll let him chime in if he wants) did a compression check and found all of the cylinders to be close to each other throughout the entire cycle (he's got some fancy thing that maps out the entire stroke cycle).

He also performed a leakdown test (which puts the cylinder at TDC) and ALL 4 cylinder were showing only about 5% leakdown, which is fantastic for an engine with 226K miles on it. So where is all of that oil coming from that's fouling the plug in cyl #1? We deduce / suspect it's the valve guide or maybe even just the valve guide seals on the intake valves.

Makes sense, since once the car is running at high rpm or at steady-state for a while, there's no misfire. But at startup and after idling for a while or under a load demand it will misfire-- all under high vacuum situations, which is when the oil will more likely be drawn down the valve guides.

If this were a "dirtier" car, we'd see clouds at of smoke at initial startup and after idling and then pulling away from a traffic light. I suspect the cats are catching a lot of that oil smoke. Because the Prius engine starts and stops so much on it's own, there's a lot of high-vacuum situations so it's staring to make more sense to me.

Once the engine is removed to make way for what's next, we'll go ahead and replace the valve guide seals and see (if we get a chance to use that motor soon) if that resolves the misfiring issue.