Are these ignition coils ready to replace or can I wait? (Pictures)

2006 Gen 2 Prius with 268,000 miles.

The engine's been ticking for as many as 8-12 months now. Louder ticking when idling, faster and quieter ticking when rpms go up. It's annoying and I don't think I can do much about it, but it's an observation that may be relevant.

I just replaced my spark plugs because my idle was rough after the car sat for 5 weeks while I waited on parts for a hybrid battery replacement and one other related job. While idling: the car shook a little bit when the engine lugged, rpms fluctuated abnormally, and it would slowly bog down. Additionally, one time I turned it on and had a horrifying clunking noise lower down in the car... The car had noticeable power loss on acceleration. Within a day or two of the 5 week period without ignition it threw P0300, P0302, and P0304. I figured I'd start with spark plugs accompanied by a few other cheap repairs on the way.

Repairs with observations:
-Ignition coils: When I made it to these I found that the top of the engine had a significant amount of dirt. The ignition coil gaskets had some grit where they're supposed to make a seal, so they may not have sealed perfectly. Coil 4 had significant moisture on the bottom of the ignition coil gasket. I carefully cleaned the schmutz away from the orifices (heh) and thoroughly cleaned the engine block where the ignition coil gaskets make a seal, I wiped the ignition coil gaskets clean, and I swapped the coils from 1 <> 3 and 2 <> 4 on reinstallation. There's a little more info on the ignition coils in my question at the bottom.

-Spark plugs: See images below. I'm asking about replacing my ignition coils because (they're expensive and) the spark plugs were likely the cause of the misfire. I've never pulled plugs this bad from a vehicle of mine... I just got this Prius 1.5 years ago and this is my first spark plug job on this car. I replaced them with OEM parts from the dealership.

-PCV valve: See images below. Nasty. Replaced with OEM part from the dealership.

-Cleaned mass airflow sensor. See images below.

-Cleaned throttle body. No images because it wasn't too bad. I followed the TSB.

After the above repairs, the engine runs very well but it still ticks. The idle is steady and the acceleration power has returned. There's no clunking noise. I only mention the ticking because I read that one potential cause is the ignition system.

Should I replace the ignition coils (see images below) or can I wait? Coils 2 and 3 have tiny cracks beginning to form and coils 1 and 4 have noticeable cracks.

 

Thank you. Per your and @BiomedO1 's replies I'll go ahead and replace the ignition coils, though I'll check for sparks in the dark. I won't perform your spark leak test since I now plan to replace them anyways.

 

Thank you for your reply! I did notice the sensor hidden deep within the plastic housing after I took my pictures so I cleaned it, too. I didn't grab a picture of it because it seemed like it would be hard to take, but I did clean there as well.

 

Update:

The car ran very well for a 1.5 hour drive out of town last night. This morning I started it up and got the following codes: P0A0F (battery code) and P3190 (engine code). I found this post with the same codes.

• I've already cleaned the mass airflow sensor.
• I've already cleaned the throttle body, though I did notice a small amount of oil-colored reside down past the throttle body in the bottom (that's the intake manifold, yeah?). I'm not sure if it's enough to be my issue so I don't think I should look in that direction.
• My gas tank is near-full. It should only be missing 1.5-2 gallons.
• My oil is not overfilled. I was 1/3 between "low" and "full" on the dipstick recently, but when I checked just now (with the engine warm) I was at the "low" mark on the dipstick. I'm due for an oil change as I just hit 5,000 miles since the last one.

What I plan to do:

• Get the oil change I just came due for (800 miles ago).
• Replace ignition coils per above post and replies. Maybe that helps with this, maybe not.
• If not, I can replace the mass airflow sensor.
• If that doesn't work, I saw Todd (from Tampa Hybrids; buy a car from him if you can. He rocks!) detail a fuel pump test in the link above. If it's my fuel pump, I'll figure out which year vehicles can donate a gas tank/fuel pump to my 2006.

I was curious about the ignition coils, but I primarily started this thread because I figured my repairs in the initial post would be the start, not the end, of my woes lol.

 

Update:
Haven't had a chance to do any more maintenance as I got in from out of town late last night.

The warning lights from my last post (red triangle, check engine) all went away as the day went on yesterday. The car functioned normally. After the lights disappeared on their own, I cleared the codes. I drove around the town I was in all day, then 1.5 hours back home with no issue after the initial error event.

The next morning, I received the same error codes. Yesterday when I got the error, the car ran on the hybrid battery alone until the battery ran out of power. Powering off and on resulted in the engine starting, the car running, and the day proceeding as described. Today, the ICE engine will not start. The car will not go into IG-READY. The codes are the same, but in addition to the red triangle and check engine light I have the VSC, swerving vehicle, and I think one of the small orange lights with the exclamation point. It may have been both of the small orange exclamation point lights but I forgot. The error lights were pretty much all on. Still just P0A0F and P3190.

I'll update again after trying maintenance. For now it seems relevant to mention that the error has only popped up when first starting the car for the day, that it temporarily resolved yesterday, and that it came back today and wouldn't fix itself.

 

Final Update:

To summarize the most recent issue (after resolving the misfire) for future troubleshooting:

The following sequence of events was highly repeatable and happened the same way every day aside from one day where I didn't have time to resolve the fact that the car wouldn't shift into drive and so I took a different car.

I had codes P0A0F and P3190. At the beginning of each day when I first started the car, these codes appeared along with the <!>, swerving car, ((!)), ABS, VSC, and check engine lights. Generally, putting the car into drive as soon as I turned it on would get the ICE to start and there wasn't an issue for the rest of the day. On a few occasions, the ICE wouldn't start. The car ran on the hybrid battery until it died. At this point, turning the car off and on and attempting to shift into drive immediately got the ICE to start.

On two occasions, the car wouldn't shift into reverse or drive. Waiting on the hybrid battery to die/turning off and on several times generally resolved this, and I could get the car into drive and start the ICE.

Once the ICE started, the car was good for the rest of the day. The second or third time I turned the car on, all warning lights except for <!> and check engine would be off. I only had <!> and check engine at this point in the day. Later in the day, ALL warning lights would disappear. The car would start and function as normal with no error lights. At this point in the day, I cleared the codes. The next morning, this process repeated.

Again, the previous observations were highly repeatable and happened every day.

Resolution:

As mentioned above, I was curious whether my ignition coils needed replacement. I ordered four new Denso ignition coils (OE Manufacturer, though cheaper than buying from Toyota) and replaced the old ignition coils. In addition, I ordered a new Denso mass airflow sensor (also OEM, though not labeled by Toyota) and replaced the old one.

One of these two replacements resolved the issue I had with codes P0A0F and P3190. It's been four days and I've yet to see the highly repeatable observations noted earlier in this post reappear. I'm marking that particular issue as resolved. I want to note that the issue with P0A0F and P3190 appeared AFTER resolving the misfire earlier in this thread. The replacements in my initial post resolved the misfire, the new codes appeared, and this is how I resolved those codes.

I also got the oil change I was due for after replacing the ignition coils and mass airflow sensor. That didn't change anything. The engine still ticks. Best advice I found for the this is to save up some money and ignore either until it's time for a new engine.

 

Hey, just saw this. I know I said it was resolved in my last post, but the same issue (the latest one described in this thread and the same one I thought I'd resolved) came back soon after and I never did sort out the issue. Here's the recurring problem that I most recently described summarized:

If I just begin driving as usual upon first starting the car each day, all aforementioned error lights come on and the car force-kills the ICE, which won't come back on. Following this, the car occasionally refuses to even let me shift into D, in which case I had to disconnect the 12V battery for long enough that the car forgot about the critical error, which could take several minutes. I would then have to perform "the ritual" once I disconnected the 12V battery long enough that she let me shift into D again. Here's "the ritual:" The issue is entirely preventable by starting the car, immediately shifting into D, and revving the engine for a minute or so.

This became a daily ritual the first time I drove each day: start car, immediately shift to D, rev engine for a minute or so, and THEN I could drive without issue. If I did the ritual, the car worked every time. If I forgot, it failed every time.

I also had intermittent severe loss of power. I could floor the acceleration pedal and the car would take 30 seconds to get up to 30 mph. It was infrequent, but it was still common enough that I changed my driving behavior to account for the possibility of the issue presenting itself.

Further, my gas mileage seemingly never got back to the 44 mpg I averaged before the issues began. I sat around 33 mpg from the time the issues in this thread began until today (in other words, despite replacing the hybrid battery, something was still broken that apparently caused a failure between the two systems).

The ticking of the engine got progressively louder over time; so much so that I was embarrassed to be seen in my dying car and I parked farther away than I needed to from my destinations lol.

I ran some of the diagnostic troubleshooting steps from the service manual for the P0A0F and P3190 codes. The next paragraphs roughly follow the order of the diagnostic flowchart in the service manual.

If I recall, I don't think I could see/knew the INF code for my P0A0F code. There's one diagnostic flowchart for INF codes 204, 205, 533, and 534 and there's another flowchart for INF code 238. I had to start somewhere, so I assumed it was not INF code 238 and focused on the former diagnostic flowchart for the other INF codes. The flowchart said only to diagnose other check engine codes, so that's what I did. I ignored the P0A0F-238 diagnostic flowchart because I didn't think I could complete it on my own. I moved on to the diagnostic flowchart for P3190.

P3190 diagnostic steps:
I had fuel. I had no obvious obstructions of the air induction system, but I still went as far as removing and cleaning my intake manifold. It then recommends "repair or replace" if there are unusual engine noises or vibrations. I had 1-2 circumstances where I had bad clunking in a span of many, many months, but I wanted to start by troubleshooting with issues that weren't extremely intermittent so I ignored this step. I also ignored this step due to the extreme nature of the recommendation: it's quick and easy to do anything that's not replacing the engine so I figured I'd do what else I could. I could not check fuel pressure so I skipped this step and never came back (my spirit was eventually broken). I used a multimeter to test my mass airflow meter and it passed. I have to make an educated guess about what I did for the following sensors because I didn't record my work. If I actually tested them then they would've passed because I didn't replace any of them: I'm almost certain I checked the engine coolant temperature sensor, crankshaft position sensor, camshaft position sensor, throttle control motor, and throttle position sensor. These are easy to test as you just check resistances.

Aside from the fuel pressure test I believe I finished the P3190 flowchart. The last step recommends replacing the ECM which I did not do. The P0A0F flowchart (excluding INF code 238, whose flowchart I did not follow) recommends replacing the ECM if no other codes exist.

That's all I did for following the troubleshooting guides in the service manual. I was too burned out to test fuel pressure. I didn't want to replace the ECM without finishing all other diagnostics, though that's one of the last remaining possible issues. All of this ignores the possible issues addressed in the P0A0F-238 diagnostic flowchart, but I didn't know my INF code for P0A0F and quite honestly I'd forgotten about the P0A0F-238 flowchart by a certain point.

I did more searching after this. I found suggestions that the ticking could be a bearing inside the engine block going out. The recommendation was that it isn't worth repairing and to just run until the engine dies, so I followed that advice and ran the car until the engine died. I was very tired of running full-speed down the rabbit hole at this point and wanted to be finished with automotive diagnostics and repairs. It ran in a quasi-stable state as described above with no maintenance aside from new rear wheel bearings (obviously unrelated). I towed it to Todd at Tampa Hybrids today. They'll go over it and so hopefully soon we can piece together what the issue was and I can share what I had to do to fix it all.