Death Rattle...Not on Start-Up

We have a 2013 Prius C with 258K miles with a death-rattle. This does not occur on start-up, and we are not losing coolant and there is no water in the oil, so I expect that rules out a leaking head gasket.

While downloading codes, B1503, Exhaust Heat Management Warning seemed to be the only code that might be related to this condition (others include AC Air Duct damper control, TPMS, and an old Turn-signal and Brake light code). The Engine Coolant Temperature Sensor is on order.

I did insert a putty blade between the EGR and its Cooler to check for a clogged EGR system, but it still started the death rattle after warmed up.

I checked/swapped the #1 and #4 Plugs and Coils after a download finally kicked out a #1 Misfire, but that did not change it’s condition.

Of note, the death rattle seems to display after the engine in warm, and low power situations. Accelerating, or higher speeds stops the condition. I will replace the Engine Coolant Temperature Sensor but am doubtful that it could cause this condition. Any other suggestions I might be missing?

 

The "death rattle" IS very dramatic...shaking and knocking terribly at low power settings once warm...not on start-up. I'll expect to work on it again today, so I'll try to get some video if it repeats after I change the coolant temperature sensor. . It's not just on shut-down. There is no coolant loss, or coolant in the engine oil. I think something is telling the computer to significantly change the air/fuel mixture. That's why I tested the EGR, and I read that the coolant temperature sensor does this too if it fails to properly detect the coolant temperature, but if I can get a video for you, you'll swear it must be something much more dramatic than a little little fuel trim fault. I'll follow up. Thanks for your time.

 

Well, I changed out the Engine Coolant Temperature sensor, but the B1503, Exhaust Heat Management Warning code still exists. My diagnostic downloading tool now suggests a wiring problem in that circuit.

On the videos, I saved a MP4 video of a normal (cold) start, one as it transitions to the rattle, and another warm start with all kinds of racket. I tried to upload the MP4 files on this post, but couldn't link to these. Suggestions?

 

Leadfoot, thanks for the feedback, I just saw your reply. I'll try some some new plugs tomorrow.

I'm just trying to come to terms with such severe shaking that only occurs when warm. I would think the head gasket would leak more when cold, but I'm starting to believe you might be right....

 

Well, the new spark plugs didn't help. Pulling the cylinder head to check that, and the EGR system to see if it's clogged...

When it started today, I could smell a bit of an exhaust smell from the engine area. We'll see...

If the O2 sensor was bad, wouldn't it show up on the download?

 

Problem solved!

To follow-up, for the benefit of others...

I did ohm checks on the fuel injectors and found that the cylinder #1 fuel injector was less than 1 ohm, where the others were around 12.6. I never did remove the cylinder head, as I just couldn’t see how it could be a bad head gasket when it ran good when cold, but terrible when warm, with no loss of antifreeze.

Similarly however, I initially discounted the fuel injectors as a possible problem as it ran good when cold. Odd.

And the terrible shaking, I heard referred to as a death rattle, was really being caused by 1 missing cylinder. Shocking.

Of note, I sprayed out some carbon inside the EGR valve, but the EGR cooler was in good shape…no clogging at all. Not bad for 258K miles. I also replaced the spark plugs.

After replacing the defective fuel injector, and dumping a can of Sea Foam in for good measure to clean up the other fuel injectors, my wife reports that the Prius runs great now.

Until next time….and thanks for the suggestions!

 

Well, 20,000 miles later, and I have a similar setback. P304 #4 cylinder misfire. I cleaned the injectors with brake cleaner, then swapped the #4 and #1 fuel injector, and also swapped the #4 and #2 coil, hoping the problem would move with the bad part, but it still says #4 misfire. I blocked the EGR, to isolate that, but it made no difference. The plugs are new from this Summer. When the engine was cold, the hard knocking would cycle in, then running great with no missing before another round, repeating that cycle. Once warm, you can hear the cylinder missing very often, which transitions to heavy knocking at times, then back to regular missing. I wondered about the Air Fuel Sensor or Mass Air Sensor messing with fuel trims, but that should affect all cylinders. No loss of coolant, and the oil looks good.

 

Well, I feel pretty silly, but I previously set the spark plug gaps way too tight. I re-adjusted the gaps, and the engine has been running smooth again. Really, it's surprising that it didn't provide any problems with the previous spark plug gap since they were replaced this Summer. Maybe the last tank of gas had quality issues? Thanks ChapmanF! I ordered a leak-down tester to have one one hand next time things are in doubt.