Cleaning egr fixed misfire

Hey all, today I wanna share my experience fixing the misfire problem on my 2010 prius. So the short version is that cleaning the EGR cooler, and all the EGR passages including those in the intake manifold fixed it. There was so much carbon buildup all up in there that clogged the passageways that either the cylinders were not getting enough exhaust air or some cylinders were getting too much while other weren't, and this was screwing up the air fuel ratios.

The long version: At about 280000 km (Canada) which was a few weeks ago, my engine started shaking really hard and making clunking noises at low acceleration and when the ICE turns off after coming to a stop. It would run ok when the engine rpm was sufficiently high. Prior to that, about 60000 km ago, it would sometimes have that rough start with the clacking noise when the engine was cold, which sounded similar to the misfire but less severe (this went away by itself). So I plugged in my obd2/torque to find codes p0301 (cylinder 1 misfire), p0303 (cylinder 3 misfire), and p0300 (random multiple cylinder misfire). Preliminary research suggested I might have clogged injectors. So the first easy thing I wanted to try was to pour in 2 fuel system cleaners with PEA into my tank at the same time, one from Gumout and one from Redline. After running that tank down I saw no improvement. I cleared the codes a few times and the the same type of codes kept coming back, but for different cylinders, like cylinder 1, 2 and 4 and sometimes other combinations with P0300. So I did some more reading and found a whole bunch of threads here about how my symptoms are indicative of blown head gaskets which is very common for gen 3s and I was like Wth but I checked my coolant overflow tank and I didn't have creamy oil coolant so I knew my head gasket didn't give out just yet.

Then I found this video:

which is a bit long because he explains all the things he tried before figuring it out, but the point of it is that he solved the problem by cleaning the EGR components (cooler, valve, pipes, intake, etc) which were badly clogged. Props to CoolAirVw Rm for making that video because without it, I'd probably have had a much harder time figuring out what to do. So I thought why don't I just try this and then if that doesn't work then at least I'll feel better about biting the bullet and getting my engine replaced.

So since I'm going to work on the engine I first decide to examine the spark plugs. The porcelain tubings for the plugs in cylinders 1 and 3 were loose because of the massive stress from all the misfires. I also took photos of inside the cylinders with my phone camera/flash through the spark plug holes and saw no coolant in any of them, which is a good sign that I didn't have a blown head gasket. Luckily I kept my old original spark plugs from when I replaced them so I put all the old ones back in and ran the engine again just to rule out bad spark plugs. It misfired again right away. So I got to work on cleaning out the egr and intake.

The videos I used (Nutsaboutbolts):
2010-2015 Toyota Prius EGR and EGR Cooler Cleanings for P0401 Code - YouTube
2010-2015 Toyota Prius Intake Manifold cleaning - YouTube

I also used CoolAirVw Rm's technique of attaching a piece of galvanized wire on a drill and physically drilling out the soot and carbon from each of the little passageways in the EGR cooler. Really you need to plunge the heck out of all those egr passageways in the EGR cooler because regular chemicals like brake clean won't work. Other chemicals would be too dangerous to use at home or be cost prohibitive. I sprayed lots of WD40 in the cooler to lubricate the drilling. Some of the bolts are tricky to reach and you need that special E8 external torx socket to do this job but other than that it is not that difficult. Also to block off the coolant hoses, I just used pieces of saran wrap folded into multiple layers and tied them off with rubber bands because I didn't have hose clamps (diy hack).

The end result of this job is that the engine runs literally like new. My fuel mileage went from 5.2L/100km (45 MPG) to 4.6L/100km (51 MPG). So the EGR cooler and EGR intake cleaning is a really important maintenance job every prius owner needs to be aware of if they want their prius to last as long as everybody says it should.

 

I don't have techstream and also hope I won't need it in the future!

 

Nope, just disconnected the electrical connection on the egr valve.

 

Good to know but the saran wrap worked well and saved me a bunch of time. It was also easier to remove the throttle body and clean it too which make the intake easier to remove. Oxy-clean sounds like a good idea and I've read oven cleaner also works well for carbon deposits, but I didn't have any of that on hand so I just used the WD40 with wire drill and flushed it out with a whole can of brake clean. The cost of the whole job was the price of one E8 socket and probably 1 and a half can of brake clean. And probably a whole afternoon.

 

Good point, misfires can have many causes. Yours might be a rare case though as the clogged egr and intake seems to be the main culprit of misfires in gen 3s from my own research. I'm glad I was able to DIY it and get rid of the misfires completely, but I'm still keeping a close eye on my coolant level and checking for any coolant contamination in my oil.