Fuel pressure regulator causing misfires?

Thanks! You saved me a few dollars from buying a coil i wouldnt need. I replaced their order again and its still cylinder 1 misfiring. This is very frustrating, and im not sure what it could be at this point. Any ideas?

 

What are the chances the transmission can be causing misfires? The reason I ask is because I was driving in EV mode really slowly and I noticed an unusual clunky transmission. I thought it was vibration from the engine but i saw the RPMs were at 0 for the ICE. So what is going on. I get different misfires in park vs drive, but none in neutral. Is it possible or

 

Yup thats what its been doing, clattering and banging.

Also, i have now replaced all spark plugs, all coils, all fuel injectors, and the MAF sensor. Still misfires same way. I think its because the fuel line itself cannot hold pressure. I am getting a code saying vapors are escaping and improper fuel to air ratio, in addition to the usual cylinder 1 misfire and occasionally the other cylinders as well.

Is there anyway for me to test the fuel line for its ability to hold pressure? Is there a guage i can get or fitting to try pumping air into the line and see if it holds?

Or better yet, i can try and re-connect the areas of connections. The paint thinner i used might of destroyed the O rings and hence why pressure might not be holding. Thats my hypothesis at this point, since i know it cant be the fuel assembly or fuel injectors due to replacing it.

 

P0101 mass or volume air flow circuit range problem
P0456 evap emission control system leak detected (small leak)
P0441 evap emission control incorrect purge flow
P0455 evap emission control system leak detected (gross leak)

I got all of these.

 

So I dont get those codes anymore and i inspected the hose and O rings to it.

But the misfire is still there. Not exactly sure what is causing it but there is a pattern that could maybe help narrow it down.

When placed vehicle in park, cylinder 2 is the only one that misfires.

When put in drive and foot on brake or slow speed, cylinder 1 is the one that misfires. Sometimes a combination of both 1 and 2, but mostly 1.

When driving at highway speeds or accelerating to high rpms, all misfires stop.

Im not getting any other code besides the misfire codes. I also know it cant be coolant flowing in because my coolant tank has been full since three weeks ago. Any ideas what is causing it?

 

Turns out it was a blown headgasket. Hope this helps anyone that is experiencing misfires between two cylinders, but no oil or coolant leak.

This is what it looked like.


Wasnt able to pin point it until I did a compression test and saw the first two cylinders were lower than the other two in terms of pressure. Thats when I knew it had to be a headgasket issue for sure.

I think I've wasted at least $300 replacing the fuel assembly, pouring coolant gasket sealants, new fuel injectors, new spark coils, spark plugs, oil additives, etc. trying to fix my problem when it was the headgasket all along. Dont be like me lol and just do a simple compression test first before anything if you are experiencing misfires.

Also: my oil leak on the back of the engine was being caused by my timing chain spring tensioner being loosely tightened. The spring load pushes against the bolts, so its one of the most common parts on the prius for oil leaks. It uses two small 10mm nuts to keep the thing in place, so its easy for it to come loose. Just needs to be retightened every now and then if you experience leaks there.

 

I used both a leak test and a compression test, but the compression test worked better. Leak test was fine too but getting the piston dead center was having me second guess my results if i did it correctly. The compression test kit that I rented gave me clear results.

To do it, i just started the car up with the sparkplugs and fuel disconnected. This will have your MG1 spin to roll your engine like a starter would, but with the absence of fuel or spark its just spinning the pistons up and down creating pressure.
I would place the hose in each cylinder, hold the start button for a few seconds, then go look at the reading and do the same for each cylinder. I dont remember the exact psi reading, i just remember that the first two cylinders were both lower compared to the other two which is how i knew it must be the headgasket.

Ended up replacing it with felpro gasket instead of OEM. The groove pattern is different in its design which might make a difference longterm, just something to consider.