No VTEC
 

I am having an issue with my vtec to where when hit about 5500 rpms it's as if i were hitting the rev limiter and my car wont go. I also have a big lost in power even without hitting vtec. Especially on hills where I'll be flooring it and it stays at the same speed or slowly goes down. It'll be more engine noice than anything. I currently don’t have a check engine light but I did have a misfire which was fixed with new spark plugs a few weeks back. Now im not sure if this lost of power and not being able to go past 5500 rpms is because of coils, the vtec solenoid itself, oil pressure or anything else. I also recently did an oil change.

Well this likely has something to do with the P0172 (running too rich) and P0170 (fuel trim issue) that you reported in your other thread. And if running pig rich, then that is likely related to your misfire issue which could have been linked to your spark plugs which possibly were fouled. And the O2 sensor you replaced per that other thread was likely fine and was actually reporting the correct thing.

You need to sort out the running rich issue first as that is most likely going to lead to fixing the other issues. So keep digging there per the comments in that other thread. MAF, IACV being stuck (but that should cause a lot more issues at idle), fuel pressure, etc.

No CELs? :ponder:

nvm

You might want to check the back pressure in your exhaust system. When cars run very rich the catalytic converter can plug up. A decent muffler shop should be able to do that. Anything over positive 5lbs is bad. Had a repair shop for a very long time. We would see this when people had bad plugs or coils. All that unburned gas would cause the cat to overheat and literally melt down. We would use an old vacuum gauge. We would drill a small 1/8 hole in the header pipe before the cat to measure it. When the cats plug up it feels like a fuel delivery problem but it isn't. Basically the motor is constipated--cant get more shit in until the old shit is gone.

Check to make sure you have not broken the vtec oil pressure sensor. It sits high up and is easily broken whole doing servicing (oil change in my case!). My symptoms were similar -- no check engine light or other indicator on the dash. It would run fine right up until vtec engagement (5500-6K) then just bog down---very noticeable. When I opened the hood and looked around, I found the broken connector hanging by the wires down by the oil filter. Bought a new sensor and installed and its fine now.

brandon, did you figure this out?

No i still haven’t been able to figure out what it is. Someone on a facebook group said it could be the upstream O2 sensor as they had the same issue but I'm not sure cause someone else responded with the same issue and said it didn't do anything for him so I'm really unsure on what to change or do but I need to figure out why I'm running rich cause my previous two codes came back a couple days ago. (P0172) (P0170)

Are you running a stock setup? Have you modified anything on the engine or exhaust? Running new spark plugs?

Everything is stock, just an intake and an invidia n1 exhaust.