Normally between 4-5k rpms in 2-4 gear i can feel a substantial difference in my cars throttle response with better acceleration under VTEC. Last week i had my oil changed and my Mechanic recommended i switch to Ardeca 5W-40. Hes been working on my cars for a while and never had any issues so i Figured i would give it a shot and take his word. Normally i stick with mobile 1 synethic 5w-30. Ever since the swap VTEC feels completely gone. Its just the same acceleration level no matter what RPM i am at. I don't hear the little kick of it either. I did a little research and I see that 5w-40 is normally used on turbo cars? He drives a Supra so i am wondering if maybe while that oil is great for his car its causing an issue with mine. The car runs great and throws no codes but it doesnt feel the same w/o VTEC.

Could this be the reason why VTEC isnt engaging or is it something completely different that i need to look into?

 

VTEC used to work... Changed oil to something odd and different.... VTEC no longer works....




Wouldn't a cheap hypothesis test be to just change back to what you usually use and see if VTEC works again? Then you can tell the mechanic he's full of shit and not go to him anymore...

 

Lol. Change your oil back.

 

and change your batteries

 

 

That's not vtec that's your intake manifold butterflies opening up. Vtec engages at ~5k rpms and above.

Use your OEM recommended oil IIRC 5w-20 and make sure you have enough oil in the car. Vtec works off oil pressure so if your below the min level it won't engage. You'll know it too because the car nose dives at 5k when this happens, feels like a fuel cutoff.

 

not if you have flash pro and are tuned

 

Of which I doubt OP has either... Especially since he allowed the mechanic to put in BS in his engine.

 

Even tuned Vit told me the engagement point is usually within a few hundred rpms of the OEM set point, at least in his tunes.

 

yea but with the oem set point at 4950, when you move a few hundred that gets you solidly into the 4k-5k range

and the non type s set point is at 4700.

 

I wouldn't feel comfortable running a 40wt oil considering the manufacturer recommended is 20wt...

 

Well i also had my air intake hose replaced due to it having a crack in it a few days prior. Could that also have been something to do with it combined with the oil?

 

True true. There are 2 kicks that you can feel in this car, IM butterflies and vtec. But if vtec wasn't engaging the car nose dives very abruptly. At least mine does for a low oil condition.

Not sure. Did you have any check engine lights anytime before and after the hose? Double check to make sure everything was connected back up correctly. Change your oil back to OEM weight check the level and see how it runs. You can also unplug your battery for a few minutes to reset the ECU and see how it feels after a few miles / couple of days.

The car dips a bit before vtec kicks in (at WOT), feels like you taking your foot off the gas for a second then back on. If your mechanic disconnected your battery the ECU is in learning mode and it takes a few miles for it to self tune and feel normal again.

 

No check engine lights before or after. The car runs perfect except for the fact i dont feel that much improved acceleration under WOT between 4-5k. My car is able to accelerate fine up to 6k so it must not be VTEC as many have stated. Its a slow steady accel up until i shift up or let off the gas. Sounds like what have others stated my intake manifold butterflies arent opening up.

The question becomes if its due to the oil, the new intake hose or a combo of both. The previous 40k miles the car never had this issue until he did those 2 things. How would i look into seeing if its the butterflies being the issue?

 

I'm not sure if you get any warnings lights if the manifold actuator isn't working, maybe someone else can comment on that?

Meanwhile, make sure it's plugged in. It's a black round thing bolted on the left side of your manifold, under the plastic cover.

 

If there was an oil pressure or vtec issue, you would have some sort of code stored, maybe the light isn't on yet but a code would at least be stored. Same thing with the intake manifold butterfly valves, but that malfunction should set a MIL. Has the car been scanned for codes or just the light hasn't come on?