Hi all, I recently purchased an Australian market 1994 Honda Integra VTI-R with a B18C2 - my first Honda. I realised recently that the VTEC has not been engaging. Since I've had the car I have noticed the coolant gauge has been sitting at around a third of the way up. I replaced the thermostat but it sits in exactly the same spot, even after extended periods of driving. My speedo works fine, I have fresh oil up to the max line on the dipstick, and I tested the VTEC solenoid and confirmed that it clicks audibly with 12V to it. I have no check engine light on (lights up with the ignition in the 'on' position but the engine off, as it should).

I'm thinking it's gotta be coolant temperature sensor related. I just don't know which ones do what and which should be replaced. Some help from a more experienced individual would be greatly appreciated

Edit: I might just add that I believe VTEC isn't working because I absolutely cannot hear or feel anything change throughout the rev range, and it feels like it runs out of breath by about 6k, you can go further but it's not very rewarding. The car has a stock exhaust and intake though, but I wouldn't imagine that would mean the crossover is completely inaudible.

 

I believe there are two coolant sensors, one in the thermostat housing and one in the cylinder head. The one in the housing goes to the coolant gauge and the one in the cylinder head goes to the ECU. I think you need to confirm that the engine coolant temperature sensor in the cylinder head is working by plugging in an obd diagnostic tool and reading the engine coolant temperature. Or you can just wing it and buy a new sensor, throw it in, say a prayer and hope for the best.

What all needs to be functioning for vtec to activate? Oil pressure, over 150F* degree coolant, in gear, over 15mph, no limp mode or CEL? Look into all those sensor values and make sure they are all functioning to spec.

 

As far as I can tell from my Googling and forum searching, there's 2 sensors in the head - one for the gauge and one for the ECU - and there's a third in the thermostat housing for the fan switch.
As the gauge and ECU sensors are separate, would it not be unlikely that they're both reading low?

 

If that is the same as the USDM B18C1 (secondary intake runners)...
VTEC is at 4400 and is damn near undetectable. The transition should be very smooth, but it should not feel like any loss of power.
Secondary (IAB) runners open at 6000 RPM, this make a more noticeable difference in the engine sound and power.

If your VTEC is not engaging, and you are not getting any CELs, you may have to look into the ECT signal. I'm not personally sure if OBD1 code readers can pull that data. I know my OBD2 reader can. Since your engine never warms up (according to your gauge) then that may be the cause of the issue.
https://www.acuraautomotiveparts.org...-sensor-2-scat

 

Honestly, after having more of a drive today after having done the thermostat, I can definitely noticed a good kick of power at 6 grand along with a strong pull to redline. I think our issue might just be solved.

Thanks for the help guys

 

Take the stock airbox lid off or put an intake on and it will definitely be noticeable. As explained above, you really can't tell by noose with a stock gsr when it kicks in, besides when the butterflies open up at around 5800.