A friend of mine has a 94 prelude with in h22.
Vtec only engages when the car is cold, it doesn't engage when the car is warm, what can be the problem? he checked the timing that seems to be good, any suggestions? if i remember correctly he said that he has no check engine light & when he runs the jumper to check for codes the check engine light stays on with no flashes.

feed back is appreciated thanks

 

VTEC is not designed to work when engine is cold. Is the engine a hybrid h23/h22 ? Check oil pressure, oil level, and VTEC solenoid valve.

 

the ecu runs through a series of checks before engaging vtec.
coolant temp, oil pressure, etc...

Sounds like as the engine oil heats up, viscosity gets lower, and lowers oil pressure, the lower oil pressure could be causing vtec not to engage.

just an idea.

 

what? when i started my car cold it ran vtec no problem... what his issue he is having is that his vtec solonoid screen is clogged or his solonoid is bad!

 

you where high. Coolant temp must reach a certain degree before ECU sends the o.k. signal for VTEC. You can rev the **** out of it going through your gears, but before you reach that coolant temp your VTEC aignt-gon-work.

 

well idk what experiences you are going through but i know when i wake up and turn the car on vtec will engage cold..... i dont like to do it because the engine isnt warm and i can face problems but when i was young and dumb i have done it when cold.

 

ok, I guess you know best. ..( .........some people just don't care to learn the facts. )

 

its not about who knows best... i dont know best. i know that. im only saying that my motor allows vtec to kick in from the start.

 

this is absolutely correct. seriously.

how do you know vtec isn't engaging? are you just going off of your butt dyno or do you have solid evidence? if it isn't engaging, it will throw a cel.

 

on an h22 its pretty obvious if vtec hits or not. there is a noticeable difference in sound and pull after 5000

 

hmmmm...
if i remember correctly my friend had over heating
issues in the pas, not sure if he finished that problem cause
he didn't finish it, he says that Vtec doesn't engage when cold cause he can notice by x-over/power

and when warn he cant notice neither.
like i mentioned above it is the H22

 

right, but he said there is no cel. if vtec isn't engaging, there would be a cel. that's why i think it might be in his head. i have driven preludes and there isn't a distinct kick when vtec engages. it is kind of subtle.

 

vtec engagement is suppose to be smooth. not abrupt. when the car is cold the ecu is usually in a open loop mode until the resistor type sensors heat up to operating temperature (ect, o2, iat). if he has a sensor that is on its way out (not completely faulty) it will not always set off a cel.

 

Just talked to my friend he said that his overheating probloms were fixed a while back ago, he is going to place the vtec solonoid to try to fix the problom Til then anymore ideas?? He also tryed to reset the ecu by disconnecting his battery. No luck.

 

i dunno man... hard to diagnose cars over the internet. i would try testing the vtec switch, if thats working then i would open up the actual vtec assembly and check for congestion around the screen.

 

if there is no cel, then i would be willing to bet nothing is wrong (unless the bulb has burned out.) some people seem to think that vtec engaging is some neck snapping experience. it isn't.

 

I know its not a necksnapping experiance but my friend and i can tell a difference from when it was working correctly and now that he is having a problom. he is going to try a diffeent ecu to see if the probloms coming from there

 

but there is no cel, right? and the bulb isn't burned out?

 

No the bulb is not burned out.

 

Problem has been fixed, the vtec solenoid wasn't working properly . He replaced it with one that he had laying around and the car is running as it should. Thanks

 

I have the same problem in my k20 euro r swap I changed oil to thicker oil still happening
redid my oil pump , still happening
Went through 3 vtec solenoids , still happening
about to do the rocker arm assembly I'm running out of reasons
I'm a k20 euro r In 04 tsx with k tuner 04-05 manual tsx direct ecu
had codes for rocker arm actuator stuck in bank one then the code went away and thats when the problem started

 

Did you manage to fix??