problem with vtec

[t_fuNk]

Hey everyone. I just recently bought a 94 Honda Civic del Sol Si.While on a trip, the VTEC seemed to have over heated. I was cruising around 75 in fifth gear, right around VTEC initialization. I had it on cruise control. It turned off after about fifty miles. I slowed to the shoulder. I cranked it and it worked fine, but while merging, I hit VTEC and it turned off. I drove it there under VTEC. After a few hours, VTEC was working fine. I haven't had any more problems with that. Does anyone know what could have happened or if it caused any permanent damage?

[ImSoYesterday]

In order to know anything about your problem you must understand VTEC technology.

VTEC stands for Variable valve Timing and life Electronic Control.

The VTEC is a method to optimize air/fuel mixture flow through the engine.

There are ways to make your engine produce more power, forced induction (compressing air-fuel more greatly in cylinders). Higher displacement, speaks for itself, the difference between a 1.6 and a 1.8... Well what Honda has done is just made everything move faster, to increase power. But this is for high speeds, and most of us with our VTEC engines dont spend our whole life redlining, is why Honda implemented VTEC. Basically at XXXX RPM Your VTEC will 'activate' and your valves will open wider, and when you are cruising the lower RPMs your valves will not be open as wide as they are when your VTEC 'activates'

What happens is the engines computer activates alternate lobes at a certain RPM to change the cam timing and valve overlap.

This will not make sence to you unless yhou understand a combustion cycle however.

In result there is a million thigns that could have been wrong, with your cam,valves, lobes, or most likely electrical. Has the car seen any unordinary acts that would f-up the ECU?

[t_fuNk]

I beleive I understand what VTEC is, I was just asking what could have happened. Before, the tach had been jumping around when I hit VTEC. I dont know if these incidents are related. Thank you for any suggestions.

[Privatebigandrew]

Originally Posted by ImSoYesterday

In order to know anything about your problem you must understand VTEC technology.

VTEC stands for Variable valve Timing and life Electronic Control.

The VTEC is a method to optimize air/fuel mixture flow through the engine.

There are ways to make your engine produce more power, forced induction (compressing air-fuel more greatly in cylinders). Higher displacement, speaks for itself, the difference between a 1.6 and a 1.8... Well what Honda has done is just made everything move faster, to increase power. But this is for high speeds, and most of us with our VTEC engines dont spend our whole life redlining, is why Honda implemented VTEC. Basically at XXXX RPM Your VTEC will 'activate' and your valves will open wider, and when you are cruising the lower RPMs your valves will not be open as wide as they are when your VTEC 'activates'

What happens is the engines computer activates alternate lobes at a certain RPM to change the cam timing and valve overlap.

This will not make sence to you unless yhou understand a combustion cycle however.

In result there is a million thigns that could have been wrong, with your cam,valves, lobes, or most likely electrical. Has the car seen any unordinary acts that would f-up the ECU?

Ok i am not trying to be a smartass, but maybe you need a lesson on VTEC operation yourself. First off, What do you mean by Honda has made everything move faster to increase power. Makes no sense to me. Valves dont open wider, that is simply impossible. They are held open longer (more duration) and open at a higher lift. (meaning, that they are pushed further way from their seat) Maybe you meant wide as in higher lift, but you forgot to mention duration. And the computer does not activate any "lobes". There is no lobe activation in VTEC. The computer reads the Map sensor, ECT sensor, TPS sensor, and engine speed to decide when to activate the "VTEC Solenoid". The VTEC solenoid then moves the spool valve which in turn engages the third rocker arm (the middle one on DOHC models), via hydrolic pressure, or engine oil pressure to be exact. When the third rocker arm is engaged, the Valves are forced to follow the cam profile of the VTEC lobe. When not engaged, The VTEC rocker arm "floats", not having any effect on the other valves. VTEC is essentially like throwing a set of high lift high duration cams in the engine when it engages, except, you don't have to suffer low RPM operation when not engaged. I hope this was informing, as i am tired of typing now

[ImSoYesterday]

I am going by the research I had done for a school project, and with the cam/lobe setup I knew to be true with DOHC motors. All of my knowlege is based off of what I researched back in school, I haven't got to take it apart yet...

[t_fuNk]

Well thanks for the information on VTEC guys. To get back to my original question, does anyone know if cruising right around the speed/RPM at which VTEC engages potentially make the solenoid engage and disengage so as to "break" or just over heat the solenoid? Has anyone else ever experienced this?

[superbluecivicsi]

people who complain about their vtec not working or "just cant feel the vtec," are just plain paranoid. if your the oil pressure or selenoid is not operating correctly your ecu will throw a CEL. its that simple.

[t_fuNk]

Well.. I don't beleive I'm paranoid about VTEC. If no one can understand what I am asking, then don't worry about it. I'll ask someone else that knows something, thanks anyway.

[superbluecivicsi]

Originally Posted by t_fuNk

Well.. I don't beleive I'm paranoid about VTEC. If no one can understand what I am asking, then don't worry about it. I'll ask someone else that knows something, thanks anyway.

dont take it so rough. too many new folks here are too sensative. the post should tell you that it is not vtec related.

as far as your car dieing, it can be anything from your description. tps, map, compression, dizzy, vac leaks, no fuel, vss, ecu to name a few.

good luck.

[flameboy79]

Don't none of you guys know about reading fault codes?

Even if your car is not throwing the CEL light automatically, there can still be a fault logged on the ECU. So when in the situation that you are in it is where I would start.

In the passenger footwell is your ECU. Bundled by the ECU will be some service connectors. You want the small two pin one. It may be housed in some rubber casing, if so just pull it out. Bridge it with something like a paperclip, turn the keys (but don't start engine) and watch the ECU cel light.

If it stays on then no problems. If it flashes then count the flashes. A long flash is 10 and a short flash is one. So... long, long, long, long, short would be fault code 41. Do a google search for Honda fault codes and compare.

There is a fault code for faulty VTEC solenoid so if that is the problem it should in theory show up.