no codes no vtec


diyek9

diyek9

diytuning
Joined
Aug 3, 2007
Messages
148
i have a 99 hb with a ls vtec swap i have no codes and no vtec car is jumped to obd1 with a chipped p28. my friend told me to hook it up to a switch direct, i heard the solenoid activate but still no vtec when i drove . i hooked it up back to the harness and im stuck.. oil is good and i know pressure should be fine since i just rebuild it like 15k ago.

any ideas guros:nice:
 
check the wire that pins up to the ecu some time's it tends to get loose make sure its secure (at both end's) if not open up your solenoid make sure the mesh is clean, if not rinse it out with gasoline and use an air blower to spray it dry. Good luck
 
Remove your vtec solenoid and inspect the filter it might be dirty not allowing oil pressure through.
 
i guess the car fixed it self. lol
last night on the way home i decided to open the throttle just for the hell of it i heard and felt it switch on so, hell yea car doesn't fell like a corolla:nice:
 
just remember vtec relies on oil pressure, coolant temperature and im sure its throttle position aswell. that happened to me once when i started the car up. it was warm but maybe not enough oil at the solenoid not letting it engage. i always now make sure not to vtec after startup. :nice:
 
iirc if the oil pressure is to high vtec wont engage? and i know if the coolant is not going over 75 degrees vtec will not engage, it does not read throttle position
 
ash-EK4 said:
iirc if the oil pressure is to high vtec wont engage? and i know if the coolant is not going over 75 degrees vtec will not engage, it does not read throttle position
Click to expand...

I think it'll only not engage if it is too low :nono:
 
Mike Duff - dc2 said:
just remember vtec relies on oil pressure, coolant temperature and im sure its throttle position aswell. that happened to me once when i started the car up. it was warm but maybe not enough oil at the solenoid not letting it engage. i always now make sure not to vtec after startup. :nice:
Click to expand...

Throttle position doesn't matter but speed does. The VSS must read 10mph / 16 kph or greater. You're spot on with the oil pressure which should be 55psi or greater and can't remember the degrees the water temp must surpass in order to engage VTEC and lastly the ECM cannot be in safe/limp mode. Hope this helps diagnose future VTEC problems.
 
Alright let me correct myself here.

Engine speed has to be 4,900 rpm or higher, a vehicle speed of 19mph/30kph or faster, and the engine coolant temperature at 140 degrees F/60 degrees C or higher, VTEC can engage. No safe/limp mode!

The rpm window varies between models i.e. CTR at 6000rpm etc etc.
 
im sure throttle position ie the throttle position sensor does come into it as if you use light throttle up the revs past the vtec engagement mark it doesnt switch over. not that you would do that anyway.
 
Honda's VTEC system is a simple method of endowing the engine with multiple camshaft profiles optimized for low and high RPM operations. Instead of one cam lobe actuating each valve, there are two: one optimized for low-RPM stability & fuel efficiency; the other designed to maximize high-RPM power output. Switching between the two cam lobes is controlled by the ECU which takes account of engine oil pressure, engine temperature, vehicle speed, engine speed and throttle position. Using these inputs, the ECU is programmed to switch from the low lift to the high lift cam lobes when the conditions mean that engine output will be improved. At the switch point a solenoid is actuated which allows oil pressure from a spool valve to operate a locking pin which binds the high RPM cam follower to the low rpm ones. From this point on, the poppet valve opens and closes according to the high-lift profile, which opens the valve further and for a longer time. The switch-over point is variable, between a minimum and maximum point, and is determined by engine load. The switch back from high to low rpm cams is set to occur at a lower engine speed than the up-switch to avoid a situation in which the engine is asked to operate continuously at or around the switch-over point.


above taken from wikipedia.org :nice:
 
okay up date on this situation for others that might encounter this. okay it did hit vtec again that once but, then stopped again i didn't have a oil pressure gauge and had a extra 3 bills laying around. so i just said screw it and bought a itr oil pump. ever since then vtec has not let me down. so the oil pump was just starting to show its signs of wear and old age basically dying on me. thank god i cought it right before it did other wise my engine would have been trashed



ps this is the only thing i didn't change when i rebuilt it lesson learned
 
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