VTEC problem


J

JamieMathieson

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Joined
Dec 27, 2012
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172
I have annoying problem with the VTEC on my b18c4.

When I drive the car from cold I drive it sensibly until its up to temperature, then when I put my foot down,no VTEC,no matter how long you drive about.

But after it's up to temperature,if I turn the ignition off for around 20 seconds then put it back on VTEC works perfect. I have to do this same procedure every time the car cools down a little after being parked of whatever.

The engine is very well serviced,had every serviceable item replaced on it before I put it in.

I'm running it off a chipped p30 ecu, it's the same even if I change chips.

I took the VTEC solenoid off,took the spool valve out,cleaned it all up,tested the solenoid and cleaned the filter screen (which was barely dirty), still the same so I tryed a different solenoid,no joy.

If anyone could help me out it would be much appreciated.

Thanks, Jamie
 

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I've tried another temp sensor (one in the thermostat housing).

But surely if it was a faulty wire it would be more random
 
I had something similar with my car, usually had to warm it up then cycle the ignition before it would vtec. Traced the fault to a bad wire between the coolant temp sensor and the ecu, must have had excessive resistance in it cause it was reading about 60 degrees coolant temp when the car was fully up to temp, but it would fluctuate around that value so that was why it wouldn't always vtec.
Ran a new wire and its been fine since, that was about 2 years ago

Think the temp sensor that sends the signal to the ecu is on the side of the head isn't it? And the thermostat housing one is used for the coolant temp gauge?
 
definately check your thermostat housing earth...usually the starting point for these sort of issues....
 
Iv just fixed exact same problem on my car it was the wire between coolant sensor under vtec solenoid and the ecu, coolant temp was surging so ecu was unsure of temp until properly warm, i ran new wire and good as new!!
 
Think this is the exact same problem I'm having too but only happens now then, bounces off a limiter at 5k soo gets no where near vtec.
 
I ran a wire,problem solved!

But for some reason I now have no temperature gauge,cleaned the earth and changed the sensor for another I had lying around,no joy.

So I stripped back the insulation tape only to find several twisted together wires! Guess the best thing to do would be to solder all of these first invade one is loose.
 

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I've soldered and heatshrunk most of the wires now. Still no temp gauge.

And I've found a few strange things. On block connector D (the small one), the wire for pin 6 knock sensor (red/blue) there is a brown and black wire spliced in, and the only brown/black wire on the engine loom is for logic ground. Any ideas why this has been done?

The same has been done for pin 7 primary heated O2 sensor 1, and it's a brown/black wire again.

Can anyone shed light on these modifications?
 
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