VTEC intermittent

[EddieMunster]

My 5g has intermittent VTEC engagement, this issue has only just appeared in the last few days.

It was "off the road" for 18 months, whilst I did loads of mechanical work to it (including full service, rocker cover gasket etc.), and before that point VTEC engaged fine. It was MOT'd earlier this morning, straight through with no issue, but hadn't really been driven for 18 months prior to yesterday/today. The full service I did in April/May included all filters, oil etc., and what came out was pretty clean, so there was nothing to suggest tired oil or heavy deposits/clag etc.

Is there an ODB code that might show the issue, could it be 18 month-old stale fuel, or, could it be the solenoid itself?

[Drax]

check the vtec solenoid, just 3 bolts to take it off - the gauze gets dirt inside it sometimes and prevents vtec.

[ATR84]

Is this your 4g or 5g?

[Vtecmec]

Check the wiring to the solenoid.

Check the little filter in the spool valve gasket and that the piston moves freely.

[EddieMunster]

Is this your 4g or 5g?

5g.

[Sailor]

Is there an ODB code that might show the issue, could it be 18 month-old stale fuel, or, could it be the solenoid itself?

I don't think 18 month old fuel would cause this.

[ek9sid]

I know its noddy but worth checking oil level. I know when mine was low on oil, the sloshing of it in the sumo would cause it to drop off vtec.

I know you said its been serviced but just thought it might be worth a check

[EddieMunster]

check the vtec solenoid, just 3 bolts to take it off - the gauze gets dirt inside it sometimes and prevents vtec.

Couldn't find any gauze, spring and actuator seem fine though.

As an aside, where's the ODB port, all I can find is the usual pin/paperclip affair???

[RattyMcClelland]

check the vtec solenoid, just 3 bolts to take it off - the gauze gets dirt inside it sometimes and prevents vtec.

Couldn't find any gauze, spring and actuator seem fine though.

As an aside, where's the ODB port, all I can find is the usual pin/paperclip affair???

no gauze. Get a new VTEC solenoid gasket.

https://www.tegiwaimports.com/genuine-h ... pMQAvD_BwE


No OBD2 port. Just the paperclip port.

Intermittent VTEC is lack of oil typically. Always been my issue. Anything below min and it goes intermittent.

[Scott560]

How strange! Can you describe the intermittency?

There are a few pre requisites to vtec engaging:

1) ECU has to know the oil is up to temperature and up to pressure in the head. VTEC will not activate when the car is cold. If the oil pressure is low at the time of calling for vtec, you will get a Check Engine Light - so rule out a pressure issue if you don't have a CEL. Oil temperature can lag behind the water temperature indicated on the cluster, so be sure its warm before trying.

2) The 'screen' that was mentioned in the gasket, this is where the vtec solenoid block meets the cylinder head (the 3 bolts going horizontally into the side of the head). If you removed the top half only of the solenoid you wont see it, you need to remove the whole block part. It would be unusual for the screen to be blocked enough to prevent VTEC however.

The VTEC solenoid is activated by a simple 12v positive feed on that single wire. You can easily hook up a test indicator (small 5w bulb, or similar, with a ground added), and have it poking out the bonnet. If it lights up then you know the ECU is calling for it fine.

Whilst you have the multimeter out, check that the vtec solenoid itself is working. Unclip the connector, and check for continuity between the solenoid and ground, i don't know what the resistance should be, but its likely to be in the 10s of ohms range. I cannot recall if you can hear it move or click when applying 12v to it. I seem to recall applying 12v to it whilst the car is idling (and connector disconnected) seemed to make the idle go lumpy after 5 to 10 seconds, this was a good indicator that the solenoid was actually changing the cam profile.

Another question - have you been driving a different car in the meantime? the VTEC switchover can be more slight than you remember - it could be working absolutely fine! no VTEC kicking in generally means you wont hit the rev limiter, it will feel like the car is completely nackered, like a blocked exhaust, it just runs out of puff on the sleepy cam... If you can hit the limiter in 2nd or 3rd then its probably working.