VTEC Intermittent Part 2

[Scott560]

I know lol, i'm a random stranger on the internet who hasn't seen your car or checked the ECT sensor resistances.

If i was you, i wouldn't buy a sensor and replace it, without doing the test.

If you don't do the test:
Order sensor - wait for delivery (suspect original honda is not much less than a hundred quid)
Remove old sensor - coolant pisses out all over your starter motor (which will probably cause it trouble).
Put in new sensor - problem might not be fixed. Time and money wasted. These sensors don't seem to fail often, let alone get tested.

If you do the test:
takes 30 mins tops. It might even show immediately without having to drive/warm up the car, 5 minutes tops to check.
Confirm sensor is knackered - Get one for free / or buy a new one.
Confirm sensor is good - no time/money wasted - save energy/time/money/patience for more diagnosis.
Might even find someone has bunged a resistor in there too fool ECU into believing its always cold to add more fuel (+20bhp ebay chip, might be near the ECU)

Can't help much more than that. I can sense you are getting to the end of your tether with it - perhaps its worth spending time/energy in a more considered manner rather than chucking parts at it (i'm genuinely curious, you say you've chucked 1k of parts onto a car in supposedly good condition?). Not trying to teach you how to suck eggs, but i hate to see owners get to the end of their tether, then forced to get rid of it because they couldn't sort it out - see it all too often.

Where are you based - if your close i'm happy to lend a hand (I always find a car buddy helps when it comes to motivation!)

Cheers,

Scott

[EddieMunster]

I know lol, i'm a random stranger on the internet who hasn't seen your car or checked the ECT sensor resistances.

If i was you, i wouldn't buy a sensor and replace it, without doing the test.

If you don't do the test:
Order sensor - wait for delivery (suspect original honda is not much less than a hundred quid)
Remove old sensor - coolant pisses out all over your starter motor (which will probably cause it trouble).
Put in new sensor - problem might not be fixed. Time and money wasted. These sensors don't seem to fail often, let alone get tested.

If you do the test:
takes 30 mins tops. It might even show immediately without having to drive/warm up the car, 5 minutes tops to check.
Confirm sensor is knackered - Get one for free / or buy a new one.
Confirm sensor is good - no time/money wasted - save energy/time/money/patience for more diagnosis.
Might even find someone has bunged a resistor in there too fool ECU into believing its always cold to add more fuel (+20bhp ebay chip, might be near the ECU)

Can't help much more than that. I can sense you are getting to the end of your tether with it - perhaps its worth spending time/energy in a more considered manner rather than chucking parts at it (i'm genuinely curious, you say you've chucked 1k of parts onto a car in supposedly good condition?). Not trying to teach you how to suck eggs, but i hate to see owners get to the end of their tether, then forced to get rid of it because they couldn't sort it out - see it all too often.

Where are you based - if your close i'm happy to lend a hand (I always find a car buddy helps when it comes to motivation!)

Cheers,

Scott

I moved it to the workshop a few months ago, to get it ready for the over-haul, and everything worked perfectly so whatever it is, it has only appeared in the last few weeks. The MOT was last week, emissions were fine, the odd throttle response has only appeared in the last few weeks so I'm confident that the ECU is intact.

The car had previously been maintained to a standard that kept it on the road, and the budget that entails, and not to the standard that I have, whereby if something needs doing then it's done once and it's done properly; it has had all new suspension (I'm currently building plates for the turrets), new discs/pads/callipers all 'round, refurbished wheels and new Rainsport tyres, full transmission overhaul including rebuild of the rear rack, gearbox fluid change, new brake lines, full engine service including valve clearances, and probably several dozen other small jobs that escape me at the moment (but I have documented).

So, if a new sensor is £50 then it's more cost-effective to just replace it, as if I'm stripping it down to check it then I'm only doing the job once. If that's not the issue, so be it, but it's something else that has been addressed and won't cause an issue later down the line. I've restored many a car, and wasted £1000's on trouble-shooting issues that have taken months to address, when in reality it would have been more cost-effective just to replace a part, see if that resolves the issue, and if not move on to the next item in the chain.

[EddieMunster]

So, further to the initial problems.....

The VTEC works, but only as the engine is about to hit "normal temperature"; once it's at normal temperature, VTEC stops engaging, when it's cold, it won't engage (as you'd expect). So, the issue is pointing towards the VTEC sensor, but which one is responsible for this function?

For the purposes of future reference, I thought I'd add the solution to this problem.

In short, it was a sticking intake valve, more than likely caused by lack of use (it'd been sat in the garage for probably 18 months without having been turned over), and so once the valve clearances were done VTEC engaged properly.

[Vtecmec]

Thanks for closing the loop on the thread.

[Scott560]

Hmm, sounds like the previous valve clearance job you mentioned was done wrong - set too tight and the valve ended up getting held open when hot/expanded (not stuck as such). If the valve was stuck open / getting stuck, it'd be a head off job to unstick it / reem the guide etc). Generally, valves never get stuck unless you have had a new head built up with new guides that are on the tight side. If you have recently had head work undertaken with new guides, id be following that up.

If you were paying to have this work done - from the previous post it sounds like the valve clearances have now been done twice - i'd be asking for a refund on the first valve clearance job as it was clearly done wrong.

Still, good to hear it is now working as intended - long may it continue (daily VTEC recommended!). Hopefully the intake valve hasn't go burned out where it was sealing poorly whilst hot.