Help - Engine Problems...

[Shane001]

I think I may have found the problem.

The rocker arm piston on the exhaust cam of cylinder 3 was not moving freely. All the others could be moved freely up and down with little effort, but this one I had to use a lot more force to lift it, and it wouldn't fall back completely on it's own without pushing it back down.

Of course if this piston doesn't lift into place when mivec is activated, the rocker arm for the mivec cam lobe won't lock into place. So with the exhaust valves on one cylinder opening to the non mivec cam lobe only, not only are they not opening fully, but they are opening to a different timing spec to the rest of the engine.

Thankfully it looks like I have been able to free it up by manually moving it up and down repeatedly until it now moves freely.

Of course it had to be the rocker arm piston at the furthest rear point of the engine though!

So now I just need to put everything back together and get some time to head down to WP to confirm the problem is now fixed. Maybe this week, if not hopefully next week. Fingers crossed!

[Shane001]

Well I'm back to 'no f**king idea' again

Same problem at SMP last weekend, so pulled the rocker covers off today expecting to find the rocker arm piston jammed up again, but no, all pistons moving freely So now I'm back to square one, no idea what's wrong. Having one set of exhaust valves not opening fully under Mivec was the perfect explanation of the problem. But it seems not so...

Anyone got any ideas? Hotlaps at SMP in December for anyone who figures this out

[Shane001]

I've decided I'm not going to spend any more time on this problem. This engine is being replaced by a fresher engine over xmas and I'm pretty sure the problem is engine related. So I'm just going to do a quick valve clearance adjustment while the rocker covers are off, then put it back together and run it as is until it comes out in December. Hopefully the problem will go away with the replacement engine.

[Taz]

Damn lol that would tick me off, knowing i never got to the bottom of it
Ive asked a few mechanics now that i know and they've all said the same things, which you've already checked.
It's got to be one of those weird one in a million problems that the solution is nothing you'd expect

[Shane001]

Yeah I'm changing the engine anyway and just don't have time to be troubleshooting further.

The biggest problem is I can't just take it for a drive up the road to test anything, I have to load it on the trailer and head down to WP.

[payaya]

I think I may have found the problem.

The rocker arm piston on the exhaust cam of cylinder 3 was not moving freely. All the others could be moved freely up and down with little effort, but this one I had to use a lot more force to lift it, and it wouldn't fall back completely on it's own without pushing it back down.

Of course if this piston doesn't lift into place when mivec is activated, the rocker arm for the mivec cam lobe won't lock into place. So with the exhaust valves on one cylinder opening to the non mivec cam lobe only, not only are they not opening fully, but they are opening to a different timing spec to the rest of the engine.

Thankfully it looks like I have been able to free it up by manually moving it up and down repeatedly until it now moves freely.

Of course it had to be the rocker arm piston at the furthest rear point of the engine though!

So now I just need to put everything back together and get some time to head down to WP to confirm the problem is now fixed. Maybe this week, if not hopefully next week. Fingers crossed!

A rocker arm should not push up and down freely. Not sure about the mivec jumbo, but in any engine if there is free play that means bad.

Lash adjuster = Take any free play out of rocker assembly.

But if its head related I will def look at the ignition side of things.

Next time it decides to show itself, pull the connected to a coil one at a time and see if it makes a difference in engine behavior.

[Bennoz]

TPS!

[Daniel2019]

TPS!

[Shane001]

I think I may have found the problem.

The rocker arm piston on the exhaust cam of cylinder 3 was not moving freely. All the others could be moved freely up and down with little effort, but this one I had to use a lot more force to lift it, and it wouldn't fall back completely on it's own without pushing it back down.

Of course if this piston doesn't lift into place when mivec is activated, the rocker arm for the mivec cam lobe won't lock into place. So with the exhaust valves on one cylinder opening to the non mivec cam lobe only, not only are they not opening fully, but they are opening to a different timing spec to the rest of the engine.

Thankfully it looks like I have been able to free it up by manually moving it up and down repeatedly until it now moves freely.

Of course it had to be the rocker arm piston at the furthest rear point of the engine though!

So now I just need to put everything back together and get some time to head down to WP to confirm the problem is now fixed. Maybe this week, if not hopefully next week. Fingers crossed!

A rocker arm should not push up and down freely. Not sure about the mivec jumbo, but in any engine if there is free play that means bad.

Sorry to be critical Payaya but again you're talking about sh*t you clearly know nothing about as though you do. Have a look at the engine manual. I'm not talking about the rocker arm, I'm talking about the rocker arm piston. This should move freely up and down, in fact if you read the section on adjusting valve clearances it clearly describes testing for this as part of the process...

[Shane001]

TPS!

Sorry Ben, no prize for you, the problem is Mivec related, if it was TPS I'd be seeing issues at idle and below 5400 rpm, as well as over 5400rpm. Please educate me if I'm wrong though

[Bennoz]

TPS!

Sorry Ben, no prize for you, the problem is Mivec related, if it was TPS I'd be seeing issues at idle and below 5400 rpm, as well as over 5400rpm. Please educate me if I'm wrong though

I was kidding mate

Sorry this tropical island (and creepy beach available wifi) is getting to me

[Shane001]

Sorry this tropical island (and creepy beach available wifi) is getting to me

C**T

Which island is that anyway, not Hawaii I hope

Edit: And that reply was more for Payaya, didn't want him going off on another tangent

[PHIL069]

I discussed your issue with a mechanic at work today, whom owns speedway cars, and we think we have come up with the answer.
As your FTO goes for a lap or two before the problem arises and the longer you drive it the worse it gets and your engine sounds like crap, we believe that your muffler has internialy collapsed and/or is blocked with soot.
Reasons.......
1. As the muffler heats up and expands the issue will become worse.
2. As the engine produces moar power/exhaust gas the problem will become worse as there will be a build up of back pressure and your engine cannot exhaust it's gasses fast enough.
3. As the exhaust gas heats up within back pressure it will heat up your extractors and in turn your block/pistons/valves and so on.
4. Your engine doesn't sound like it should, What produces the final sound of your engine? What resinates the correct tone of your engine? The muffler.

Try a different muffler/exhaust
I hope this helps.

[Taz]

Well i was the first one to suggest this (which went unheeded lol) so if it turns out to be the exhaust (or even more specifically the cat) then i should rightfully get a few hotlaps

[PHIL069]

Don't run a cat. I run extractors out a side pipe with a Lukey muffler.

[aza013]

If you need a track pipe to test this Shane I have one. It's the same set up as you but with out the muffler just a small hot dog in it.

[Taz]

Don't run a cat. I run extractors out a side pipe with a Lukey muffler.

I still said exhaust - and for a point of argument i said the cat converter as a possibility of collapsing as i said it was probably getting blocked

[fraz91]

Since you assume it's Mivec related, is there any chance it could be a partial blockage of the mivec head? I remember reading somewhere that the mivec activated by the heads flooding with oil, which changes the pressure. If you've got a small blockage somewhere along the line and the wrong pressure is being fed into the head, then the Mivec won't be activating correctly.

Feel free to toss this theory out the window though, as it's just me spit-balling.

[Shane001]

Since you assume it's Mivec related, is there any chance it could be a partial blockage of the mivec head? I remember reading somewhere that the mivec activated by the heads flooding with oil, which changes the pressure. If you've got a small blockage somewhere along the line and the wrong pressure is being fed into the head, then the Mivec won't be activating correctly.

Feel free to toss this theory out the window though, as it's just me spit-balling.

Yeah that's exactly what I think the problem is now, when this engine comes out in December I'll dismantle the heads and have a closer look, but yeah I think maybe something may be blocking one of the oil lines.

Phil, we thought of that as well, but the change in exhaust note happens right on the rpm point that Mivec kicks in. If it was a collapsed exhaust we would be hearing it throughout the rev range, not just over 5400rpm.

[Astron_Boy]

Yeah that's exactly what I think the problem is now, when this engine comes out in December I'll dismantle the heads and have a closer look, but yeah I think maybe something may be blocking one of the oil lines.

Given it simply is a factor of an oil change, have you tried an oil flush?