High rpm misfire but no OBD fault code

[Ardent]

not sure about laptop
 but the torque app is rather good. def works on andriod don't know about fruit based gizmos

[jonbill]

I have dash command on my iphone which seems ok.

[Ballistic]

Thanks guys.

I don't have any fruit based products and I've found having a laptop with Windows 10 and no bluetooth is quite limiting.
Lots of software out there but not much compatible with WiFi.
I'll give it whirl on my Android phone tomorrow but it's not up to much, being fairly old and having not much memory left - quite appropriate for it's owner really...

[Ballistic]

Try a new maf, no error codes for a broken one. Also the random flashin eml is telling you it is multiple missfire. Had it on mine due to really old petrol

Sorry, I forgot to acknowledge your suggestion.
I'll certainly bear it in mind but I'll try some less expensive alternatives first   s:) s:)

[Ardent]

any local members that lend

[Ballistic]

any local members that lend

Hmmm ... just had a look at the map - how come I'm not on it?   s:? :? s:?

[Ardent]

The map might be in stasis.

I was rather hoping members might come along and offer, as has been done before.

Not sure if this only applies to cold close loop. But if you disconnect the MAF does alter the issues you are experiencing. Better - worse

[Ballistic]

The map might be in stasis.

I was rather hoping members might come along and offer, as has been done before.

Not sure if this only applies to cold close loop. But if you disconnect the MAF does alter the issues you are experiencing. Better - worse

Ah, thanks I'll try that.
I'm running out of ideas to be honest - well, cheap ideas anyway.

I was just wondering if the noise filter could have an effect along these lines...
It's in good nick judging by external appearances.

[beavisrules]

The noise filter just a capacitor (had mine break off and had to ask here what it was). can be mostly OK'd by a simple multimeter.
It should have infinite resistance , possibly starting low resistance and rising off the scale within a second or 2.

[Carolyn]

In the prehistoric days of points and coils, a misfire at high RPM was often down to an ignition coil on its way out.  Could it be a coil pack?  Or even a spark plug?  I stand to be corrected.

[Ballistic]

In the prehistoric days of points and coils, a misfire at high RPM was often down to an ignition coil on its way out.  Could it be a coil pack?  Or even a spark plug?  I stand to be corrected.

I fondly remember checking my points almost weekly - I coluld pretty much measure 25 thou just by looking   s:lol: :lol: s:lol:  
Checking the timing, adjusting the valve clearances - all good fun. Much simpler then - happy days.

Meanwhile, back in the 21st Century... I've been looking on the generic car parts websites for a noise filter and they're not stocked, which I take as an indication that it's not a common item for replacement. Doesn't rule it out though, but reduces the likelihood of that being the problem.

I've already changed the spark plugs, being one of the cheapest 'fault-find-by-replacement' actions I could take. Replacing a coil is one of the next options but I'm leaving that until I run out of cheaper alternatives. On my VW Polo GTi I had similar problems with the coil pack but the CEL helped me out in that case... although as I'm writing this I seem to remember it didn't stay on but did store a fault code. Hmmm...

[Carolyn]

In the prehistoric days of points and coils, a misfire at high RPM was often down to an ignition coil on its way out.  Could it be a coil pack?  Or even a spark plug?  I stand to be corrected.

I fondly remember checking my points almost weekly - I coluld pretty much measure 25 thou just by looking   s:lol: :lol: s:lol:  
Checking the timing, adjusting the valve clearances - all good fun. Much simpler then - happy days.

Meanwhile, back in the 21st Century... I've been looking on the generic car parts websites for a noise filter and they're not stocked, which I take as an indication that it's not a common item for replacement. Doesn't rule it out though, but reduces the likelihood of that being the problem.

I've already changed the spark plugs, being one of the cheapest 'fault-find-by-replacement' actions I could take. Replacing a coil is one of the next options but I'm leaving that until I run out of cheaper alternatives. On my VW Polo GTi I had similar problems with the coil pack but the CEL helped me out in that case... although as I'm writing this I seem to remember it didn't stay on but did store a fault code. Hmmm...

Maybe someone local has a surplus coil for checking purposes?  I've got a few but I'm a long ways away.

[Ballistic]

Well that didn't work   s:( s:(  

I bought a cheap coil, (£40), and tried it out on each cylinder in turn - no difference.

Tomorrow I'm going to widen my search for loose connections using the circuit diagrams. Absolutely anything related to egine control is going to be looked at.

[Carolyn]

Well that didn't work   s:( s:(  

I bought a cheap coil, (£40), and tried it out on each cylinder in turn - no difference.

Tomorrow I'm going to widen my search for loose connections using the circuit diagrams. Absolutely anything related to egine control is going to be looked at.

A non-electronic musing... checked your valve clearances?  Most mysterious,

[Ballistic]

Well that didn't work   s:( s:(  

I bought a cheap coil, (£40), and tried it out on each cylinder in turn - no difference.

Tomorrow I'm going to widen my search for loose connections using the circuit diagrams. Absolutely anything related to egine control is going to be looked at.

A non-electronic musing... checked your valve clearances?  Most mysterious,

No, I haven't done that. (Not that I know how - yet).
I've been trying to concentrate on stuff that may have been affected by something changing: corrosion, loose connections following maintenance, dodgy petrol, lack of use for long periods etc.
I'll give it a whirl, but what might cause valve clearances to go out of tolerance? This all happened rather suddenly.

What would be the effect if the OCV wasn't operating over its full range? ie if it was a bit gummed up at the ends?

[Carolyn]

Valves go tight as the valve seat wears down.  At some point it gets tight enough to affect performance.  I'm not saying it's your problem - but it is something you can measure to rule in or out.  I doubt a bit of lack of travel in the oil control valve will have this effect.  You're losing effective combustion.  So  spark? fuel? compression?  You've pretty much beaten spark to death.  Two left to go?
To do the measurement, take the cam cover off, get some feeler gauges, measure the clearances when both cam lobes are up on each cylinder in turn. By that I mean, check number one, rotate the crank check the next to come to fully closed and so on.

[Ballistic]

Valves go tight as the valve seat wears down.  At some point it gets tight enough to affect performance.  I'm not saying it's your problem - but it is something you can measure to rule in or out.  I doubt a bit of lack of travel in the oil control valve will have this effect.  You're losing effective combustion.  So  spark? fuel? compression?  You've pretty much beaten spark to death.  Two left to go?
To do the measurement, take the cam cover off, get some feeler gauges, measure the clearances when both cam lobes are up on each cylinder in turn. By that I mean, check number one, rotate the crank check the next to come to fully closed and so on.

Thanks Carolyn, I've been looking at the manual. Fairly straightforward to check but I'm in a bit of doo-doo if the clearances are out. Not like the old days when it was just a case of adjusting a locknut - sorry, I'm going all nostalgic again   s:oops: :oops: s:oops:

[Anonymous]

You tried a maf? Even if you borrow one for a quick test.

[Carolyn]

Valves go tight as the valve seat wears down.  At some point it gets tight enough to affect performance.  I'm not saying it's your problem - but it is something you can measure to rule in or out.  I doubt a bit of lack of travel in the oil control valve will have this effect.  You're losing effective combustion.  So  spark? fuel? compression?  You've pretty much beaten spark to death.  Two left to go?
To do the measurement, take the cam cover off, get some feeler gauges, measure the clearances when both cam lobes are up on each cylinder in turn. By that I mean, check number one, rotate the crank check the next to come to fully closed and so on.

Thanks Carolyn, I've been looking at the manual. Fairly straightforward to check but I'm in a bit of doo-doo if the clearances are out. Not like the old days when it was just a case of adjusting a locknut - sorry, I'm going all nostalgic again   s:oops: :oops: s:oops:

You're right about the do-do!  Buckets can be changed easy enough - but bad seat wear would be a Bad Thing.  There's also fuel pressure to consider.  Bring back the Good Old Days.

[shnazzle]

Valves go tight as the valve seat wears down.  At some point it gets tight enough to affect performance.  I'm not saying it's your problem - but it is something you can measure to rule in or out.  I doubt a bit of lack of travel in the oil control valve will have this effect.  You're losing effective combustion.  So  spark? fuel? compression?  You've pretty much beaten spark to death.  Two left to go?
To do the measurement, take the cam cover off, get some feeler gauges, measure the clearances when both cam lobes are up on each cylinder in turn. By that I mean, check number one, rotate the crank check the next to come to fully closed and so on.

Thanks Carolyn, I've been looking at the manual. Fairly straightforward to check but I'm in a bit of doo-doo if the clearances are out. Not like the old days when it was just a case of adjusting a locknut - sorry, I'm going all nostalgic again   s:oops: :oops: s:oops:

You're right about the do-do!  Buckets can be changed easy enough - but bad seat wear would be a Bad Thing.  There's also fuel pressure to consider.  Bring back the Good Old Days.

Now this was before my time..but having read a fair bit out of pure interest, carburetor tuning and setup sounds like an absolute pain in the petuti. All hail EFI

[ChrisGB]

Problem is misfire related to engine speed but not load condition. We can assume from this that the engine has sufficient valve clearances and can breath well enough up to the point it starts to miss fire. As it happens under zero load state, we can discount a number of things as being highly unlikely: vvti system, fuel pressure, afr, injector function. You have already eliminated coil packs, so spark quality seems good.

I remember someone a couple of years ago having exactly these symptoms and it was fixed by cleaning up the earth point for the crank position sensor shielding shroud. Got to be worth a go before spending more cash.

[ChrisGB]

 l viewtopic.php?f=11&t=34816&p=417504&hilit=Crank#p417504 l

[Wabbitkilla]

Valve clearances extremely unlikely, i've never seen or heard of any 1zz wearing to the point where valve clearances caused problems.
Having worked on rebuilding two engines with well over 100K miles on them the variation from valve clearance tolerance was pretty minute and only affected 25% of the valves at most.

Still sounds like a dodgy maf or earth point to me ....

[shnazzle]

Going back to one of Nic's earlier posts;

Not sure if this code would ever show up unless you had a more complex reader, but P1335 does not light the EML at all and is around crankshaft position sensor and/or its sensor plate.
I'm not convinced about this myself as the crankshaft sensor only reads 34 teeth on the plate, so it'll have read all 34 teeth at least a billion times by the time you get to 4500rpm. However, if the earth is bad, it's dirty, etc etc then maybe around 4500rpm is where the signal goes by too quickly for it too read it.
So, backing up the "earthing point" as well. Specifically of the crankshaft pos sensor.

If I remember correctly, as I've just had to deal with one recently, it actually has it's own earthing point with a ring and bolt through it onto the engine.

[Ballistic]

With regard to the last 3 posts:
By a staggering coincidence this afternoon I had another go at the crankshaft position sensor and its earthing point. Previously I'd only cleaned up the separate earthing point, even though it appeared to be clean.
This time I removed the sensor as well and the earth point did seem a little manky so I cleaned it up and restarted the engine with hope in my heart...

No change   s:( s:(  

Every time I've tried something I've been checking the symptoms and 'firming-up' a picture of what's happening.
Just to recap:
Under load, misfire occurs at around 4500 - 5000 rpm, unable to rev higher than this. No misfire accelerating up to this point.
Under no load, misfire occurs around 5500 rpm and 'hunts' around those revs. Hard pressing of the gas pedal results in misfires up through the revs until 5500.
CEL flickers during misfires but doesn't stay on and no fault code is stored.

I've checked the MAF and the resistance is within the tolerance specified in the manual. I haven't checked for a voltage fluctuation when connected but if I try to start the engine with the MAF disconnected it fires once then cuts out.
Looking at some other threads it would seem that MAF sensors can be tricky little sods and the ideal way to eliminate it would be, as has already been suggested, to try a 'known good' one.
Problem is I haven't got one and buying one is an expensive gamble.

Incidentally, if I do check the valve clearances do you reckon I could get away without renewing the cam cover gasket? (Just to save money).