High rpm misfire but no OBD fault code

[cabbydave]

I have a spare car at home that i'm currently not driving so if you want to lend any bits for yours bob over if the car will make it to Stockport.

[Ballistic]

I have a spare car at home that i'm currently not driving so if you want to lend any bits for yours bob over if the car will make it to Stockport.

Thanks, that's very kind of you. The car will certainly make it,(it's been to Plymouth and back with this defect), but unfortunately the limiting factor is me.
My 24/7 caring role means that I'm stuck in Leyland - I can only leave the house briefly for quick half-hour shopping trips etc. until I get a few days respite towards the end of April.
Much appreciated though   s:) s:)

[shnazzle]

What about camshaft sensor? Also, have you checked these sensors for electronic tolerances?

[Ballistic]

What about camshaft sensor? Also, have you checked these sensors for electronic tolerances?

Not yet. It's on my 'to do list' ... my ever expanding 'to do' list   s:roll: :roll: s:roll:
Still, as long as there's something more to check I can't say I've come up against a brick wall   s:) s:)

[Ballistic]

It was a sunny day yesterday for a change so I used the opportunity to check the valve clearances in accordance with http://workshop-manuals.com/toyota/mr2_spyder/l4-1.8l_%281zz-fe%29/engine_cooling_and_exhaust/engine/cylinder_head_assembly/valve_clearance/system_information/specifications/page_1035/

The tolerances are:
Intake -   0.006" - 0.010"
Exhaust - 0.010" - 0.014"

My measurements:
Intake -   7 valves 0.021", 1 valve  0.023"
Exhaust - 5 valves 0.032", 3 valves 0,031"

So mine are out by an approximate average of 0.013"(intake) and 0.020"(exhaust) with no huge variations.

The car has done 68500 miles and has been regularly serviced. Does this sound like normal wear for that mileage?
And, the BIG question, could this be a factor in my high rev misfire?

[Carolyn]

That's a lot of wear.  Not the wear I expected to see, though.  I thought the valves might have gone tight rather than loose.  It is, however, well out of spec which would affect actual valve timing (opening late and closing early).  According to others on here who have more experience of these engines than I do, valve wear is most unusual.  Without looking at it, it may be that there is excessive wear on the cam bearings.  Something is not right in the cylinder-head department.

Make double sure you've used imperial feeler gauges and not metric. (Thousands on an inch as opposed to tenths of a millimeter.  Easily done.

[krazysteve]

Couple of questions, does the car still have the precat fitted? Have you replaced the maf sensor?
I bought one of those cheap Chinese copies 2 years ago works perfect still.
Just had a look on ebay, selling for as little as a tenner. new lol..
 m http://www.ebay.co.uk/itm/Toyota-Lexus- ... Sw~otWg5Sk m

[CrazySX]

Sounds to me like a coil pack breaking down under load. I had this on the 200sx.

Try and source a good used coil pack and swap them out one at a time and take it for a rev.

[Ballistic]

That's a lot of wear.  Not the wear I expected to see, though.  I thought the valves might have gone tight rather than loose.  It is, however, well out of spec which would affect actual valve timing (opening late and closing early).  According to others on here who have more experience of these engines than I do, valve wear is most unusual.  Without looking at it, it may be that there is excessive wear on the cam bearings.  Something is not right in the cylinder-head department.

Make double sure you've used imperial feeler gauges and not metric. (Thousands on an inch as opposed to tenths of a millimeter.  Easily done.

Well this is embarrassing   s:oops: :oops: s:oops:  
I've had that set of feeler gauges over 30 years and yesterday I checked and double checked that they were imperial. Yep, British, definitely imperial.
Just checked again and they're metric   s:shock: :shock: s:shock:  
I think I may have been hallucinating due to tiredness   s:? :? s:?  

Anyway the good news is that means my valve clearances are all within tolerance. Phew!

[Ballistic]

Sounds to me like a coil pack breaking down under load. I had this on the 200sx.

Try and source a good used coil pack and swap them out one at a time and take it for a rev.

I did try a brand new coil in the way you suggest (although it was only a cheap one), and the results were identical.
Even given that the new coil is not great quality, I would expet it to work OK for a while, enough to prove it's not a coil problem.

[Ballistic]

Couple of questions, does the car still have the precat fitted? Have you replaced the maf sensor?
I bought one of those cheap Chinese copies 2 years ago works perfect still.
Just had a look on ebay, selling for as little as a tenner. new lol..
 m http://www.ebay.co.uk/itm/Toyota-Lexus- ... Sw~otWg5Sk m

I've tried a replacement MAF sensor, (very kindly lent to me), with no difference to the misfire.
As far as precat goes, I don't know. I haven't got an O2 sensor socket so I can't have a quick look.
I've checked the car's history and there's no record of it - to be honest, before I came on here with this misfire problem I'd never heard of the precat issue.
It's the next priority after I've sorted this current problem out.

[CrazySX]

Sounds to me like a coil pack breaking down under load. I had this on the 200sx.

Try and source a good used coil pack and swap them out one at a time and take it for a rev.

I did try a brand new coil in the way you suggest (although it was only a cheap one), and the results were identical.
Even given that the new coil is not great quality, I would expet it to work OK for a while, enough to prove it's not a coil problem.

Hmm.. that rules that out then. I presume you checked the plugs?

[Ballistic]

OK, I think I may have found it.

A couple of weeks ago (Wed 23rd March) I mentioned the noise filter, then promptly talked myself out of it a day later due to it not being available on generic car parts websites, presumably because they're not a common item for replacement. I did check it with my multimeter but as expected it showed infinite resistance.
So then I promptly forgot about it.

I've just tried running with it disconnected  and guess what? No more misfire. Maybe it was breaking down under high load creating a partial earth.
I've done a test run and the car drives normally although there is now a misfire at about 6000 rpm but I wonder if even that would disappear with a new noise filter...

After all this time I'm wary of jumping for joy just yet in case this is another red herring hiding the real defect but I can't help allowing myself to have a little bit of optimism this time   s:D s:D

[Carolyn]

Sounds like you've got it.  New filter in order.

Very well done, Sir.  That was a tricky one.

[Wabbitkilla]

Well that's a new one .... but sounds like it makes sense.
It is really just a capacitor so they can get leaky, ignition noise causing interference with ..... ignition   s:lol: :lol: s:lol:  
Let's see what a replacement does for you   s:) s:)

[CrazySX]

What's a noise filter and where does it live?

[Wabbitkilla]

What's a noise filter and where does it live?

What used to be called a suppressor.
Was very relevant with points and distributors and it dampened the electrical noise caused by the inevitable sparks in the distributor cap and the plugs.
Not as much of an issue these days but you're still generating sparks in the plugs so an element of electrical suppression is still needed.

[Ballistic]

What's a noise filter and where does it live?

It's bolted to the left end of the cam cover secured underneath the plastic protection sheath for the ignition leads.
It has a single black/red lead with a plug & socket arrangement.

[beavisrules]

Had mine break off , not sure when (could have been before I got the car even) and it made no difference to the running.

[Ballistic]

Had mine break off , not sure when (could have been before I got the car even) and it made no difference to the running.

Yeah, that's one reason I haven't cracked the champagne yet   s:wink: :wink: s:wink:  
Although to be fair, it has made a difference in this case.

Did you replace it? Or just leave it off?

[cabbydave]

I think I have a few of those kicking about if you want one

[beavisrules]

Had mine break off , not sure when (could have been before I got the car even) and it made no difference to the running.

Yeah, that's one reason I haven't cracked the champagne yet   s:wink: :wink: s:wink:  
Although to be fair, it has made a difference in this case.

Did you replace it? Or just leave it off?

I reshaped the broken bracket and bolted it somewhere near.

I think this does show you probably have an electrical issue rather than mechanical though.
the filter is attached to the live of the coil igniter circuit. would guess at coil , harness or ecu problem from that.
but its a guess  s:( s:( .  I'd buy/borrow/(sale or return?) ECU(+key) & harness to rule out

also on the off chance , check fuses/relays in engine bay boxes aren't corroded.

[CrazySX]

What's a noise filter and where does it live?

What used to be called a suppressor.
Was very relevant with points and distributors and it dampened the electrical noise caused by the inevitable sparks in the distributor cap and the plugs.
Not as much of an issue these days but you're still generating sparks in the plugs so an element of electrical suppression is still needed.

I gathered as much but couldn't comprehend how it would affect spark?

I thought the surpressors were purely for stereo noise damping.

Let's see what it does once fixed.

[CrazySX]

What's a noise filter and where does it live?

It's bolted to the left end of the cam cover secured underneath the plastic protection sheath for the ignition leads.
It has a single black/red lead with a plug & socket arrangement.

Thanks bud another part in the engine bay identified  s:) s:)

[CrazySX]

Had mine break off , not sure when (could have been before I got the car even) and it made no difference to the running.

Yeah, that's one reason I haven't cracked the champagne yet   s:wink: :wink: s:wink:  
Although to be fair, it has made a difference in this case.

Did you replace it? Or just leave it off?

I reshaped the broken bracket and bolted it somewhere near.

I think this does show you probably have an electrical issue rather than mechanical though.
the filter is attached to the live of the coil igniter circuit. would guess at coil , harness or ecu problem from that.
but its a guess  s:( s:( .  I'd buy/borrow/(sale or return?) ECU(+key) & harness to rule out

also on the off chance , check fuses/relays in engine bay boxes aren't corroded.

Beavis is on the right path for sure.