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[Liam]

Hello folks,

Some may recall I've been having some engine trouble recently! To cut a long story short, one camshaft pulley came loose, met its neighbour, they ate each other a little bit, locked into mesh, stripped several teeth off the cambelt and bent some valves.

Compression test said I got away with it on one bank so I did just one head swap. Taken me ages on and off to get it done, having other things to do and finding other little things needing replacing like a faulty hydraulic lifter etc etc. New cambelt timing checked and checked and rechecked.

Finally got it reassembled a few weeks ago now and started her up. Never started a car after such major work before but sort of had an idea what to expect. Took a lot of cranking before fuel came through and it finally fired up. I guess not helped by the fact I serviced the lifters on the head i swapped so they must have taken a while to pump up and actually be able to move the valves a decent amount.

Started up on 5 by the sounds of it, soon started running on all 6, sounded like a bag of spanners at the top end, but quietened down when the lifters pumped up. All was good I thought. However as it warmed up it started briefly dropping out every 5-10 seconds or so, this got worse then it cut out.

That's where I am today. It can idle initially, but as soon as it's warmed up a little and the 'choke' (warmup enrichment) backs off and idle speed wants to drop to normal, it just cuts out. I can keep it going if I hold some throttle on and it is smooth and can rev. Just can't idle.

There's a slightly worrying sound though I can hear seemingly from the top end/plenum area. Every now and then, normally when I come off throttle a little, a metallic sort of sucking/scraping sound. Ch ch ch ch - a bit like a turbo wastegate chuffing. Definate metallic ring to it though, and I'm really not sure if it's a scrape (hope not) or a suck.

If it's a suck perhaps I have an air leak somewhere? That could also explain why it can't idle, maybe? Be buggered if I know where it's from though. I didn't replace inlet manifold/plenum seals but haven't in the past either and have been fine. I have the plenum off now - didn't miss an o-ring which i was hoping could be an obvious cause.

Idle control valve? Was fine before but maybe not now? I can blow through it easily off the car - should it be closed by 'default' when disconnected, or maybe it's stuck open? How to tell?

I'm also convinced it sounds a bit more rumbly than before. Exhaust blockage? Family of mice moved in while it's been off the road? Any idea how to tell?

Any advice greatly appreciated! I'll be damned if I'm putting all this time and money into my baby and failing to fix it!! But a little lost as to what to investigate next

Cheers,

Liam

[alank46]

Hi
First of all, which car is it, your profile doesn't say.
Do a paperclip/pedal test for fault codes and report back.
Alan

Hello folks,

Some may recall I've been having some engine trouble recently! To cut a long story short, one camshaft pulley came loose, met its neighbour, they ate each other a little bit, locked into mesh, stripped several teeth off the cambelt and bent some valves.

Compression test said I got away with it on one bank so I did just one head swap. Taken me ages on and off to get it done, having other things to do and finding other little things needing replacing like a faulty hydraulic lifter etc etc. New cambelt timing checked and checked and rechecked.

Finally got it reassembled a few weeks ago now and started her up. Never started a car after such major work before but sort of had an idea what to expect. Took a lot of cranking before fuel came through and it finally fired up. I guess not helped by the fact I serviced the lifters on the head i swapped so they must have taken a while to pump up and actually be able to move the valves a decent amount.

Started up on 5 by the sounds of it, soon started running on all 6, sounded like a bag of spanners at the top end, but quietened down when the lifters pumped up. All was good I thought. However as it warmed up it started briefly dropping out every 5-10 seconds or so, this got worse then it cut out.

That's where I am today. It can idle initially, but as soon as it's warmed up a little and the 'choke' (warmup enrichment) backs off and idle speed wants to drop to normal, it just cuts out. I can keep it going if I hold some throttle on and it is smooth and can rev. Just can't idle.

There's a slightly worrying sound though I can hear seemingly from the top end/plenum area. Every now and then, normally when I come off throttle a little, a metallic sort of sucking/scraping sound. Ch ch ch ch - a bit like a turbo wastegate chuffing. Definate metallic ring to it though, and I'm really not sure if it's a scrape (hope not) or a suck.

If it's a suck perhaps I have an air leak somewhere? That could also explain why it can't idle, maybe? Be buggered if I know where it's from though. I didn't replace inlet manifold/plenum seals but haven't in the past either and have been fine. I have the plenum off now - didn't miss an o-ring which i was hoping could be an obvious cause.

Idle control valve? Was fine before but maybe not now? I can blow through it easily off the car - should it be closed by 'default' when disconnected, or maybe it's stuck open? How to tell?

I'm also convinced it sounds a bit more rumbly than before. Exhaust blockage? Family of mice moved in while it's been off the road? Any idea how to tell?

Any advice greatly appreciated! I'll be damned if I'm putting all this time and money into my baby and failing to fix it!! But a little lost as to what to investigate next

Cheers,

Liam

[Liam]

Ah sorry - could have sworn I filled out my profile ages ago?? It's a 98 mini-facelift 3.0 elite auto. I should have mentioned - no engine light, but I'll paperclip it anyway and see what it says.

[Liam]

I was hoping this wouldn't be necessary...



Anyone . I mean this must happen all the time, right?

[aaronjb]

Air leak sounds reasonable, and ISTR that the idle control valve should be 'normally closed' when electrically unconnected so that is an avenue to investigate..

What happens if (when it's warm) you restrict the air feed to the idle valve? Maybe it's leaning up to the point of dying.

I suspect you really need to get it on to a Tech2 or something that can pull live data though and see what is up at the point that it stalls.. do you have anyone nearby with a Tech2/similar?

[cem_devecioglu]

Hello folks,

Some may recall I've been having some engine trouble recently! To cut a long story short, one camshaft pulley came loose, met its neighbour, they ate each other a little bit, locked into mesh, stripped several teeth off the cambelt and bent some valves.

Compression test said I got away with it on one bank so I did just one head swap. Taken me ages on and off to get it done, having other things to do and finding other little things needing replacing like a faulty hydraulic lifter etc etc. New cambelt timing checked and checked and rechecked.

Finally got it reassembled a few weeks ago now and started her up. Never started a car after such major work before but sort of had an idea what to expect. Took a lot of cranking before fuel came through and it finally fired up. I guess not helped by the fact I serviced the lifters on the head i swapped so they must have taken a while to pump up and actually be able to move the valves a decent amount.

Started up on 5 by the sounds of it, soon started running on all 6, sounded like a bag of spanners at the top end, but quietened down when the lifters pumped up. All was good I thought. However as it warmed up it started briefly dropping out every 5-10 seconds or so, this got worse then it cut out.

That's where I am today. It can idle initially, but as soon as it's warmed up a little and the 'choke' (warmup enrichment) backs off and idle speed wants to drop to normal, it just cuts out. I can keep it going if I hold some throttle on and it is smooth and can rev. Just can't idle.

There's a slightly worrying sound though I can hear seemingly from the top end/plenum area. Every now and then, normally when I come off throttle a little, a metallic sort of sucking/scraping sound. Ch ch ch ch - a bit like a turbo wastegate chuffing. Definate metallic ring to it though, and I'm really not sure if it's a scrape (hope not) or a suck.

If it's a suck perhaps I have an air leak somewhere? That could also explain why it can't idle, maybe? Be buggered if I know where it's from though. I didn't replace inlet manifold/plenum seals but haven't in the past either and have been fine. I have the plenum off now - didn't miss an o-ring which i was hoping could be an obvious cause.

Idle control valve? Was fine before but maybe not now? I can blow through it easily off the car - should it be closed by 'default' when disconnected, or maybe it's stuck open? How to tell?

I'm also convinced it sounds a bit more rumbly than before. Exhaust blockage? Family of mice moved in while it's been off the road? Any idea how to tell?

Any advice greatly appreciated! I'll be damned if I'm putting all this time and money into my baby and failing to fix it!! But a little lost as to what to investigate next

Cheers,

Liam

two questions come to mind,

are you sure the other bank have no damage ?

is the timing belt correctly set up?

and dont you have any eml light?

if its an air leak the engine must work better when it warms up imo.. but you can check this by spraying carb cleaner around engine.. :-/

[Kevin Wood]

I wonder if the metalling sound you describe is the result of a lean mixture. I have seen this before where the engine "coughs" back into the intake when lean and the sound you hear is the pressure wave hitting the throttles.

How does it run with the MAF disconnected?

Kevin

[Liam]

Thanks guys. Leaning out till it dies would be my thoughts. If you've heard a similar noise in that sort of situation, kevin, that's possibly encouraging!

I'll pop the plenum back on and see how it runs with no MAF. What should that tell me?

Cem - the extent of my confidence the passenger side bank survived the original 'incident' is simply a compression test :-/. It also runs fine (albeit sounding a little deep/rumblier than usual) at anything other than idle where it cuts out. So I'm fairly sure the original mechanical damage is gone, but half wishing I'd delved into that head too to check!

Cambelt was timed up with the kit and checked and rechecked.

No EML when running but I am going to try a paperclip to see if there are any codes stored. Although might i just get a whole load thrown up as when cranking for compression tests etc etc I've essentially been running with tonnes of stuff disconnected, and maybe those codes wont have cleared yet??

Cheers

[aaronjb]

I wonder if the metalling sound you describe is the result of a lean mixture. I have seen this before where the engine "coughs" back into the intake when lean and the sound you hear is the pressure wave hitting the throttles.

Ditto.. about 18-19:1 on the MR2 it starts to sound very odd and unnatural (right about when it starts struggling to hold an idle).

[cem_devecioglu]

Thanks guys. Leaning out till it dies would be my thoughts. If you've heard a similar noise in that sort of situation, kevin, that's possibly encouraging!

I'll pop the plenum back on and see how it runs with no MAF. What should that tell me?

Cem - the extent of my confidence the passenger side bank survived the original 'incident' is simply a compression test :-/. It also runs fine (albeit sounding a little deep/rumblier than usual) at anything other than idle where it cuts out. So I'm fairly sure the original mechanical damage is gone, but half wishing I'd delved into that head too to check!

Cambelt was timed up with the kit and checked and rechecked.

No EML when running but I am going to try a paperclip to see if there are any codes stored. Although might i just get a whole load thrown up as when cranking for compression tests etc etc I've essentially been running with tonnes of stuff disconnected, and maybe those codes wont have cleared yet??

Cheers

nope.. dont remember exactly but you will need 15-30 succesful starts something like that :-/

honestly still I dont think your poblem is airleak or ICV..

and imo dont trust the compression test :-/

[Liam]

Hmmm - mechanical damage remaining is playing on my mind, of course, but it seems unlikely to me. On the compression test after the 'incident' I got three equal at about 200PSI on the passenger bank, and on the driver bank I had one at 200PSI, one with nothing at all, and one about 50PSI down at about 150PSI. On inspection the cylinder with no pressure had two very bent valves, and the cylinder down to 150PSI had two only very slightly bent valves so that they were just cracked open instead of seating, hence the low pressure.

Is it really possible I have valves even less bent than those in the other bank such that there isn't even a lower pressure in a compression test, and for that damage to cause the symptoms I'm observing - i.e. can run but wont idle? Not sure to be honest.

Cheers

[cem_devecioglu]

Hmmm - mechanical damage remaining is playing on my mind, of course, but it seems unlikely to me. On the compression test after the 'incident' I got three equal at about 200PSI on the passenger bank, and on the driver bank I had one at 200PSI, one with nothing at all, and one about 50PSI down at about 150PSI. On inspection the cylinder with no pressure had two very bent valves, and the cylinder down to 150PSI had two only very slightly bent valves so that they were just cracked open instead of seating, hence the low pressure.

Is it really possible I have valves even less bent than those in the other bank such that there isn't even a lower pressure in a compression test, and for that damage to cause the symptoms I'm observing - i.e. can run but wont idle? Not sure to be honest.

Cheers

the answer "yes" means you need to take the head off.. cant take that responsibilty..

[Kevin Wood]

the answer "yes" means you need to take the head off.. cant take that responsibilty..

I don't know. :-/

I would say if you've got 200 psi of compression there's nothing wrong with the valves myself.

Kevin

[cem_devecioglu]

the answer "yes" means you need to take the head off.. cant take that responsibilty..

I don't know. :-/

I would say if you've got 200 psi of compression there's nothing wrong with the valves myself.

Kevin

Kevin, imo the valves may be dont leak when cold but whatever happened there it may leak when hot ..
but you cant do a compression test when its hot

edit: also if there is some friction increase with warm up, its not possible to measure that..

[Kevin Wood]

Kevin, imo the valves may be dont leak when cold but whatever happened there it may leak when hot ..
but you cant do a compression test when its hot

edit: also if there is some friction increase with warm up, its not possible to measure that..

True but I would say the lifters would have to be pumping up to increase valve clearances when hot, and it would have to take out at least 3 cylinders or it would still idle.

A few other ideas:

EGR valve leaking? This will screw up the idling. Might be worth blanking off to eliminate it.

ICV sticking?

Crank sensor? OK, there's no code 19 (or is there - worth a paperclip?) but the wiring to this sensor is what fails and it might well have been disturbed during recent work.

Voltage from a crank sensor is speed dependant so could be that as the revs sink to hot idle speed the signal gets too weak for the ECU to decode.

A few things to eliminate before taking it apart, IMHO.

Kevin