Another misfire - aargh!

[1969Mk3Spitfire]

A few weeks ago I had a misfire. Symptoms were “instant” mis and “instant” recovery. Frequency was about once per mile. I posted to seek input before I raised a spanner to the car. Consensus from the wise was spark plug and indeed number 2 (only) was sooty.

I drove the car yesterday for the first time since that event. I did about a 10 mile circuit, mixture of south Manchester congested traffic and open countryside. About a mile from home the car started to misfire again, this time with quite different symptoms. It felt more like fuel starvation. I had a kangaroo in the tank and the engine would not pull. It would clear after a few seconds but return another few seconds later. I feared the indignity of having to call my wife for a tow but managed to limp home.

No 2 plug was again very sooty, No 1 looked good. I removed the fuel pump cover and the mesh filter was clean. I cleaned the plug and leaned the front carb by one flat. I drove again, but not as far, probably 4 miles, and all was well.

Not sure if heat from a longer journey plays a part.

I’m planning to go to Tatton Park show on Saturday but I’m a bit nervous due to this issue.

Number 2 sooting is probably a valve issue, pretty much all ignition components have been measured, checked and/or changed. Removing the cylinder head is a winter project.

Any ideas? Many thanks.

 

[PeteH]

Couple of suggestions to be going on with?. Uncle Pete`s dreaded "slivers"? (carburator). Crap under/around the tank suction?, comes and goes as you drive?. If you suspect that try blowing the fuel line back to the tank and see if it improves?. Also air being drawn into the fuel line, rubber connections can get porous?.

Pete

[Pete Lewis]

yes bits of rubber that get sliced off when fitting the metal pipework , a lot to do with old nasty fake hose sold by many 

the recovery happens when the pressure drops and the little sods float back till it returns 

proper fuel hose like gates barricade sold by club and others is much tougher and seems ok 

other can be the fuel pump needs a refit, old hoses downstream sucking air and check the Coli  igniton  is wired polarity correct 

wired back to front gives all sorts of funnies 

Pete

[1969Mk3Spitfire]

Many thanks Pete and Pete,

The tank is new, fitted in 2020.  Not sure of the grade of fuel hose but tank outlet to pump inlet was replaced in 2019 as part of full resto.  I doubt that it's air but it would explain the symptoms.

I use E5, high octane fuel. A weak fuel pump would explain it, too, but I have a very light right foot and all seems fine again now.  If I go to Tatton tomorrow I'll probably reach Vmax (60 mph) so a good test.

No reason to doubt coil polarity (3 ohm version) but I'll check.  The revvy and willing engine has performed very well in the 3 years that I've had the car until late last year when No2 plug sooted-up quickly and readily.  I've tried beating the car with the branch of a tree but this didn't improve matters.

 

 

[Pete Lewis]

the ht coil 12v reversed polarity can work fine for ages then you get the hic up and burp and a stall , get out  kick a few things and it restarts 

it happens a lot and its a simple check , but has driven guys mad ,  and the fix is  so easy 

hopefully yours is ok 

Pete

[Wagger]

Number 2 cylinder on my Vitesse regularly misfires on starting. I clean it then all is ok for a while. So far, it has not misfired during a run. All plugs are black, but leaning off results in terrible running. I need to do a run, pull into a layby and check all of them when hot. No other plugs have ceased to fire (Yet).

There is a 'Ching' sound from front of engine at 2000 rpm which is a pushrod being held and dropped I believe. I suspect a sticking valve or rocker is the culprit.

Waiting for sciatica to disappear before more investigation, but you may have a similar problem. (Not with sciatica, I hope).

I intend to do a compression test and watch the valves whilst running with the rocker cover off.

 

[1969Mk3Spitfire]

4 hours ago, Pete Lewis said:

the ht coil 12v reversed polarity can work fine for ages then you get the hic up and burp and a stall , get out  kick a few things and it restarts 

it happens a lot and its a simple check , but has driven guys mad ,  and the fix is  so easy 

hopefully yours is ok 

Pete

Thanks for raising it and glad I checked because the polarity was reversed, the loom white +ve was connected to coil -ve.

It looks like a brand new (now 3 years old), unmarked coil. I’ve previously measured its resistance but not noticed polarity.

In what was does reverse polarity manifest itself?

There’s a car on the drive blocking the garage door so a test drive will have to wait until she moves it tomorrow morning 😁

[1969Mk3Spitfire]

4 hours ago, Wagger said:

Number 2 cylinder on my Vitesse regularly misfires on starting. I clean it then all is ok for a while. So far, it has not misfired during a run. All plugs are black, but leaning off results in terrible running. I need to do a run, pull into a layby and check all of them when hot. No other plugs have ceased to fire (Yet).

There is a 'Ching' sound from front of engine at 2000 rpm which is a pushrod being held and dropped I believe. I suspect a sticking valve or rocker is the culprit.

Waiting for sciatica to disappear before more investigation, but you may have a similar problem. (Not with sciatica, I hope).

I intend to do a compression test and watch the valves whilst running with the rocker cover off.

 

I really don’t understand my sooty No 2 plug issue. The car seemed to run very well, albeit low mileage, for my first couple of years ownership, post resto. It could be that I simply never looked for the issue, though.

At the end of last season I noticed the sole, sooty plug. I’ve changed most all of the usual ignition suspects.  There is virtually no play in the dizzie shaft. Cylinder CRs are within 5% of each other. Tappet clearances are ok. I’m currently of the view that it’s valve seat and/or guide but removing the head has to wait.

Perhaps I check it now too often but the plug fouling seems to happen very quickly. The first misfire was fairly recent and (I thought) was solved by cleaning the plug. This last misfire episode was different and I’m not as yet sure that I either understand it or have fixed it.

Sorry to read about sciatica, not pleasant. Hope it resolves.

 

[Pete Lewis]

as i said earliier they can run fine for years then it all starts to play up  misfires/ hicc ups /stalls/ dead wont run  

you get out and kick a tyre or two  have a coffee and the ruddy thing starts and you continue untill it starts to get more frequent untill 

full death reveals a coil failure  

this has been a age old problem that even happened in the 60s  it is daft but can cause complete chaos 

putting it right may not show up much  but you now know its correct 

there is a long answer  as to what goes wrong but  youve eliminated one problem thats good enough 

Pete

[Wagger]

1 hour ago, 1969Mk3Spitfire said:

I really don’t understand my sooty No 2 plug issue. The car seemed to run very well, albeit low mileage, for my first couple of years ownership, post resto. It could be that I simply never looked for the issue, though.

At the end of last season I noticed the sole, sooty plug. I’ve changed most all of the usual ignition suspects.  There is virtually no play in the dizzie shaft. Cylinder CRs are within 5% of each other. Tappet clearances are ok. I’m currently of the view that it’s valve seat and/or guide but removing the head has to wait.

Perhaps I check it now too often but the plug fouling seems to happen very quickly. The first misfire was fairly recent and (I thought) was solved by cleaning the plug. This last misfire episode was different and I’m not as yet sure that I either understand it or have fixed it.

Sorry to read about sciatica, not pleasant. Hope it resolves.

 

 

[NonMember]

2 hours ago, 1969Mk3Spitfire said:

In what was does reverse polarity manifest itself?

If you reverse the coil polarity, you get the wrong HT polarity. This means that you're trying to pull free electrons from the colder body electrode of the plug, instead of the hot centre electrode. Being hot frees up lots of electrons. So by having the wrong polarity you are fighting against the way things want to be. The spark you generate is weak and may not even happen. So you get misfires, under some conditions, sometimes.

At one point, a lot of modern cars used a "wasted spark" ignition system which connected the coils between pairs of plugs. This meant half your spark plugs were always running the wrong polarity. It didn't cause problems but only because the (computer controlled) coils were high energy types that packed a whole load more wallop than we get with our distributor systems.

[Wagger]

Just now, Wagger said:

Message disappeared, so started again.

Lovely day, so took the vitesse for a 15 mile spin with the sunroof open. All ok within the 40mph zone, but in the rural bit misfires started above 2700 rpm together with the chinging noise. Below 2700 rpm, ran like a dream.

On return, looked at all plugs. 4, 5 & 6 all ok. 1 & 3 half sooty, half ok. No 2 sooty. I am now convinced that number 2 inlet valve is sticking open due to a weak or broken spring or a sticking rocker. This would result in fuel not getting into cylinders 1 & 3 as number 2 valve  open would reduce the vacuum. . I did not risk further investigation in case sciatica went from a five to a ten (again).

The plus's of the journey were, no overheating even sitting at the level crossing in a very slow queue. (22 deg C here today). No water, petrol or oil leaks apparent, even when cooled down. AND, the gearbox does not whine in top gear.

Sciatica not apparent whilst driving either. Will probably pay for all of this later, but I was so..... bored.

Hope that this gives you another lead. Will post my findings when I've had the rocker cover off and done more investigation.

[Pete Lewis]

the compression test you did seemed to say all was well  

i would have thought any valve or spring /rocker problem would have given a lower reading  

and any misfires now ????

Pete

 

 

[Wagger]

Hi Pete. The original post was by 1969mk3spit. I was comparing his problem with mine.

My Vitesse runs superbly at up to 2700 rpm, then I get a random metallic 'Ching' from the left front, which, I believe, is a pushrod. Dropping the revs instantly restores normal running.

The engine produces no smoke and the compression test is only at cranking speed, showing nothing at all right now. Annoyingly, this is not quite 50 mph, so I am not going on a longer run til I have sorted it.

When my blessed sciatica abates, I'll take the rocker box off and do more investigation. I dare not lean over the engine right now.

(Cannot contemplate that gearbox either). Could really do with a fellow mechanic. It's halfway through the year and I want to use this car.

What was, or is, the rack you used for sciatica? I'd love to kick this into touch.

 

 

[Pete Lewis]

its a Human Touch massage chair  it  has a leg support that grabs your legs  arches the back and give you the stretch 

got mine from the idea home exhibition and its worked well for years , Doug was up for a trip and he could hardly walk but 15mins on  The Rack and he was so impressed went and found one on ebay   they are very heavy and quite powerfull

prices all over the place 

[Colin Lindsay]

1 hour ago, Pete Lewis said:

its a Human Touch massage chair 

Yes but does it fit in the Herald or do the floorpans require modification?

[Pete Lewis]

ching noises  ...Hmmm   loose fan    timing chain zone 

had a local spitty made a terrible front end noise   it was the cam sprocket  some clown had centre popped its face (was the back face) 

so whilst it was bolted up securely it clattered , a buzz with a file and peace reigns 

some noises can be quite obscure things 

even a rocker makes contact with the rocker cover will make some odd noises 

Pete

[Pete Lewis]

2 minutes ago, Colin Lindsay said:

floorpans require modification?

if you fit it in Herald you need HD spring on one side  and its more for bed pans than floor pans 

Pete

[Wagger]

13 minutes ago, Pete Lewis said:

ching noises  ...Hmmm   loose fan    timing chain zone 

had a local spitty made a terrible front end noise   it was the cam sprocket  some clown had centre popped its face (was the back face) 

so whilst it was bolted up securely it clattered , a buzz with a file and peace reigns 

some noises can be quite obscure things 

even a rocker makes contact with the rocker cover will make some odd noises 

Pete

Another member had this, maybe on another forum. Can't find the post now, but he filmed it and the valve was sticking down, then releasing so that the pushrod collided between cam follower and rocker, making a Xylophone type 'Ting'. It was completley random and occurred at 2 to 3 thousand RPM. (Tricky to watch, as it is opening 25 times per second. He played it back in slow motion). My car stood for seven years without being run, so it is a miracle that it is not much worse. 

Thanks for the vibrating chair info. There is one in our shopping mall. Another way is to book a weeks trial in a new Audi with these features, then not actually buy the car.

[Pete Lewis]

most of our valve guides are worn so rattling good  fit rather than sticking 

Pete

[Wagger]

My son has a 2500S in Scotland hat he has owned since 1998. It suffers sticking valves too due to lack of use and spending 3 months in a shipping container from UK to Oregon in 2005, then back here in 2018. Rusty stems in the inlet tracts and sticky gunge beneath the stem seals. His was a head off job. I have other plans for mine before resorting to even more heavy work.

I won't do an electric conversion and fit a sound system to simulate the exhaust note.

 

 

[Pete Lewis]

but you wont have stem seals on the Vitesse so more oily  etc 

Pete

[Wagger]

10 minutes ago, Pete Lewis said:

but you wont have stem seals on the Vitesse so more oily  etc 

Pete

Ah, but this is a 2500TC Engine, same as my sons.

[Pete Lewis]

there you go all these improvements spell chaos 

Pete

[Wagger]

Not sure any of it was an improvement. PO's long expired so cannot ask when or why. At least they fitted the late GT6  3 rail Gearbox and a 3.63:1 diff. Never fitted the J type overdrive in the spares box.

My plan is to take the rocker cover off, then try each valve in turn carefully with a bike tyre lever to see if I can make any of them stick. Check all rockers with the screws backed off. I will then check that the cam followers are not sticking with the pushrods free of the rockers. (An aquaintence with a TR6 had those stick and write his camshaft off). I am hoping to find something. If not, I'll set the tappets tight (say 2 thou) then run it at low rpm and see if the problem worsens. If I find nothing, then it is re-adjust and start again.

Now for the most stupid question. How do I make my profile appear on each post, so all know my car details? That would avoid confusing everyone.