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Please help me diagnose my erratic tickover
bumpy - 26/5/15 at 12:47 PM

This is driving me mad, so any help would be appreciate

Symptoms
Engine starts and runs just fine, aside from the fact that the tickover has always been erratic since I've owned the car and to me the exhaust sounds a bit rich. The car has the early contactless distributor

Engine
2 litre Pinto totally standard except for having a 'mild GT' cam fitted. Standard 32/36 Weber with standard jets, standard exhaust

I've tried without success
New plugs
New HT leads
Change of distributor including advance retard
New distributor cap
New mechanical fuel pump
Mixture screw taken from v. weak to v. rich with obvious changes to the engine speed but no change to the erratic tickover
Distributor taked from over advanced to over retarded with obvious changes to the engine speed but no change to the erratic tickover
WD40 sprayed all around the carb and manifold with engine running to eliminate the possibility of air leaks
Choke seems to be fully off with engine hot.

https://www.youtube.com/watch?v=QxWTy4bE3YU

[Edited on 26/5/15 by bumpy]

mcerd1 - 26/5/15 at 03:23 PM

WD40 is probably not volatile enough to really show you if you've got a small vac leak - try something like easystart instead

steve m - 26/5/15 at 04:05 PM

perhaps the carb has some crud in it, and needs a good clean and a blow gun through the jets ect

what about the compression on all cylinders, are they the same?

steve

bumpy - 26/5/15 at 05:24 PM

quote:
Originally posted by mcerd1
WD40 is probably not volatile enough to really show you if you've got a small vac leak - try something like easystart instead


A less volatile liquid will get sucked in and give smoke in the exhaust, but WD40 will block any leakage pathways and there will be a change in engine note, so providing one appreciates this, I think the test is valid.

bumpy - 26/5/15 at 05:28 PM

quote:
Originally posted by steve m
perhaps the carb has some crud in it, and needs a good clean and a blow gun through the jets ect

what about the compression on all cylinders, are they the same?

steve


The idle jets have been out more times than I remember and the carb inlet filter is perfectly clean.

The cylinders are all fine and I even had the head off about 2000 miles ago (for a different reason!).

All the spark plugs are a perfect colour.

rusty nuts - 26/5/15 at 06:27 PM

Check the valve timing using a DTI and timing disc not just by lining up the timing marks . Set to the correct figures for the cam you are using. Also make sure the valve clearances are correct for your cam . Some Pinto engines may??have a valve clearance setting just for timing the cam in?

bumpy - 27/5/15 at 11:18 AM

quote:
Originally posted by rusty nuts
Check the valve timing using a DTI and timing disc not just by lining up the timing marks . Set to the correct figures for the cam you are using. Also make sure the valve clearances are correct for your cam . Some Pinto engines may??have a valve clearance setting just for timing the cam in?


The cam is of unknown origin, so I don't have any info on how it should be set up, but have gone for the standard valve timing.

Today I will substitute a different coil and different ignition control unit.

DW100 - 27/5/15 at 11:27 AM

So the cam could be a hotter profile than you think? They are very often stamped on the end ( back of head )

How erratic is the idle? What speed are you trying to get it to idle at?

One of the trade offs for a hotter cam is lumpy idle. This is worst with a twin choke carb and better with throttle body type injection set up properly.

bumpy - 27/5/15 at 12:29 PM

quote:
Originally posted by DW100
So the cam could be a hotter profile than you think? They are very often stamped on the end ( back of head )

How erratic is the idle? What speed are you trying to get it to idle at?

One of the trade offs for a hotter cam is lumpy idle. This is worst with a twin choke carb and better with throttle body type injection set up properly.


It's not easy is it, but I have been trying to track down the source of the cam for some time.

http://www.locostbuilders.co.uk/viewthread.php?tid=185777

The engine builder described it as a mild road cam / GT cam and could remember no more.

I do appreciate that 'sporty' cams will affect the tickover. Mine varies by about 300rpm when set at 800, 900 1000 or even 1100 rpm. I would like an idle of about 900 rpm

Thanks for helping

DW100 - 27/5/15 at 01:20 PM

Ok so if it is a standardish Ford cam then it should tick over fine.

Have you tried blanking off things like the crank case ventilation and vacuum advance pipe to see if it makes any difference?

bumpy - 27/5/15 at 01:48 PM

quote:
Originally posted by DW100
Ok so if it is a standardish Ford cam then it should tick over fine.

Have you tried blanking off things like the crank case ventilation and vacuum advance pipe to see if it makes any difference?


Not yet, but will give it a go

Exchanged the coil and ignition control unit but still the same.

mcerd1 - 27/5/15 at 02:08 PM

If it were me I'd want a better idea of the cam's specs, just to know what kind of behavior to expect....

I doubt anyone could find you the ID from the code stamped on the end - and even if they could who's to say its not been reground to a different profile?

If you've got a DTI and protractor to adjust the timing properly - then you've also got the tools you need to measure the cams lift and duration (well max lift and valve opening/closing timings at least - then you can work the maths backwards)

What did you use to time the cam ? The timing marks on the block aren't that accurate, and skimming the head or block will also affect the timing just using these marks...
Do you have a adjustable cam pulley ?

quote:
Originally posted by bumpy
quote:
Originally posted by mcerd1
WD40 is probably not volatile enough to really show you if you've got a small vac leak - try something like easystart instead

A less volatile liquid will get sucked in and give smoke in the exhaust, but WD40 will block any leakage pathways and there will be a change in engine note, so providing one appreciates this, I think the test is valid.


I thought that with my zetec in the tintop, but no amount of WD40 made any difference to the way it ran no matter where I sprayed it and that was such a big leak that you could clearly hear it!

but eazystart type stuff made the engine pick up instantly - turned out to be a massive split in the block breather hose just out of sight......


Your carb doesn't have an automatic choke does it ?

[Edited on 27/5/2015 by mcerd1]

bumpy - 27/5/15 at 02:54 PM

quote:
Originally posted by mcerd1
If it were me I'd want a better idea of the cam's specs, just to know what kind of behavior to expect....

I doubt anyone could find you the ID from the code stamped on the end - and even if they could who's to say its not been reground to a different profile?

If you've got a DTI and protractor to adjust the timing properly - then you've also got the tools you need to measure the cams lift and duration (well max lift and valve opening/closing timings at least - then you can work the maths backwards)

What did you use to time the cam ? The timing marks on the block aren't that accurate, and skimming the head or block will also affect the timing just using these marks...
Do you have a adjustable cam pulley ?

quote:
Originally posted by bumpy
quote:
Originally posted by mcerd1
WD40 is probably not volatile enough to really show you if you've got a small vac leak - try something like easystart instead

A less volatile liquid will get sucked in and give smoke in the exhaust, but WD40 will block any leakage pathways and there will be a change in engine note, so providing one appreciates this, I think the test is valid.


I thought that with my zetec in the tintop, but no amount of WD40 made any difference to the way it ran no matter where I sprayed it and that was such a big leak that you could clearly hear it!

but eazystart type stuff made the engine pick up instantly - turned out to be a massive split in the block breather hose just out of sight......


Your carb doesn't have an automatic choke does it ?

[Edited on 27/5/2015 by mcerd1]


Several questions in there so I will try and answer one at a time

I am finding it very frustrating not knowing the camshaft specs! I don't have a DTI and protractor and set the timing (with new belt) on the timing marks. I have tried to read about the effects of cams opening too early and too late, but they all refer to changes in performance - if its out, its wrong, but surely that will be a constant systematic error so why the erratic behaviour at tickover? If erratic behaviour is definitely a sign of a poorly timed camshaft I may concentrate there.

On your recommendation I will have another go at the leak check. Would carb cleaner do as I have some of that?

My carb does have the water actuated choke. When up to temp the butterflies are fully open.

bumpy - 27/5/15 at 03:14 PM

quote:
Originally posted by bumpy
quote:
Originally posted by DW100
Ok so if it is a standardish Ford cam then it should tick over fine.

Have you tried blanking off things like the crank case ventilation and vacuum advance pipe to see if it makes any difference?


Not yet, but will give it a go

Exchanged the coil and ignition control unit but still the same.


Blanking off all the vacuum take-offs around the carb and inlet manifold made no difference to the erratic tickover

Irony - 27/5/15 at 08:51 PM

I have been messing with my carb for a while now. A vacuum leak in my case caused a high idle. It was caused by a open VAC pipe. I had the carb professionally cleaned and it came back without a blanking but on the VAC pipe. Nothing like what your seeing.

mcerd1 - 27/5/15 at 09:11 PM

quote:
Originally posted by bumpy
I am finding it very frustrating not knowing the camshaft specs! I don't have a DTI and protractor and set the timing (with new belt) on the timing marks. I have tried to read about the effects of cams opening too early and too late, but they all refer to changes in performance - if its out, its wrong, but surely that will be a constant systematic error so why the erratic behaviour at tickover? If erratic behaviour is definitely a sign of a poorly timed camshaft I may concentrate there.

it could be just out enough to give you a rough idle, if that's the case then it probably means your loosing power when you rev it too....


if you look on ebay/amazon etc, you'll get a usable DTI and a stand for about £10 - 20 - then you never need to guess again
the timing disc / protractor normally come with adjustable pulleys or new cams, but burtons and the likes sell them for a couple of £
also it might be worth making up a 'piston stop tool' from an old spark plug to help you find an accurate TDC quickly (stick it into google - there are plenty of guides on making them)

[Edited on 27/5/2015 by mcerd1]

bumpy - 27/5/15 at 09:40 PM

Thanks Guys for all your help.

I have taken a decision on this one and that is to remove the unknown cam and replace it with a standard Sierra cam. These standard cams can be bought brand new for only about £70 with followers.

The GT/fast road/Stage 1 cam offers little if any value to the Pinto engine unless its accompanied by other improvements such a twin carbs, four branch manifold etc. which I dont have or intend getting.

All I am getting currently is an erratic tickover, a very noisy rasping exhaust note, an engine that is less tractable at lower revs, probably higher fuel consumption and black magic guesswork when it comes to ignition and valve settings.


Now to work out a way to get the camshaft out without removing the head from the engine - why did Ford design it back to front?

[Edited on 27/5/15 by bumpy]

mcerd1 - 28/5/15 at 12:28 PM

I'd still want to try and measure the valve lift and timings - if nothing else it'll mean you know the cams spec if you want to sell it

While you could measure the cam lift once its been removed and use that to calculate the valve lift, working out the timing / duration would be very difficult to measure with it removed.....

Besides it might not be a very extreme cam - so why go to the effort of changing it until you know its the problem

I know it seems like you've tried everything else, but it could still be something silly that's been missed and changing the cam might do nothing....


If you get / borrow a DTI you'll be able to answer alot of questions and its still good tool to have even with an OE camshaft.
Similarly adjustable cam pulleys let you get the best out of any cam - even an OE one...
(obviously its less critical with milder cams)


I don't know where shouts in the country you are, but I'd happily give you a hand with this....

[Edited on 28/5/2015 by mcerd1]

bumpy - 29/5/15 at 11:15 AM

quote:
Originally posted by mcerd1

I don't know where abouts in the country you are, but I'd happily give you a hand with this....

[Edited on 28/5/2015 by mcerd1]


That's a really nice offer, thanks, but we're hundreds of miles apart.

jacko - 29/5/15 at 04:13 PM

What type of dizzy are you using ? one with a vacuum if so remove the top and suck on the vacuum pipe and look to see every thing is moving free
also oil with light oil on the plates
Check the valve clearance also
Jacko


[Edited on 29/5/15 by jacko]

bumpy - 18/6/15 at 08:13 AM

For those that helped me, there is a happy end to this story. I decided to bite the bullet and replace the Stage 1 camshaft with a new standard profile cam (from Burtons)

The engine performs beautifully now. Thanks to all those that offered suggestions.