Stick valve/lifter

arthuy

arthuy

Well-Known Member
Hi,

I am looking for some hints to same me a bit of hassle.


The v8 is running a little rough at the moment.

It runs but every 8th or 16th fire it misses. I have traced this to the rear right hand cylinder by removing the ht leads until I found the one that didn't affect the running.

I have checked the plug was clean and correctly gaped. I then put my colour tune in place of the plug and it does fire although the mixture appears rich compared to the others.

This is why I think that the lifter or the valve is sticking.

So is there anyway of rectifying this without stripping bits down? I am considering an engine flush and oil change. I think the oil is only a 1500 miles old replaced back in January.

Has anyone ever managed to sort out this sort of problem this way or is it time to get the spanners out.

Colin
 
Have you done a compression test ?
People reckon Wynns Hydraulic Lifter Additive is good
Could be a worn out camshaft - I think mine has the same problem
 
When you remove the lead from the affected cylinder does it have no effect on the running?(is it misfiring intermittently or only running on 7 cyl. all the time?)
 
I am sure it is only firing on 7 cylinders all the time.

I don't think it is the cam shaft being worn as the engine has only done 80,000 miles.

I think it may be a gunk related issue, I did an oil flush and change back in Jan this year but I seem to remeber that the filter looked like it had been on for a few years.


Colin
 
Change the plug on the misfiring cyl with one that is working,see if the misfire moves with it.Then do the same with the lead.Then check the dist. cap.Then do a compression check wet and dry.That should eliminate those as problems.
 
I have already change the plug for a good one and it also missed with the colour tune fitted.

I will do a comp test on it.

Colin
 
I bought my V8 with a misfire on the rear cylinder on the right hand bank. When the car was ticking over it would miss now and again, but as soon as you tried to drive it, the misfire would become worse. I got the car cheap, as the owner thought that the camshaft had failed. He was right!

I would be tempted to remove the rocker cover, and make sure that the valves are fully opening and closing on the offending cylinder. Camshaft failure is not that uncommon on V8's that have done relatively low mileages, if the oil changes have not been done regularly. A good indication of this is an engine that is full of black sludge. You can inspect the camshaft by removing the inlet manifold, and the valley gasket.

Camshaft replacement is a fairly easy job that can be done in situ, without having to remove the cylinder heads. Always replace the follwers, and make sure that they rotate easily in their bores in the block. I replaced the timing chain and sprockets as well, and also removed the sump for 2 reasons- You have to split the front timing case from the front of the sump gasket, and also all that ground up metal has got to have gone somewhere!
I bought all the parts for mine from a local motor factors. It worked out a lot cheaper than buying from a specialist.

Have you checked for air leaks on the inlet manifold? These are great for causing random misfires!! I had this problem with my wifes Mk2 Escort, on number 1 and 2 cylinders, and gave the same symptoms as you are suffering with. I sprayed the inlet to cylinder head joint with penetrating oil, and sure enough it started dragging it in. The plug leads were fine, and the sparkplugs were all in good condition. I had tried the same as you, with swapping plugs and leads around, to see if the problem moved to another cylinder. In the end the problem was a warped inlet manifold! ???

Hope this helps
Best Wishes
Richard :)
 
Thanks for that,

I am going to go simplest/cheapest first.

The thing is I don't want to spend lots of time and money on this car. The reason being I have a 2200tc on long term restoration and I only got this v8 a year ago as it was needing a bit of welding. I had hoped to have it sold by now.

I will let you know how it goes.

Colin
 
I have a similar problem of misfire to the above with OK start and idle but a misfire on acceleration. The engine is a replant with a 9.35:1 CR (identified as SD1 from J taylor book) with engine no. 10A40340. The previous owner stated it came from a technical college where it had been donated by BMW.

Engine runs fine at low revs but misses at higher revs.

I did a compression test and got 158 psi on five cylinders 154 on two cylinders and 150 on the front RHS. Given the accuracy of my reading the gauge is only+/- 2psi this sound OK to me. Does anyone disagree?

The oil is clean. I topped up the dashpots with auto trans oil as suggested on the forum (to within 1/2" of top). I inspected the black distr cap carefully with nothing seen. I inspected the plugs and they are gapped fine but sooty (with less soot on some). I used a HT tester that flashes when you insert it between the plugs and leads and all plgs are firing.

Finally I looked at the old electric pump in the boot flow on ignition (seemed slow) so I changed the fuel filter fitted in front of the carbs. I also changed on lead where it felt loose. I cleaned the points but didn't check the gap. The coil is a newer Lucas high power type.

Result was an improvement but still a definite misfire on acceleration as you put your foot down.

My next move is to replace all leads, condenser, cap and points and check the gap. If this makes no difference I will check the manifolds for an air leak. I have Wynns valve lifter oil - should I shove that in anyway?

Can anyone suggest better approach? I've only had the car two weeks so I'm a little disappointed so I hope to cure it quickly as I've got some clunks form the front to chase down as well.

Many thanks

John Macdonald - disappointed P6 new boy
 
Sounds like an ignition problem, I bet its ok once you do the plugs/leads/cap/points/condenser Maybe worth picking up a spare coil too just in case.
 
hi,
try the advance and retard vacuum, is it working, if not it will cause uneven running when revved.

ianp6man
 
Thanks for the advice on the misfire. I checked the advance by trying to suck through it. Advice I'd read is that if you can then the diaphragm is split. I reckon its split. Can you get a separate vacuum advance without a new distributor.

I also checked the coil using resistance measurements. The advice I had was that the LT resisitance should be between 0.4 to 0.7 ohms. The reading was 1.5 ohms. The HT resistance was also out of spec so I presume the coil is weak as well. I will have to find a coil suitable for connection to a ballast resistor. I'll let you know if its cured.

John Macdonald
 
Hello again. I still have my misfire after changing coil, leads, condenser and cap. I'll change plugs next. I know the advance unit has a split diaphragm. I have had Ray Weeklys send me a new advance unit but it fouls the cap. Likewise the points don't fit. Does anyone have an old set of points and vacuum unit they are willing to sell for me to fit/compare. I'll return a cheque to cover the postage and value of parts (Based in Swindon). My distributer part number is 41393.

Thanks

John Macdonald
 
Colin Gould over in Faringdon fitted a new advance/retard to our V8 which also fouled the dizzy but he just filed a bit out of the cap which is what he told us he would have to do beforehand as the original units aren't available. It does no harm.
 
Hello again. Just to let you know that the misfire was cured by new plugs (of correct rating NGK BPR 5ES) and by spending some time running the HT leads to avoid them being too close to one another.

I will file down the cap to let the Triumph advance unit fit.

Thanks for the responses

John Macdonald
 
macdonj said:
Hello again. Just to let you know that the misfire was cured by new plugs (of correct rating NGK BPR 5ES) and by spending some time running the HT leads to avoid them being too close to one another.
Click to expand...
look at the haynes manuals - they show the routing for the leads - the later books, SD1 fixes some erros in earlier lay out.

the leas should not be parallel if possible and when they cross, it is a t right angles to prevent misfiring.

you can get the v.a. unit from wadhams; the lugs may be different if you have the rarer dizzy (guess whcih one was minbe?) but can be sorted easily by drilling and tapping a hole in the dizzy body.
 
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