Constant Mis-fire

[salmon]

Had the car for nearly a year now an never had any running problems (150pi, running lumenition ignition otherwise standard). Was ok on the way to work, however car has developed a misfire on the way back, seems to be constantly running at a guess 4-5 cylinders. Seems to tick over OK, and drives OK just not firing on all. Nothing seems to be loose but not massively mechanically minded, can anyone advise where are the first places to look, apologies for being vague as I know there could probs be loads of causes just not sure if this is a common problem and if there is anything obvious I can check. Only time it has done this before is when its been started after being hot, but this generally clears after running 20 seconds or so.

 

Thanks in advance

[Geoff Davies]

Had the car for nearly a year now an never had any running problems (150pi, running lumenition ignition otherwise standard). Was ok on the way to work, however car has developed a misfire on the way back, seems to be constantly running at a guess 4-5 cylinders. Seems to tick over OK, and drives OK just not firing on all. Nothing seems to be loose but not massively mechanically minded, can anyone advise where are the first places to look, apologies for being vague as I know there could probs be loads of causes just not sure if this is a common problem and if there is anything obvious I can check. Only time it has done this before is when its been started after being hot, but this generally clears after running 20 seconds or so.

 

Thanks in advance

 

Hi, if you see my posts on misfire I had one for around two years and spent a lot of time and money on it to no avail. Eventualy I gave in and let Carl at TR Trader have a look at it. He sorted it in a couple of hours ( super service). My advice would be to let a profesional look at it as in the end it could save you money.

[BryanD]

Just before you take it to a specialist the two most obvious things to check are:

 

a) that one of the injectors isn't 'firing'. Its easy to check; just touch each injector lead in turn and see if you can feel a 'pulse'.

If one lead feels different, then its very easy to remove the injector and blow it through with an airline. A common cause is a bit of crud holding it open. You will need to bleed the air out of the line afterwards if you do this. Lots of other posts on this subject if you care to search back.

 

the general condition of plus and leads and rotor arm. If nothing is obvious, but they look elderly then its good practice to replace them anyway as they are regular service items. Poor quality rotor arms are a particular problem at the moment and the cause of many a mysterious misfire.

 

Good luck

[salmon]

Checked last night by taking each lead off in turn, and its the front most cylinder thats not firing. Tried a different lead last night which made no differance, no idea when the plugs were last changed so thats probs next port of call, but will also give check the pulse thing as above cheers.

[Richard Crawley]

It might just be a fouled plug; happens easy on the 6 PI if you don’t thrash it enough! Give it (give them all!) a good clean & check you have a spark before putting it back in; if not, check/swap the HT lead; if still no spark check/change the cap & rotor. If you have a spark but still a problem, bleed the injector (see archive posts). If that still don’t cure it, come back!

[marks]

Hi

Start with the easy bits before suspecting somthing really bad. I had a similar occurence a while back, checked the plugs all "looked" fine but couldnt verify age. Put in a new set and bobs yer uncle, goes like a rocket again.

 

Mark

[salmon]

Going to go for the NGK plugs, can anyone tell me if these are the correct ones? Looks to be the right part number, just lots of variations..

 

http://www.sparkplugsrus.com/shop/index.cg...181736530-29613

 

Sorry that link doesn't seem to go to the correct place. Searched for the BPR6ES, just seems to a lot of varations.

Edited June 13, 2007 by salmon

[Rob Salisbury]

Never got on with the resistor series plugs, I prefer the cooler running BP7ES, they seem to last forever.

Cheers, Rob

[Eyetee]

If still not cured with new plugs, try a compression test, kit replaces each spark plug in turn and checks compression on said cylinder, no need to runn engine just turn over with battery.

[salmon]

Fitted new plugs and then wouldn't start at all. Decided to get AA man out as needed the car quite urgently for work. He was baffled for a while as the spark was really weak, and guessed it was the coil. After a bit of fiddlling noticed the HT leaed wasn't sitting hte coil properly as the rubber was pushed down too far. Doh. Fitted properly and runs spot ion again. Cheers for all help above, eawy fix in the end, v lucky!!

[BryanD]

Thanks for coming back and telling us.

 

So often the folks here dispense their opinions and never get to hear the outcome!

 

It also helps to add to the overall value of the forum.

[salmon]

Well, the bl00dy constant misfire is back..

 

There is now a decent spark at the end of the lead and its had the set of new plugs, so don't think its that. Noticed the fuel hose was a bit cracked at the end so I've taken that off and cut the dodgy bit off. Which is somthing else, whats the easiest way to get the hose back over the lugs on the injector, as I can only get it over 1 not both? There is defo a pulse in all the fuel hoses, which I think rules the Mu out?. Have taken the injector out, and it seems to drible on tick-overs, however it does the correct oval spray pattern at higher revs, does this mean its blocked? Guessing its not an airlock if there is fuel coming out?

 

Any ideas anyone?

[Jersey Royal]

Well, the bl00dy constant misfire is back..

 

There is now a decent spark at the end of the lead and its had the set of new plugs, so don't think its that. Noticed the fuel hose was a bit cracked at the end so I've taken that off and cut the dodgy bit off. Which is somthing else, whats the easiest way to get the hose back over the lugs on the injector, as I can only get it over 1 not both? There is defo a pulse in all the fuel hoses, which I think rules the Mu out?. Have taken the injector out, and it seems to drible on tick-overs, however it does the correct oval spray pattern at higher revs, does this mean its blocked? Guessing its not an airlock if there is fuel coming out?

 

Any ideas anyone?

Salmon,

 

You need to be 100 per cent sure that all your plastic injector hoses are connected securely, you dont want them comming loose and spilling out all over the engine.

 

Unfortunately i cant comment on how to fit them, as i have stainless steel ones, although i believe there is a special tool for it that can be made up. Try a search..

 

With regards to dribbling injector sounds like the inner rubber seal inside the injector is on its way out. Although new rubbers can be fitted, dependant on your mechanical experience, you may be better off doing an exchange for new or recon injectors from one of the TR Suppliers.

 

I used to have problems pulling away after the car had been ticking over at lights, would run ruff for a bit then clear at higher revs, it gradually got worse, so i replaced all six injectors, worked a treat and also i now the history of the injector.

 

My thoughts

 

Guy

 

Ps .. See if some one from your local group can help you out.

Edited July 26, 2007 by Jersey Royal

[Richard Crawley]

whats the easiest way to get the hose back over the lugs on the injector, as I can only get it over 1 not both?

 

You need a special little tool to fit the plastic injector pipes or you will find it almost impossible to get the plastic pipe back over the ferule ridges without kinking. It’s easy enough to make & is basically a block with a hole drilled through it cut in half. The Leyland manual shows how to make the tool & specifies nylon but you can use any hardwood offcut & it will last long enough to fit several sets of pipes.

 

Have taken the injector out, and it seems to drible on tick-overs, however it does the correct oval spray pattern at higher revs, does this mean its blocked? Guessing its not an airlock if there is fuel coming out?

 

The O ring has had it; what happens at low revs is that fuel dribbles past the seal instead of being forced through the nozzle. This causes misfires at lows revs & poor slow speed pick up.

[salmon]

Salmon,

 

You need to be 100 per cent sure that all your plastic injector hoses are connected securely, you dont want them comming loose and spilling out all over the engine.

 

Unfortunately i cant comment on how to fit them, as i have stainless steel ones, although i believe there is a special tool for it that can be made up. Try a search..

 

With regards to dribbling injector sounds like the inner rubber seal inside the injector is on its way out. Although new rubbers can be fitted, dependant on your mechanical experience, you may be better off doing an exchange for new or recon injectors from one of the TR Suppliers.

 

I used to have problems pulling away after the car had been ticking over at lights, would run ruff for a bit then clear at higher revs, it gradually got worse, so i replaced all six injectors, worked a treat and also i now the history of the injector.

 

My thoughts

 

Guy

 

Ps .. See if some one from your local group can help you out.

 

Hasn't been out of the garage since, as like you say I was worried about the hose coming off, as well as that its only running on 5 cylinders. Think the injectors were changed by the previous owners relatively recently, But I'll have to check.

 

Starting to think taking it to a specialist is the way forward. Anybody know of any specialists in the north east?

[salmon]

Managed to get the hose back onto the injector (with great difficulty), and tested into a milkbottle. Was doing the correct pattern, so obviously not a fuel issue. Had checked and there was definately a spark, although very weak at the gap in the plug. Tried putting one of the old plugs back and back to running on 6, so one of the new plugs must have been dodgy..

 

All running OK now so I'm a happy lad.

[trimprop]

Can someone clarify this for me, as I've seen it raised before, but not answered.

 

When I take the HT leads off one at a time, the removal of certain ones causes the tick over to drop... but others don't seem to have an effect. Is this normal, or do I have problem cylinders?

 

I think my best option is going to be taking it to a decent TR specialist. Can anyone recommend someone in West Sussex?

 

Thanks guys - this forum is excellent.

[Richard Crawley]

Can someone clarify this for me, as I've seen it raised before, but not answered.

 

When I take the HT leads off one at a time, the removal of certain ones causes the tick over to drop... but others don't seem to have an effect. Is this normal, or do I have problem cylinders?

 

I think my best option is going to be taking it to a decent TR specialist. Can anyone recommend someone in West Sussex?

 

Thanks guys - this forum is excellent.

Removing each HT lead in turn (aftre putting the previous one back) should have the same effect with all cylinders; tickover should drop & the motor will run slightly lumpy.

[salmon]

Removing each HT lead in turn (aftre putting the previous one back) should have the same effect with all cylinders; tickover should drop & the motor will run slightly lumpy.

 

This is how I found which one of mine wasn't firing, there was a noticable differance in each apart from No 1 which ran as per before. Sounded bloody awful when it was only running on 5, so if you have more cylinders off must sound sick as a dog..

[raydrink]

When I take the HT leads off one at a time, the removal of certain ones causes the tick over to drop... but others don't seem to have an effect. Is this normal, or do I have problem cylinders?

Hi Trimprop,

 

Re your query and your own topic entitled 'Newbie with a stuttering car', you seem to have done 90% of the work needed to solve this problem but given up on tying up the loose ends. For example, did your garage, after sorting out the timing and the correct points, tell you that you now had a good spark at each plug (even though the dizzy was sloppy)?. If they did, the sloppiness in the dizzy can be sorted out later. The issue to be addressed is why do I have lumpy running when I have replaced all the electrical items and have a good consistent spark?

 

It sounds like you might have answered this yourself - pulling a plug lead off one or more plugs makes no difference to the engine speed. What you didn't confirm was whether those leads gave a good spark when earthed.

 

If they did, and assuming the new plugs are OK, then you are likely to have a dribbling injector, either because it is being held open by crud (yes by all means clean the fuel filter to stop it happening again) or because the 'O' ring is kaput.

 

Don't give up now; read up on pulling the injectors while the engine is running if you are apprehensive, and go for it! It's the only way I learned (with lots of help from Richard Crawley and others). Taking the injectors apart, renewing the 'O' ring and, in my case, tightening up the allen screw in the end of the injector to give a good spray pattern, was most satisfying. Don't start thinking in terms of valve seats and compression until you've gone down the injector route.

 

Having had a car that would not run consistently well for almost 2 years, and the uncertainty that brings when driving it, I can say that having just completed the TR Register Isles Tour, doing 1543 miles without a hitch, I have renewed confidence not only in the car but in my ability to fix it. You can't beat it!

 

Please let us know how you go on.

 

Ray

Edited July 31, 2007 by raydrink

[salmon]

Yet another update, as mis-fire is back again. Think now that cylinder 1 is getting too much fuel. Seems to be soaking the plug, so that the cylinder stops firing, then when its swapped with another plug runs OK. Seems to be on start up, so not sure if its a problem with the choke (although the car needs v little choke to start).

 

Going to get it in somewhere to get set-up, anyone know of anywhere in the Newcastle/North East area?

[raydrink]

Seems to be soaking the plug, so that the cylinder stops firing, then when its swapped with another plug runs OK.

 

Hi Salmon,

I had exactly this problem and I eventually measured the resistance between the plug electrodes and found that there was a path to earth where there should have been none. I too concluded that I'd got a bad plug. But it kept happening, every time the plug got fouled with fuel - and they all also got sooted up after less than 50 miles, necessitating cleaning!

 

Having started with NGK 7ES plugs, I moved onto 6ES with no improvement so went even hotter to 5ES and the problem's gone.

 

It might be worth trying a hotter plug.

 

Ray

[salmon]

Hi Salmon,

I had exactly this problem and I eventually measured the resistance between the plug electrodes and found that there was a path to earth where there should have been none. I too concluded that I'd got a bad plug. But it kept happening, every time the plug got fouled with fuel - and they all also got sooted up after less than 50 miles, necessitating cleaning!

 

Having started with NGK 7ES plugs, I moved onto 6ES with no improvement so went even hotter to 5ES and the problem's gone.

 

It might be worth trying a hotter plug.

 

Ray

 

cheers, certainly worth a go for a couple of quid.

[jr.clarkson]

Hi Salmon,

 

I had all sorts of issues with misfiring and lumpy running. Went down all sorts of garden paths (ther is no one here to take it to). Replaced timing chain and gears, ignition back to points, leads, coil, blah blah bah. Turned out to be not enough fuel pressure, horrid up to 2k revs then seemd to run better. Had a guage made up to check pressure and pointed me in the right direction. I replaced the Lucas pump with a Bosch (left eveything else including filters as original, cost of around GBP95 for everything, including fitting kit). Started to run okay but still not right. Took the injectors out and dismantled on the kitchen table (waited until wife was out). Found out that was had a worn spring. Replaced all the o-rings with Vitons (about 15p each), put it back together and pulls like a school boy, right from idle.

 

Don't give up, try the fuel pressure first, it may be as simple as carbon build up.

 

CHeers

 

John

[salmon]

Hi Salmon,

 

I had all sorts of issues with misfiring and lumpy running. Went down all sorts of garden paths (ther is no one here to take it to). Replaced timing chain and gears, ignition back to points, leads, coil, blah blah bah. Turned out to be not enough fuel pressure, horrid up to 2k revs then seemd to run better. Had a guage made up to check pressure and pointed me in the right direction. I replaced the Lucas pump with a Bosch (left eveything else including filters as original, cost of around GBP95 for everything, including fitting kit). Started to run okay but still not right. Took the injectors out and dismantled on the kitchen table (waited until wife was out). Found out that was had a worn spring. Replaced all the o-rings with Vitons (about 15p each), put it back together and pulls like a school boy, right from idle.

 

Don't give up, try the fuel pressure first, it may be as simple as carbon build up.

 

CHeers

 

John

 

Cheers for the advice, pretty sure its something to do with the fuelling or the plug as it is soaked when I take it out. Going to try the hotter plugs first, then going to try and find somewhere to get it set up properly. Think the fuel pressure should be OK as its had a new fuel pump relatively recently, but certainly worth a go if the those don't fix it.