Plugs

stina

stina

New Member
Hi guys , Had to go out this afternoon so i took the rover . Only a short drive . Started pretty well as usual but as soon as i accelerated i knew all was not right . Had a misfire and was running on 7 cyl's . Last night i had to move her out of the garage so hubby could get at some gear for work , so was running for about two mins on choke . I mention this as i had a misfire about 6 weeks ago after the same situation that cleared after a mile or so as she warmed up . Today it wouldn't clear and was still missing when i got home . Took the plugs out on the left bank and the first one was wet , not firing . I cleaned in up and replaced , still missing . Cleaned up an old one and went out for a run and she runs lovely . Rest of the plugs on that bank were fine , nice gray brown . Didn't have time to look at the other bank or see the point as i'd found the problem . The plugs are only 800 miles old , NGK bp5hs . Apart from these two issues she has run lovely for the last 800 miles . I've read through a fairly recent post on plugs and opinion seems divided . I have p6b heads . What are the best plugs ? and where to get them ? Is this related to running on choke for a short time then switching off , oiling the plugs , or a suspect plug ?
Thanks in advance . Will have to answer any replies tomorrow as going to bed now . early start !
Cheers
stina
 
You could have a problem with your cap or lead.

I have a cheap little plastic thing which you fit between the plug and the lead. When it fires if lights up so you can tell it is everthing is ok. You could do the same if you have a colour tune if you have one of those.

Other thing you could do is swap leads and see if the fault moves with the lead.

Colin
 
Hi Stina,

It could just be a suspect plug or it could be something more. What is the compression ratio of your engine?

Ron.
 
stina said:
Is this related to running on choke for a short time then switching off , oiling the plugs , Thanks in advance .
stina
Click to expand...

I had this problem, but it mostly occured in conjuction with poor quality fuels, in my car was always the drivers rear side plug that fouled first, sometimes more than 1 plug would foul but usually from one carburettor (obviously running richer on one carb) but most times cleared after about a KM of driving however some occasions required a clean.

Cure was to use a hotter plug and use good fuels, no problems since.

Graeme
 
Hi guys . still would like to know what plugs best to use ! Compression is 9.25:1 , always use 99 octane fuel with booster/lead replacement . Cap / leads new and well separated ( not cross firing ) . The thing that goes between lead and plug and flashes , seen them before , any ideas where to buy one or what their called ?
Ron what sort of "something more" do you mean ? Your making me nervous !
stina
 
Hi Stina,

Sorry for making you feel nervous. The NGK plugs do work well with the 9.25 : 1 engines, but less so with the 10.5 : 1 engines, hence my question. Running on choke for a few mins means is not always a good idea, especially if you don't take it for a run straight afterwards. Glad that the old plug cured the problem, so likely a dud plug.

Ron.
 
i had this problem gradually getting worse denso plugs with little miles, didnt cure it with new magnecor leads,the cap and rotor were already new,fitted ngk,s been ok since including long trip , i also wonder if fuel was to blame , i use tesco a lot and we cant get 98 anyway,regards rich
 
Ordered a few of those testers . Tempted to buy 8 and sit in the garage with a beer or two getting phychedelic watching it flash to the beat !
I'll post back when i know more .
looks like i'm running the right plugs , prob needs a good hard run eh ? !!!
 
I think its fuel quality and not octane rating that is the main issue, I run my 9.25:1 on 91 octane with no problems whatsoever, no timing readjustment was needed and the engine does not pink or knock just smoothe power delivery.

Graeme
 
Hi guys . Update . Drove up to my allotment this morning . The misfire had returned , not as bad as before , sometimes it would pull quite well , it was more of a problem at low revs picking up . I tried a few things while i was there , different plug , rotor arm . I drove the long way home and gave her a bit of blast down the spur road . At 80 ish it would still splutter now and then , generally not running good .
Anyhoo , i decided to go through everything when i got back ,took all the plugs out , nice gray brown , cleaned and separated the leads ( new 900 miles ago ) checked vacuum advance was working , then checked the timing . It had slipped back to 4deg btdc . I set it at 6deg and it sounded better straight away , smother tick over . Took it up the road and it ran lovely . Gotta do a good few miles tomorrow so we'll see how she behaves .
Question , would 2 degrees make that much difference ? Why would the timing of slipped ? The bolt was pinched up well . Any thoughts ?
Stina
 
I had a v8 that did that once... Timing chain went completely and took the engine out. I'm no expert but as the timing cogs on the v8 are known weaklings it needs to be checked IMHO....


Rich
 
Hmmm , way out of my league at the moment and more than i was thinking . If as you say . Would it of jumped exactly 2 degrees , and would the cam timing not be out now that the ignition is reset ?
At no time during this little saga have i heard rattly chain noises ! ! !
I hope :?
 
i dont know... I'd just see if anybody else replies on here. I had a 74 v8 which did what you've described. I hadnt scientifically set the timing so when it shifted i just turned the dizzy round thinking the dizzy had shifted round because i hadnt tightened it up properly, but that wasnt it. The engine died a couple of days later. Would hate that to happen to anybody else...

Rich.
 
I am sure that the chain can stretch and also it can jump a few teeth if really worn.

When you previously set it all up did you do it when the car was warm and the vac removed? The rotor arm could have been not firmly seated or as I have had the little locating lug chipped which caused the timing to go out.

Probably nothing to worry about.
 
Hi Stina,

The variation in timing that you saw could well be down to the timing set as Rich pointed out. The OEM timing sets on all the P6B engines consists of a steel crankshaft cog, an aluminium alloy main cog with nylon teeth which are connected by a Morse type chain. It provides a very quiet set up, but accurate camshaft timing is something well beyond its capabilities, especially when an engine has covered say anything over 50,000 MIles (80,000km). My original timing set ran for just over 203,000 MIles (327,000km) and only two of the nylon teeth remained. All the others had broken off in addition to the aluminium alloy wheel being cracked. The chain was so loose it was a complete engine failure in waiting. Here is a link to some pics. viewtopic.php?f=5&t=4901

Another alternative is that the engine speed when you set and then checked the timing was slightly different, which would lead to the small drop you observed.

Ron.
 
Back to basics, Stina!

I can't remember whether you have electronic ignition. If not, then the timing shifting is completely allowed by wear on the points, either the nylon foot or the surface of the points themselves.

Likewise plug gap affects timing.

And have you checked that the vacuum advance still has an intact diaphragm by having a suck? ( :oops: )

Only after this can you start to panic about timing sets. But the timing set doesn't only affect ignition timing, it also affects valve timing. So your newly reset 6 btdc will still feel very down on power if that is what has happened. My advice would be not to panic, and see if it does it again. Then we'll panic with you!

Chris
 
Phew... Good to know there's something small it could be. Points are beyond my motoring experience... Even my 1979 datsun had electronic ignition.... Sorry if I made you panic stina!
 
Hi guys another update . Started well this morning . On the way out to the spur road had the odd cough on choke . decided to push on , Once your on the spur road it's 8 moles before you can get off again . sat at 60 it didn't feel as if it had much power . When you touched the throttle before it would leap forward . When i got to the roundabout i decided to abort and came back . It also used about 2 gallons to do the 20 miles !
Since getting home i have put the timing light on it , still at 6 deg . The vacuum advance works but you have to give it quite a hard suck to get it to move . Does that sound right ?
Chris , yes electronic ignition .
How can i check if the timing chain has slipped ?
stina
 
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