2.25 petrol - an annoying miss

[series3]

Good afternoon my faithful brains trust,

I have a light, intermittent miss on my 2.25 petrol 2a. I took a short video to show you what I mean..

2a2.25 missing - YouTube (http://youtu.be/n0dwuvqMz2c)

I have recently done the tappets, set the points gap, set timing to a point that it drives really well, replaced all of my HT leads, and pulled apart/cleaned the carby a couple of times. Doing these things hasn't assuaged the problems.

My next thing will be replacing the condenser and maybe the coil, but I thought I would throw it out to the general populace for discussion. Are intermittent misses indicative of something in particular?

It still drives smoothly (other than the odd power-loss fart) and powers along well on the road.

Cheers,

Sam

[Brad110]

I wouldn't think the units themselves would be a problem intermittently if its running so well but certainly a connection or short. You didn't mention fuel.....

[series3]

The fuel is less than 1 week out of the bowser, if that is what you mean.

That's a good idea. the low tension wiring is looking a bit worse for wear these days, I cleaned some of the contacts, but not all. They could do with replacing...


Sam

[Cobber]

Plugs?

[tangus89]

Sam, i had a similar miss in mine, it still revved up alright, and ran ok.

I checked compression, timing, points, I changed the coil and the leads. Finally I changed the plugs and it runs without a miss now.

The last time it had a miss it ended up being the dizzy cap.

[korg20000bc]

It may be worth replacing the rotor button.
Apparently when worn it can slip on the distributor spindle and cause a miss.

[Blknight.aus]

it could also be the condensor fialing

[gromit]

it could also be the condensor fialing

I had a similar problem with a cheap condensor.
Occasional misfire when hot. Then it would run OK, then the car would stop completely. Eventually fitted the old original condensor and fixed the problem.

I'd used a cheap condensor from a Land Rover parts supplier and it karked it after a few days use.
I now use Bosch GL103 from SuperCrap.


Colin

[vnx205]

Maybe a leaking inlet manifold.

Can a valve stick intermittently? Is it worse when cold?

[shorty943]

Sticky valve? That can happen, mostly when the engine is hot.
I had a similar problem come into the shop some years ago with a Harley Sportster, seems it had a tiny bend in one exhaust valve stem from brand new.

Could also be a leak in the inlet manifold, that should make a squeaking noise or a timed hissing sound so pretty easy to hear with the bonnet up.
Found that one on an old Ford V8 with a cracked carby gasket, that would normally stop it from revving to full throttle though.

Or, it could be "D" all of the above suggestions made by all members.

Tricky things to isolate intermittent missing.

[series3]

Thanks everyone, a few options to sort through. I'll throw a new condensor in it firstly, and have a look at the plugs. I have been trying to set the timing through trial and error, but it has mostly been error until now, so maybe the plugs are sooted up. They aren't that old, at least.

Sam

[series3]

Regarding a leaking inlet manifold, what's the best method for diagnosis?

Cheers,

Sam

[isuzutoo-eh]

Spray some start ya barstard around the head/manifold join whilst the engine is running, and see if revs increase...

[series3]

A new Bosch gl103 in, yet the miss still persists... I will move into plugs tomorrow, and then check out the manifold leak.

Cheers

Sam

[UncleHo]

Are you running a straight 12volt coil or a 12 volt resistor coil, I.E. Bosch 12 or 12r as they only had a straight 12 volt one, how old are your leads? Carbon type need to be replaced every 2-3 years max.

Plugs at 32 thous inch that's about .8 from memory.

[wrinklearthur]

A new Bosch gl103 in, yet the miss still persists...

I looked up thatCondensor on the Bosch web site and it's for the Land Rover stage one V8, I don't know if that matters.

I would be now looking at the leads, condenser and making sure the points gap is spotless.


Check that the points gap isn't closing up as the rotor turns around, due to a worn distributor.

One or two of the plugs maybe shorting out under load, look up the correct heat range plug for your ambient temperature, get a range hotter then recommended only if the engine is using oil.
.

[JDNSW]

I looked up that coil on the Bosch web site and it's for the Land Rover stage one V8, I don't know if that matters.
...
.

That GL103 is a condenser, and according to the Bosch website, is the right one. (Condensers are not critical - if it fits it will work).

John

[series3]

My coil is either a GT40 or GT40r, i cannot remember which at the moment, about 3-4 years old. I'll check later tonight.

My leads are now new Boschies, 2 days old.

I'm leaning towards the plugs now being either wrong, buggered or sooted up. Any reccomendations on replacements?

About time most of this stuff got replaced anyway!

Sam

[wrinklearthur]

Ref;
http://ngkntk.co.uk/wp-content/uploads/2011/03/sparkplug-cat-2013-new.pdf

LAND ROVER
DEFENDER 2.5 6 90Õ BP6E 7529 BP6ES 7811 0.8
3.5 8 90Õ BPR5E 7075 BPR5ES 7422 0.9
DISCOVERY 2.0 4 93Õ06/97 BKR6E 6962 BKR6ES 3783 0.9
1 & 2 3.5 8 CARB 89Õ BP6E 7529 BP6ES 7811 0.8
3.5 8 INJECTION 89Õ BPR6E 6464 BPR6ES 7822 0.9
3.9 8 3950cc 94Õ98 BPR6E 6464 BPR6ES 7822 0.9
4.0 8 3950cc 09/98Õ PFR6N-11 3546 X
4.0 8 FACELIFT MODEL 3950cc 06/02Õ PFR6N-11 3546 X
DISCOVERY 3 4.4 8 10/04Õ IFR5N10 7866 X
FREELANDER 1 1.8 4 18 K16 10/97Õ06/05 PFR6N-11 3546 X
2.5 6 KV6 09/00Õ06/05 PFR6N-11 3546 X
FREELANDER 2 3.2 6 09/06Õ ILFR6B 6481 X
SERIES I,II&III, 2.3 4 7:1 COMP Õ85 B5ES 6410 0.8
90 & 110 2.3 4 8:1 COMP Õ85 BP5E 4669 BP5ES 6511 0.8
2.5 4 08/85Õ BP6E 7529 BP6ES 7811 0.8
2.6 6 B6ES 7310 0.6
3.5 8 Õ86 BP5E 4669 BP5ES 6511 0.6
3.5 8 86Õ BP6E 7529 BP6ES 7811 0.6
RANGE ROVER 1 3.5 8 12.7mm Reach Plugs CARB Õ76 BP5HS 4111 0.6
3.5 8 19mm Reach Plugs CARB 76Õ85 BP5E 4669 BP5ES 6511 0.6
3.5 8 INJECTION INJECTION 85Õ10/89 BPR6E 6464 BPR6ES 7822 0.8
3.9 8 10/89Õ10/95 BPR6E 6464 BPR6ES 7822 0.9
4.2 8 10/92Õ12/94 BPR6E 6464 BPR6ES 7822 0.9
RANGE ROVER 2 4.0 8 P38 Model 09/94Õ12/98 BPR6E 6464 BPR6ES 7822 0.9
4.0 8 P38 Model 99Õ PFR6N-11 3546 X
4.6 8 P38 Model 10/94Õ12/98 BPR6E 6464 BPR6ES 7822 0.9
4.6 8 P38 Model 99Õ PFR6N-11 3546 X
RANGE ROVER 3 4.4 8 BMW M62 01/02Õ04/05 BKR6EQUP 3199 X
RANGE ROVER 4 4.2 8 SUPERCHARGED AJ41 04/05Õ IFR5N10 7866 X
4.4 8 AJ41 04/05Õ IFR5N10 7866 X
5.0 8 SUPERCHARGED AJ133 07/09Õ ILKAR6C10 95843 X
RANGE ROVER 4.2 8 SUPERCHARGED AJ41 06/05Õ IFR5N10 7866 X
SPORT 4.4 8 AJ41 06/05Õ IFR5N10 7866 X
5.0 8 SUPERCHARGED AJ133 04/09Õ ILKAR6C10 95843 X

[wrinklearthur]

Model ------- Engine size - Cyl- Comp -- Date -- Recmd --Stock-- Gap --- Alt --- Stock

SERIES I,II&III, -- 2.3 ----- 4 -- 7:1 --- <85 --- B5ES --- 6410 -- 0.8

SERIES I,II&III, -- 2.3 ----- 4 -- 8:1 --- <85 --- BP5E --- 4669 -- 0.8 --- BP5ES -- 6511

SERIES I,II&III, -- 2.5 ----- 4 -- 8:1 -- 08/85> - BP6E --- 7529 -- 0.8 --- BP6ES -- 7811

.

[JDNSW]

To get the right plugs, check the compression ratio - later cylinder heads had a square boss cast on top of the head between the carburetter and the rocker cover. If this boss has an "8" stamped on it, it is 8:1, if it has a "7", is unmarked, or it is an early head with no boss, the ratio is 7:1. (Unless it has been reground after manufacture!)

It is most likely 7:1 if sold new in Australia. (But either the head or the engine may not be original!)

John

[chazza]

Buy good quality plugs such as NGK - Champion is rubbish.

Having used the Iridium plugs on my Disco, I now fit them to everything, despite the extra cost, because they will last for a very long time and out-perform the copper-cored ones,

Cheers Charlie

[series3]

The plugs have been replaced with some (gapped) NGK iridium ones.. Yet the miss is still there. It may have been smooth for the first little while, but I am not sure. I have played with the dizzy timing to lessen the miss as much as possible, but will rip out the timing light tonight to see if I am in the right ball park.

Here are the plugs that came out, the two middle are quite blackened and pretty bad considering they were not very old at all. Is this a sign of running rich?

https://www.aulro.com/afvb/images/imported/2013/06/37.jpg

When it does miss, putting your hand over the exhaust gives you little droplets of fuel.

Can it be something to do with the extractors? Or carby?

Regarding compression, I always assumed my 2.25 was a 8:1, due to being right at the pointy end of the 2a production. (241 548 80A). CalVIN says this was used for both early 2a motors and early 3.

But what JDNSW says is making that a little murkier...

Here is the front-most part of the head,
https://www.aulro.com/afvb/images/imported/2013/06/38.jpg

The back,
https://www.aulro.com/afvb/images/imported/2013/06/39.jpg

and the middle.
https://www.aulro.com/afvb/images/imported/2013/06/40.jpg

The motor has been refurbed during my tenure, so even if it is a 7:1 head, it could be 8:1 anyway. Incorrect plugs wouldn't give it a miss like this though, would it?

Cheers everyone

Sam

[series3]

My coil is either a GT40 or GT40r, i cannot remember which at the moment, about 3-4 years old. I'll check later tonight.



GT40. no R.

Sam

[JDNSW]

The boss with the CR on it is the extension of the seat for the headbolt in the picture showing the middle of the head.

The sparkplugs suggest to me two cylinders (which ones?) are fouling due to stuck rings or plugs are too cold. Alternatively, two cylinders too rich, the other two about right - suggesting a manifold leak affecting those cylinders, with the mixture set to compensate for this, resulting in being two rich for the other two, and resulting miss.

John

[chazza]

If the plugs you show are in order, it may also suggest a blown head gasket between nos 2 and 3 cylinders, resulting in incomplete combustion.

Do a compression test dry and then wet, when the engine is hot.

If all is good there, investigate the rest of the ignition sytem; be prepared to change the high-tension leads; points; capacitor; possibly the coil; distributor cap and rotor arm. Beware of cheap repro. rotor arms that don't work properly - google the Distributor Doctor.

Check for manifold leaks as John suggests,

Cheers Charlie