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MG TD TF 1500 - Intermittent miss at idle TF1500

Hi guys:

I'm having an intermittent miss at idle. Increasing the RPM's seems to help, and it runs fine at speed, but it just may not be as noticeable then. I'm thinking it may be plugs and wires need replacing.

That said, I'm running Autolite 404 spark plugs, and the wire set is what I bought from Moss 15 years ago. (Champion)

Any suggestions for a perhaps a different plug and wire set? Or...any idea what else may be causing the problem?

I saw an earlier thread about some number stamped on the engine that would indicate if the plug should be a long or short reach. Can't recall exactly what thread that was or where the stamped number is located. So, assume that number indicates a long reach plug....how do you determine if a sparkplug is actually a long reach or not? I assume a specific length threaded portion?

What about the points? I'm not thinking that's the issue, but since I'm asking, perhaps it is?

The plugs are lightly sooted, so likely a bit rich, but I also don't drive it all that much either.

Thanks,

Jim


Jim Rice

IF it is the 1500cc original engine the head will be marked AEF118, if so then long reach plugs (3/4")
Ray TF 2884
Ray Lee

Not very scientific I know, but try looking at your engine running at night time, preferably a slightly damp or misty night with no lights. You could be surprised to see where sparks can leap.

Matthew.
M Magilton

Jim, Also check to see if there's any wobble on the distributor shaft, hopefully just wires plugs or cap. PJ
PJ Jennings

Ignition misfires usually get worse when the engine is under load. That said I would have a look at all of the connections of each plug wire and coil wire and make sure you do not see any signs of corrosion. Check the rotor for burn on both the tip and the contact. The black ones made 15 years ago are always suspect. The red versions sold the last several years are quite good. Check the contacts inside the distributor cap while you are there. Do not change the condenser. Check the points for pitting or burn marks.

Plugs should be 2/4" reach unless the head has been swapped for an early TD version. Personally, I will not walk out the door with Autolite plugs. We used to put them in a fork lift at my wifes business but the last set we got were awful right out of the box. Had a look and sure enough....made in China. Just terrible. Yours may be fine and perhaps they have improved manufacturing. Never the less you might want to invest in a new set of plugs of your choice while you are there.

While you are fiddling under the bonnet I would have a look inside the float bowls. A float that is starting to fill with fuel would give the symptoms you describe as it would raise the fuel in the bowl and cause the engine to run rich. Might also check that the jet tubes are fully up with the choke released.

Just my thoughts.
L E D LaVerne

Thanks guys!

The head is stamped AEF118. The plug says Made in U.S.A - 16 (no idea what the -16 means), and the threaded portion is 3/4" long.

Matt...actually I was going to run it in the dark last night but decided not to...will do so tonight just to see, as well as check if there is a wobble on the shaft.

Regarding the wires, rotor/cap/plugs....any other brand you guys rely on other than what Moss may sell?

If that does not fix it, I guess I'll need to tackle the carbs. Yikes!

Jim

Jim Rice

I'm using some modern plug wires Jim, but they take some fabrication to make them work. There shouldn't be anything wrong with Moss wires if you have the yellow/black stripe copper strand stuff. The only issue would be at the connections on both ends which can become nasty over time. Particularly if moisture gets in there. They can usually be cleaned up fairly easy if you find any corrosion.

I think the last number of the 16 would be the heat range on the plug. A cross reference check doesn't match up with the normal Champion N5's or the NGK's that many people use. I have no idea what difference if any there might be.
L E D LaVerne

Update:

Ran the engine tonight, pitch black, and no stray sparking visible anywhere.

I see the heat range on the Champion and NGK plugs between 5 & 6. The Autolite is an 8. Don't know if that makes any difference or not.

The hunt continues....!
Jim Rice

If it's like Champion...the higher the number, the hotter the plug. NGK on the other hand, the higher the number the colder the plug.
L E D LaVerne

If you have an inductive strobe (one that you clip around the plug lead) try it on each lead at tick over. If one plug is not firing properly you will see an intermittent or irregular flash.

I had a hesitant throttle response and it was due mis-alignment of the carb spindles but I also has a poor tickover.


Jan T
J Targosz

NGK (7432) B6ES or Champion N5C correct 3/4" reach plugs. Change those first. Then suggestions above. Search archives for modern type plug wires if you want to go that way. Make sure rotor is not black or brown. Besides corrosion, the plug/coil wires can pull loose or burn off at the ends inside the cap or coil. George
George Butz III

If the car and engine have done a lot of miles there is a good chance that the distributor is worn out, causing a misfire, and needs rebuilding or replacing. If low mileage then probably one of the other suggestions.
Dave H
Dave Hill

Update:

I ordered a replacement rotor (red), distributor cap, points, and NGK B6ES plugs. I also ordered replacement plug wire in bulk from a company called The Brillman Company. Interesting place I ran across today. The wires have a cloth-braided cover in 15 or so different colored weaves. Copper core and multiple sizes including 7MM diameter. They do sell it by the foot if anyone may be interested. Have no idea how well this product will work, but it will give the engine compartment a rather unique look.

No wobble in the distributor shaft. So, if this electrical "fix: doesn't work, then the problem may very well be in the carbs.

Jim
Jim Rice

Latest update:

It looks like the miss may be fixed! I replaced the plugs and rotor and fired her up....no missing! I still need to do some driving and see if the issue is really fixed or not. The plugs are new, so if there was any fouling issues, that might not show up until later after driving it a while. I also replaced the distributor cap and plug wires. I attached a pic.

Cheers....Jim

Jim Rice

Jim, I quite fond of those spark plug wires. Where did you get them?

Thanks.

Jud
J. K. Chapin

J.K.

I got them from a company called The Brillman Company. They have about 20 different cloth braided colors/weaves in 7MM. www.brillman.com. The do sell it by the foot, so you can buy only as much as you need. I bought extra in case I screwed up some. They are located in Mt. Jackson, VA. The wire is copper braided, so it works well! Figure about $1.92 a foot...less if you buy more.

BTW....I have no affiliation with the company. Just happened to run across them last week when I was looking for bulk sparkplug wire.

Cheers.

Jim
Jim Rice

Jim, Thanks. Jud
J. K. Chapin

For clarification.....I meant copper strands so they can be spread like they should be.

Jim
Jim Rice

I just had to have a set.
I color matched them to the XPAG.
They are a bit to the orange but still good.

Jim B.

JA Benjamin

Jim B.,

How many feet did you purchase.

Thanks,
Jim N.
James Neel

Not being sure I figured 6’ and ordered 12.
I have 6’-6” left.

Jim B
JA Benjamin

Oh Yes;
The Spark Plug wire spacer AS 35-085 was too tight. I had to open up the holes a bit, Letter K drill.
Mine is very old. its red fiber. I dont know what the new ones are.
It was even tight on the 30 year old, black rubber wires.

Jim B.
JA Benjamin

Jim B.

Those looks good! Adds a nice splash of "colour" to the engine bay. I forgot about the wire spacer. Will need to get one next time I order parts. Didn't have one from before.

Cheers!

Jim Rice
Jim Rice

Jim B, In your picture above it shows your outer steering column isforward about 3" too far. The fatter diameter part next to the three screws that contains the felt bushing is supposed to be clamped next to the firewall. George
George Butz III

Thanks George;
It apparently came loose and was rotating free.

I fixed it today.

Jim B.
JA Benjamin

Ordered 10 feet, same price as 8 feet, gives me room to screw it up, will try to keep them shortish and labelled.

Hopefully I will have them next week.

Like the Red with Black/Yellow

Peter
P G Gilvarry

This thread was discussed between 03/04/2019 and 10/05/2019

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