Topic
How to change Distributor/Rotor arm and HT leads. 9 years 11 months ago #144281
This is an easy DIY job and using this guide, changing the distributor cap / rotor arm and HT leads is a job you needn't fear or shy away from doing yourself. 
The problem?
On a pre 2001 Mpi engine an intermittent misfire or 'stutter' when trying to accelerate with engine below about 2000 rpm, which gets progressively worse over time could be down to a worn distributor cap/rotor arm or HT leads that are breaking down (an ignition coil on it's way out gives similar symptoms too). As these parts do not form a part of the regular service schedule they are often overlooked. They should last around 40 - 50,000 miles but can develop a fault a lot sooner.
Fortunately these parts are not expensive and are quite simple DIY jobs for even the least experienced mechanics amongst us.
Tools needed:
Cross head screw driver, 8mm socket, 10mm ratchet spanner.
The Fix
Purchase your replacement parts
All these together came to £33 from my local motor factor.
Firstly you need to gain access to the engine, for this you will need to remove the main engine inspection cover found under the rear parcel shelf. click here to see the instructions on how to remove the engine cover. Note: if you use a ratchet spanner you can remove the engine cover without having to remove the T-Bar
A quick tip is using an elasticated bungee cord to keep the roof out of the way whilst you work on the engine.
With the inspection cover removed you can see the location of the distributor cap on the passenger side of the engine block....
... and the cover (held on by two screws) on the engine under which you will find the HT leads and spark plugs.
To remove the distributor cap you need to pull off the HT leads (a little twisting action also helps) and then undo the two retaining screws
You will then be able to see the rotor arm
Behind the rotor arm is a black plastic cover, this is the flash guard.
The rotor arm is held in place by a bolt. In order to get to the bolt you need to gently move the flash guard forward (it can not be removed with the rotor arm in place so do not try) taking care not to damage it.
Using an 8mm socket you can now remove the bolt, releasing the rotor arm and flash guard.
As you can see in this photo the rotor arm attaches to the distributor spindle. This is D shaped and so you cannot put the new rotor arm on in the wrong position.
Fitting the new rotor arm is the reversal of the above instructions. Do not forget to reinstall the flash guard at the same time.
With the bolt tightened you can now fit your new distributor cap.
The cap is asymmetrical and so will only fit on in one position.
It is now time to fit your new HT leads.
There are five leads
One goes from the center of the cap to the ignition coil (this is located under the inlet manifold, under the fuel injectors)
The other four have a large plug to fit on to the spark plugs.
These four are all different length leads. The longest goes to cylinder No. 1 and the shortest to cylinder No. 4 which is located nearest the distributor cap.
The photos above show the position for each lead. These must be put in the correct position, if not the engine either will not run or will badly misfire.
It is very important that you push these leads firmly on to the distributor cap. If you only gently push them on the outer rubber grips but the center connector does not make a good connection.
Phew, it takes longer to read this than it does to do the job.
All that remains is to go for a drive and enjoy the fruits of your labour, which should result in the car no longer misfiring
The problem?
On a pre 2001 Mpi engine an intermittent misfire or 'stutter' when trying to accelerate with engine below about 2000 rpm, which gets progressively worse over time could be down to a worn distributor cap/rotor arm or HT leads that are breaking down (an ignition coil on it's way out gives similar symptoms too). As these parts do not form a part of the regular service schedule they are often overlooked. They should last around 40 - 50,000 miles but can develop a fault a lot sooner.
Fortunately these parts are not expensive and are quite simple DIY jobs for even the least experienced mechanics amongst us.
Tools needed:
Cross head screw driver, 8mm socket, 10mm ratchet spanner.
The Fix
Purchase your replacement parts
All these together came to £33 from my local motor factor.
Firstly you need to gain access to the engine, for this you will need to remove the main engine inspection cover found under the rear parcel shelf. click here to see the instructions on how to remove the engine cover. Note: if you use a ratchet spanner you can remove the engine cover without having to remove the T-Bar
A quick tip is using an elasticated bungee cord to keep the roof out of the way whilst you work on the engine.
With the inspection cover removed you can see the location of the distributor cap on the passenger side of the engine block....
... and the cover (held on by two screws) on the engine under which you will find the HT leads and spark plugs.
To remove the distributor cap you need to pull off the HT leads (a little twisting action also helps) and then undo the two retaining screws
You will then be able to see the rotor arm
Behind the rotor arm is a black plastic cover, this is the flash guard.
The rotor arm is held in place by a bolt. In order to get to the bolt you need to gently move the flash guard forward (it can not be removed with the rotor arm in place so do not try) taking care not to damage it.
Using an 8mm socket you can now remove the bolt, releasing the rotor arm and flash guard.
As you can see in this photo the rotor arm attaches to the distributor spindle. This is D shaped and so you cannot put the new rotor arm on in the wrong position.
Fitting the new rotor arm is the reversal of the above instructions. Do not forget to reinstall the flash guard at the same time.
With the bolt tightened you can now fit your new distributor cap.
The cap is asymmetrical and so will only fit on in one position.
It is now time to fit your new HT leads.
There are five leads
One goes from the center of the cap to the ignition coil (this is located under the inlet manifold, under the fuel injectors)
The other four have a large plug to fit on to the spark plugs.
These four are all different length leads. The longest goes to cylinder No. 1 and the shortest to cylinder No. 4 which is located nearest the distributor cap.
The photos above show the position for each lead. These must be put in the correct position, if not the engine either will not run or will badly misfire.
It is very important that you push these leads firmly on to the distributor cap. If you only gently push them on the outer rubber grips but the center connector does not make a good connection.
Phew, it takes longer to read this than it does to do the job.
All that remains is to go for a drive and enjoy the fruits of your labour, which should result in the car no longer misfiring
How to change Distributor/Rotor arm and HT leads. 9 years 11 months ago #144839
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- John and Sue
- Offline
- Master MGer
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- 06 TF 135. One of the last from Longbridge.
- Posts: 4732
- Thanks: 1138
A great how to.
To hold the hood up at the back I open the drivers door and fasten a cable tie around it just at the back of the door.
Avoids the risk of those pesky 'bungee hook springing off and tearing an eyeball from your skull' moments....
To hold the hood up at the back I open the drivers door and fasten a cable tie around it just at the back of the door.
Avoids the risk of those pesky 'bungee hook springing off and tearing an eyeball from your skull' moments....
It will be all right in the end. If it isn't all right yet, then it is not yet the end..
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