HT lead - Sparking

What about ht leads maybe a break down in 2

Sounds like electrical interference. Check under the bonnet with the engine running in the dark. Get someone to give the motor a bit of a rev while looking under the bonnet, see if you can see any sparking or tracking from any of the spark plug leads. You probably wont see them sparking in the daylight.

The following are the general instructions on the start of diagnosing any electronically controlled engine or transmission problem.

The engine and the automatic transmission (transmission control is only for automatics, engine is still computer controlled no matter the transmission type) in this vehicle are computer controlled and in most cases when a fault occurs a fault code is stored in the memory of the computer control module. There are exception to this, such as the Mass Airflow Meter and fuel pressure problems. What must be done is to have all the basic testing done such as a scan of the system for fault codes as well as a check with a live data scanner tool for engine functions that are not within range of normal, a trained technician is required to know what is correct and what isn't, then based on careful diagnostics done from a factory repair manual the correct part is replaced or the wiring repaired or the computer replaced (known as the PCM or ECM,ECU), which is very rarely the problem. Other basic checks must be done as well such as mechanical problems with the engine as well as engine state of tune and mileage on the engine. The transmission can have mechanical issues as well such as no gear engagement at all or a failed pump or other pressure related problems. Also engine mechanical problems can and do cause many drive-ability related problem such as rough idle and other symptoms.

yes bad leads will be one of the faults
run the motor in the dark raise the bonnet look for sparkle trails
on the leads

coil pack could be faulty

compression test will tell if it is a leaky valve

back fire can be running lean or timing

Hi Dave
If you have changed the spark plugs and you still have a misfire then I agree, the next logical step is to replace the leads. Before you go to the expense of buying a full set, you should be able to identify which individual lead / leads are causing you the problem. Firstly remove all covers so that you can see the leads clearly, now wait until after dark or if you have a dark garage. (the darker the better) Lift the bonnet and start the car. This is better if you have someone in the car who can rev it up whilst you look under the bonnet. If you have a faulty lead, then as the engine is reved up you will see a blue spark jumping from your lead to the engine block, this could range from a very bright to a vary faint spark, that is why it is better to do this in the darkest place possible. This spark means that the lead insulation has broken down and the current is going to earth and not your spark plug. You need to inspect your leads very thoroughly along their entire length, taking care not to touch them or you will receive a nasty electric shock. If you find that your leads are in good condition, you could have a crack in your distributor cap. This would give the same syptoms.

look under the bonnet at night with the engine running see if the coil is sparking around the top or are the ignition leads sparking all over the place DO NOT TOUCH ANYTHING HT VOLTAGE CAN KILL if there are sparks around the coil top change it and the plugs and leads if the problem persists check the distributor please take the time to rate this if it helps

check your ht leads try turning the engine over in the dark looking under the bonnet to see any sparking on ht leads get someone to turn over the engine while you look if you see sparking chang the leads they have cracked

Hi if your car is petrol then you need to check that the plugs work try swapping them round with 1 and 2 if they work you then need to check the leads you can do this by taking the plugs out of 3 and for and then connect them to the spark plug leads then rest them so they are earthing out in the engine bay( you need to make sure its just the end of the spark plug resting onto metal then turn the engine over and you should see if the plugs are sparking it should be bright and regular spark. (its better to do this in the dark ) before you remove the plugs wait till its dark then with the bonnet up get someone to turn the car over and nif their are any sparks coming from the leads on 3 and 4 if their is then the leads need replacing.

IF no spark at plug and no short on the leads then you need to check the distributer this is where all the plug leads go into check this for any crack when you remove it.

Once removed look inside at the four contacts make sure they are clean and free from contaminents such as oil as their is a seal just behind this might have gone you can use sand paper to clean the terminals to ensure the electric can be sent from the rotary arm to the distributer so check its clean als use fine sand paper on the end of the rotary arm then refit and check for sparks again if its now sparking then give the car a try.

If you are getting a spark at all four of the plugs and the spark is good all round then the only problem you could have would be with the head gasket.
Are you sure the leads are fitted correct way round before you start any work.

If you have checked all leads and you have good spark then it can only be the head gasket this can be tested by using a sniff test or a compression tester these can both be brought from car spares shops but prices can vary.

Let me know how you get on or if you need further assistance ok

Hi ....... Sounds alot like you have a grounding problem on your HT leads (central one from coil esp'ly). At night when it's dark open the bonnet/hood and start the engine. Look for any sparking or arching from plug leads, coil or ignition box. Stop engine. Find where your leads come from, four will come from a central point and make sure all conections are tight. Even remove and look for corrosion, only take off one at a time to avoid confusion and when you're happy that they're OK buy some WD40 and spray near coil and over leads and allow to dry off. This will help to prevent moisture to penetrate and will cure the problem short term.
Let us know the outcome.

check spark plugs, if one or more damaged this will explain rough running, and the smell of unburnt fuel, while you have plugs out give them a good clean. if they are wet with fuel then they are not sparking, wipe with soft cloth. to check if plug is sparking, take one out, leave it in the HT lead, get someone to hold it against the top of engine block and turn over engine. WARNING: HT LEADS CARRY A BIG CHARGE DO NOT HOLD LEAD WITH BARE HAND, USE SOMETHING NON CONDUCTIVE TO HOLD IT DOWN WITH ie, A BIT OF WOOD. if it sparks, its fine, put it back in, and remove another, and repeat the procedure and so on.