V6 HT Leads replacement

Clivejag · Post by **Clivejag** » Fri Feb 27, 2015 11:59 pm

Hi I've a 1998 v6 that has suddenly developed a lumpy idle/misfire so I thought I should replace the plugs, leads, distributor cap and rotor arm. A quick inspection of the job has shown me that the passenger side ht leads run over the top of the engine, under a plenum chamber(?) Can I route these leads round the front of the engine or do they snag on rotating stuff or just not reach? I assume it's not viable to use the existing routing without removing the plenum thing? Any tips would be appreciated.

Clivejag · Post by **Clivejag** » Sat Feb 28, 2015 12:01 am

Apologies, that should read drivers side ht leads run under the plenum thing.

Post by **Simon Jones** » Sat Feb 28, 2015 12:24 am

They should go like this and are quite easy to route them as required. You don't need to unbolt anything just make a note of how they go (a photo is the easiest option) and fit the new ones in the same way. Genuine Mazda leads are worth paying the extra for as some of the cheaper versions have been known to cause poor running.

Drivers side:

Passengers side:

mikeWalsall · Post by **mikeWalsall** » Sat Feb 28, 2015 2:00 am

As Simon says .. the Ht leads will 'feed' through without dismantlingany engine components ..

Mazda HT leads are good and mine lasted 15 years before I routinely changed them for a set of English pattern parts (which are guaranteed for life) ..

You can get a complete kit .. including a set of pattern part leads (my V6 is a 1998 and uses 7) .. complete with dizzy cap / rotor / 6 new spark plugs ..

http://www.mazdabongo.com/catalog/electrical

I got my 7 leads from ...

https://www.ignitioncarparts.co.uk/Part ... on%20Leads

Fitted spot on and no problems since ..

Although the dizzy cap ...

... and rotor ..

... can be a bit of a fiddle to access / change ..

Clivejag · Post by **Clivejag** » Sat Feb 28, 2015 10:48 am

Excellent photos, thanks very much. I don't suppose the numbers on the cap correspond to the cylinder numbers? I was going to rely on the workshop manual exploded view in case I muck up refitting the leads. Is that safe to do?

Post by **Simon Jones** » Sat Feb 28, 2015 11:17 am

The numbers on the cap correspond with the cylinders but it worth having a label somewhere to show which cylinders are which. The firing order is 1-6-2-4-3-5 and the cylinders are (front to back):

Passenger side: 2-4-6
Drivers side: 1-3-5

Clivejag · Post by **Clivejag** » Sat Feb 28, 2015 12:56 pm

Fantastic thanks to you both for the info, job done and no more misfiring so your help is much appreciated.

rita · Post by **rita** » Sat Feb 28, 2015 1:47 pm

OK Clive Spill, what did you do (have done) to cure the miss.

Post by **Simon Jones** » Sat Feb 28, 2015 2:33 pm

Clivejag wrote:...so I thought I should replace the plugs, leads, distributor cap and rotor arm

Presumably all of the above.

Clivejag · Post by **Clivejag** » Sat Feb 28, 2015 2:39 pm

Just replaced plugs, leads, distributor cap and rotor arm. So I don't know which was the exact culprit but visually I'd guess it was the leads cos the rest looked fine.

Post by **Simon Jones** » Sat Feb 28, 2015 2:48 pm

Definitely worth replacing the whole lot as all the insulation will break down with age which can result in tracking of the HT voltage. Apart from changing the plugs in a few years, you should be good for the next 15 years

.

mikeWalsall · Post by **mikeWalsall** » Sat Feb 28, 2015 3:22 pm

Mine started to have lumpy tick over when cold(ish) and first switching over to LPG while in traffic .. when really warm the engine ran fine ..

So I did a complete swapsy job .. dizzy cap .. rotor .. leads and NGK 'normal' plugs (closed to 1.0mm) and it made a vast improvement ..

With mine I now tend to think .. new plugs .. and a dremell with a small .. very fine brass brush polishing the old rotor and dizzy cap contacts may have sufficed ..

As the V6 spark plugs are such a simple / quick job to do .. and 6 'normal' NGK BKR5E-II are relatively cheap .. (around £10 for six delivered (http://www.ebay.co.uk/itm/290783772008? ... EBIDX%3AIT) .. it is worth while changing them each year ..

'Old' Plug ..

With alloy heads ... it's always best use some anti seize 'grease'..

My V6 Alphard may be in this week for an LPG / cambelt kit / water pump change .. as the MZ-FE Lexus engines plugs are notoriously difficult to change I may get the autogas guy to fit some NGK / Silverline LPG plugs at the same time he is doing the conversion ..

Job & price wise ... they will only be getting changed every four years ..!!

Clivejag · Post by **Clivejag** » Sat Feb 28, 2015 9:48 pm

Yes for the time and cost of doing the plugs it's a no brainer. Next job us an oil change. Hopefully that will prove as straight forward!!

mikeWalsall · Post by **mikeWalsall** » Sat Feb 28, 2015 10:17 pm

If yours as an auto transmission sump drain plug (my V6 as one .. some Bongos do not) it's worth while draining / refilling that ..(I took the sump off mine de greased it then put it in the dishwasher along with the fluid filter) ..

The sump showing drain plug ..

You will only get around half the total contents out .. but still worth while .. as you can do it again a bit later to freshen up the remainder of the fluid ..

I use fully synthetic engine oil .. and semi synthetic Dexron3

Clivejag · Post by **Clivejag** » Sun Mar 01, 2015 12:05 am

Thanks for the prompting on doing the auto. I hadn't thought about doing it. Blanked it out of my mind cos it's a bit scarey.

V6 HT Leads replacement

V6 HT Leads replacement

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Re: V6 HT Leads replacement

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