When to change Spark Plugs?

[AndyCheltenham1]

I have a 1993 LS400 that has done 101000  miles. The spark plugs were changed about 12 years ago at around 60/65000 miles by the previous owner . I've had the car for 10 years and the engine is still running fine. I've put off replacing the spark plugs as the car is  running  perfectly ok.  Is the replacement down to miles or length of time-if they need changing every 60000 miles does that mean I should not replace them until 120000 miles ( even though they will have been in the car for many years by then) ???

The main ones on eBay seem to be NGK or Denso iridium Power(£57 for 8)-is there much difference between the two makes?

Any idea of how long a job it is to change all 8 plugs?

Thanks for any advice.

 

[ColinBarber]

Every 60k miles or every 6 years, whichever is sooner, I believe is the official line. There is probably no reason to replace them due to age, as it is the mileage that causes the wear however I would remove them every 6 years, or at least loosen and retighten them, to avoid them seizing.

Don't run them past the recommended mileage, they can wear and part of the electrode can come away and damage the cylinder wall.

Not much between Denso and NGK. I alway use Denso, keeps it in the family as Toyota own part of Denso.

Don't know how many covers need to be removed to get to the plugs on your age of LS, I'd guess 1 to 1.5 hours in total - hopefully others can give a more accurate time.

[dendonc]

Personally, I would not buy anything like that from >anyone< on eBay, I might if it were a known main dealer

Why not find out the price from a denso approved main dealer, the price you've quoted seems VERY cheap.

Denso distributer lists

https://www.denso-am.co.uk/where-to-buy/

[steve2006]

I also bought a new set of NGK iridium plugs but struggled to get the plug leads off even though the leads and plugs were replaced around six years ago and I put the dielectric grease on the plug caps.

With them being deep in the cylinder head I was worried about breaking the leads or damaging them with excess tugging so job abandoned for now.

Tutorial below covers plugs and leads but just skip the lead bits.

http://www.lexls.com/tutorials/ignition/sparkplugs.html

[dendonc]

Seems many of the mechanicly minded & knowldgable members on here have had problems changing plugs, I'd be interested to know what a local Lexus dealer would charge

[runsgrateasanut]

I changed my plugs after about 120k. Of course they could have been changed by a previous owner? I put in Brisk plugs as they run hotter allegedly for LPG (please don't go there as the debate on this subject is elsewhere) but more importantly IMO is to change the leads. So I did,  but the result was that I found I was running on Seven cylinders when I started the Car 

The Black plastic Casing in putting it back (oil filler cap side) had spliced through one of the leads.  They are that fragile, and of course they must be properly aligned. Bit of a pig which is why you see some Cars without the black casing in situ.  Not something I could live with.

 Can't say I saw any degradation on the plugs removed and I've never heard of part of the plugs coming away after a long period of use.  The Car would have had to be runnign very badly for a long time to damage the electrode as you might see on an old Tractor or some other ancient engine. 

 

[is200 Newbie]

Not an LS but a 250 with the same sort of issue.

Car is 12 years old - has 27k on the clock. Has a full Lexus service history so I would presume that after 6 years they would have changed the plugs? Question now is that should they really be replaced now as its a further 6 years on ... Not the correct forum to ask but would a squirt of WD40 be adequate at this point to ensure they have the best chance of being removed in the future if sprayed down the plug recesses?

Its going to be approx. 7 or 8 years + until I will get the car to 60k where due to the mileage, the plugs will require changing again.

I guess it is worth asking Lexus if the plugs had been replaced at the first 6 year point...

[Hadrian]

If the plugs had been changed, wouldn't it show up in the service history ?

Assuming you have an itemized invoice when it's serviced.

[ls400lpg]

I have changed all 7 spark plugs. They were on really tight.

However the last spark plug net to the master cylinder will not come out, no matter how much brute force I am putting. Please please any ideas???

I used extension socket. I have heard of P B Blaster overnight for 3 days would do it?

[ambermarine]

Hi

Use a air or Battery powered  impact wrench with extension.

[dendonc]

Quote -I have heard of P B Blaster overnight for 3 days would do it?

I checked on google & there are quite a few 'severe' warnings about it, the link below is to a P1 Google search result.

https://www.google.co.uk/search?client=opera&amp;q=p+b+blaster+warnings&amp;sourceid=opera&amp;ie=UTF-8&amp;oe=UTF-8

.

[Tinonline]

I'd change them for that "peace of mind" state and you can then forget about them for a long time.

They are awkward considering in the good old days whipping plugs out was a few minute job; although you had to gap them...

I used a myriad of tools and extension bars - all tiny as possible to get the leverage. I did not use any grease on the threads going back in as per factory.

I've attached my guide...I used Denso. 

 

Changing LS 400 Spark Plugs.compressed (2).pdf

[AndyCheltenham1]

Thanks for all your comments and very interesting guides for how to fit them from Simon(timonline) and Steve2006. It seems that the job can be relatively easy or could cause problems  with the potential to cause some damage. I think the Denso plugs I seen on eBay may not be original parts due to the low price so will give them a miss. When I have it serviced in a few weeks I will see what the mechanic thinks but at the moment I'm probably 50/50 whether to change them now or hold on a bit longer and avoid any potential problems.

[Cotswold Pete]

Andy,

I asked my mechanic the other week and his reply was, 'If it is not misfiring no need to change the plugs'. 

Not so sure that this is the best advice I have had, and he said that the plugs were expensive - I think what he meant was compared to your average £3 plugs, the LS is not so cheap

Also given the throttle body gets gunked up, that is indicator of how dirty fuel is, and so the plugs after 50/60K miles are not going to be in tip top condition.

I remember when I used to take the plugs out for a good clean every 10K miles in the olden days, and was amazed at how a good clean pepped up the old banger I had  then.

Be interested to here what your mechanic says.

[Verbout]

Does your “mechanics” advice stretch to “Don’t put fuel in until it stops”?   😂

[Cotswold Pete]

5 minutes ago, Verbout said:

Does your “mechanics” advice stretch to “Don’t put fuel in until it stops”?   😂

Not so sure they are that bad, but I often think mechanics think customers are just drivers of cars, so they should not be asking questions about plugs, or any of that other complicated stuff under the bonnet.

Thats the great  thing about this forum, plenty of people who know there stuff, but I have known many a mechanic poo-poo forums (on what basis I am not sure)

C'est la vie🙁

[Verbout]

I have to admit my local Indy is not averse to going on forums for information. 

When tracking my 159’s wheels I pointed him in the direction of the Alfa forum. A good old lad had posted information that didn’t agree with the official Alfa output, but was a better setup.

[rayaans]

Change them based on mileage. The usual Lexus service books actually say 60k miles but dont have a time frame for when they need changing. 

Green Spark Plug Co is good for spark plugs, and genuine. I usually buy all of mine from them - need about 8 every year for servicing the lawnmowers, chainsaws, trimmers etc etc and never had an issue.

[Verbout]

Lawnmowers? 

[Verbout]

Lawnmowers? 

[MLW]

On ‎5‎/‎16‎/‎2018 at 10:17 AM, Cotswold Pete said:

Andy,

I asked my mechanic the other week and his reply was, 'If it is not misfiring no need to change the plugs'. 

Not so sure that this is the best advice I have had, and he said that the plugs were expensive - I think what he meant was compared to your average £3 plugs, the LS is not so cheap

Also given the throttle body gets gunked up, that is indicator of how dirty fuel is, and so the plugs after 50/60K miles are not going to be in tip top condition.

I remember when I used to take the plugs out for a good clean every 10K miles in the olden days, and was amazed at how a good clean pepped up the old banger I had  then.

Be interested to here what your mechanic says.

60k is an awfully lot of miles. Old plugs in the 'old' days were 12k at best. If it ain't broke' theory has some merit, but when my brother changed his Ford Focus plugs at my house (I had the correct socket) and they were really bad, Huge gap etc. I told him he needs to break-down more often. He needs his car and does not have sympathetic ear for it. My old neighbour had a car that rarely started. As I pushed it down the hill again, I would ask how old are the plugs? No idea!

Look, 60k ever 6 years for about £70-80 is not bad given you have the best plugs in the world. Think of what a 2% gain in petrol means in money.

The key to running an old car is to over-service it.