Pinking

[cleverdick]

My 1990 LS400 has a tendency to 'pink' on acceleration - this only seems to be a problem during a hot spell. At first I put it down to bad fuel, but over two tankfulls from different petrol stations the problem remains. By the way, I have only ever used premium unleaded. My local Lexus mechanic claims that these cars aren't noted for this. However, whilst waiting to cross the road today (again, a very hot day), an LS400 of the same year as mine drove by - pinking raucously!

So, should I be worried?

[Davey Boy]

My 1990 LS400 has a tendency to 'pink' on acceleration - this only seems to be a problem during a hot spell.  At first I put it down to bad fuel, but over two tankfulls from different petrol stations the problem remains.  By the way, I have only ever used premium unleaded.  My local Lexus mechanic claims that these cars aren't noted for this.  However, whilst waiting to cross the road today (again, a very hot day), an LS400 of the same year as mine drove by - pinking raucously!

So, should I be worried?

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Hmm, Pinking?

Right, from experience in the trade, its most likely the ignition coils. the tend to break down and cause poor accel.

it happens in hot weather as the componets expands and loose contact.

[ColinBarber]

I've heard that carbon build up in the heads can cause this and it's not uncommon on very old LS400s.

[MacRS200]

I've heard that carbon build up in the heads can cause this and it's not uncommon on very old LS400s.

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I've heard that too, it is supposedly caused by the carbon heating up to a point where it detonates the mixture before the plug sparks causing pre-detonation and that distinctive rattle.

Possible cause could be the engine running on a weak mixture which causes overheating, link that with the hot weather and a conclusion of a possibly dirty or defective air temperature sensor messing up the mixture?

Only a thought.

[Mr Morse]

Slightly but I also get this pinking on the missus Starlet and it got worse when I changed the plugs.

What's the best way of de-carbing the engine?

[MacRS200]

Slightly    but I also get this pinking on the missus Starlet and it got worse when I changed the plugs.

What's the best way of de-carbing the engine?

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Pinking can also be caused by the ignition timing being too far advanced. Don't know the Starlet engine is it electronic ignition?

The only real way of de-carbing an engine is to take the head off and physically clean it

[Mr Morse]

It's electronic ignition - I'll also check the coils. It's probably par for course since the car has done 115K

[andy haw]

My 1990 LS400 has a tendency to 'pink' on acceleration - this only seems to be a problem during a hot spell.  At first I put it down to bad fuel, but over two tankfulls from different petrol stations the problem remains.  By the way, I have only ever used premium unleaded.  My local Lexus mechanic claims that these cars aren't noted for this.  However, whilst waiting to cross the road today (again, a very hot day), an LS400 of the same year as mine drove by - pinking raucously!

So, should I be worried?

←

Richard, It might be worth a try adding some Forte fuel treatment to your tank and see if that helps.

I have used some when car was lumpy and it cured that.

You will need two bottles for a full tankful.

It is only available to the trade but you can purchase on eBay.

[cleverdick]

Hi guys,

Thanks for your replies so far - I appreciate it.

I might give the Forte Gas Treatment a try - probably the easiest option! But is this stuff any better than good ol' Redex? I did consider removing the plugs and pouring Redex into the holes in true 'old-school' style, but was concerned about trashing the O2 sensors or cats etc. But all the Forte additives look like they might be beneficial to my car! Anyhow, thanks again for all your comments - keep 'em coming!

Regards,

R.

[ColinBarber]

fault could also be faulty knock sensors. Also what plugs are you using, the recommended ones?

[Monster-Mat]

as said before, cokeing up is a very common problem.

AndyHart had this very problem with his LS,

[cleverdick]

fault could also be faulty knock sensors. Also what plugs are you using, the recommended ones?

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Plugs are new, Denso iridium, which I fitted personally about 3 or 4 months ago.

Where are the knock sensors, and what do they look like?

In the meantime I've ordered some Forte Gas Treatment, so will let you know if this makes a difference.

R