Ecu Capacitors

[Andy TT]

I have an 80,000 mile '93 LS400 and have read a lot on other forums about the ECU capacitors failing through old age, humidity, heat etc. I thought my car ran pretty well but as I am intending to keep it I decided to have the capacitors replaced before they leak and possibly damage the ECU circuit board. I sent the complete ECU to a guy in America who has replaced the capacitors [which were just in fact beginning to leak] with the correct spec Japanese replacements and I refitted it tonight. I have to say the difference is remarkable. The car feels much quicker off the mark, needs notably less throttle to accelerate, the gear changes are smoother and the kickdown is quicker. I must stress this is an unscientific 'seat of the pants' feeling but it really is remarkable the more so because the car didn't seem to have any issues in the first place and it was intended as preventative maintenance. I'll also monitor the fuel consumption over the next few weeks and see if it changes - hopefully improves! Does anyone else have experience of replacing the capacitors?

[steve2006]

Yes but the job is not for the average DIY solderer.

The printed circuit board for the ECU is "multilayer" and therefore has the tracks on both sides of the PCB.

Removing the old capacitors is fairly straightforward but clearing the holes to fit new ones is a delicate job to avoid damaging the solder pads.

I have found a UK source of all but one of the recommended specification replacement capacitors with the other due in early May so I will then order them and make up the kits.

[Rupert Dubreaux]

Hi Andy ,I found the same thing with my Mk2 after replacing the ECU capacitors ,ran almost like a new car not one with a 165,000 miles on the clock. If only there was a cheap fix to restore the bodywork.

I have now done the ones in my Mk3's although response seems better there was not the dramatic effect like the older car had .The Mk2 ECU is a lot easier to remove from the car as well.

As Steve points out this is not a job for those without soldering skill and the correct tools ,unless you want to mess up your ECU .

[cleverdick]

Yes but the job is not for the average DIY solderer.

The printed circuit board for the ECU is "multilayer" and therefore has the tracks on both sides of the PCB.

Removing the old capacitors is fairly straightforward but clearing the holes to fit new ones is a delicate job to avoid damaging the solder pads.

I have found a UK source of all but one of the recommended specification replacement capacitors with the other due in early May so I will then order them and make up the kits.

Steve,

Would you be kind enough to let me know the values (before I remove my ECU to check)? PM me if you wish.

I don't have any running issues but nonetheless I am interested in this.

Just for info, I have found the Rubycon RX30 series to be excellent in every respect, particularly ESR. They also have a 130 degree rating. Given the choice I would use these. Elna and Nichicon are good, too.

There are brands of capacitor to avoid at all costs - I say this through long experience - but obviously I can't mention them publicly.

[ROYT]

Steve, I'm up for this job, let me know when you get them!

[Cotswold Pete]

Steve,

Be up for details when you have source for parts.

Not sure if I am average solderer or not, but repairing Stereo and TV's on and off for last 30 years, so might consider this as a DIY job.

My engine at idle has mild cyclic judder and I get some weird downhill gear changes which make no sense at low speed, so I suspect new capacitors worth a try.

If not up to it myself, I have got a mate (also with LS) who runs his own little electrical engineering company.

[cleverdick]

Hi Guys,

I'm interested in doing this job on my own car ('94 LS), but before embarking on it I really need to know the values. Chances are I have them already, but I don't want to pull the ECU out to find that I haven't [got them] and have to put it all back together again for another day.

To those that have done this and are looking to make up repair kits: Good work, and if I didn't have the component stock that I do I'd probably take you up on your offer(s).

I presume that removal/refitting of the ECU doesn't require any warning lights to be reset? And what about the odometer reading - is that stored in the ECU?

Thanks in advance for any info.

Rich

[Andy TT]

I just re-installed the ECU, turned the ignition on for around 30 seconds [that was the advice of the person who fitted the capacitors] and started the engine. The car ran perfectly from the off. The overall mileage is retained [the trip mileages are lost though] and I had to re-tune the radio as I had disconnected the Battery but apart from that nothing else was necessary.

[Rupert Dubreaux]

Rich hi ,my experience was very similar to Andys , just let the ECU acclimatise for a minute or two after instal before firing it up.

I always disconnect the Battery to be on the safe side when working on the electrical s , the ECU on theMk2 is located behind the passenger kick panel and is fairly easy to remove.

Below is the link to the US Lexus site with all the info about the capacitors you need ,you cannot use any old electrolytic caps they have to be the correct types .

http://www.clublexus.com/forums/ls400/656360-all-my-crazy-lexus-issues-solved-ecu-leaking-capacitor.html

It is well worth doing ,a great low cost improvement .Took my number 3 Mk3 which is the most recent one I have done this on out for a spin last Friday and the improvement in performance was quite noticeable .

Good luck with yours .

[1Tahir]

Thanks Rupert for the link I'm thinking of doing the same!

[Mybikes a cx500]

Yes but the job is not for the average DIY solderer.

The printed circuit board for the ECU is "multilayer" and therefore has the tracks on both sides of the PCB.

Removing the old capacitors is fairly straightforward but clearing the holes to fit new ones is a delicate job to avoid damaging the solder pads.

I have found a UK source of all but one of the recommended specification replacement capacitors with the other due in early May so I will then order them and make up the kits.

Kits? Just caught up with this post and I'm keen to change my Caps. If your making up kits, I'm a customer.....

[Ruud]

Depending on price.....count me in as well :)

maybe stupid question, but will these kits be suitable for the entire Ls400 range?

[Malc]

Likewise please.

Malc

[steve2006]

OK here's the update, I ordered 20 of each value so this will obviously make up 20 kits for the whole year series.

The downside is once again one of them is on back order until 28/05/2014 ( must be heavy demand from LS400 owners!)

Once they arrive I will get them sorted.

[cleverdick]

Well, despite not having all of the correct values immediately to hand I could not resist the temptation of at least carrying out a visual inspection.

Struggled a bit with the kick panel, and the glovebox liner wasn't exactly a breeze either, not helped by that airbag connector on the right-hand-side flap.

I am relieved to say that the electrolytics on the ECU board were absolutely pristine. I checked them for ESR too and all were under 1 Ohm. Of course, I was not able to check them for DC leakage on the board.

A burst capacitor is normally caused by (1) reverse polarty, (2) excess ripple current, or (3) overvoltage. (A failed regulator on the alternator would do this...) General ageing usually results in (1) high impedance, (2) a reduction in capacitance, or both. Once again it's not necessarily possible to measure capacitance in-circuit.

So I think I can put this job off for a little while. Steve - I'd be interested in a kit of replacements but would like to know the specifics (make, range etc.).

Took the opportunity to remove and clean the cabin filters, now that was worth doing!

[Mybikes a cx500]

Are all these capacitors dc smoothing then?

Seeing as they are 16 odd years old, I'm inclined to change mine regardless of their current visual condition.

The US thread mentions checking for ripple at the temperature sensor, as this is fed from the 5v rail via a resistor, I am always looking for a reason to justify my new oscilloscope, but waiting for the rain to stop...

[Mybikes a cx500]

Was out playing with the scope between showers yesterday, my reading were 15mV ripple, across a 2.2K "pretend" temp. sensor, which equates to 34mV total ripple across the 5v ECU rail,

( Measured 2.2V DC across the 2.2K resistor so the internal resistor must be about 2.8K)

which is roughly about 22mV RMS which at the end of the day, is half the 40mV suggested top limit. However new caps apparently result in about 5mV. ripple.

So going to change mine if kits become available.

[ambermarine]

I suppose that equates to two and a half turns on the mixture screw and a couple of nudges on the distributor collar fifty years ago .Ho how times have changed.

[cruisermark]

could somebody translate that into plain English please LOL

[Mybikes a cx500]

could somebody translate that into plain English please LOL

OK, New capacitors get you a 5, My car is a 20, ( 40 is borderline needs sorted)

And don't forget to wipe the distributor rotor on the tire to clean it

[steve2006]

Ok guys at last the capacitors have arrived from the USA so I am now making up the kits.

Cost for all the required parts plus P+P is £5.00.

Please PM me for further details and the model year kit required.

Fitting is your own responsibilty not mine :)

Apologies for those members asking for the capacitor details,they are detailed on the link below.

http://www.clublexus.com/forums/ls400/656360-all-my-crazy-lexus-issues-solved-ecu-leaking-capacitor.html

[Malc]

pmd you Steve, thanks

Malc

[SHELLDRAKE]

How do I P.M. u Steve I tried on the profile but nothing has happened

[Bluesman]

How do I P.M. u Steve I tried on the profile but nothing has happened

First make sure you are signed in and then click on Steves profile and you will see three oblong boxes on the right hand side one says "Send me a message"

Hope this helps. Mike

[Malc]

I think Steve's away, he's not responded yet

Malc