Erratic idle

[shanra]

I have recently when cold had a higher than normal idle and taking a while to get down to normal 650 rpm. But today having warmed up the car first to clear frost after a couple of miles driving the revs dropped low and when stopping at a junction dropped to 200rpm and then stalled it happened again at some traffic lights. I then parked up and did some shopping and when starting up again it was revving about 1200rpm but didn't drop back down for a few miles (the engine was at normal operating temp) also having what feels like an extra gear change between 40 and 50 mph although this has been happening for quite a while when cold. When I got home the revs settled back to about normal having travelled 4 miles from the shops. Brake pad warning light coming on recently when I brake although pads looked good a month ago having only done about 15,000 miles on them. When car dropped to very low revs brakes felt strange a couple of times almost like traction control kicking in only the car doesn't have it being an early '97. Temperature sensor came to mind and possible vacuum problem also. Any input would be gratefully received.

[Razor61]

This may be helpful😉

 

[shanra]

Thanks Paul.

[Cotswold Pete]

As per Razor61 port, pretty certain this is ECU problem.  I had it on my Mk3, once it started happening the deterioration was quite rapid.  I never got around to sorting out ECU as gave car to a mate for parts to use on his.

There are a couple of places that will install new capacitors if you can get the ECU out, but this was very common problem with cerain capacitors of that era (not just in ECUs).

I thought I had some notes on where in UK you could get this done, but seem to have lost my notes on computer 

But this link may be useful How to check ECU

[shanra]

Thanks Pete. I have ordered a coolant temperature sensor and I will take it from there. Has anyone got a set of the caps for the ECU? I was going to have the ECU done the year before last as I was near Devon (think this was one place to get it done) but I never got around to ordering the parts! Any other suggestions on where to get the ECU done will be gratefully received.

[shanra]

Is it still these 6 Capacitors to replace?

Qty. 2 of 10uF - 50v
Qty. 1 of 47uF - 63v
Qty. 2 of 100uF - 10v
Qty. 1 of 220uF - 16v

[Razor61]

4 hours ago, shanra said:

Is it still these 6 Capacitors to replace?

Qty. 2 of 10uF - 50v
Qty. 1 of 47uF - 63v
Qty. 2 of 100uF - 10v
Qty. 1 of 220uF - 16v

According to the post below that is correct but they need to be the correct make and type, there are a few different ECU's which are interchangeable for the MK3 10.1994 - 07.1997 and just one ECU for the MkIV  07.1997 - 08.2000. This is according to website:   Lexus parts catalog (epc-data.com) I presume your car is a MK3? If it is a MK3 then, being a 97 car, the ECU is probably part number 89661-50351 which is the latest version of ECU for Europe (also see the post below about ECU Combability)

I purchased the capacitors from DigiKey in the USA but there is a UK website as well:   DigiKey Electronics United Kingdom | Free Delivery On Orders Over £33

I have an earlier ECU revision for sale on here in the 'Buy and Sell' section along with 5 x sets of capacitors, ECU isn't any use to you but the caps are the same. PM me if interested.

Just one other point, if your ECU is a 89661-50351 then maybe find a second hand unit in decent condition, have the caps replaced then swop it out.

Info for capacitors with correct make and type.

All my crazy Lexus issues SOLVED!! (ECU-leaking capacitor) - ClubLexus - Lexus Forum Discussion

ECU compatibility, this was applicable to the 1995 Mk3 I had.

 

[steve2006]

IIRC there was a recall for this problem and an upgraded ECU was supplied and fitted.

Other items to consider are the IACV and Throttle Body cleaning.

[shanra]

Thanks Steve I did the throttle body cleaning about 10,000 miles ago. I am purchasing the caps and they will be with me soon and now I need some recommendations for where to get them done. Was there a recall in this country?

[Malc]

I understand the recall was avoided by Lexus in the UK sadly 

Mine still rarely plays up 

Malc

[shanra]

I have also in the last couple of years replaced leads, dizzy caps, rotors, plugs and oxygen sensors.

[plexus914]

ECU / 89661-50350 (08.1996 - 11.1996 / 97 model year) has 9 caps.:

2 x 10μF - 50v

2 x 47μF - 63v

2 x 100μF - 10v

1 x 220μF - 16v

2 x 15μF - 35v

[shanra]

Thanks Plexus but I think my ECU is a 89661-50351 but not certain as I have not yet removed it, but when I do I had better count them I guess!

 

[shanra]

Plexus914 have you had your ECU repaired?

[Howplum]

Out of curiosity I rang Lexus Parts Direct to establish the build date of my 1996 model, which apparently was built in April 1995. It was helpful because these are the options on Amayama's website, and it saves dismantling to investigate. For example, my ECU, which was only used for 8 months, is 50251, substituted by 50252, but not 50351. Hopefully this helps.

 

No	PNC# (SUB)	OEM part number	Required per car	Production period	Name	Applicability	Please order in advance
01	89661	89661-50250	01	10.1994 - 01.1995	COMPUTER, ENGINE CONTROL	UCF20..EUR	2,163.08 USD
	(SUBS)	89661-50251	01				2,163.08 USD
02	89661	89661-50270	01	10.1994 - 02.1995	COMPUTER, ENGINE CONTROL	UCF20..RHD..EUR SOUTH AFRICA SPEC	2,174.96 USD
	(SUBS)	89661-50271	01				2,163.08 USD
03	89661	89661-50251	01	01.1995 - 08.1995	COMPUTER, ENGINE CONTROL	UCF20..EUR	2,163.08 USD
	(SUBS)	89661-50252	01
04	89661	89661-50271	01	02.1995 - 08.1996	COMPUTER, ENGINE CONTROL	UCF20..RHD..EUR SOUTH AFRICA SPEC	2,163.08 USD
	(SUBS)	89661-50410	01
05	89661	89661-50310	01	08.1995 - 08.1996	COMPUTER, ENGINE CONTROL	UCF20..EUR	1,782.76 USD
	(SUBS)	89661-50351	01				2,139.31 USD
06	89661	89661-50350	01	08.1996 - 11.1996	COMPUTER, ENGINE CONTROL	UCF20..EUR
	(SUBS)	89661-50351	01				2,139.31 USD
07	89661	89661-50400	01	08.1996 - 11.1996	COMPUTER, ENGINE CONTROL	UCF20..RHD..EUR SOUTH AFRICA SPEC
	(SUBS)	89661-50401	01
08	89661	89661-50351	01	11.1996 - 07.1997	COMPUTER, ENGINE CONTROL	UCF20..EUR	2,139.31 USD
09	89661	89661-50401	01	11.1996 - 07.1997	COMPUTER, ENGINE CONTROL	UCF20..RHD..EUR SOUTH AFRICA SPEC

[shanra]

Having got the glovebox off I can see it's a 89661-50350.

 

[shanra]

Does anyone have Chemi-Con capacitors 1 x 47μF - 63v and 2x 15μF - 35v ? It would save sending to America for them.

[ColinBarber]

36 minutes ago, shanra said:

Does anyone have Chemi-Con capacitors 1 x 47μF - 63v and 2x 15μF - 35v ? It would save sending to America for them.

Panasonic FR are more than good enough - high temp, high endurance, low ESR.

47μF - 63v - 13p from RS, problem is you need to purchase 200 of them 😞 

https://uk.rs-online.com/web/p/aluminium-capacitors/9232827/

 

Farnell will sell you one, but is going to cost you over three times that of RS, at 41p. They have over 15,000 of them in stock!

https://uk.farnell.com/panasonic/eeufr1j470/cap-47-f-63v-20/dp/2760347

 

[shanra]

Thanks Colin but still need the 2x 15μF - 35v and it's USA for them I think.

[steve2006]

I have those in stock and also an equivalent “Automotive Grade” version to the specs mentioned previously by Colin.

I can also fit them for you 😀

[shanra]

Thanks so much Steve let me know the cost and where to send. I will have the other six which I can send with the ECU. It's just the three I am missing.Thanks again.

[shanra]

Got the temperature sensor today so decided to fit it, going along nicely when I realise one of of the screws on the ignition coil is burred try moving it but no go, sit back look at it and see it held on by a frame with two bolts so remove that and then the temp sensor put the new one on hurredly and doing it up and think that it should be tight enough but I pop home and get a Torque wrench (one I've had for ages) set it to 14lb ft and proceed to tighten and tighten, I am now thinking this has to be tight enough and should have stopped but instead of popping home again to get a smaller more expensive and accurate Torque wrench  (which I couldn't find earlier) I press on and then you know what happens I of course break the bloody sensor! So refit the old one and thats another £70 down the pan. No fool like an old fool. Had I been watching anyone else doing the same thing I would have told them to stop  and revaluate. I am trying to blame the Torque wrench for it's inaccuracy but I know deep down who's to blame, it must be those leprechauns I saw on the way to work!!

[Cotswold Pete]

12 hours ago, shanra said:

 thats another £70 down the pan. No fool like an old fool. 

I hate it when I do not listen to my brain telling me to stop. Plenty of expensive mistakes made over the years.

[shanra]

Well I have fitted the next new coolant sensor and tested the old one and it passed (maybe I should have done this already) and that's one more part that probably won't fail for the life of the luxury palace on wheels!

[Razor61]

23 minutes ago, shanra said:

Well I have fitted the next new coolant sensor and tested the old one and it passed (maybe I should have done this already)

I think you did the right thing replacing it, the sensor works with very small increments (millivolts I think) so it wouldn't take much to give the wrong reading to the ecu. To quote a post from another forum - "Coolant Temperature Sensor is the "MAIN SENSOR" for the computer. This sensor has more control over the computer than any other sensor". Testing to see if the voltage changes according to temperature on the sensor and testing that it's not open circuit  is one thing but whether it's actually accurate is another thing. It was the accuracy aspect that prompted me to change mine.