Stalling/Rough Idle. 1993 LS400

AndyCheltenham1 · December 2, 2018

My car has been running perfectly until last week when I was parking in a car park in a tight space and on full steering lock when the car stalled. It started up again no problem and after I 'd been shopping I drove home about 2 miles with no problem.

The next day I started the car in the morning and it started perfectly, but when I put it into reverse to back out of the drive it stalled. It would not re start-the engine was turning over ok but just would not start.

I left the car for a few days and when I went to start it it started up fine-I went forwards/backwards a few feet and all seemed ok. I didn't drive the car as I need to reverse onto a very busy road and can't chance that stalling half way out onto the road.

I got a mobile mechanic to come and look at it a few days later-once again it started perfectly ok. He thought it could be the throttle body/valve causing the problem so cleaned it all out. He said it was pretty gummed up so was hopeful this would cure the problem. Once he was finished I took the car out on about a 2 mile trip and all was good.

Went to start it again today and it started instantly but when I put it into reverse- to me it was idling a bit rough and lumpy and again I wouldn't want to drive it like that.

I asked the mechanic whether it could be a fuel problem but he said unlikely as it WAS running well while he was working on it.

The only work carried out recently was I had all the spark plugs and wires changed ( about 4 months ago ) and it has been running fine since then.

Any ideas what the problem could be??

Andy

The-Acre · December 2, 2018

Possibly a coil pack going south? The MK2 has two, unlike the later ones which have 8. The first to go is often the right hand one looking from the front as it gets the hottest.

runsgrateasanut · December 3, 2018

I've just purchased a coil pack to put with the rest of the small stuff under the Boot rug, that could be useful for certain emergencies.

I'm hoping when it arrives it's genuine Delphi as these cost twice as much via Rock Auto. Just run to OEM set of Rotors and Distributor caps - also just in case! As not cheap, decided not to go for OEM coil pack which is most expensive alternative to OEM.

Should you need one.

https://www.ebay.co.uk/itm/Lexus-LS-400-Genuine-Delphi-Ignition-Coil/292196150006?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649

PS you should pehaps do a diagnostic test - something that I keep meaning to do!

AndyCheltenham1 · December 3, 2018

Thanks for details of a coil pack,I will keep the details in case I do need one.

Looking on the USA forum there seems to be a lot of people that have had problems with stalling and rough idling but there are there are no simple solutions-you could end up replacing many items before you find the fault!!

I started the car this morning and it started perfectly again and seems to be running smooth when go backwards and forwards. I will try it again tomorrow and take it for a run.

I just did a diagnostic check using the paper clip method and there are no error codes showing at all ( not sure how accurate these old systems are )??

runsgrateasanut · December 3, 2018

Will a paper clip work or does it need be copper cable for conductivity?

Rupert Dubreaux · December 4, 2018

Metal ones work fine , not sure about the plastic coated ones mind .

AndyCheltenham1 · January 11, 2019

I've hardly used the car since the problem started just over a month ago. It seems that the problem is very intermittent as I have used it maybe 5 days in a row ( only short journeys of about 3 miles) and it runs perfect and the next day it is running a bit rough. Looking through the forums there seems to be many possible problems it could be: ECU (capacitors failing), EGR Valve, Coil pack, Idle air control valve?

I've given up on the mechanic who cleaned the throttle body as he hasn't got a clue what to try next, but another mechanic who seems more knowledgeable has suggested the next step could be to block off the EGR valve by fabricating a plate but has said it could be like finding a needle in a haystack to try and locate the problem!

Has anyone had any experience of blocking off the EGR valve or know of how much work is involved in this?

I feel I could be throwing lots of money at this before I find a cure and maybe it is time to get rid of the car, not something I would like to do as I have owned it for 11 years now and it has been near totally reliable with only a few very minor faults in all that time.

Malc · January 11, 2019

I think there might be posts on here about the EGR valve being blanked off/removed

I know there are others more knowledgeable here with better advice.

The EGR valve is absent on other countries cars, it's superfluous i believe .......... shouldn't be a big big issue taking it off and blanking it surely !

Malc

what year is your Ls400 by the way ?

AndyCheltenham1 · January 11, 2019

Malc,

There are a few posts on the USA forum about blocking it off but their advice seems to vary from being a very simple job and others saying it can take 6 hours to do?

My car is a 1993

runsgrateasanut · January 11, 2019

Don't know if this clip may help you or you can make sense of it?

I seem to recall replacing some sort of sprung device by the Oil dip stick once. 'Fraid my memory doesn't tell me what it did or does, but near to the part referred to in this clip. Whatever it was I doubt it actually needed replacing. Sorry can't help.

https://www.bing.com/videos/search?q=where+is+the+EGR+valve+on+a+lexus+ls400+engine&view=detail&mid=20659664EF169EFFA6FC20659664EF169EFFA6FC&FORM=VIRE

runsgrateasanut · January 11, 2019

Additional to my last reply you may want to check the rubber pipe to the IACV or it could be MAF sensor related.

Have you changed the Air filter in recnet times?

On my Car the connecting small bore tube next to the the throttle body aperture where the IACV rubber hose clamps had almost broken free, thereby enabling more air to be sucked in, post MAF sensor.

Here's another link for you to consider as possible cause.

https://www.carsdirect.com/car-repair/how-to-tell-if-you-have-a-faulty-mass-airflow-sensor

AndyCheltenham1 · January 12, 2019

Thanks Stuart for your advice. I need a competent mechanic to look at it (hopefully I've found one) to go through all the simple things first. I looked at the link for faulty maf sensor and a lot of those symptoms do relate to my car. Not sure how easy it would be to check as it says do a computer diagnostics check which you can't do due to age of car.

I changed my air and fuel filter within the last 5000 miles so they should be ok.

My problem is finding a decent mechanic who knows what they are doing-a lot of mechanics seem to be wary of the LS400 as they think it will be very complicated to work on-to me it is just a car and if you are a good mechanic surely any car (within reason) works in exactly the same way??

Malc · January 12, 2019

17 hours ago, AndyCheltenham1 said:

from being a very simple job

take that route then .. you've had the car a very long time and if it really is something relatively simple then I'd explore that too ..... some people do try to overcomplicate issues sometimes

Malc

runsgrateasanut · January 15, 2019

Quote

The next day I started the car in the morning and it started perfectly, but when I put it into reverse to back out of the drive it stalled. It would not re start-the engine was turning over ok but just would not start.

Unquote

This seems to be the most worrying aspect of what you've said in your threads. This may suggest that the ECU is at fault, unless you stopped the Car before reversing, which starting again can overfuel and clog a newly started car. ? You can look at the Air intake plastic part that connects to the Throttle body to see that the small bore rubber pipe is not split and that it is still OK going in to the main black plastic body. Suggest worth taking a look yourself and ruling out as a possible cause. My Mechanic has never bauked at doing anything to the Car and at a reasonable price but there are Cowboys out there and sounds like you've experienced a few.

Perhaps give your location (Cheltenham?) and ask members for a recommendation?

ps I recently listed a 1993 ECU for sale on eBay, as surplus to requirements, condition explained.

runsgrateasanut · January 15, 2019

Afterthought - did you leave the handbrake on?

AndyCheltenham1 · January 15, 2019

Stuart,

I moved away from Cheltenham 2 years ago so that is why I have not yet found a mechanic I can 100% trust, because I've had no real problems with the car (apart from 2 springs) I've not yet experienced how good a mechanic is/isn't until you get a problem like this!

The mobile mechanic I tried was totally useless so I am going back to an older mechanic who seems to be on the ball who fitted the new springs for me.

I've got it booked in on Thursday and he will go through all the obvious and simple things that could be causing the problem but he is not too confident of finding the problem. With it being intermittent it could run perfectly ok when he is testing it and if nothing obvious is at fault I could end up replacing several parts until the fault is found, it could be egr valve,ecu,iac valve, bad leads and maybe something else??

You said that you had put an ecu for sale on ebay-have you still got that for sale and if my fault was the ecu how easy are they to take out and re fit-do you have to re programme anything or is it just a case of plugging the new unit in??

I will know more after Thursday but at the moment I can see me selling it on eBay for pennies as a spares or repair car!!

runsgrateasanut · January 15, 2019

Hi Andy,

Good question, on the installing a replacement ECU. Not too sure myself as didn't do it in the end. I did remove and refit my own after the Caps had been changed. There's a useful link to removing the ECu but its not completely accurate for your model. Others on this forum know the answer or perhaps try a US forum via google and see if you can find the answer. Just put the Q into google for your Car model and age.

It seems a pity to sell the Car as scrap when you've enjoyed it so long and it doesn't sound as though its terminal. Did the previous Mechie tighten up the throttle body or do the job properly. Did you see it after cleaning and before re-installing. I'm a cynic.

Yes the ECU is on t'bay I only listed it last week.

To get a decent car (and who knows with older cars what will not be a money pit (though glossy on the outside) you'll have to spend some money. Better the Devil etc. especially if its good in all other respects, tyres and a nice interior etc.

Short journeys which you mention can cause difficult starting, but as you say there are lots of other things to consider. I've not read on this forum of a MAF sensor failing but once again put it into the forum search box or let google do the walking by putting Q's into the search line. A lot of reading but may find some useful clues. Frustrating for youI understand.

runsgrateasanut · January 16, 2019

Andy I think Scotty Kilmer answers your Q. Slight difference in process with your '93 and it lies flat rather than upright, but similar and there is a lexus video on removal but you'll get the gist that its not Rocket Science.

https://www.youtube.com/watch?v=pOSEJu7_Upc

AndyCheltenham1 · January 16, 2019

Thanks Stuart for details of Scotty Kilmer video on you tube-it really is a simple job to remove and replace the ECU. I noticed that the LS was newer than mine so he was able to plug in a scanner which confirmed that the ECU was at fault which you can't do on mine. I read through all the comments and it seems that this can be a common fault on older LS's. Scotty commented that he did not recommend having the unit repaired as he has had a lot of problems with repaired units and the mechanic who is looking at my car tomorrow doesn't have a lot of confidence in repaired units either?

Speaking to a company that does repair them they charge around £150 and gaurantee it for 2 years. Will see what the mechanic says tomorrow when he checks the car over.

Stupot · January 16, 2019

I've just removed/re-installed my 98 LS ECU and I have to say it was not super easy, but do-able with a 6/10 PITA factor.... the Scoty Kilmer video rather craftily does not show the removal of the upper bracket nut which is behind another small box of electrical tricks with it's own little bracket that hides the upper nut... this little box does not seem to budge, but wiggle wiggle got it out, eventually!! But as Stuart says, your 93 LS ECU is laying differently, so hopefully easier to remove.

I purchased the ECU capacitors separately as a kit from eBay and I had a local ECU repair company remove the old and solder them in for £40 (took about an hour). Repair prices I've seen quoted on here range from £30-£80, so £150 sounds a lot.

I don't think you should sell the car until you've tried replacing the ECU capacitors. Check this thread out https://www.clublexus.com/forums/ls-1st-and-2nd-gen-1990-2000/656360-all-my-crazy-lexus-issues-solved-ecu-leaking-capacitor.html

AndyCheltenham1 · January 16, 2019

Thanks Stupot for the info. I wouldn't try and take out the ECU myself, I am far too clumsy to go anywhere near it. I had a look on eBay for the capacitor kit but there are none available for a 1993-I've emailed the seller to see if he has any more available. There are no ECU repair companies close to me, so I need to find a reputable one that I could post the ECU to.

AndyCheltenham1 · January 16, 2019

Have just got a reply from the eBay seller and he has got more for a 1993 and is going to list them soon

Stupot · January 17, 2019

Hope I did not make the ECU removal sound too difficult, I'm sure you could do it.

Imagine you've got your Freeview TV box, separate HiFi system, Broadband router etc all behind the glovebox of your car, all you have to do is remove the glovebox and un-hook them all (take photos of every step to aid re-install) and then put them back and re-hook them all up... sometimes while lying on your back in the front footwell. It's awkward, but not difficult.

runsgrateasanut · January 17, 2019

Wouldn't say it was a doddle, so leave it to someone confident. Hidden screws under the Glovebox lining flummoxed me for a while as I mentioned on a thread here at the time, screaming for help.

A few things to consider. Firstly, there is a port for reading error codes on your Car and I've put a link below. Its a rectangular box under the engine bay easy to spot. (edit - sorry you've done this) Secondly, I would want to be sure that the seller of the Caps has imported them from a legit producer or is a member of this forum. Ask for an image of a Receipt to show they purchased them from America and that they are not Chinese imitations that have flooded the market and that this person is making a mint selling as genuine. Trouble ahead if not genuine. Lastly, I'm amazed it would only take an hour to do the job of replacing all eight Caps, bearing in mind the complexity of sandwich pcb and possible leakage from originals. (see expert level soldering) Lastly, lscowboy (in Stu's video link) told me he pays £1000 for a litre of flux and the job takes him some time to do. How you find someone to do it for £40 I can't understand but as long as they don't screw the ECU then who can complain.

http://www.lexls.com/tutorials/intro/codereading.html?utm_source=LexusOwnersClubUK&utm_medium=ForumLinks

https://www.youtube.com/watch?v=Vynb_HdEIDU

Stupot · January 17, 2019

2 hours ago, runsgrateasanut said:

Wouldn't say it was a doddle, so leave it to someone confident. Hidden screws under the Glovebox lining flummoxed me for a while as I mentioned on a thread here at the time, screaming for help.

A few things to consider. Firstly, there is a port for reading error codes on your Car and I've put a link below. Its a rectangular box under the engine bay easy to spot. (edit - sorry you've done this) Secondly, I would want to be sure that the seller of the Caps has imported them from a legit producer or is a member of this forum. Ask for an image of a Receipt to show they purchased them from America and that they are not Chinese imitations that have flooded the market and that this person is making a mint selling as genuine. Trouble ahead if not genuine. Lastly, I'm amazed it would only take an hour to do the job of replacing all eight Caps, bearing in mind the complexity of sandwich pcb and possible leakage from originals. (see expert level soldering) Lastly, lscowboy (in Stu's video link) told me he pays £1000 for a litre of flux and the job takes him some time to do. How you find someone to do it for £40 I can't understand but as long as they don't screw the ECU then who can complain.

http://www.lexls.com/tutorials/intro/codereading.html?utm_source=LexusOwnersClubUK&utm_medium=ForumLinks

https://www.youtube.com/watch?v=Vynb_HdEIDU

Luckily, because of your posts Stuart and others on the USA Lex forum, I was well prepped to find the hidden glovebox nut and then give it a good pull to remove it.

I agree... I was nervous about buying those ECU caps kits on eBay as I was aware of there being fakes around from the USA thread, indeed, I started a thread on here asking if anyone knew about the seller or if it was a forum member etc, but no replies, so i guess no one knew. I took a punt anyway and bought a kit. The seller on eBay is also selling some Lexus diff oil and the other items they have for sale make me think they are genuine. So I purchased a second kit of ECU caps for a 98-2000 LS just in case I changed my LS for another in the future. The second kit of ECU caps came in a small bag with some 'Digi-key' labelling which gave me comfort as this is the recommended USA outlet for buying the caps from.

Lastly... I watched the guy take my ECU apart and remove the first capacitor and clean up so he knew how long it was going to take him in order to give me a quote.... he said come back in an hour, which I did, he had just finished and he had the old removed capacitors to show me. He knew his stuff and he was proud to show me his special flux which you can not buy anymore. He's obviously been doing this kind of work for decades. This was the outfit I used https://www.dieselecurepairs.co.uk/