1994 LS400 random misfire

[Farqui]

Odd that it ran without issue back from France. Good tho, as you wouldn't want the hassle on a long haul.

Well done locating the potentially faulty part and fingers crossed that you're past the frustration of not knowing what's causing the issue.

Good luck.

[garagestmarien]

Well, everything seems to be running fine now, but a new question now arises.

I decided to adjust the throttle/gearbox cables and the tps.

I notice that if i try to adjust the tps by the book, it cannot be done, as the play in the linkage gives about a 4 mm gap before the throttle shaft starts turning. So I can't adjust by the book.

Or am I doing it completely wrong?

 

[garagestmarien]

Update.

Still problems.

Today went to the shops 10km deive, everything fine.

Leaving the shops to return to the house and less than 1km and the check engine light and trac off light came on. The car surged and cut on the throttle a couple of times, and then did what it did before and run with very little power.

I think it sets itself in 2nd or drive as acceleration is non exisitant, but eventually it slowly picks up speed. This is quite a problem in this part of France as it is very hilly.

I got the car back to the house, checked everything I could which looked fine. Checked for and stored codes, none found.

After about 30mins I strated it up and everything running fine again.

So, now I am wondering if I have ECU problems. I plan to take it off in the next day or 2 and check if I have capacitor problems. I can't think of anything else.

I also have to return back to Netherlands next week for work, but think I will have to go by train or fly, my confidence in the car at the moment is at an all time low.

I do hope someone can offer me advice on maybe something I have missed.

[garagestmarien]

Okay,

Back from france minus the car.

On stripping and checking the ecu, I found 2 capacitors leaking and some pcb track damage. So I have brought the ecu with me to repair, then take it back and fit it.

I think maybe there should be some rule, that if any odd problems are experienced,  the ecu should be checked first (unless it has already had the capacitors done).

I was convinced mine was good and I was wrong. I still don't know if this will cure the problems I am having, but I think it is highly likely.

It will be about a month before I can get back and try, but I will post the results.

[steve2006]

On 08/07/2017 at 11:23 AM, garagestmarien said:

Okay,

Back from france minus the car.

On stripping and checking the ecu, I found 2 capacitors leaking and some pcb track damage. So I have brought the ecu with me to repair, then take it back and fit it.

I think maybe there should be some rule, that if any odd problems are experienced,  the ecu should be checked first (unless it has already had the capacitors done).

I was convinced mine was good and I was wrong. I still don't know if this will cure the problems I am having, but I think it is highly likely.

It will be about a month before I can get back and try, but I will post the results.

If you are not savvy with PCB track repairs, correct capacitor polarisation,type and voltage ratings and fine soldering do not attempt the repair yourself, the boards are multi layer and easily damaged beyond repair.

[garagestmarien]

6 minutes ago, steve2006 said:

If you are not savvy with PCB track repairs, correct capacitor polarisation,type and voltage ratings and fine soldering do not attempt the repair yourself, the boards are multi layer and easily damaged beyond repair.

Thank you steve.

As I said at the begining of my post, haven't been on here for a while. But I still have the caps I ordered back in 2014 so only have myself to blame.

Being a research and development engineer for electric buses, cars and bikes the pcb is no problem.

I have cleaned and checked the tracks and all is good. Now replacing the caps.

Then when ecu done, post it to france to be fitted and tested on car and if all good, I go back and get it in a few weeks.

[runsgrateasanut]

I would be interested to see photos of your work with the Caps.  Good idea to photo just in case you forget which way round the Capacitors sit.  I'm probably running on borrowed time, as like you I've had the caps for two years?  

The other thing you could have checked is your Battery earthing terminal and all other earths.On an MR2 an earthing problem  could lead to a fire and on the Suzuki Wagon R a poor earth has been known to earth via the throttle cable. This is just a thought and probably can be debunked as having any relationship to your symptoms.   

[garagestmarien]

 

23 hours ago, runsgrateasanut said:

I would be interested to see photos of your work with the Caps.  Good idea to photo just in case you forget which way round the Capacitors sit.  I'm probably running on borrowed time, as like you I've had the caps for two years?  

The other thing you could have checked is your Battery earthing terminal and all other earths.On an MR2 an earthing problem  could lead to a fire and on the Suzuki Wagon R a poor earth has been known to earth via the throttle cable. This is just a thought and probably can be debunked as having any relationship to your symptoms.   

It is fairly easy to do the caps and get them the right way round. The caps have a striped side for - and usually the negative lead is shorter, but i would never judge them that way, stick to the stripe on the side. In the same way the board is quite well marked to show the - connection for each cap.

Yes, I also ran on borrowed time and think I have now paid the price. My ecu is finnished, tomorrow I post it to my other half who will fit it and run the car up and film and report back how it is. She has had full instructions and training from me, so I have no problems there. If everything runs well, then I will be off to get the car in about 3 weeks.

As regards to the terminals on the car, before I knew the ecu was at fault (although I still dont know if this is the cure, but fingers crossed.....) I cleaned every contact and plug I could find. I also replaced the neg wire on the Battery with a nice 50sq,mm section cable to body and engine, so I know circuit wise everything should be good. Also total new ignition components, alternator (Gen Denso) and Battery (Varta blue). Throttle body has been cleaned and engine full service, air,oil,fuel filter and Mobil 1 5w30 esp oil.

Mechanically the engine is perfect, just weird electronic problems, which with luck I have cured.

Pics show before, after (where you can also see the repaired tracks I did) and last one, just sprayed with pcb laquer.

 

[garagestmarien]

Update. Nearly solved.

I have replaced the ecu and the car now runs fine. 

It appears to do what it should.

But on second day of test driving, my trac off light and abs light came on. After i had stopped for a while the car started up and everything was good again, but after a 30km drive the lights both came on again. I have to check for codes, but wonder if this is a coomon fault. These are the only lights to come on.

[garagestmarien]

Well, did a 1000km trip Yesterday.

Car runs fine. After 400km the trac light came on, then after filling it stayed out for another 400 or so. It may be due to all the adjustments i did before working on the ecu.

The car is back home now, so I will go over it and make all the correct adjustments.

It ran the whole journey perfect, even being in traffic jams at Paris and Antwerp.

So I think I can safely say, the main problem was solved and it was all down to leaky caps in the ecu.

Average consumption was 30mpg which is pretty good I think. Mostly done on cruise control at 130kph.

[Newbie1]

A great result. Anyone keeping a car over 15 years really should pull the ECU(s) every now and again and inspect them, if only to ensure that no water has made its way into them, which is no uncommon given their location in footwells and firewalls.

Now, are you going to offer your expertise at fixing LS400 ECUs to the good folks here?

[runsgrateasanut]

Great photo's of the ECU.  The PCB doesn't easily seem to lend itself to being held in a revolving clamp with the two ribbon connectors to a second board.    How did you work on it if you don't mind me asking?

[garagestmarien]

1 hour ago, runsgrateasanut said:

Great photo's of the ECU.  The PCB doesn't easily seem to lend itself to being held in a revolving clamp with the two ribbon connectors to a second board.    How did you work on it if you don't mind me asking?

I stood it like a book to be able to remove the old capacitors.

I also stood it like this to fit the new ones in, but only soldered the bottoms of each capacitor.

Then I let it sit solder side down flat on the table while i did the inner solder joints.

Hope this informs.

[garagestmarien]

22 hours ago, Newbie1 said:

A great result. Anyone keeping a car over 15 years really should pull the ECU(s) every now and again and inspect them, if only to ensure that no water has made its way into them, which is no uncommon given their location in footwells and firewalls.

Now, are you going to offer your expertise at fixing LS400 ECUs to the good folks here?

Always happy to help if I can.

 

[runsgrateasanut]

Being short of one capacitor 63v 15uf I bought these on eBay.  Marked with the name and also with PW(M)  0 degrees and105 degrees C

Supposedly Nichicon and sent to me in a bag franked Semicon Ltd., Manchester m9 4pz

Nos. 20 for the small price paid.!  I do wonder if they are genuine Nichicon?  how do I test?

http://www.ebay.co.uk/itm/20x-UPW1J150MED-Capacitor-electrolytic-THT-15uF-63V-Ø6-3x11mm-Pitch2-5mm/201795301444?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

[dendonc]

On 6/22/2017 at 1:44 PM, ambermarine said:

They were only fitted to USA imports

In  that case it's 'probably' 'possible' thats some mechi here, at some point, fitted something for a UK designed car which is in some way affecting this US designed car

[runsgrateasanut]

On 26/08/2017 at 11:15 AM, runsgrateasanut said:

Being short of one capacitor 63v 15uf I bought these on ebay.  Marked with the name and also with PW(M)  0 degrees and105 degrees C

Supposedly Nichicon and sent to me in a bag franked Semicom Ltd., Manchester m9 4pz

Nos. 20 for the small price paid.!  I do wonder if they are genuine Nichicon?  how do I test?

http://www.ebay.co.uk/itm/20x-UPW1J150MED-Capacitor-electrolytic-THT-15uF-63V-Ø6-3x11mm-Pitch2-5mm/201795301444?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

Anyone with some knowledge on the subject - please reply.

[rz1c13]

Hi,

If I may chip in my answer, here is what I have learned doing my own research and working with a friend with over 25 years experience servicing medium and enterprise range inverters and backup power supply systems.

Get your capacitors from a supplier that can guarantee/ tell you how long these have been sitting on a shelf before you buy. Electrolytic capacitors are known to have rather short shelf life (2-3yrs) and deteriorate their parameters randomly when not in use. Also if you need to replace more than one piece of a kind, say 100 uF, make sure  ALL these 100 uF for your PCB come from the same batch, have the same manufacturing date, come from the same factory of a top notch producer. Maybe look for NIPPON, PANASONIC, EPCOS... Check maybe if UK Farnell can get you some, rather  than eBay...

If you have an LCR meter check them for C and ESR.

https://electronics.stackexchange.com/questions/8794/do-electrolytic-capacitors-have-a-limited-shelf-life

I wouldn't waste too much time, but if interested, here may be a good start for a further reading:

https://www.researchgate.net/publication/3191479_Shelf-Life_Evaluation_of_Aluminum_Electrolytic_Capacitors

http://www.rubycon.co.jp/en/products/alumi/pdf/Performances.pdf

https://en.wikipedia.org/wiki/Capacitor_plague

 

Hope this helps, and you get your car sorted.

Btw, your subject just made me think that I maybe should do some prev. cap change on my 2004 ls430...

 

[garagestmarien]

Well, I did another run to France and back. About 2000kms total.

The trac light and abs problem turned out to be a broken front brake back plate that was twisting back and forth and pulling on the abs sensor wire.

Finally set the tps up properly.

Had a broken egr pipe, which i removed and blanked off.

Finished the new stainless dual exhaust system including 120 cell race cats. Notice more power at 4000rpm and above. Below I don't feel much difference).

The car flew through its yearly test, emissions good.

The 2000km trip was flawless. Average speed over 200km runs on the trip on some motorways 130 -170 (80 - 110mph).

So no difference noticed with the egr removed.

Average consumption on 98 ron 1ltre to 11km (about 28mpg) So everything seems fine.

So I think I can safely say the problem is solved.

[runsgrateasanut]

Thats great news.  Problem solved and years of happy motoring ahead.

We've just returned from a 1650km  trip around South West and the Beaune region of France and car going well with only one exception which keeps telling me I must sort the Caps. Its the overdrive.  Not sure that it actually kicks in, which alarms me. There's a judder but no noticeable change in speed which tends to alarm me when I'm a million miles from home with a weight of tools and stuff in the Car  Just don't think it feels right, which could be a caps problem.

Thanks to Rupert for sending me a set of Caps.  Admit I'm having sleepless nights worrying about this solder job. Keep looking at vutube for soldering advice etc. . One guy doing a late LS seems pretty casual with the way he works. Putting a needle through presumbly from the Cap side before they are poked through seems to require three hands. I have an older Soldering iron with angled head.Its copper tip is nicely tinned but maybe not the best to use.  Also, a Parkside pointed tip Iron and holder which I don't like the heavy cable and fat handle and can't seem to tin the tip too well. Today I lit a butane gas iron that I've had for years to see if it might do the job.  Nice feel to it and no cables. It has a spade tip nicely tinned but only about 1.5mm and I think perhaps 2mm is probably the ideal size. 

Let me know what size tip and iron you used. I'd be interested.

 

[SirCoolant]

On 6/27/2017 at 3:14 PM, garagestmarien said:

Okay,

I am back.

I left for France and drove 880kms without any problems.

Then the car sat for 2 days. Today 27/6/2017 the plan was to go to some shops 30kms away. After about 10 kms the loss of power and missfire cam back and to not be stuck in the middle of nowhere I turned round and slowly drove back to the house. Had a cup of coffee and then went to check the car. As before, it started and ran perfectly. This time i had more than half a tank of fuel, so i could rule that out and also no pressure built up in the tank. The last 2 times this has happened, the car has run faultless for many kms. So off on the journey to the shops again. This time made about 20kms trouble free, then it started jerking up and down the revs, so i pulled in to park and take a look, as i was parking it cut out completely. So I waited a few minutes and restarted, which it did, but held the idle at 1800rpm, i stopped and restarted 2 more times and the same thing. So i figured these were enough revs to make it back to the house where my tools were so i could take a better look. Long story short i made it back. Another cup of coffee and then back to check. Started and ran fine, so i deceided to take a closer look at the connectors. But first i unplugged one coil and founf the car wouldnt start, so plugged it back in and unplugged the other one. The same, wouldn't start, which makes me realise that before when i thought i had lost 4 cylinders, must be wrong as i would not have been able to start it. So while it was idling normal i looked at the vacuum lines and electrical plugs, When i touched the plug on the tps it cut out straight away. It restarted and then when i moved the plug about the idle would go up and down and the roughness would appear that i had before. So i removed the plug and checked the wire and terminals which all looked fine. but i cleaned them up anyway. Since refitting the car runs fine and no amount of wiggling causes the problem again. To the poimt if i unplug the tps while the engine is running the revs rise and when i plug it back in it goes back to 650rpm (at normal temp). So it looks like that may have been my problem all along.

Tomorrow I try to reach the shops again and see what happens. If all is good, I may just order new tps and traction tps modules to be sure.

I will let you know how it goes, I hope this is the answer and I would really like to end this post with FIXED IT! We will see and on one note, to date, I still haven't found the charcoal cannister.

John

Was wondering if you have fix your problem, I'm experiencing very similar issues that you where facing 

[Malc1]

8 hours ago, SirCoolant said:

Was wondering if you have fix your problem, I'm experiencing very similar issues that you where facing 

Rylan hi and welcome to this Forum

Can you tell us a little more about your car and your ownership and what you’ve already done to try to deal with this issue please

It might help in our understanding better going forward

There’s a potential wealth of knowledge here and we’re all here to try to help

Thanks 

Malc