djbrown01

Just bought this car, thought I got a good deal blah blah blah I'll get right to the problem
1995 LS 400 with 191K on it
Ran perfect the 300 Mile drive home
Now a couple weeks later and I have this
P0300, P0301, P0304, P0305, P0306, P0307
Those are just the codes that were pulled tonight, It has had misfires on all cylinders over the past two weeks, I just havent reset the light recently
The ECU was changed according to the previous owner, the original is in the back seat and came with the car, It only misfires after it warms up, dead cold it runs fine
Idling after it warms up you can here the misfire but if you give it some RPMS it smooths right out
Under load it's real bad, bucking and jerking until its around 2000 or 2500 and then it will start to smooth out but just tonight the CEL started flashing at me, meaning I was doing damage to my cats
I pulled the plugs out and threw those junk bosch ones in the trash to begin with and replaced with NGK, I didn't want to start throwing parts at it, so I had a coil laying around to try that the other day when I wasn't getting as many misfire codes, needless to say that didn't change anything so I removed it and returned it to our parts guy
Now I'm at a loss, I read somewhere about someone having similar issues to me and it ended up being the Fuel Pump relay resistor, so i removed that, and tested it with the Ohmmeter and it tested bad, and at 69 dollars from the dealer it's a cheap place to begin my process and the book says it's out of spec and should be replaced
All the knowledge of this site I'd like to hear some more opinions on what has happened to you in the past, and this does have a tuneup that is less than two years old according to receipts and the conditions of parts I saw..

LScowboyLS

when I had misfire and rough running on my '96, it turned out to be leaking ECU capacitors

Yamae

This symptom is a typical behavior of aged electrolytic capacitors. I think your ECU has electrolytic capacitors about to leak or already leaking the liquid some. Changing them may fix your problem,I bet.

djbrown01

Ok, I'll definitely look into that, but I opened the spare one I had that came with the car and found nothing that I could tell was out of the ordinary, it looked as if everything was perfect, could both of thesee ECU's be bad?

Also I've only had this car like a week or two and when I tried getting the glovebox out to get the ECU out to check that one and possibly swap them out I wasn't able to, I may have been missing a step and I didn't want to go busting a bunch of delicate plastic pieces already, I know this was the right place to come for some insight and maybe you could offer some tips and tricks to removing this just so I could get to the ECU?

LScowboyLS

due to a known design defect, all LS400 ECU's may well have these problems eventually, so YES! - they likely BOTH need new capacitors, but the job is pretty painless!


PS - sometimes there are no visible signs of bad capacitors, mine looked fine a month before they leaked and almost ate up one of my ECU main circuit boards

LScowboyLS

there is a hidden bolt or two inside the glove compartment behind a secret panel (not joking about this) - not sure if they show up in this diagram, but hopefully it will help some:

Attachment 498614

LScowboyLS

there are typically only six capacitors in a 1995 to replace, so both sets (12 in total) can be ordered and delivered, enough to to do both ECU's, from the links in my post, for under $15 to your door for everything for both, including shipping.

djbrown01

Do you have any detailed photos of the board itself and the locations of these capacitors? I can't seem to find any or after I get the caps themselves I'll just understand and know where they go?
Also is there a detailed list on what exactly 6 caps I need to order? And are there only 6 caps in the whole board that I need to change to solve this issue? Thanks so much

djbrown01

alright well just now I ordered all the caps listed on that ECU leaking cap forum that is so informative, 7 in total that were listed although you said I only needed 6 I got them all just to be safe, Any other tips or tricks or How to posts or something I could take a look at? Or just follow the directions and when I open the ECU up I'll understand?

LScowboyLS

the 95-97 models have 6 capacitors - make sure you used to correct list for your year range in post #1 - it is best to pull the ECU and verify which ones you have before ordering, but the list from my thread is likely the same values as what you have - once you have them ordered, then you can reinstall the ECU in 5 minutes (leave the lower glove compartment out), and you can drive the car if needed while you wait for them to arrive - the capacitors look like the ones in post #8 of my thread - no other components on the board look like these, so the 6 capacitors are fairly easy to spot!

djbrown01

I ordered 7 caps, all the ones that were listed on the post, well 14 total enough to do both ECU's, I didn't pull the old one to verify yet but hopefully I got the right ones, and if not I guess I can just order more and get the right ones, thanks for the help

LScowboyLS

I copied this from my main post, hope it is what you ordered
2 ECU's would only require 12 caps, not 14

1995-97 LS400 needs 6 caps as follows:

Qty. 2 of 10uF - 50v
Qty. 1 of 47uF - 63v
Qty. 2 of 100uF - 10v
Qty. 1 of 220uF - 25v


the one to get in 10uF is the 50V Chemi-con KZE EKZE500ELL100ME07D
also very good is the 50V Panasonic FC EEU-FC1H100L
also very good is the 50V Nichicon PW UPW1H100MDD


in the 47uF - the 100V Panasonic FC EEU-FC2A470
in the 100uF - the 35V Rubycon ZLH 35ZLH100MEFC6.3X11 --- better than the 16V model due to the much lower ESR

in the 220uF - the 50V Chemi-con KZE EKZE500ELL221MJ16S

djbrown01

So it's been nearly a month since I last posted here, and after taking your advice I had all the caps changed in the ECU, I reinstalled everything, ran fine at first and then the misfire came back. Cylinder 6 this time, And i had the cover off the drivers side timing belt cover and I heard something that sounded like arcing.. I'm completely lost now, and don't want to throw parts at it. Anyone think I should go through the ignition system if that is the last thing that could cause this misfire?
Runs perfect when it's dead cold, after it hits 195 degrees thats when the problems start to occur, can hear the miss out of the exhaust, but I would have to say the miss isn't as pronounced now that the computer issue has been worked out
Any and all input would be appreciated

LScowboyLS

did the person who replaced the caps use the ones stated in my post above exactly, as far as brand and series?

djbrown01

Yes I used the exact ones specified in your post above, and the guy who replaced the caps for me is an electronics wizard.. Where do I go now in your opinion