williamb82

Same issue again this morning, the source of the problem still eludes me.

skytechja

ohhhhh dam..... sorry to hear.. i was actually keeping my fingers crossed....


something is up with some temp related issue on startup....

maybe need to get an electrical manual and look through it thoroughly

williamb82

I have it, and have. My degree is in electronics. Anyway, I ordered new O2 sensors. I haven't replaced them since I got the car, so why not. $26 for the pair shipped for Bosch. They "shouldn't" have anything to do with starting cold, but who knows. Maybe they are giving a false rich condition so the ecu isn't giving fuel when trying to start cold. That is what the issue seems to be, as odd as that is. I have spark when cold, so that means its a fuel delivery issue, and the pump is new, and the fuel filter isnt clogged, so seems the ecu isnt firing the injectors, or at least not with enough pulse width to fire the car. Un plugging the tps puts it in a limp mode which dumps extra fuel. You can smell it running really rich when it starts this way. After the o2 sensors, I will swap my extra injectors. at that point, I have to assume maybe they are out of spec enough that they are incapable of the duty cycle being commanded in the situation. They do have over 340k miles on them after all, and injector cleaner has already been run through twice so I know they are not sticking. Just getting pissed off at this dumb problem.

skytechja

welll the O2 sensors is a plausible cause ...... they shouldnt be sending any signal when cold though..... they only do that when heated.....

you can however take off the O2 sensors and test em with ur meter though..... but since you havent changed em from you got the car, yes its a good idea to change em.

fristgengs

Fear not my friend I've also been at this for some time now, this is what I've got so far, if it's not your "fuel control module" Aka fuel ecu. Then check out your actual ecu and make sure none of those resistors have leaked. I've replaced everything from tps to egr to water temp sensors, everything you have done wires plugs new disturbuator ect. This is what I got, the fuel pump primes only at about 9.6 volts instead of your cool 12.5 Thus putting in a new 12v pump is out the question because it will just start and die, it is the "fuel pump module" that stays in communication with the cars ecu where I think your problem is. These "fuel pump modules" are famous for getting wet from rain and car washing that's how mine went out. Hope this helps anyone most importantly "check all grounds" Ngk gots a good kit for the frist gen gs300

kene

iTrader: (2)

I once had a slight onset of this problem. The car sat for a very long time, and then finally I went back and de-soldered the old ECU capacitors and reinstalled new electrolytic capacitors with the same capacitance values, but higher voltage ratings. And this made the cars idle awesome. The somewhat loosly lugging idle was gone, and it now had a nice strong idle.


If you attempt this, route you may want to look into buying another ECU (if you haven't already) w/ the same features that your car has.

Try www.car-parts.com and you can find a used ECU for $25 to +$50. After I would first install the one you bought, and see if the problem is solved, then if not I would de-solder the caps from the one you bought. Solder in the new caps, and install and see the results.

I changed to the caps in the ECU and in my instrument gauge cluster to resolve 2 different issues. Lexus used some capacitor that with time begins to fail/ stray from its true capacitance. They are brown in color and from the company "Ninchon" I believe.

There is a post on here called "all my crazy Lexus issues solved". It is about the capacitor issue and it explains in detail why they give problems.

I hope this helps.

williamb82

I already replaced the ecu, same issue. I will likely pull it apart and change the caps in at least one of them though. Im just getting fed up with it. I also may just bypass the damn fuel pump ecu and run a relay triggered by B+ to run the fuel pump. Its annoying. The last few days, if I hold the button I installed to prime the pump for 5 seconds or more before turning the key, it will start, but it is a rough start. I did replace a cap in the fuel pump ecu, but used a 35v instead of a 50v as it is what I had on hand, guess I ought to just order both of the caps in it and change them for one more try at that.

williamb82

Still same issue. Swapped my o2 sensors when they came in, no change. Also put an actual N/A IACV in as I realized the tip on the tt and N/A are different. Idles better, slightly higher, but no change in the cold start issue. Had the problem after work the other day because it rained literally all day. I am ready to find a new engine harness at this point. The only thing I can figure is that somehow, some way, there is something wrong in the harness causing this. Maybe something exposed and the dew in the air when its cold is causing something to short and drop the 12v signal for the sensors etc... I have no idea. Just sick of having to open the hood when its cool outside to start the damn car.

williamb82

Ok, found if I just wiggle the tps wire, without unplugging it, it will start. Sooo, I changed the timing belt and front seals Saturday, and Sunday I pulled the upper intake manifold and tore into the harness. Nothing wrong with any of the wires in that location. I pulled the plastic shield apart and saw nothing wrong with any of the wires inside of it etc... Makes no damn sense. So, I traced the wires across the front of the engine, and te only thing I found was a crack in one of the black/rd wires for the iascv after the distributor. I fixed this and soldiered a new connector on as my old one was busted anyway. Put it all back together. This morning, same problem, wont start. Pull on the tps wire just a little bit, and boom, it starts instantly. It makes no damn sense at all. Tomorrow im going to try and unplug the vsv thats right there and see if that makes a difference instead of touching the tps wires. This is really making me mad. I need to find a new engine harness asap.

skytechja

traced tps wiring???

wonder if changing the throttle body it self will do u any good..... or if u have one you could just try

williamb82

TPS wiring is fine. My SAFC2 sees the throttle percentage fine and I have checked the continuity to the ECU quite awhile ago. Im going to take my spare ECU apart and try to find the values for all of the caps and order them to replace. Im grasping at straws now.

williamb82

I just pulled apart one of my ECU's. The one I replaced a little while back. My ecu is a 175000-30690. 93-94 GS300. Here are the values and parts I ordered from digikey. They are the low ESR caps recommended in the LS400 ECU cap thread.

https://www.clublexus.com/forums/ls-...capacitor.html

10uf 50v x2 http://www.digikey.com/product-detai...1702-ND/756218
47uf 63v x2 http://www.digikey.com/product-detai...1734-ND/756250
220uf 16v x1 http://www.digikey.com/product-detai...458-ND/2433592
100uf 10v x2 http://www.digikey.com/product-detai...300-ND/3134256
15uf 35v x2 http://www.digikey.com/product-detai...1718-ND/756234

When getting the values, I could tell at least 5 of them were leaking, so I will have to clean up the board before installing the new ones. Hopefully this is all it is.

williamb82

Parts arrived today. i changed all the caps in one of the ecu's and swapped it in. Starts right up and runs better, but the od off light is on, regardless of what the switch is set to, so apparently I messed something up. Gonna have to pull it back apart and check for a solder bridge somewhere or a bad trace on the board. Wish I could find a schematic of the ecu somewhere.

Edit: Got it sorted out. Found 2 things. 1, a lead I clipped off of a new cap was somehow laying inside. Also, found a tiny transistor that had a soldier bridge. Probably happened while desoldiering the cap near it. Getting the old caps out was a huge pain. Going to go for an extended test drive now.

Edit2: Just drove it till it fully warmed up etc.. Shifts much better now and doesnt shift into overdrive too early anymore. Ill see if the cold start issue is resolved in the morning. So far so good.

williamb82

Still the same issue. I unplugged the "noise filter" next to the ignition coil this morning and left it unplugged. Gonna see if that makes a difference. I figure the capacitor inside it could be faulty.

williamb82

Well, today it wouldnt start again like normal, I turned the key all the way to off like normal, opened the hood, and this time, I just put a finger on the intake manifold, nothing else. Figure, lets try a little experiment, Damn thing started right up. Sooooo, Im going to try adding a ground from the intake manifold itself to the body.

Now, onto something else, on the way to work this morning, it started missing and smoking. I pulled over and smelled like pure gas. It seems an injector got stuck open. I fiddled with it awhile. I was able to unplug injectors 1-4, and they made differences, so it has to be either #5 or #6. I pulled the #5 plug wire, and it seems to make the least amount of difference, so I am leaning to #5, however I have a spare intake with injectors, so will swap all 6 to be sure. After a few min, the injector unstuck, and then I just had some blueish oil smoke for about 5min while driving and it stopped. Car seems to be running fine right now, but I will be swapping the injectors and changing the oil asap.


Edit 11/20/15: Turns out it was the ecu. It happened again on the way hme from work as soon as I pulled out. Swapped in the other ecu and the problem went away and did not return the whole trip home.

Edit2 11/21/15: I took the ecu apart. I traced the lines or the injectors and found where the transistors are. Well, one of the caps I replaced is next to a transistor. It has a big soldier glob that was laying on top of one of he traces, so I chipped it off with a pic. I went over the whole board and removes any extra soldier that looked like it could possibly cause any issues in the future. Swapped the ECU back in, and its running great so far. Fingers are crossed.