DPONCE

So I scoured the forums for a possible related problem that is equivalent to mine, and most of them seem to be having the same problem as mine.

Here's the scoop, my lexus for the last 3 months has had this intermittent sputtering/jumping rpm problem that has left me stranded a total of 3 times now. I work for a toyota dealer so thankfully I was able to get diagnostics done to the car for cheap. The first mechanic who looked at the car(Who is a Certified MDT and is very knowledgeable with lexus/toyota) said that there was no power to my fuel pump or the relay, so he changed out the relay and switched some relays around and BAM car ran just fine no sputtering or jumpy rpms. However 3 weeks after that my car started to do the sputtering and jumpy rpms. I talked to him again and he said that it could very well be my fuse panel that has some corroded wires and that I should lift up the panel in the engine bay and look around for some corrosion. I haven't done this yet and I plan on looking at it very soon. Also the car sometimes likes to do the jumpy rpm thing at cold start.

Now fast forward to about a week ago. I brought my car in to get the timing belt and water pump replaced because the pump was making noises and I figured what the hell you practically have to do a timing belt to do the water pump so I got the whole nine yards taken care of. He finishes up the job and before he drops it I let him know that the sputtering and jumpy rpms have been happening still but less frequently. So he said to check my harnesses that run under my fenders and voila there are some wires that are rubbed through exposed. So he tells me to take care of that ASAP and I planned to do that this very sunday...BUT that night on the way home, I had just filled up on gas and pulled out of the station and the car literally just dies....No jumpy rpms or any warning signs showing that the car would die. So i call a service advisor at my work who comes by with his tacoma and tows me back to the dealer. The next day ANOTHER Certified MDT tells me he'll fix my wiring harness for me for free because of the ****ty situation im in. Today he finished my harness up and said she fired right up no problems. On my way home though my car sputtered a little bit, and almost died on me twice with no warning signs or anything like that.

This car is my only means of transportation and its starting to frustrates me that I don't have a reliable car to transport my fiance and kid around without the fear the car dying and leaving us stranded.


And I replaced my cap and rotors, my spark plugs(OEM Toyota). I dont think its a problem with the fuel filter because like my mechanic friend said it seems that the power is getting cut off to the fuel pump/relay.

LScowboyLS

Well it could be several things from your description, but for a heck of a lot of 90-97 LS400 owners, the problem turned out to be failing defective ECU capacitors. Not saying that is for sure the problem, but it tends to be the one that no one can find, and it is a pretty big epidemic at this point, so definitely worth a read!

You can also pull the ECU and sometimes see visible evidence of the problem, or you can also perform Yamae's ECU ripple test. I have the ripple test capacitors if you need one, I give them away to folks here at Club Lexus.