Hello, this is my first time posting here. I've read a few threads pertaining to my particular issue, but figured I'd post more regarding my specific issue.

TLDR Symptoms: started driving from a standstill, car hesitated, CEL turned on, won't rev past 2k, won't go over 20mph, regardless of throttle input, acceleration seems constant until 2k rpm, then stops. stronger than usual fuel smell from exhaust.

The other day I was driving to work in my 93' LS400 and I came to a stop at a stop light. When the light turned green as the cars in front started moving, I began to accelerate and immediately felt a hesitation. At this point the CEL came on and the engine would not rev past 2k, regardless of throttle input. I put my hazards on, and made my way off the road to see what was going on, but while driving I was not able to accelerate past 20mph, and regardless of throttle input acceleration seemed limited. Shut the car off, and turned it back on. Stepped outside the car and noticed a stronger than normal fuel smell coming out of the exhaust. Popped the hood and double checked to make sure no fuel lines popped off or were leaking, couldn't find any. There was a parts store down the street so I limped it over, but they couldn't help so I called a buddy of mine who lived near by. Limped the car to his house and he let me borrow his GS to get to work (big single turbo 2JZGTE swap, riot of a car). Went on to the forum that night to do some research. Figured it might be the coil packs. Next morning went back to my buddies house and we swapped the coils off his SC onto my LS, no change. Pulled spark plugs wires from drivers side, and all 4 were sparking so we assumed it was not the distributor since 2 of them would not be working since each distributor powers two plugs on each side. At this point we threw in the towel and he drove me home.

Next day I called my buddy up again and him and his cousin did some more digging. They swapped in camshaft position sensors, no change. They tried checking codes, but were not successful. I sent him the link to LexLS where they go over diagnostics and he said that is what they followed, but could not get the CEL to flash to read codes, CEL is still on. I know there is the issue of the capacitors on the ECU, but since the CEL is on I figured maybe it isn't that, is this incorrect? My other guess would be the TPS, since the throttle needs to be closed to read codes, but if the TPS is busted and doesn't see it is actually closed it won't read the codes. My next thing to check would be the fuel system, maybe clogged filter, but the stronger than normal smell of fuel from the exhaust would assume it is getting fuel into the engine that isn't burning, but a leaking fuel filter could also cause the smell. Didn't check to see if the cats were red. Another thing I read would be the IAC valve. That was going to be my next check. MAF is another potential culprit from what I've read.

This is one of 3 cars, so I'm not concerned with the length of time this car is down. One other issue I had was that through February the car was parked all month due to snow. Started it up maybe twice towards the beginning of the month to move it in the driveway, but besides that it sat, longest being 2.5 weeks. When I went to start it again, at the beginning of March, it would not start. Tried a few times and got nothing, only a clicking sound and all the lights in the car would dim. Battery was low. Pulled battery, charged it overnight, and car started right up. Leading up to the car going into the limp mode described above, it felt slightly off, as if the acceleration was not the same like it was, but very minor, nothing alarming. Figured maybe it was the slightly warmer weather, or my lack of driving it for a month (other car is a WRX, significant more pep).

Any suggestions would be helpful, and thank you in advance!

 

I would figure out what’s going on with the ECU before going any further. The diagnostic blink codes are crucial to diagnose an EFI car. If you can’t get the blink codes, I’d start suspecting the ECU or wiring. Did you jumper TE1 and E1? (That’s what I used to jumper in my old Supra)
Try to inspect the wiring in the engine bay from top to bottom for animal damage, since the car has sat for a long time. They like to go into the valley under the intake manifold and snack on the knock sensor wiring among other things.

 

My buddy attempted to check the codes by jumping TE1 and E1, but was not successful. I'm going to give a go on Tuesday when I can go back up to check. I'll look through all the wiring as well at this time. Thank you!

 

So today I was able to get back to my buddies house to take a look at the car. He started pulling the spark plugs and they were black. I decided to try and check engine codes, but was not successful. Decided to pull the ECU, opened it up, and found two capacitors that had leaked out. Pulled the ECU and looking for reputable repair shops to send it out to.

 

Outstanding, good job. Think you found the issue there.

 

Another ucf10 fallen prey to the infamous capacitors...hope that is the issue! In the meantime, it would be good reassurance to check every fuse and relay you can find that is relevant to fuel/spark/engine operation in general. It's good maintenance, juuuust in case.

 

The ECU repair guy you are looking for is Josh Beaumont. You can find him on Facebook

 

Thank you to everyone who posted suggestions. I just wanted to post an update on my car. I sent the ECU out for repair, and of course UPS lost my package for a week. It finally arrived at the repair shop, and they got it back to me this past Wednesday, 4/21. Plugged the ECU in to the car and she started right up, but was idling rough and low. The car eventually died, but we chalked it up to sitting with potentially flooded cylinders. We started it back up and it died right away. We started it again, but this time held the throttle and kept it around 2k for a few minutes. Tons of smoke from the exhaust, and a strong gas smell. After a few minutes of just burning stuff off, we slowly let off the throttle and the car held the idle and kept the engine running, expect idle was significantly lower than before. After letting it sit for a few minutes, there were no lights on the dash, and everything seemed to be running fine. Idle was low, but smooth, so I decided to drive it home, my buddy had it at his house cause it broke down near there. 30 minute trip home and she drove like nothing was wrong, by the time I got home everything was idling smoothly and at a slightly high rpm than prior. So looks like the ECU repair worked! I got all new parts to do a full tune up since we pulled a couple of the spark plugs and they were completely black. Going to replaced, plugs, wires, distributors, rotors, coil packs, and the coolant temp sensor. Should be running like a brand new LS in no time.

 

Who did your ECU repair?

 

Change your oil ASAP. Like yesterday.

 

I second this question seeing how I might just keep my LS400 for another 6 months til prices of used cars drop a bit. Plus I'm tired of shifting the car just so I can drive it with 1/4 throttle. Been driving this way for a few years but eh, it still goes.
Also, I wouldn't change the coils unless they're known to be bad. No sense just throwing money into it with unneeded parts.

 

I got mine done by a local phone repair place. If you've got any near you, call them up and ask if they'd mind soldering some caps in an ECU.