Meat

My 93 LS400 ran great until a few weeks ago. I started it leaving work and it was down on power. Felt like it was running on 4 cylinders. I got it home and replaced both coil packs. It ran great again. Well, for the 30 minute commute to work anyway. As I was pulling up to work it felt like it missed or something briefly. I shut it off and went inside.

Later on, I cranked it and it would fire for a split second, then die immediately. It repeated this a dozen times, then fired. I drove it home and it ran fine. The next day, it again ran great for the 30 minute commute, then died down the street from work. It fired right up, drove a few feet, then died again. It did this a few times until I go tg into the parking lot. After work it fired up immediately but died 4 times before I got out of the parking lot. It fired up again and drove fine. I decided to try to get it home. Made it almost all the way, but it died on the freeway and I had it towed home.

I replaced the fuel pump, but nothing. I checked the crank sensor and it's on tight. I bypassed the fuel pump resistor (FP & B+) and could hear the fuel pump loud and clear. It would still fire for a split second, then die immediately. Without bypassing the resistor I can't hear the fuel pump. Bypassing it, it's loud and clear. But does the exact same thing either way.

I'm about to drive (push) this thing off a damn cliff!!

Yamae

Why don't you replace the fuel filter?

bradland

Agree with Yamae...
Fuel filter is the first thing that entered my mind when I read the symptoms.

dicer

And you can't check a ckp or cps by looking at it. You ask is it a fuel issue? Pressure check time.

Meat

Fuel filter was also replaced. I don't know all the acronyms on here so I don't know what "ckp or cps" means.

deanshark

CKP = Crankshaft Position Sensor

CPS = Camshaft Position Sensor

Yamae

Have you checked the ECU measuring the ripple voltage?

Moarpower

Might not even be fuel. If it smells rich at all you likely have a spark problem.

So caps, rotors, leads plugs. Also co sixer that injectors may be dirty.

Meat

Update: I used a jumper clip to read the code. Code 15 ignition coil. Both coils were replaced, so I'm at a loss. I remember reading something about a similar issue involving a wire behind the glove box that triggered a Code 15, but now I can't find the post.

fsuguy

"My 93 LS400 ran great until a few weeks ago. " - then you replaced the coils - check the coils you removed to see if they are out of spec - there should be some resistance values for the primary and secondary windings on both coils. It the measurements on the removed coils are out of spec, then you may need to check your work on the replaced coils - are the connectors fitted on tightly and correctly, etc.

For what it's worth, sometimes these coil connectors which are plastic become brittle and can break when you push them onto the pins, often resulting in incomplete connection, even though it may look like it is connected on the outside.

Good Luck.

timmy0tool

iTrader: (7)

also what coils did you replace them with? OE (original equipment - Toyota/Lexus) or aftermarket replacement?

dicer

Look on youtube for the igniter test, that would also test the coil if memory serves. If all that is good next is to check for signal that triggers it all, that starts at the cps, ckp.