My wife reports the engine running rough and the yellow check engine light flashing.

No previous problems ever with this 1996 LS400. Low mileage.

Any thoughts? Approaches?

Thanks.

 

I have the same issue on my 99 es 300 smells a little foul too

 

Your car has the OBDII system and much more complex to check than the 1990-94 LS400. You will have to have the check engine light code read to find out what your issue is. There could be a number of reasons your car is running poorly.

From the DIY Lexus site...

If you have a 1995 LS on up then you have an OBDII system. Reading codes from these systems requires you to use an OBDII code reader. They typically run around $100. They're not cheap but they can provide many more codes and this makes diagnosis easier. All you need to do is plug the scan tool into the diagnostic port and it displays any codes.

 

Your car has a misfire. Keep driving like that and you will fry the catalytic converter. A flashing CEL is bad news. You might have a bad ignition component (cable, plug wire) or fuel injector.

 

hes right about that thats why normally it doesnt flash thats like saying just get around to fixing it haha but when it is flashing its saying fix me or im going to cost you more money autozone and advance autoparts usually scan obd2 96 up in most cases ,for free

 

I got a 1996 ls400 and when I start it it idles rough in park and neutral where the rpm’s fluctuate, and when I put it in reverse or drive, the idle stops fluctuating, but when it’s in parking in neutral it fluctuates, and my speed on my speedometer is stuck at 20 and when I drive it, my throttle response is awful and it bucks all around and then it doesn’t accelerate I replaced plugs and wires and I have no clue what else to do. It also sounds like there’s a clicking sound at the fourth plug on the passenger side. Any ideas I’ve never had this problem before? And it won’t let me read the codes of my code reader. It just says error, and the check engine light flashes rapidly when idling.

 

I can't help with diagnosis other than to tell you that a blinking CEL denotes immanent engine damage if it's continued to be driven. In most cases, the damage occurs to the emission control system in general, damage to the catalytic converter in particular. I've had a blinking CEL on two different vehicles. In both cases, it was fuel related; one had a stuck open injector, the other was an injector that was plugged (GM CPI is known for this).

In your case, not being able to read trouble codes is a red flag. I would locate another code reader and try to read them again to confirm your reader is functioning properly. There is an alternate method of reading the stored codes (do an internet search for the method).

I would also try determine why you're getting a clicking sound in No. 4 plug; sounds like voltage is arcing to ground before it gets to the plug. A misfire like this would cause the O2 sensors to read a severely rich condition (unburned fuel) and cause a blinking CEL.