93ls400gc

I just bought this car on EBay. It was a one owner with 81k miles. From 2002 to 2011 the car only went 23k miles in 9 years. The car had a strange slight pulsation when speed leveled out. It idles smoothly and accerlates sometimes without a problem. Soon after it arrived the water leaked so we replaced the pump, thermostat and belt, tensioners, pulleys. We also did a complete tune up: NGK iridium/platinum plugs, Bosch silicone wires, Bosch dual distributor caps, rotors, both coils were replaced, pcv, fuel filter.

This did not fix the problem so I sent the ECM to be checked out, they said they changed some capacitors (who knows) - did not fix the problem. I ohm 6 of the 8 injectors and they all showed the same. I used Lucas and Miracle oil in gas... did not help.

I recently took it to Germain Lexus in Dublin Ohio and their trouble shooter technician diagnosed it as a TPS sensor... did not fix the problem. They told me they could no longer help.

I started using Sea Foam and it seems to helping. I have driven 300 miles and it still has a little mis-fire. Today at freeway speed, under cruise control I was going uphill and it miss-fired a couple of times. I have had cars with coil pack failure and this feels like that type of problem but I have changed everything I can think of electrically. Could it be a fuel injector and will Sea Foam fix it???

deanshark

It's the mysterious stumble and hesitation that most of the older LSs have, including mine. If ya fix it, let us know. Check (Ohm) your AFM to see if it's in spec. And 1 more thing you can change is the ECT, I don't know if it will fix this problem but it will help revive the engine a little and also give ya better gas mileage. Use the search feature at the top of the page and you'll get alot of helpful info. Welcome to CL. This might help you a little. https://www.clublexus.com/forums/sc-...on-issues.html

johnnyg66

Yep, my 92 does that only when in 3rd gear. When its in overdrive it don't have that same feeling. I have done all the usual checks nothing. It is so slight now i don't even care and i only leave it it in OD.

Best of luck.

93ls400gc

UPDATE... Sea Foam has improved the misfire by 80 percent. It's only been approx 300 miles since using the additive...so I hope it will continue to improve. It accelerates much better but at freeway cruising speed you can still feel something... a slight misfire maybe. What role does the fuel pressure regulator play in this???

I forgot to mention in my original posting... I only notice the problem when the car reaches normal operating temps. I don't notice it when its the engine is cold. My analog gauge shows normal just below half way.

longuyen88

Did you try seafoam through the brake booster? Any updates? My car does the same thing

93ls400gc

UPDATE... I installed OEM wires and a new EGR valve. It stall had a misfire and I discovered the EGR has a vacuum leak. I cleaned my old EGR and installed it. It ran better but I am awaiting the new EGR to see if this is the final part needed to correct the misfire.

Has anyone had this type of problem and it was the torque converter or transmission. Does this car have a computer for the transmission only?

longuyen88

I seafoamed my car through the brake booster and added 1/2 bottle to the gas tank. It runs about 90% better. It felt so good that I decided to give it a second seafoam treatment via brake booster and a whole can in the tank the second time around about about 200 miles of driving. After the second treatment, it runs better still!

My car was driven by the original 80 year old owner for 93k miles, so I think it just needs a good cleaning. Please update the thread once you replace the EGR.

Thanks!