I have a 1993 Lexus sc400 no mods just replaced a few parts. Problem is when I go to start the car it would run but only if keep my foot on the pedal and give it a lil gas though when I stop it would cut off but the electronics would still work like the lights on the dash, lights etc.. havent figured out why yet just have suspicions I did have to replace the battery every 3-6 months so maybe something is corroded or not attached well with the battery? Not sure..

done to the car:
Had the spark plugs and wires, timing, cooling system, intake, distrib caps, rotor buttons, gaskets, battery terminals, sealed any rips/holes, alternator and MAF sensor replaced and cleaned the lower and upper intake manifold.

 

Hello and welcome! We'll try to help. My first question is: did you actually clean your MAF sensor? Because if you did.... then it's toast. With SC300/400's and most 90's Toyotas that use a Karman-Vortex MAF Sensor you shouldn't EVER clean it!! Liquids can get get inside and permanently screw it up. This then causes an issue where it's impossible to get the car started or keep it running for more than a few seconds even with very heavy gas pedal application. You will also smell an extremely rich unburnt fuel mixture coming from the tailpipes as it attempts to run.

The only solution is to replace the actual sensor part of the MAF (not the whole aluminum housing) with a used known good working OEM unit. There are aftermarket remanufactured 1992-1997 SC300/400 MAF sensor units out there, some on RockAuto for instance, but not all are created equal and so far I still find that the OEM units if still in good working condition are the best.

So long as they are never cleaned or waterlogged in any way they tend to last near indefinitely. But... once you clean them they will be toast.

After having done that entire tuneup the thing I would immediately suggest IF you did clean your MAF sensor with any kind of liquid at all is to find a good working replacement sensor from eBay using the same part number embossed on its plastic casing. Some years of the GS300 also used that same sensor.

Also I would recommend getting new Denso O2 sensors for your model year AFTER you have found and installed a new good working OEM MAF sensor part (again, you do not need the whole aluminum housing, just the sensor unit itself).

I hope this helps!

 

oh oops my apologies i worded it wrong. I meant I had all those parts replaced and the only thing I cleaned was just take intake manifolds. Also the MAF sensor was Fr eBay as well lol I have 3, 2 from parted sc400 and 1 new from eBay I used the new and tested with all 3 and did even tried testing without the MAF sensor

ALTHOUGH I did leave my car outside with no cover and it did rain a lottt just sitting there for about 4 months and ran perfect for a week after I replaced some parts but stopped for another 2 months and counting

 

Unless you left the hood off and allowed rain to pour all over the unguarded engine you were fine to leave the car outside.

As long as you have tested more than one MAF sensor (and good that you have at least one good spare just in case it will ever be needed) my next question is, have you ever had the ECU sent in for new capacitor replacement servicing? If you have not then that is the very next thing I recommend that you do as this is more than likely your problem.

Main ECUs suffering from tired or leaking old capacitors tends to be such a common thing now given the age of these cars we recommend sending your ECU in for the capacitor refresh servicing even if there are no issues just to get ahead of it. Sometimes malfunction symptoms show up gradually and sometimes they manifest quickly. In some cases phantom CEL codes show up that, upon attempted diagnosis, lead to no actual culprit at all.

It's a very common thing to re-cap an SC300/400 ECU to give the brain of the car a new healthy baseline again. Once done as long as the board traces are all intact or were able to be repaired to normal function the ECU will be good for another 20-30 years of malfunction-free service.

Tanin Auto Electronix who have been helping our SC community for over 20 years can perform this ECU repair service by special request. Also there is SIA Electronics who do the same type of service.

Both companies will be using the same high quality brand name and electrical value capacitors that originally came in these ECUs.