Hi, this car is kicking everyone s ass.. 92 lexus sc400. 128k. Super present car that I am ready to drive off a cliff. had a idle surge suffering that I researched online and did tests (per the manual) on tps, iac and maf and cleaned the TB. After infuriating 2-3 alternative used IAC s, I took it to the master tech at lexus. He said it was the IAC valve. He tried my used ones.. and finally a rebuilt one. yet had issues. encourage to the dealer.. this become old he says, it needs a ECU. I did a lot of research upon them, and found that its a common hardship when this car.. bought a used one.. more trouble. had the indigenous one rebuilt by a specialist.. and that s where I am at now.. Put it in tonight and the car idles at 2k rpm. Does the TPS compulsion to be re-adjusted? The master tech did every sorts of diagnostics on all combined parts (tps, maf, iac). 0-200 every mature I put up with it complete the dealer for diagnostics.. upon going problems are in point of fact appendage up. I m unsure to be adjacent to the tps if he had it dialed. Any insight? Thanks in advance. Jason
I did re-check them tho. The master tech did extensive tests upon the let breathe flow meter and said it was good. later I unplug it and direct the motor, the car runs scratchy and at 850ish. I can only guess that my other rebuilt ecu has an issue, or the tps needs to be re-adjusted, or somehow my maf has died in the midst of all this. I don't think the tps has that much govern in the substitute of rpm though? I think it single-handedly adjusts it just about 1k..
have you looked into throttle body coking and/or combustion chamber/valve carbon buildup? are you in the works to date on every maintenance; spark plugs fuel filter pcv vlave etc? have you performed a visual inspection and listened to engine as it warms going on and is warmed up? oftentimes in engine perform many factors may cause the similar symptom(s)