Hi, this car is kicking everyone s ass.. 92 lexus sc400. 128k. Super broadcast car that I am ready to drive off a cliff. had a idle surge difficulty that I researched online and did tests (per the manual) upon tps, iac and maf and cleaned the TB. After trying 2-3 every second 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. back to the dealer.. this epoch he says, it needs a ECU. I did a lot of research on them, and found that its a common trouble taking into account this car.. bought a used one.. more trouble. had the native 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 habit to be re-adjusted? The master tech did all sorts of diagnostics upon every amalgamated parts (tps, maf, iac). 0-200 all mature I bow to it do the dealer for diagnostics.. on going problems are truly adding up. I m undecided to adjoin the tps if he had it dialed. Any insight? Thanks in advance. Jason
Its furthermore worth getting the fuel pressure checked as if this is low due to a blocked filter or faulty regulator or even a not at your best pump will all repercussion in insufficient fuel monster delivered to the engine. Might plus be worth cleaning out the idle eagerness direct motor / valve as these get clogged in the works past carbon and some brake cleaner washed through helps clear things off.
have you looked into throttle body coking and/or combustion chamber/valve carbon buildup? are you up to date upon 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 proceed many factors may cause the same symptom(s)