88 corvette everything new high idle been through this car over and over and cant find prob? idle stay over 1000 every possiable
Test done nothing bad no vacum nothing leaks new ecm air control motor
mas air something is telling ecm to idle up funny part is runs fine mas air unpluged Cam Idle sound lol but will not idle
600 rpm -800 when reconnect mas air any ideas in this wonderful website
If that detail comes from a scanner...then its fair to say that its a sensor issue not a mechanical problem.
This can come from dirty electrical connections to the various sensors and their grounds/power source.
1st step in diagnosing ANY eng electrical issue is to be assured of clean grounds. Locate G-104 bundle and make certain that bundle of ground wires is sterile. If there is a jumper post with hot wires clean that as well.
All sensor plugs need to be cleaned and sealed with silicone grease. The eng control comes from variable electrical resistence. Dirty or corroded contacts in plugs alters that resistence value, so the ECM alters its performance based on bad input.
You MAY have a bad eng temp sensor, or worn injectors. The scan should show the temp sensor and what its doing. Bad injectors will add too much/too little fuel and the ECM reads this thru the o2 sensor and tries to compensate.
The eng runs better with the MAF unplugged because its now running on the Cal-Pak (calibration-package in the ECM) that gives it the ability to run and get you home with a failed sensor or control servo.
What I'd do......
adjust the TPS.
Clean and test the IAC motor.
Consider replacing the o2 sensor.
Ohms test the injectors.
Clean and test the EGR valve.
Clean all harness grounds and power source leads. (NOT the battery cables, the doz or so grounds to frame from the harness.)
The most important is located near the oil filter on the block or bellhousing. <-critical point of contact.
If you are doing the work yourself, get a REAL FSM. Its the best $100 you're ever going to spend while owning a Corvette. If the shop is doing the work, make SURE they have C4 experience AND their own FSM on file or in book form, otherwise I'd pull the car out and take it to a shop that knows and understands the C4 system. Its very different than a 1990 impala or anything else. This is a plastic car. That fact makes the electrical system unique and most shops do not appreciate that or know how to diagnose the electrical system.
