Smoke test help (Page 2/2) ketstang SEP 20, 04:49 PM Yes, I replaced that sensor over the past weekend. quote Originally posted by Vintage-Nut: And you replaced GM 25036979 Sensor, engine coolant temperature for the ECM- yes? Edit A Tip when you check the brake booster vacuum line and IF your brake booster vacuum line will hold pressure: *Keep the cap/seal on the vacuum line at the booster end *Connect the vacuum line to the plenum/manifold *Run the engine - the high idle problem is still here or gone? IF Still Here - I bet that the booster is 'okay', but keep the cap/seal on the vacuum line at the booster end as you troubleshoot. IF Gone - Check the Booster Check Valve Gasket and as Ogre said it maybe leaking internally. Vintage-Nut OCT 13, 10:31 PM Hey 'ketstang' - did you got your high idle problem solved or.......? ketstang OCT 19, 10:40 AM I replaced the engine coolant temperature for the ECM and initially didn't think it solved my high idle problem, but after driving about 100 miles with the new sensor the idle has settled down to 800-900rpm. I am so happy to have finally found a solution. Thanks everyone! quote Originally posted by Vintage-Nut: Hey 'ketstang' - did you got your high idle problem solved or.......?