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Intermittent high idle I've been chasing for a month
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Jahagafut
New User
Jun 28, 2023, 7:08 AM
Post #1 of 7
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Intermittent high idle I've been chasing for a month
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I've got an 03 Buick Lesabre, 3800 Series II, predictably after an hour of driving the idle starts to get high, it used to go to 3500 but I've since replaced the parts I'll list at the end and it now hangs out around 1800. Sometimes I can sit parked and it goes back to 700 for a minute. If you let it sit turned off it will go back to 700 but quickly start idling high again unless its sat long enough to cool down. I'm thinking either the ECU has circuits that are separating once very heated up, or that there was a leak between the upper intake manifold and the throttle body that opens up under heat, and since I've replaced the intake manifold it's dealt with half of the high idle but the TB is warping under heat, though it's made of steel and has a brand new gasket. I've been to a shop to read live data and he said sensors all look normal but he thinks he hears a vacuum leak but can't find it listening with a tube and we sprayed lots of brake cleaner everywhere and noticed no different idle from sucking it in. I've also played around with the vacuum hoses I could find and hose clamped the slightly warped brake booster line Here's what I've replaced Upper intake manifold and gasket Throttle body gasket and throttle plate cleaning Throttle Position Sensor Idle Air Control Valve MAF sensor MAP sensor PCV Valve Spark plugs Spark plug wires Coil packs Fuel pressure regulator Fuel filter Injectors Trans fluid and filter Air filter Oil and filter Thermostat Radiator cap Engine coolant temperature sensor Removed and cleaned EGR valve Parts I have but haven't installed: Oil pressure sensor Crankshaft sensor Camshaft sensor O2 sensors There are no OBD codes except when I first got the car there was a stored code for the rear o2 sensor circuit low .
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Hammer Time
Ultimate Carjunky
/ Moderator
Jun 28, 2023, 7:41 AM
Post #2 of 7
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Re: Intermittent high idle I've been chasing for a month
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The first thing I hope you have learned by now is that you don't fix problems by throwing parts at them. I would do a smoke test to look for any leaks. You can determine determine if the temp sensors are reading correctly by looking at data in the scan tool. Wiggle the sensor wires around while watching the temp values, especially while the problem is occuring. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Jahagafut
New User
Jun 28, 2023, 7:58 AM
Post #3 of 7
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Re: Intermittent high idle I've been chasing for a month
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The parts were purchased after I thought I had fixed the issue, just general maintenance I wanted to do to bring the car back to good operating status. The sensors and wiggling I've done, and as for a smoke test are they able to perform that while it is running and in that state? It only happens after a whole
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Hammer Time
Ultimate Carjunky
/ Moderator
Jun 28, 2023, 8:01 AM
Post #4 of 7
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Re: Intermittent high idle I've been chasing for a month
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No, the car is smoke tested with the engine off. Those parts you replaced were not maintenance. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
(This post was edited by Hammer Time on Jun 28, 2023, 8:02 AM)
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Jahagafut
New User
Jun 28, 2023, 9:12 AM
Post #5 of 7
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Re: Intermittent high idle I've been chasing for a month
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All of that was maintenance I wanted to do with money I had except for the engine coolant temp sensor Leaking intake manifold Dead MAF Seized IAC Original plug wires and coils Black oily plugs Worst air filter I've seen Leaking fuel pressure regulator Original PCV MAP was cheap Original trans fluid and filter Plugged fuel filter Filthy throttle body Sticking TPS Original dirty injectors Crank and Camshaft sensors and oil pressure unit six to they cost hardly anything so I bundled them for backups Leaking radiator cap Original thermostat Just because I had the money and wanted to overhaul the engine doesn't make it not regular maintenance.
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Hammer Time
Ultimate Carjunky
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Jun 28, 2023, 9:16 AM
Post #6 of 7
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Re: Intermittent high idle I've been chasing for a month
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You should include the mileage with your question. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Jahagafut
New User
Jun 28, 2023, 9:18 AM
Post #7 of 7
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Re: Intermittent high idle I've been chasing for a month
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Yeah I should have, it's 250,000km
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