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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
(893 views)
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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
(887 views)
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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.
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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
(884 views)
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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
(881 views)
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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
(868 views)
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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
/ Moderator
Jun 28, 2023, 9:16 AM
Post #6 of 7
(864 views)
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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
(861 views)
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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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