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bigmac8
New User
Feb 24, 2013, 10:35 AM
Post #1 of 10
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90 Lumuna runs badly
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Have 176,00 miles on 90 Lumuna. Car runs good with water sensor disconnected. With sensor connected it hardly will run. 3.1 engine
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speed
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Feb 24, 2013, 10:59 AM
Post #2 of 10
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Re: 90 Lumuna runs badly
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Replace your coolant temp sensor then, if it runs better unplugged its obviously telling a bad reading to the computer
GM ASEP 26 SCC Milford ASE certified in Brakes and Electrical on Thursday April 5th 2012
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Discretesignals
Ultimate Carjunky
/ Moderator
Feb 24, 2013, 11:28 AM
Post #3 of 10
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Re: 90 Lumuna runs badly
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Car or Van?
When you unplug the sensor, it will also cause the computer to increase injector pulse adding more fuel to the engine. If the engine is running lean for some reason, you might be hiding the problem by disconnecting the ECT sensor.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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bigmac8
New User
Feb 24, 2013, 11:31 AM
Post #4 of 10
(1556 views)
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Re: 90 Lumuna runs badly
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Lumuna Car
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Sidom
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/ Moderator
Feb 24, 2013, 11:32 AM
Post #5 of 10
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Re: 90 Lumuna runs badly
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I kinda agree with DS here....
Which sensor are you talking about? The coolant temp defaults to -40 when disconnected so that shouldn't make it run better....
I've had a few in the year range that had bad coolant level sensors in the radiator short out & pull down the ref voltage......Those if you disconnect when their bad will make the engine run better....
Is the check engine light on?.....If it is, pull the codes on it..
(This post was edited by Sidom on Feb 24, 2013, 11:33 AM)
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bigmac8
New User
Feb 24, 2013, 11:44 AM
Post #6 of 10
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Re: 90 Lumuna runs badly
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With the water temp. sensor connected the engine light doesn,t come on.
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Sidom
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Feb 24, 2013, 12:28 PM
Post #7 of 10
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Re: 90 Lumuna runs badly
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Well as it's already been said, when that sensor is disconnect it will default to a very cold temp which get the comp to add more gas.....So usaully unhooking this sensor will make the engine run worse if everything is good..
Does the check engine light ever come on?.....With the key on & engine off? When the temp sensor is disconnected?
I don't know what kind of tools you have to use on this but you probably what to look at a datastream to see what temp the sensor is showing and some other data to see if it's running lean....
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speed
User
Feb 24, 2013, 12:48 PM
Post #8 of 10
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Re: 90 Lumuna runs badly
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Sidom doesnt the ECM default to calibration for that sensor when it sees that reading because it knows for a fact it is inaccurate when its the low i think it defaults to -40 doesnt it? so it tells the computer its invalid and it goes to a default setting like open loop?
GM ASEP 26 SCC Milford ASE certified in Brakes and Electrical on Thursday April 5th 2012
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Hammer Time
Ultimate Carjunky
/ Moderator
Feb 24, 2013, 1:05 PM
Post #9 of 10
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Re: 90 Lumuna runs badly
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Speed...............Even open loop doesn't ignore the CTS.
Please stop derailing threads by asking your own questions.
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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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Sidom
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Feb 24, 2013, 1:18 PM
Post #10 of 10
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Re: 90 Lumuna runs badly
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Yea that's exactly what it does. The coolant temp is a primary input, so the comp goes with that reading and if it really was that cold out then the engine would need a lot more fuel to run right . In the summer this can actual cause a no start due to too much fuel.
You would think the pcm would look at the air temp sensor and realize something wasn't right and maybe adjust for that but the air temp isn't a primary input so it goes with ECT reading...
So with this engine...If everything was good, when he disconnected the ECT you would see the temp in the datastream go to -44 degrees and it should go real rich and run bad.....Now if there was a big vacuum leak, restricted fuel filter, weak pump....something causing a real lean condition making the engine run bad, disconnecting that sensor would add more fuel, compensate for the lean condition and it would run good...
I haven't pinged the OPs location but I suppose if he was at then North pole and it really is -40 out and the sensor is skewed high where it is saying it 100 degrees then disconnecting would make it run better.
Thats why I asked him about the coolant level sensor in the radiator.....That sensor uses the 5v ref and I seen a few of those go bad & pull the ref voltage down to 2.5v and the engines run real bad until you disconnect the bad sensor...
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