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New member/operating issue

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Old October 30th, 2018, 9:00 AM
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Hello all! New to this forum here. I joined the Chevy Malibu forums but there isnít a lot of activity going on these days over there I guess, so Iím hoping you seasoned veterans could help me out. Just recently I purchased a 2004 Chevy Malibu Maxx 3.5 liter. I just had this issue yesterday with a rough idle, between 700-1200rpm, until it warmed up and smoothed out. The next morning, more erratic idle, and the ďreduced engine powerĒ message. I just recently cleaned the throttle body (didnít remove it, just sprayed with carb cleaner) and replaced 4 of 6 plug wires. These engines have an electronic throttle body, so is there an IAC valve? Could the throttle body is TPS be the issue? I donít have any codes read yet as the check engine light was already on due to the coolant/engine not reaching a certain temp by a certain time (P0128)
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Old November 2nd, 2018, 2:41 AM
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Originally Posted by 04malimaxx View Post
Hello all! New to this forum here. I joined the Chevy Malibu forums but there isnít a lot of activity going on these days over there I guess, so Iím hoping you seasoned veterans could help me out. Just recently I purchased a 2004 Chevy Malibu Maxx 3.5 liter. I just had this issue yesterday with a rough idle, between 700-1200rpm, until it warmed up and smoothed out. The next morning, more erratic idle, and the ďreduced engine powerĒ message. I just recently cleaned the throttle body (didnít remove it, just sprayed with carb cleaner) and replaced 4 of 6 plug wires. These engines have an electronic throttle body, so is there an IAC valve? Could the throttle body is TPS be the issue? I donít have any codes read yet as the check engine light was already on due to the coolant/engine not reaching a certain temp by a certain time (P0128)
Replace/clean the IAC motor (frankly I'd just get a new one) and if that doesnt work, then throttle position sensor . I'd clean the MAF out as well.
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Old November 2nd, 2018, 6:31 AM
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I was able to get the car to act up again...rough idle, stall, and throw a DTC. All leading to a malfunctioning MAF. I blew it out with air, cleaned the connection, reset the system, and it started and ran fine. This morning, started the funny idle again. Iím going to get some MAF and throttle body cleaner and replace the air filter and hopefully thatíll do the trick. If not Iíll replace the MAF.
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Old November 2nd, 2018, 9:43 PM
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Originally Posted by 04malimaxx View Post
I was able to get the car to act up again...rough idle, stall, and throw a DTC. All leading to a malfunctioning MAF. I blew it out with air, cleaned the connection, reset the system, and it started and ran fine. This morning, started the funny idle again. Iím going to get some MAF and throttle body cleaner and replace the air filter and hopefully thatíll do the trick. If not Iíll replace the MAF.
Sounds like a good plan. I would stay away from Fram filters
however. Wix, Purolator and AC Delco filters are much better.
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Old November 2nd, 2018, 10:16 PM
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Throttle body and MAF cleaner was no go. Still horrible idle. I ended up getting a fram filter. I watched a video on YouTube of a mass air flow sensor malfunctioning, saying that if you unplug a working MAD sensor, the engine should shut right off. And if the MAF is malfunctioning, it would stay running. How true is this theory? Mine stays running after unplugging.
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Old November 3rd, 2018, 3:48 AM
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Originally Posted by 04malimaxx View Post
Throttle body and MAF cleaner was no go. Still horrible idle. I ended up getting a fram filter. I watched a video on YouTube of a mass air flow sensor malfunctioning, saying that if you unplug a working MAD sensor, the engine should shut right off. And if the MAF is malfunctioning, it would stay running. How true is this theory? Mine stays running after unplugging.
Yes it will run unplugged in open loop mode, It wont run properly but it will run. I'm not a fan of Fram oil filters, (check out the Youtube vids on how cheaply they are made) but their air filters are okay.
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Old November 3rd, 2018, 2:49 PM
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Replaced the mass air flow sensor...still the same idle issue on startup. Up and down idle. I let it run for about 10 minutes to let it just run itís course. Ran some throttle tests, for example slowly increasing the RPM to 3k. There are some dead spots around 1500rpm where it sputters. Itís also likes to just quit when letting off the throttle.
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Old November 3rd, 2018, 4:10 PM
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The engine will run in closed loop mode without the MAF, won't run correctly, but will not or should not die. It will adjust fuel/air from the last data, biggest issue is large temp difference since the last data, and current conditions.
The throttle position sensor is nothing more than a reostat (expensive one at that). If the wiper moves to a bad spot on the resistor it can cause fluctuations either side of the resistor, in other words the dead spot can be causing intermittent or no signal to the pcm. If you have a ohm meter you can test it. I replaced one on my 3.1 because of this issue, around 50 bucks.
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Old November 3rd, 2018, 7:17 PM
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I wish my throttle body was $50. The one for my car is $130 on rock auto. Was kind of hoping to not have to replace that and that something else would fix the issue.
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Old November 3rd, 2018, 7:54 PM
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Is the throttle position sensor not replaceable?
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