New member/operating issue
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CF Beginner
Joined: Oct 2018
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New member/operating issue
Hello all! New to this forum here. I joined the Chevy Malibu forums but there isn’t a lot of activity going on these days over there I guess, so I’m 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 “reduced engine power” message. I just recently cleaned the throttle body (didn’t 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 don’t 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)
CF Monarch
Joined: Oct 2017
Posts: 4,605
Likes: 269
From: USA
Hello all! New to this forum here. I joined the Chevy Malibu forums but there isn’t a lot of activity going on these days over there I guess, so I’m 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 “reduced engine power” message. I just recently cleaned the throttle body (didn’t 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 don’t 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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CF Beginner
Joined: Oct 2018
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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. I’m going to get some MAF and throttle body cleaner and replace the air filter and hopefully that’ll do the trick. If not I’ll replace the MAF.
CF Monarch
Joined: Oct 2017
Posts: 4,605
Likes: 269
From: USA
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. I’m going to get some MAF and throttle body cleaner and replace the air filter and hopefully that’ll do the trick. If not I’ll replace the MAF.
however. Wix, Purolator and AC Delco filters are much better.
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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.
CF Monarch
Joined: Oct 2017
Posts: 4,605
Likes: 269
From: USA
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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CF Beginner
Joined: Oct 2018
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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 it’s course. Ran some throttle tests, for example slowly increasing the RPM to 3k. There are some dead spots around 1500rpm where it sputters. It’s also likes to just quit when letting off the throttle.
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CF Monarch
Joined: Jul 2011
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From: kevinkpk
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.
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.