Rough Idle - Mazda 6 Forums : Mazda 6 / Mazda Atenza Forum

kidklone03 · 10-02-2009, 01:07 PM

Hey guys, I have a 2003 2.3L 4 cylinder with 150,000+ miles. Lately, I've had a very rough idle where my car has stalled a few times, but it mostly jerks when I am stopped at a light because the idle is revving on its own. I cleaned the MAF and that didn't seem to do anything. I'm going to try to look at the IAC and the EGR over the weekend, but I'm not sure of either are going to fix my problem. Anyone have any thoughts on what may be the problem?

MrTea · 10-02-2009, 02:13 PM

any other symptoms? nothing at full throttle or heavy load? start all of a sudden or slowly getting worse?

3 key things for your issue are: MAF, vacuum leak & TB issue

you've checked the MAF, so good there. have you checked all the rubber lines that go to the manifold and the boots for the intake? after 140k something might have dried out or developed a tear? it's hard to troubleshoot the tb, some just have issues at some point and you have to deal with the problems of our electric tb's.

plugs COULD be an issue, but typically you can feel them at heavy load as well.

kidklone03 · 10-02-2009, 04:43 PM

Thanks for the help. Car runs great at high speeds (anything over 30mph). My problem is only at idle. After I cleaned the MAF, the idle seemed fine but as the engine warmed up, it became more rough. I do have a vacuum leak somewhere because there is a squeal sound but I can't locate it. Maybe it's the intake gasket? I checked a few of the vacuum hoses near the intake and they all seem fine. I know the vacuum leak is a problem, but I'm not sure it's related to the rough idle problem. I had a P0171 CEL, but that was erased when I unhooked the battery to clean the MAF. That CEL is probably related to the vacuum leak. I didn't have time to take the TB off to inspect it but I took the accordion air hose off and the throttle body looked fine from that end.

MrTea · 10-02-2009, 05:54 PM

well, the vacuum leak is most likely your MAIN problem, not just part of it. the reason idle is ok when it's cold is the ecu bumps up rpm's, just like when driving, you won't see a small leak when you are on the gas. the issue comes down to low rpm, low air velocity and the ecu trying to make sure the right amount of air keeps the car running. as the air gets in the leak, it leans out, ecu sees this and adds more fuel so it revs a tad and gets normal, cuts back fuel and then it's lean again....and so on.

so take the time to figure out where it's coming from and that will solve your problem.

10-02-2009, 02:13 PM	#2 (permalink)
MrTea Super Moderator Join Date: Mar 2003 Location: Huntington Beach, CA Posts: 8,139 Thanks: 0 Thanked 1 Time in 1 Post Groans: 0 Groaned at 0 Times in 0 Posts iTrader: 0 reviews	any other symptoms? nothing at full throttle or heavy load? start all of a sudden or slowly getting worse? 3 key things for your issue are: MAF, vacuum leak & TB issue you've checked the MAF, so good there. have you checked all the rubber lines that go to the manifold and the boots for the intake? after 140k something might have dried out or developed a tear? it's hard to troubleshoot the tb, some just have issues at some point and you have to deal with the problems of our electric tb's. plugs COULD be an issue, but typically you can feel them at heavy load as well. __________________ '03 Lapis(mostly) 6i...Tranny swap by Gillis Motorsports : MTX-75 5speed tranny, 4.06 gears, Torsen LSD & chromoly axles, Engine build by Gillis Motorsports: 9:1 Supertech Pistons, Crower rods, Supertech valves, springs & retainers, ARP head & main studs, F2 Stage2 Turbo, Custom F2 engine/tranny mounts, 3" Turboback exhaust, Tein Basic Coilovers, Brembo Big Brake Kit and Rotora Rear Rotors, RacingBeat Front & Rear Sways, Seibon OEM hood, VF Engineering rear engine mount, Powdercoated Valvecover, TEIN hood dampers, Some sort of Body Kit from some company usually last dyno 8/23, 10psi...260HP/267TQ Still need: Seat, cage, Gillis suspension...then i'm DONE!!

10-02-2009, 05:54 PM	#4 (permalink)
MrTea Super Moderator Join Date: Mar 2003 Location: Huntington Beach, CA Posts: 8,139 Thanks: 0 Thanked 1 Time in 1 Post Groans: 0 Groaned at 0 Times in 0 Posts iTrader: 0 reviews	well, the vacuum leak is most likely your MAIN problem, not just part of it. the reason idle is ok when it's cold is the ecu bumps up rpm's, just like when driving, you won't see a small leak when you are on the gas. the issue comes down to low rpm, low air velocity and the ecu trying to make sure the right amount of air keeps the car running. as the air gets in the leak, it leans out, ecu sees this and adds more fuel so it revs a tad and gets normal, cuts back fuel and then it's lean again....and so on. so take the time to figure out where it's coming from and that will solve your problem. __________________ '03 Lapis(mostly) 6i...Tranny swap by Gillis Motorsports : MTX-75 5speed tranny, 4.06 gears, Torsen LSD & chromoly axles, Engine build by Gillis Motorsports: 9:1 Supertech Pistons, Crower rods, Supertech valves, springs & retainers, ARP head & main studs, F2 Stage2 Turbo, Custom F2 engine/tranny mounts, 3" Turboback exhaust, Tein Basic Coilovers, Brembo Big Brake Kit and Rotora Rear Rotors, RacingBeat Front & Rear Sways, Seibon OEM hood, VF Engineering rear engine mount, Powdercoated Valvecover, TEIN hood dampers, Some sort of Body Kit from some company usually last dyno 8/23, 10psi...260HP/267TQ Still need: Seat, cage, Gillis suspension...then i'm DONE!!

10-02-2009, 01:07 PM	#1 (permalink)
kidklone03 Learners License Join Date: Sep 2009 Posts: 3 Thanks: 0 Thanked 0 Times in 0 Posts Groans: 0 Groaned at 0 Times in 0 Posts iTrader: 0 reviews	Hey guys, I have a 2003 2.3L 4 cylinder with 150,000+ miles. Lately, I've had a very rough idle where my car has stalled a few times, but it mostly jerks when I am stopped at a light because the idle is revving on its own. I cleaned the MAF and that didn't seem to do anything. I'm going to try to look at the IAC and the EGR over the weekend, but I'm not sure of either are going to fix my problem. Anyone have any thoughts on what may be the problem?

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10-02-2009, 04:43 PM	#3 (permalink)
kidklone03 Learners License Join Date: Sep 2009 Posts: 3 Thanks: 0 Thanked 0 Times in 0 Posts Groans: 0 Groaned at 0 Times in 0 Posts iTrader: 0 reviews	Thanks for the help. Car runs great at high speeds (anything over 30mph). My problem is only at idle. After I cleaned the MAF, the idle seemed fine but as the engine warmed up, it became more rough. I do have a vacuum leak somewhere because there is a squeal sound but I can't locate it. Maybe it's the intake gasket? I checked a few of the vacuum hoses near the intake and they all seem fine. I know the vacuum leak is a problem, but I'm not sure it's related to the rough idle problem. I had a P0171 CEL, but that was erased when I unhooked the battery to clean the MAF. That CEL is probably related to the vacuum leak. I didn't have time to take the TB off to inspect it but I took the accordion air hose off and the throttle body looked fine from that end.