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Idle Stumble During Warmup


CapnJack

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Hey all!

 

I've run into a problem recently with my 07 LGT 5MT. This seems to happen when it's below 20 degrees. When the car is cold (blue light on), it idles great about 1100 RPM. From the time the blue light goes off to when it reaches operating temperature, when the car is idling, it has a real lumpy idle at about 500 RPM. The car will rev up just fine and accelerate just fine from this state. Once the engine reaches full operating temperature, the idle is normal again at about 900 RPM. This was all on a factory map.

I thought the problem might be with the factory map so I loaded a stage 1 map on it and the problem remains. I've also treated the gas tank with seafoam without success. Any ideas what it might be? It's not throwing any codes.

Help!

 

Edit - This problem seems to have started since the dealer did a coolant system flush, but could be coincidence since they did it right before it got cold.

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Hey all!

 

I've run into a problem recently with my 07 LGT 5MT. This seems to happen when it's below 20 degrees. When the car is cold (blue light on), it idles great about 1100 RPM. From the time the blue light goes off to when it reaches operating temperature, when the car is idling, it has a real lumpy idle at about 500 RPM. The car will rev up just fine and accelerate just fine from this state. Once the engine reaches full operating temperature, the idle is normal again at about 900 RPM. This was all on a factory map.

I thought the problem might be with the factory map so I loaded a stage 1 map on it and the problem remains. I've also treated the gas tank with seafoam without success. Any ideas what it might be? It's not throwing any codes.

Help!

 

Edit - This problem seems to have started since the dealer did a coolant system flush, but could be coincidence since they did it right before it got cold.

 

I'm new to this forum, but is there a way to perform a idle air relearn on the ECU? That should solve this issue...especially after switching out maps.

 

Good luck.

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****! Car was doing it again today, -8 F out there. Was driving my car home, about 15 mins into the trip and bam, Car goes from S# to S, Traction control goes off, Check engine light comes on and Cruise starts flashing. Had to finish the trip home, another 10 mins (no place to park it) and then I pulled the codes, PO171, PO303 and PO304, Fuel trim Malfunction, Cylinder 3 & 4 misfire. Fan-friggin tastic, had the car in the Subaru Dealer on Monday too...

 

Check your car man

JDM'd All to hell

:cool:

Thanks Jimmy @ Hkc-Speed.com!

RIP Coxx & Thanks

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I got the same thing yesterday morning. The car started idling really rough and then died. I got the P0171, P0301, P0302, and P0303. I pulled the TMIC off this morning looking for the blue T fitting that tends to pop off and can't find it. I've also pulled the MAF sensor and it looks a little dirty.

The one thing I did notice is that when I pulled the BOV there was ice built up on it???

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****! Car was doing it again today, -8 F out there. Was driving my car home, about 15 mins into the trip and bam, Car goes from S# to S, Traction control goes off, Check engine light comes on and Cruise starts flashing. Had to finish the trip home, another 10 mins (no place to park it) and then I pulled the codes, PO171, PO303 and PO304, Fuel trim Malfunction, Cylinder 3 & 4 misfire. Fan-friggin tastic, had the car in the Subaru Dealer on Monday too...

 

Check your car man

 

 

Did you ever take your car in to see if they could track down the issue?

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Yup, just got the car back today, I had to have it flatbedded. MAF shit the bed and royally f'd my air fuel mixture, which leaned the car out and pretty much acted like frozen lines. Since your MAF looked dirty I'm gonna say that it most likely is the problem.

JDM'd All to hell

:cool:

Thanks Jimmy @ Hkc-Speed.com!

RIP Coxx & Thanks

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  • 2 weeks later...
I had the same symptoms followed by the same check engine light. The dealer pulled the code and bank one was rich. They tested everything and everything came back in spec. Even drove it around while monitoring everything. The only item of note is that the MAF was just within spec; borderline. But because it was within spec they didn't replace it or anything else. They've noted it so if I have another problem down the road it won't be an issue to have it replaced. If my idle gets that rough again I'm taking it back in.
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  • 3 weeks later...
  • 2 weeks later...
I'm having this exact same problem but have no codes and my idle is about 800 or so. took it to the dealer and it happened but by time they checked it the idle was fine and they kept it one more day and that morning it was fine for them:spin: this is driving me nuts...
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  • 1 year later...
I guess I just joined this club. My MAF was just at spec...and while idling erratically...it bounced over spec and back to right at max spec. I cleaned it and it didn't change anything. Do MAF sensors just go bad? It's 140 bucks to replace.
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