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Issues after Downpipe install


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I bought a car with the stock downpipe and unmarried Cobb AP and I got around to installing a DP (catted) that was provided with the car and used for the custom tune.

 

I loaded up the tune with the new DP and have been having problems since. RPMs at idle go up and down while sitting at idle. And after driving or revving a bit in neutral, RPMs drop down to almost 0 and the car shakes like it's about to stall but stays on. Doesn't happen every time but definitely occurs more often than not.

 

I have since put the stock DP back on and unmarried the AP but the issues still persist. Car was running perfectly fine before. My guess is there is an exhaust leak somewhere? I did the work myself and might have goofed something up. I did use all new gaskets though.

 

Any ideas as to what's going on? Afraid to drive the car in its current state.

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If you are just doing a downpipe you shouldn't see any issues even if you have a leak. The only thing is that you would really hear the leak--it would be loud-ish, even at idle.

 

Is it possible that the car is just relearning after flashing the new map? For some cars it takes a couple drive cycles and can feel like it's going to stall a bit.

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If you are just doing a downpipe you shouldn't see any issues even if you have a leak. The only thing is that you would really hear the leak--it would be loud-ish, even at idle.

 

Is it possible that the car is just relearning after flashing the new map? For some cars it takes a couple drive cycles and can feel like it's going to stall a bit.

 

Forgot about that bit -- A very likely culprit, depending on the tune.

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Forgot about that bit -- A very likely culprit, depending on the tune.

Ah I'm hoping that's it. Thanks for the help.

 

One thing I forgot to mention is when I had the DP and tune, there was what sounded like exhaust backfire almost every time I shifted gears, even at lower RPMs and speeds as I was driving around my neighborhood. That's gone with the stick DP and tune back on but still weird behavior.

 

Oils pressure is also bouncing between 40-80+ according to my Defi gauge. That one has me worried...

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Does the car have stock exhaust from the mid pipe back ?

 

My 09 has a cated DP and 3" mid pipe, it will pop when I shift unless I have the stock mufflers bolted on.

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Does the car have stock exhaust from the mid pipe back ?

 

My 09 has a cated DP and 3" mid pipe, it will pop when I shift unless I have the stock mufflers bolted on.

 

I have the Invidia Q300 exhaust so it is 3" at the mid-pipe and mates up directly to the 3" catted DP. Is that normal to have backfire/popping noises with this setup?

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I have the Invidia Q300 exhaust so it is 3" at the mid-pipe and mates up directly to the 3" catted DP. Is that normal to have backfire/popping noises with this setup?

 

Bigger exhausts, especially combined with rich tunes tend to get a little 'poppy', yes.

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Bigger exhausts, especially combined with rich tunes tend to get a little 'poppy', yes.

 

Thanks! Glad to hear that one isn't a big issue.

 

If the ECU is indeed relearning the reflash, how long would it take? I drove it around my neighborhood for maybe 5 minutes and the issues still persist.

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Thanks! Glad to hear that one isn't a big issue.

 

If the ECU is indeed relearning the reflash, how long would it take? I drove it around my neighborhood for maybe 5 minutes and the issues still persist.

 

After that amount of time, I'd start looking for vacuum leaks. Something's unhooked, then. Did you remember to unplug the green test connectors after reflashing?

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You will want to drive it more than that. If it is indeed learning you should be able to sit at idle with no issues but once you blip the throttle it will seem like it wants to fall on its face.

Also if you have a way to log it check the IAM, if it is 1.0 then it should be learned up. If it is .5 then it is still learning.

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After that amount of time, I'd start looking for vacuum leaks. Something's unhooked, then. Did you remember to unplug the green test connectors after reflashing?

I did not, what exactly does this entail? I was thinking a leak somewhere too but all I did was take off the DP and install the new one. I didn't touch anything else besides the 5 bolts/nuts on the turbo to DP connector, the o2 sensor, the DP hangar bolt, and the 2 that connect to the mid-pipe. Knowing me though, I probably goofed something up...

 

You will want to drive it more than that. If it is indeed learning you should be able to sit at idle with no issues but once you blip the throttle it will seem like it wants to fall on its face.

Also if you have a way to log it check the IAM, if it is 1.0 then it should be learned up. If it is .5 then it is still learning.

Sitting at idle is ok but the RPM needle does move up and down slightly but once I blip the throttle the car feels like it wants to stall for a few seconds than goes back to somewhat normal idle.

 

Can I check the IAM with the Cobb AP?

 

 

Appreciate the help all!

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I did not, what exactly does this entail? I was thinking a leak somewhere too but all I did was take off the DP and install the new one. I didn't touch anything else besides the 5 bolts/nuts on the turbo to DP connector, the o2 sensor, the DP hangar bolt, and the 2 that connect to the mid-pipe. Knowing me though, I probably goofed something up...

 

 

Sitting at idle is ok but the RPM needle does move up and down slightly but once I blip the throttle the car feels like it wants to stall for a few seconds than goes back to somewhat normal idle.

 

Can I check the IAM with the Cobb AP?

 

 

Appreciate the help all!

 

Yes, you can see the IAM with the AP - you know where to find that, right? (Live Data)

 

You said you touched the O2 sensor. . . I'd maybe check that out and make sure the connections are good and tight and that the sensor tip wasn't damaged. .

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I spoke with the previous owner and he said what I'm experiencing is normal and the ECU just needs to relearn. He recommended driving 20-40 miles and it should sort itself out.

 

I'll check the Cobb AP live data to see what the IAM is at. Hopefully I didn't damage the O2 sensor but I was trying to be really careful with it.

 

I didn't remove the intercooler and it's an AVO top mount. I was able to reach around and from the bottom with various wrenches to get the nuts/bolts off and on without the heat shield.

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When i was flashing stg.1 on my 5EAT the first couple times i turned it on it did exactly what you said happened with the low idle, but my car actually stalled. after 5 minutes of trying to get it to start it finally didnt stall and i let it idle for 5-10 minutes, then went for a drive for about 30 and havent had an issue since
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