Hello All - I have a 2005 SRT6 Roadster with the following modifications: Larger crank pulley (ASP), NeedsWings single intake, Eurocharged tune, low temp thermostat, NeedsWings catch can and pulley saver kit. It is a fair weather car that has just under 13,000 miles on it. I am having a high and rough idle issue that is throwing me for a loop. Have left the battery disconnected for much time, performed many throttle body resets, etc. And the issue comes about whether the engine is hot or cold.
It started with a pull when stopped, say, at a stop light, where the throttle would go up to 1,500 or so. I replaced the intake manifold gaskets (with NeedsWings), and then it jumped to 1,500-3,000 RPM when started. I then replaced the CPS, though issue remained. Just replaced the throttle body with a new Bosch unit and issue remains.
Curious what thoughts may be. No problem going back to stock if needed. Other than a new intercooler pump a few years ago, there have been no other issues.

Thank you and I hope everyone is doing well during this time.

 

To me, it sounds like a VAC leak. I would channel my energies on looking for a vacuum leak. Good luck!


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check the throttle body spacer/gasket, the rubber may have degraded and cracked. if that looks good continue to look for a vacuum leak, could also be the charcoal canister or brake booster line from the supercharger inlet.

 

Thank you for the replies. I ordered a stethoscope and will report back what is found.

 

Is there a trick to getting the bottom bolt out of the throttle body spacer? I have a replacement gasket. Also, seems I can hear a vacuum leak somewhere on passenger side of engine near back of engine. Will get closer when stethoscope comes in. Thanks.

 

Update: Stethoscope in and not sure it is helping. I did notice that the exhaust pipes behind the engine, right where the O2 sensors are, glow red hot when running and bouncing RPMs during idle. Now wondering if perhaps O2 sensors or catalytic converter. Anyone seen this before?
Thank you.

 

Are you getting any codes?

 

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First, I am not an expert. That said, you MIGHT have a failed Cat. Posting the CODES might help.


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Thanks. CEL comes on after a bit. Code reads: P0507, 'Idle Air Control System RPM Higher Than Expected.'

 

i would say either your timing is off or your cats are clogged. are both sides glowing? if so check your catback, there was a guy that had a rodent filling up his muffler with dog food once.

 

Thanks. Both sides glowing red hot. Catback looks clear and seems to have normal-ish flow.

 

You should never see anything glowing red hot unless its running at redline. What is glowing red hot?

 

Exhaust behind engine, where O2 sensors are. These are glowing hot when at bouncing/rough idle. Thanks.

 

Strange... I am wondering if your exhaust check (thinking partial plugged cats) is misleading since it seems the cats are glowing like this. Maybe way too much unburned fuel is present at cats?

A lot more information (like a good code reader made to tap into the MB codes and test data) looks like a must


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Update - I will get the car over to a mechanic in the coming weeks and will report back. Thanks All.

 

There is a vacuum line under the battery. It deteriorates because of battery acid. It has been know to cause rough idle.

 

You most likely have a LARGE leak. The supercharger outlet has a short rubber hose to the Y pipe. On my car one of the clamps failed and caused the hose to partially come off. My car ran at 3000 rpm at idle until I found the broken clamp and replaced it. Take your time and look for something unusual out of place like my broken clamp.

Les

 

Update: Hauled the car to a recommended shop a couple of hours away. The issue was the intake manifold gaskets. Picked up the car last night and runs great. Just wanted to close this out. Now on to the rear window adhesion issue.
Thanks.