General Tech Good at troubleshooting? Have a non specific issue? Discuss general tech topics here...

Idle Instability after Exhaust & Intake Mods

  #1  
Old 09-07-2007, 12:53 PM
Thread Starter
Join Date: Sep 2007
Location:
Posts: 611
Default Idle Instability after Exhaust & Intake Mods

911 996 Carrera 2 2003 3.6 litre. Car has RevoChip, Sports Stainless Steel Exhaust (Manifolds Cat, and Mufflers)and Full Flow Air Intake System. Now appear to be suffering from low speed idle problems when hot. Engine appears to run rich and "hunts". Have replaced Mass Flow Sensor. Small improvement. Apart from "Idle" the car has fantastic improvement in performance.
Any ideas. Thanks Bob
 
  #2  
Old 09-07-2007, 04:38 PM
Super Moderator
Join Date: Apr 2005
Location: Overland Park, KS
Posts: 3,532
Default RE: Idle Instability after Exhaust & Intake Mods

What brand intake and exhaust were used?
 
  #3  
Old 09-08-2007, 03:06 AM
Thread Starter
Join Date: Sep 2007
Location:
Posts: 611
Default RE: Idle Instability after Exhaust & Intake Mods

Thanks for getting back to me Porsche Doc. The Exhaust System was "Supersprint" ex Porsche Shop, and the Air Intake system was "High Flow Induction Kit" also ex Porsche Shop. See Porsche Shop Website for both under Exhausts and Performance respectively.
Re the Revo Chip, I returned the car back to stock as a check. This did not alter the characteristics.
The car also appears to be getting better with use, possibly as the electronics "adapt" to the new inputs!
Thanks Big Bob
 
  #4  
Old 09-08-2007, 10:37 AM
Super Moderator
Join Date: Apr 2005
Location: Overland Park, KS
Posts: 3,532
Default RE: Idle Instability after Exhaust & Intake Mods

The new motronic system is a learning system, meaning it will adapt the more you drive the car. The revo software is probably not mapped for the intake and exhaust changes, meaning that it may take longer to adapt. Typically I see this happen with the change in intakes on occasion. Unfortunately I don't know anything about that intake system.
 
  #5  
Old 09-08-2007, 02:27 PM
Thread Starter
Join Date: Sep 2007
Location:
Posts: 611
Default RE: Idle Instability after Exhaust & Intake Mods

Thanks Porsche Doc. I had a feeling I needed to be patient and just use the car. Thanks for the reassurance. Regards Big Bob
 
  #6  
Old 09-19-2007, 08:31 AM
Thread Starter
Join Date: Sep 2007
Location:
Posts: 611
Default RE: Idle Instability after Exhaust & Intake Mods

Dear Porsche Doc
While the car is learning the new characteristics and adjusting, have you any advice regarding the Engine Check Warning Light, that has come back on again. It has been "off" since replacing the Air Mass Sensor in the intake, which my OPC covered under my Porsche Warranty.
Should I also get my OPC to check the Exhaust Sensors to verify they are withinoperating specification. I understand getting them out of the Original Cats was difficult. Porsche Shopsaid they were OK, but as they will be I assume covered by the Warranty, are they likely to help from your experience?
Any advice you can give would be appreciated.
Thanks Big Bob
 
  #7  
Old 09-19-2007, 11:55 AM
Super Moderator
Join Date: Apr 2005
Location: Overland Park, KS
Posts: 3,532
Default RE: Idle Instability after Exhaust & Intake Mods

I would read down the code and see what it is first, it may be related or not. Once we know the code, then we can take a stab at what the problem is. Some software upgrades are known to cause CEL lights, but I didn't *think* Revo was one of them. Check the codes and let me know what they are....
 
  #8  
Old 09-20-2007, 03:20 PM
Thread Starter
Join Date: Sep 2007
Location:
Posts: 611
Default RE: Idle Instability after Exhaust & Intake Mods

Porsche Doc
Your suggestions are in hand. The Air Intake System may hold the clue to the "Warning Light" saga. It is in fact a Fabspeed 996 Cold Air System that Porsche Shop supply. This has an oiled Filter from Porsche Shop. Small amounts of oil from the filter may be contaminating the Mass Air Sensor and causing the resistance etc of the sensor to be affected causing rogue results. I'm taking the car to my OPC to get the fault code read. I'll reinstate the standard Porsche dry filter, and clean the Mass Flow Sensor as well as rechecking for air leaks. Revo also have seen similar issues on Audi RS4s and BMW M3 in the UK using super unleaded fuels from our larger supermarkets (Tesco/Sainsbury). Suggestion from Revo is to run fuel down then partially refill with Shell V Power or BP Ultimate plus some injector cleaner, then refill with Shell or BP. Revo also suggested contamination of Mass Air Sensor. I know its nothing to do with the Revo chip because the problem is stiil there when the program is returned to stock.
Anyway when I havemore data I'll keep you posted.
Thanks Big Bob
 
  #9  
Old 09-27-2007, 12:04 PM
Thread Starter
Join Date: Sep 2007
Location:
Posts: 611
Default RE: Idle Instability after Exhaust & Intake Mods

Hi Porsche Doc
After a visit to my OPC, the cause of the Warning Light wasoil contamination of the AirMass Flow Sensor, and the Throttle Body, coming from the oiling of the Fabspeed Filter Body. This has been addressed by going back to a dry filter.
Also found that the Plugs for the Diagnostic Ports in the Cats had vibrated out, probably fitted but not tightened by the cat suppliers. This will obviously allow the Exhaust Sensors to sniff extra oxygen, and thus when hot the fueling may be sensed to be weak as a result, so the systemprobably compensates by up fueling.
Will get the plugs fitted on Monday October 1st. I'll update then. In meantime car is running much better at idle.
Thanks Big Bob
 
  #10  
Old 09-27-2007, 01:30 PM
Super Moderator
Join Date: Apr 2005
Location: Overland Park, KS
Posts: 3,532
Default RE: Idle Instability after Exhaust & Intake Mods

Sounds like you have it under control!
 

Thread Tools
Search this Thread
Quick Reply: Idle Instability after Exhaust & Intake Mods


Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.