I have a 2005 S Type R, 62k miles. Replaced the EGR valve about a month ago and then the battery about 2 weeks ago. Check engine light came back on yesterday and my mechanic told me the car is running rich. As far as performance the car runs very smooth, the only thing i have noticed is that at idle the car will sometimes dip ever so slightly below the normal idle rpm and almost die on me. The car always catches itself and brings the RPM up again. The (restricted performance) message will come on and go off very randomly, sometimes i drive all day without seeing it, other times its on as soon as I turn the car on. Besides a Caldofy intake elbow I installed about a year ago and a K&N intake filter, the car is stock. I have driven it on very quiet roads and at different speeds, trying to pick up any abnormal noise or vibration but the car seems to be running as smooth as silk.

Anyone run into this problem before? Is this a job for the dealership? I appreciate any and all advice.

 

Read fuel trims, read actual codes.

 

Without the codes we have no clue. You are lucky because you have had a trouble light come on so there should be something stored.

Can you get the codes read and post back?
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And get the actual fuel trims - if you're not going to DIY these simple things then I'm wondering why you've posted....

Worth your while to use Advanced Search, just this forum, words like
fuel trims
rich

to see what others have posted.

 

If it's something simple like an oxygen sensor as I've read is sometimes the issue then it's something I would do myself. I did search the forum and found a few posts but all where inconclusive and didn't help much. I will be stopping by my mechanic tomorrow to get the codes and any other info he can give me.

 

OK finally had time to take the car to a Jag dealership and received the following codes. P0103, P0172, P0175. Was told my Caldofy intake tube and K&N air filter need to be taken out and brought back to stock in order to eliminate those items as being possible causes for these codes. I believe both of these Items are fine, Caldofy intake tube and K&N filter has been on the car for like a year now, never had an issue until recently. So having to take those out is bullshit in my opinion. The car is saying its running rich but the Jag mechanic told me it is unlikely that's true, that the running rich code is being brought up by the first code. Anyone have any insight into this? Have had this check engine light on for like a month now, My mechanic and the Jag mechanic both seem to not really know why its on. As i mentioned before the car runs absolutely fine, smooth as silk just cant get that damn engine light to stay off. Or even know why its on in the first place.

 

Find and fix P0103 and see what next. Read codes PDF (in stickies & JTIS, both free) to see known causes.

K&N is a suspect any time MAF is an issue, as here.