Daveymonkey Posted September 3, 2015 Share Posted September 3, 2015 I recently had a pair ARK Resonated HFCs fitted to my 350z (2005) along with a new Y-pipe by a reputable exhaust manufacturer. Upon leaving, everything seemed fine and sounded great. However, when I pulled off the motorway and the revs dropped as I went down the slip road, I heard a loud knocking under my feet. The same knocking occurred when going over rumble strips, or any unevenness in the road for that matter. At home, I took a look under the car and realised the driver side cat had been fitted such that the Helmholtz resonator was resting up against the chassis I rang the garage who stated it could be a manufacturer defect as the cats were not made by them. However, they agreed to take a look at the car when I returned from holiday. I'm now back and have gone out in the car again to check the symptoms are still there. When I hit motorway speed there was suddenly a distinctive "whooshing" sound immediately followed by the CEL light coming on. Having checked the code it was a P0420 "Catalyst System efficiency below threshold bank 1" which I understand is the driver side cat in question. Not sure if it's significant, but Torque app tells me that bank 1, O2 sensor 1 is 0.3 whereas bank 2, sensor 1 is double that at 0.6 at idle. I also noticed that at v.low speeds, but when the engine is under load (e.g. uphill, sharp turn in carpark), a couple of times there was a distinctive rattling sound from under the bonnet. I also feel like I've lost some power compared to leaving the garage throughout the range, but I guess this is subjective. My initial searches have got me worried that I could now have a cracked manifold, resulting from the knocking of the cat against the chassis . I'm going to take it back to the garage as soon as possible, but I wanted to put this out there in case anyone has experienced anything similar or has any other advice or ideas about what this could be? Quote Link to comment Share on other sites More sharing options...
ZMANALEX Posted September 3, 2015 Share Posted September 3, 2015 Go back to the garage that supplied and fitted your exhaust stuff and get it sorted asap. The longer that you leave it, the more they will wriggle. 1 Quote Link to comment Share on other sites More sharing options...
Ekona Posted September 3, 2015 Share Posted September 3, 2015 Agreed, get it back there sharpish. Quote Link to comment Share on other sites More sharing options...
MrE004 Posted September 3, 2015 Share Posted September 3, 2015 Can't agree more with what has already been said. Hope you get it sorted easily and all the best. Quote Link to comment Share on other sites More sharing options...
Dynamic Turtle Posted September 3, 2015 Share Posted September 3, 2015 Nightmare, be firm with the garage to get it sorted, zed manifold won't be expensive enough for them to deal with serious customer hassle. Quote Link to comment Share on other sites More sharing options...
Daveymonkey Posted September 4, 2015 Author Share Posted September 4, 2015 Yep, agreed. I've already been on the phone to them -I just have to sort a time to get it in and looked at. Thanks for the comments guys, I keep you posted Quote Link to comment Share on other sites More sharing options...
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