Infiniti FX Diesel: High Fuel Usage & Strong Exhaust Smell

Hey there! I've got some experience with cars. Had a similar issue with my 2011 Infiniti QX70 Diesel last year. The symptoms you're describing sound exactly like what I dealt with. Turned out to be a faulty connection between the secondary air valve and pump. My trusted mechanic found that the cables and plug were corroded and making poor contact. Got it fixed for around 95 Euro basically needed to replace some wiring and clean up the connections. Made a huge difference fuel consumption went back to normal and that nasty diesel smell disappeared. Before I share more specifics though, how many miles/km on your FX? Have you noticed any rough idling? Any other warning lights besides the check engine? Might help pinpoint if we're dealing with the same exact issue.

Thanks for the reply! I'm at 209118 KM and just had my service last month. Yep, definitely getting some rough idling, especially when cold, but no other warning lights besides the check engine. Your experience sounds pretty similar to what I'm dealing with. Gonna check those connections first really hope it's just a wiring issue like yours was. Would be a relief if it's just that and not something more serious!

Hey again! Thanks for those details. Yeah, those numbers and symptoms are ringing even more bells now. My QX70 was around 198,000 KM when I had the same drama, so we're in the same ballpark. Just to share a bit more from my experience that rough cold idling was exactly what I had too. You know, in my case, after fixing the wiring issue, I also ended up discovering that the valve itself had some carbon buildup (pretty common at our mileage). My mechanic cleaned it out while he was in there, and honestly, it made an even bigger difference than I initially mentioned. Quick tip based on what I learned: before you take it in, try listening near the front of the engine when it's cold if you hear a slight whistling sound, that's another telltale sign it's definitely the air valve system. That's what helped my mechanic confirm the diagnosis on mine. Since we're dealing with such similar cases here, I'd bet good money you're looking at the same fix. Just watch out for any shifty mechanics trying to upsell you on a complete valve replacement cleaning and rewiring did the trick for me! Keep us posted on what you find out, yeah? Always curious to hear if these fixes work out for others too!

Thanks so much for all the detailed info! Just checked and I can definitely hear that whistling sound you mentioned can't believe I didn't notice it before. This is super helpful! I've got an appointment with my mechanic tomorrow morning, and I'll definitely mention the wiring and carbon buildup issues you experienced. Really appreciate you taking the time to share all this, especially that tip about not jumping straight to valve replacement. I'll definitely update the thread once I get it sorted. You've saved me a lot of worry (and probably money too)! Thanks again!