I cleaned my throttle bodies today on my 2015 Q40 and overtightened the top "one" bolt on the drivers side till it broke. I removed the piece out with a pair of pliers and bought new o rings. Now I'm getting a P0300 code and my cars can barely drive. It smells like sulpher inside if I run it for a couple minutes. I checked for cracks on the plastic intack manifold where the TB screws into and havent eyeballed any craks and spraying carb cleaner around hasnt changed the idle.

Anyone have any ideas?

 

Did you by any chance do an idle relearn? If you replaced the bolt and everything seems perfectly fine I don't think you will be getting a P0300. Check for any vacuum leaks, might have not tighten the clamps for the intake tubes.

 

Did you replace the top bolt that broke?? Like @Said Amir mentioned, if you cleaned the throttle bodies, you need to do the idle re-learn procedure.

 

If you have a P0300 just after cleaning the throttle bodies, you have an intake leak somewhere.
I would suspect a crack in the intake where you broke the bolt or you slightly pulled out the metal insert for the throttle body bolt.

It can be very difficult to spot a hairline crack in black plastic... good luck!

 

well, the code wasnt because I overtightened the throttle body cause I did it again today LOL. I bought the cheap click type 3/8s torque wrench from harbor freight and that sucker doesnt always work Ive just found out. I'm taking all the sensitive delicate instruments (multimeter,etc)I ever bought from them back tomorrow with the broken bolts and demanding my money back.

btw the p0300 code was for a bad maf sensor

 

I haven't done the throttle bodies to know myself, but you're not mixing up in/lb and ft/lb, are you? A 3/8 torque wrench seems a bit much for what's probably only an 8mm/10mm bolt.

 

yea it was a 1/4 inch, sorry...no I got two torque wrenches, one foot and one inch lbs. bothe harbor freight and total crap from the looks of things.

 

Just for reference (and for those who may come across this thread one day), the torque spec for the throttle body bolts is: 75in./lbs. (or approx. 6¼ft./lbs.:

 

I never used a torque wrench for those TB bolts. Just hand tight them as much as you can with an allen key. Never had an issue.

 

Smoke test the system to find out where you have a vacuum leak. Not doing the throttle re learn will definitely cause the car to have odd pedal response and likely not idle, but it won't cause a P0300 or sulfur smell. A true misfire will definitely cause those issues.

 

Just beating a dead horse, but some things you can try before doing a smoke test.

- New hardware (extract old bolts and replace with new bolts, seals, etc). Hand-tighten is good (I also messed up the first time I did it)
- Accelerator pedal relearn, throttle closed relearn, then idle relearn per Motorvate ( ) or Idle Relearn with NDSIII Lite App
- Check for any additional codes (P0300 is a misfire code that can be caused if there's an intake leak); usually if a leak is prevalent enough, it would eventually cause a lean cylinder
- If no leaks, then check MAF sensors (they can get be damaged when the intakes are moved out of the way for throttle body removal)

Suphur smell is likely unrelated to this, though can be a sign of failing catalytic converters. You may get a P0420 for this when they do.