r/Cartalk • u/Technical-Purpose-12 • Oct 04 '21

Can anyone help me figure this out? Exhaust

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133

u/Impossible-Scar-7226 Oct 04 '21

Does it smell sweet? If so you're burning coolant.

74

u/Technical-Purpose-12 Oct 04 '21

No, it smells like burnt plastic at first then super rich gasoline.

62

u/abooth43 Oct 04 '21

You said in other comments O2 sensor codes, and smells like a messed up air fuel mixture, there's a possibility there's an intake vacuum leak somewhere behind the MAF.

If the MAF thinks less air is coming in, the expected range the O2's see would change.

I've ran into O2 codes for vac leaks on my bmw e36 and a buddies older Nissan Altima.

15

u/greenskeeper-carl Oct 04 '21

Could also be air getting in somewhere upstream of the O2 sensors, right? Outside air mixed with the exhaust, sensors read it and think the car is running lean and starts dumping more fuel?

14

u/abooth43 Oct 04 '21

Possibly a leak on the exhaust manifold, though I imagine the exhaust pressure wouldn't allow air in.

6

u/Technical-Purpose-12 Oct 04 '21

Well right as I got it, me and my bud automatically thought exhaust leak, but I didn’t look too deep into it and my mechanic said he couldn’t find anything during a deep inspection

6

u/greenskeeper-carl Oct 05 '21

Can you hear a lot of valve clicking too? And a rattling under there? I mean I’d still start with O2 sensors. If you know those are bad.

4

u/Technical-Purpose-12 Oct 05 '21

No clicking at all. Engine bay sounds fine, and I don’t know for sure if the 02 sensors are bad just getting codes

4

u/CTSVR Oct 05 '21

An exhaust leak won’t produce white smoke. Most likely you’re pushing your head gasket, burning oil.

4

u/Krypt1cAsylum Oct 05 '21

Generally you'll hear an exaust leak as the car will sound abnormally loud. Some people say you can hear vacuum leaks too but I can't so couldn't tell ya how lol doin a vacuum test would tell ya if either of those conditions exist though

3

u/dsmaxwell Oct 05 '21

Yeah, exhaust has a positive pressure (DeltaP) inside, so any holes would leak exhaust out, not let air in. This is the opposite to the intake air which is sucked in with negative pressure (delta P) inside the cylinder, so leaks there suck in outside air.

1

u/Ffssomethingwork Oct 05 '21

U would hear whistling