Update had a Smoke test done and they think it’s comin from the throttle body. Could a bad throttlebody gasket cause this? 171 and 174 codes? I recently had my local Mercedes dealer replace the intake manifold and intake gaskets due to a start and immediate shut off situation I would like to think if they would need to remove the throttle body from the manifold theyd put a new gasket in… They replaced intake gaskets and now the car starts and drives great however I still have two lean codes the infamous 171 and the 174 running too lean on bank 1 and 2. I have some pictures of the more in-depth details behind the fault codes. I’m hoping someone has had something similar happen and found a solution or knows what problems my readings are most likely leading towards. Please please please anyone with any knowledge of fuel trim values or maybe can give me a rough idea of whatever you think is going on would be life saving. Thanks in advance
Yes
Also yes, but also an exhaust leak, a bad fuel pump, dirty fuel filter, bad fuel pressure regulator, dirty MAF and vacuum leaks.
Have a mechanic put a fuel pressure gauge on it and drive it around. It should make and hold pressure to spec.
I’ve never had a problem like this until replacing the intake manifold so I’m sure it’s not a exhaust leak or filters or fuel related…Mercedes dealer said I have fuel pressure, I’m almost sure it’s a vac leak. But while doing the intake I removed and inspected the Tb cleaned it and used the old gasket , the gasket had to have been original. The smoke test said they think they’re getting smoke from the throttle body… but needs more time to make sure (not charging me extra) I’m just curious if it could Be my o2 sensors and how I could possibly tell if they’re working correctly
When I have had TB issues with air leaks, it has been the gasket first followed by the throttle shaft bores. They can wear and leak. The fix is to either install bushings or to replace it. Might be worth checking the amount of slop around the shaft to see if that’s it.
I’m going to have to agree with basically everyone here… Whomever is working on your car should know how to figure out which item is causing the lean condition… Many often miss the fact that exhaust leaks will do this as well…especially in or near the Cat
So consider the possibility of 2 bad O2 sensors… failing at exactly the same time? Very unlikely.
Personally, I’m leaning towards a fuel pressure problem or a faulty MAF
Until somebody posts what the measured fuel pressure was for the vehicle, koeo and koer, fuel pressure is going to remain on my list of suspects
Same thing for the MAF . . . it’s a common problem, and it could certainly affect both banks
And not all faulty MAF will make the vehicle feel undrivable and low on power
And I agree with @Honda_Blackbird on one obvious point . . . whoever is working on the car should have figured it out by now.
The 43% fuel trim means the computer is having to inject 43% more gasoline to satisfy the o2 sensor, than it thinks it would be injecting based only on the MAF, TPS, and engine coolant temp sensors. If you got a vacuum leak that big it would usually show up like gangbusters w/a smoke test or a propane/starter fluid search of the engine parts test. Those tests are where I’d start.