I have a 2002 c240. I just had the MAF sensor replaced to fix a po171
code last week and now when the car runs for 20 minutes or so it turns
off and does not start back until it has cooled. is it the fuel pump or
the guy who replaced the MAF has mess something up?
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Replace the MAP Sensor again. alot of times they are botb. (Bad out of the box) I realize how much of a pain this is but, like with any computer component that has no way of testing it these things happen. Good luck.
This is a tough one could be mass air flow sensor ,oxyegen sensors,a fuel filter. a vacum leak, a pcv valve if i missed anything just google po 171 &174 look for fix ya this issue has been addressed many times first check the vacum lines includeing the line on the pcv valve for cracks or splits in the lines .I would do the fuel filter if it hasnt been changed in the last couple of years , if still a problem the MAF sensor if your happy with my advise please leave me with great feedback
Check the engine for vacuum leaks in the small rubber hosing around the inlet manifold, run the engine and spray wd40 around the hoses if the engine revs rise you've a vac leak. Could also be a faulty MAF sensor which is located near the airbox with an electrical connector running to it. That fault code means your ECU thnks the engine is running lean so is compensating by adding fuel. Either you're gettng extra air into the intake that shouldn't be there or the MAF sensor is sending the wrong signals.
PO171 refers to "system too lean - bank
#1", This means that the upstream oxygen sensor detected too much oxygen in the exhaust. Cleaning out the MAF (mass air flow) housing and sensor will help eliminate the PO171 code. It's also necessary to clean the upper portion of the engine and fuel injectors, to make sure they are not clogged or "fouled." check for vacuum leaks and around intake manifold. spray around manifold with engine running, if it flares up you have a leak. in most cases. cleaning the MAF sensor does the trick !
engine running lean--check engine for vacuum leaks. Look for cracked or unhooked hoses. Also test intake manifold gasket. I spray ether on the gasket with engine running. If the engine speeds up, there is a leak. Let us know f you have more questions.
Code PO171- Lean mix of Bank 1. Code PO174- Lean mix of Bank 2.
Most of the time a P0171 and P0174 is caused by either a vacuum
leak--more than likely the PCV hose and valve or a dirty or defective Mass Airflow (MAF)sensor. Low fuel pressure can also cause this condition.
The PCV hose is located on bank one but can affect both sides because
the other end is located on the back of the upper intake manifold.
Usually they deteriorate and get a hole in it.
Clean the the MAF sensor with MAF cleaner, which you can pick up at any Auto parts store and also pick up a bottle of fuel injector cleaner. Good luck and hope this helps.