Vaccum Leak?
08-25-2007, 01:15 PM
#1
Member
Thread Starter
Vaccum Leak?
Hi,
I just got a '98 F-150 4.6 v8 after driving for a few days the check engine light came on the codes are po171 and po 174. I reset the codes, but they come on every couple of days, I have been told it could be a vaccum leak. does that sound right and how do i check for a vaccum leak. Thanks.
-Jeff
I just got a '98 F-150 4.6 v8 after driving for a few days the check engine light came on the codes are po171 and po 174. I reset the codes, but they come on every couple of days, I have been told it could be a vaccum leak. does that sound right and how do i check for a vaccum leak. Thanks.
-Jeff
08-25-2007, 02:52 PM
#2
Senior Member
Those codes mean that both banks of the engine are still running lean after the computer has done all it can to correct.
A vacuum leak is a likely culprit. One method is to take carb cleaner and CAREFULLY spray it along the gasket lines and grommets of the intake assembly, listening for a change in engine pitch or RPM. Another similar method is to take water and spray it along the gasket lines, looking for places where it appears to be sucked in - a little safer approach but more difficult to see changes.
Be sure to include the PCV assembly and hoses, and power brake hose. The leak has to be in the intake section that's under vacuum somewhere after the air flow sensor through to where the manifold joins the engine.
Another possibility is with your air flow measurement - a faulty or dirty sensor. Check for the vacuum leak first - it's the cheapest, easiest, and most likely cause.
A vacuum leak is a likely culprit. One method is to take carb cleaner and CAREFULLY spray it along the gasket lines and grommets of the intake assembly, listening for a change in engine pitch or RPM. Another similar method is to take water and spray it along the gasket lines, looking for places where it appears to be sucked in - a little safer approach but more difficult to see changes.
Be sure to include the PCV assembly and hoses, and power brake hose. The leak has to be in the intake section that's under vacuum somewhere after the air flow sensor through to where the manifold joins the engine.
Another possibility is with your air flow measurement - a faulty or dirty sensor. Check for the vacuum leak first - it's the cheapest, easiest, and most likely cause.
08-31-2007, 11:53 AM
#6
Mass air flow sensor might be going bad on it.. Clean the whole intake and it should work out better.. and replace/clean your air filter.. 2 good cleaners for the intake are STP THROTTLE BODY CLEANER & armorall..yes armorall.. trust me it works... BUT DO NOT GET THE IAT OR THE MASS AIR SENSOR WET.!!. plus in addtion clean the throttle body while you at it.. better flow of air.. should gain you minimum of 2-3 mpg.. I did it and worked for me..