Got p0171 come up,p0174 hasnt.A vac leak?
Any help please

Clive

 

Vehicle details such as MY, engine displacement, description of cause would be helpful.

 

2002 STR,sorry

 

How many kilometres/miles are on the vehicle?

What work, if any, has been recently completed?

Check the STFTs and LTFTs along with fuel pressure by using a smart phone with the Torque app to connect to the vehicle's PCM (Powertrain Control Module) via the OBD port with a Bluetooth interface.

Check the vacuum line and connector from the inlet manifold to the brake booster to see if the grommets have perished or the line is cracked. Inspect the inlet plenums for cracks and tears, or have a Jaguar specialist perform a smoke test to find any vacuum leak(s).

 

No work has been done,for a longtime.Vally hose about 5 years ago.
She has 159k
STFT is wavering + and - above 15 both
Clear code (just one,P0171) and she'll drive all day,no problem,no misfires,runs like a dream

 

What is the fuel pressure at idle and WOT?

 

You're fooling yourself - it's got a problem and it may well be doing damage.

If the trim drops when you rev then you for sure have a vac leak.

 

Ok,I know theres a vac leak,trying to find wheres most lickely

 

Hi S-typeclive,

In addition to the brake booster vacuum pipe fitting at the induction elbow that NBCat mentioned, some of the most common points for unmetered air ingress are: loose clamps on the main air intake pipe, or cracks, especially between the accordion folds or at the ultrasonic welds where the Helmholtz resonators attach to the main pipe. Also, the camshaft cover gaskets, oil filler pipe O-ring and oil filler cap O-ring, crankcase breather pipe O-rings (and cracks between the ribs of the pipes), the crankcase vent valve ("PCV" valve) O-rings, the variable valve timing solenoid valve seals, etc.

An obvious clue is if you can see oil leaking out anywhere. If oil is getting out, air is getting in under engine vacuum.

Another potential cause of P0171 and P0174 is a dirty or tired MAFS, so it's worth carefully cleaning the IATS bulb and internal wires in the MAFS with about half a can of CRC Mass Air Flow Sensor cleaner spray or similar, taking care not to touch any of the wires inside the sensor housing. At this age, I consider it prudent to replace the MAFS with a new Denso and keep the old one as an emergency spare. I have not had any luck with aftermarket MAFS brands, so look for an OEM Denso.

Cheers,

Don

 

When you post an intro as is customary with a quic hello and car details you help yourself in many ways