Lean codes + fuel delivery problem
#1
10-08-2019, 08:31 PM
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Lean codes + fuel delivery problem
2004 Jaguar XJ8 184000 miles
CEL 1 week after buying car. Came on soon after first FULL tank fuel-up with high-quality fuel. Code reader found P0174. I had noticed that the flood lights being turned on triggers the traction control to become unavailable (every time). So some electrical problems are present, I had the battery checked it was no good and not the proper battery for the car so I got a new one. This did not change anything.
Brought the car in to a couple different mechanics I was advised to get a new MAF (didn’t change anything)
A smoke test found a vacuum leak under the PCV which a sealed with a gasket sealer. Codes continue to come back and with worsening misfires on startup P0174 P0171 P0300 etc
I rented a fuel pressure gauge and this is where I made some progress....
With the ignition on and engine off the fuel pressure is between 0-2 psi (I thought I screwed it in wrong)
Surprisingly enough the car starts even with the low rail pressure the fuel pressure begins raising to 47 psi where is sits but the car shakes and stumbles and misfires as it gains pressure
if I cycle the key activating the pump over and over again it builds about 6 psi per key turn I can build it as high as I want.
this is where it gets weirder because the fuel pressure actually holds for a long time and it takes hours for it to drop down under 10 psi
if I pull out the fuel pressure sensor vacuum with the engine running it raises 5-7 psi like it should ..no liquids in the vacuum line
When driving the car you wouldn’t know there is anything wrong with it, the fuel pressure raises under load It does not drop at all. The biggest problem In performance is the reduced performance that comes up with CEL on startup. If I clear codes which I’ve done several times after small repairs it tricks me into thinking the car is fixed because it drives like a dream until the CEL /reduced performance come back next start up.
Other random factors are the VVT solenoid seals are leaking oil I just replaced them. I cleaned the PCV but don’t understand the thing or how to tell if it is stuck open or working right. Oh and I’ve replaced the fuel filter. Which directly after it seemed like the pressure was working again but as soon as it sat overnight the cold start brought back the lean codes and low fuel rail pressure before the engine is started.
The car is in perfect condition and was obviously owned by responsible owners I got the car for a very low price and I expected to have to put money into the car but these early on problems and expensive misdiagnosis’ are making me think I made a mistake with the high mile jag. So if anyone can help me out and restore faith in this beautiful car I would very much appreciate it!
Thank You!!
CEL 1 week after buying car. Came on soon after first FULL tank fuel-up with high-quality fuel. Code reader found P0174. I had noticed that the flood lights being turned on triggers the traction control to become unavailable (every time). So some electrical problems are present, I had the battery checked it was no good and not the proper battery for the car so I got a new one. This did not change anything.
Brought the car in to a couple different mechanics I was advised to get a new MAF (didn’t change anything)
A smoke test found a vacuum leak under the PCV which a sealed with a gasket sealer. Codes continue to come back and with worsening misfires on startup P0174 P0171 P0300 etc
I rented a fuel pressure gauge and this is where I made some progress....
With the ignition on and engine off the fuel pressure is between 0-2 psi (I thought I screwed it in wrong)
Surprisingly enough the car starts even with the low rail pressure the fuel pressure begins raising to 47 psi where is sits but the car shakes and stumbles and misfires as it gains pressure
if I cycle the key activating the pump over and over again it builds about 6 psi per key turn I can build it as high as I want.
this is where it gets weirder because the fuel pressure actually holds for a long time and it takes hours for it to drop down under 10 psi
if I pull out the fuel pressure sensor vacuum with the engine running it raises 5-7 psi like it should ..no liquids in the vacuum line
When driving the car you wouldn’t know there is anything wrong with it, the fuel pressure raises under load It does not drop at all. The biggest problem In performance is the reduced performance that comes up with CEL on startup. If I clear codes which I’ve done several times after small repairs it tricks me into thinking the car is fixed because it drives like a dream until the CEL /reduced performance come back next start up.
Other random factors are the VVT solenoid seals are leaking oil I just replaced them. I cleaned the PCV but don’t understand the thing or how to tell if it is stuck open or working right. Oh and I’ve replaced the fuel filter. Which directly after it seemed like the pressure was working again but as soon as it sat overnight the cold start brought back the lean codes and low fuel rail pressure before the engine is started.
The car is in perfect condition and was obviously owned by responsible owners I got the car for a very low price and I expected to have to put money into the car but these early on problems and expensive misdiagnosis’ are making me think I made a mistake with the high mile jag. So if anyone can help me out and restore faith in this beautiful car I would very much appreciate it!
Thank You!!
#2
10-09-2019, 02:56 PM
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