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Q: Performance restriction

asked by on March 06, 2018

Started with engine lights 171 and 174 found by WOW software. Slightly rough idle 4 last year. I replaced the upstream down stream oxygen sensors with an after market & found I was still having a problem up stream. Switched sides & discovered one of the sensors was bad after reading codes again. Bought 4 Denso U & D stream & installed. Decided to replace throttle Body & a new gasket to correct the rough idle of 200 rpm fluctuation. MAF sensor was carefully replaced new 7 months ago. Now I am getting a PO171 and a PO174 with a P1646 code reading along with a performance restriction light. At idle RPM it does not fluctuate at all. Seems strong & relatively smooth up to about 60 to 65 MPH & half throttle. Past half throttle it begins to shut down in a jerking behavior. Let up & at half throttle it drives good. Turned off codes 4 times & again last night & took it on the highway. Punched it 5 times + full throttle. Beautiful. Started it this morning-its back same codes & RP

My car has 91000 miles.
My car has an automatic transmission.

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Based on the symptoms you’re having, I would recommend having your vehicle inspected by a qualified professional with a check engine light is on inspection. This will be able to determine the exact cause of this issue. Consider YourMechanic as this can be done at your home or office.

Jaguar
2004
V8-4.2L
XJ8
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