HVE A 2001 xk8 4.0 was hesitating starting from a stop. Ok after going. Changed plugs used Bosch 4418 platinum + 4.

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Customer: HVE A 2001 xk8 4.0 was hesitating starting from a stop. Ok after going. Changed plugs used Bosch 4418 platinum + 4. Checked all vacuum lines. Changed fuel filter.
Now really running crappy. Hesitaitng really bad and backfiring. Wrong plugs?
Answered by Richard in 17 mins 11 years ago
15+ years of experience

19,890 satisfied customers

Specialities include: Automotive Mechanic, Small Engine Repairs, Auto Body Repairs, Diesel Engine Repairs

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Can you describe this hesitation? DOes the engine rev up then go into gear when accelerating from a stop or does it hesitate while you are already moving? Have any fault warning lights or messages come on?

No check engine or fault lights. Engine does not rev up and then go into gear. Starts moving then hesitates. Sitting in garage starts fine idles rough and when accel is pushed
gulps air and sometimes backfires.
Ok we may have a problem with the air flow meter sensor on the air cleaner. SOmetimes if you disconnect it your problem would go away if the sensor is the problem. In some cases however the engine may not run with the sensor disconnected. I also think we should check fuel pressure with a gauge on the fuel rail service port. The other possibility is the engine has jumped timing. I see issues with the secondary timing chain tensioners failing which can cause the chain to move a tooth off on the exhaust cam. The cam is not monitored so no fault codes or warnings may come on.
Disconnected the mass airflow sensor. starts but will not idle. Seems to run ok at higher rpm.
Thats what I figured. Without a Jag factory scan tool or one that can read live data it is hard to pinpoint if the sensor has a problem. I do recommend we check fuel pressure as well.
going to get a fuel pressure guage
We have a winner. The MAF fixed the problem. Thank you very much.
You are very welcome. I am glad I was able to help. Thank you for using justanswer.com.
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