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Steve
Steve, Auto Service Technician
Category: Car
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Experience:  25+ yrs experience as a professional working technician; ASE L1 master technician
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2002 chrysler pt cruiser: park and rev engine..4000 rpms..jerks..mpg

Customer Question

2002 chrysler pt cruiser while in park and rev engine around 4000 rpms it will rev up and down and when driving it jerks once in a while and gas milage has gone from 26 to 20 mpg
Submitted: 11 years ago.
Category: Car
Expert:  Steve replied 11 years ago.

 (1) the surging when revved to high speed is normal;   the tach may be displaying 4,000 rpms, but that is an average; actual RPM is probably running somewhat higher, at which teh rev limiting feature programmed into teh powertrain control software will momentarily shut the engine down untill it drops below a preset speed at which point it comes back to life.  The net result is a surging type of condition when the engine is raced with no load, and a high tach reading.   THis is a normal safety feature to prevent engine damage, and does not indicate a problem.


(2) The usual cause of the intermittent jerking/ misfire/ drop in fuel economy on this engine is a failing plug wire, allowing high voltage ignition current to jump between a plug wire and ground, down inside the spark plug well.    This is impossible to see with the wires installed, but the result is that the spark plug on the affected cylinder does not fire when it should, effectively cutting your power and fuel economy by 25% momentarily.   Plugs and wires should be replaed periodically for maintenance (check your maintenance schedule in teh back of teh owners manual).  If you have not done this recently, try performing the maintenance by replacing the plugs and wires first.  If this does not help, then you may need to have the problem diagnosed professionally if you want an accurate diagnosis...

Customer: replied 11 years ago.
Reply to Steve7654's Post: what if i accept and this does not cure the problem otherwise will be happy to pay
Expert:  Steve replied 11 years ago.

There is no possible way to abslutely guarantee a diagnosis or the quality of repair work performed on a car you cannot see or test yourself, even if you are present in the same room with it; to expect some sort of guarantee of results would not seem to be a realistic or reasonable thing to ask, dont you agree?


What you are provided here for your money is a professional opinion, as best as can be provided under the circumstances, for much, much less than if you called your local dealer service department and requested the same information.


I have a high cofidence in the research I have done for you, and the answer I have provided, and that is the best anyone could reasonably be expected to provide from a symptom description...

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