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Old 08-13-2009, 22:09   #1 (permalink)
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2003 P71 with stumble/shudder

hi and thanks for taking time to read this. i have a 2003 P71, with 100k miles. the motor runs well, with the recent exception. under load it stumbles or shudders between 30-70 mph. at first i thought this was a bad torque converter lockup, but, changing the throttle position sensor reduced the stumble/shudder by a good 80%. it will also micro-stall at idle, not often. today i changed the fuel filter, and checked the fuel pressure. before and after readings were similar, 28-32psi at idle, 40-44psi at snap wide open throttle, and 32psi at "held" open throttle.
are these readings correct for a 2003 crown victoria?
could my stumble'shudder come from a fuel pump that isn't delivering correct and consistent fuel pressure?

again, thanks for taking time to read this!

Dave
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Old 08-14-2009, 16:43   #2 (permalink)
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Re: 2003 P71 with stumble/shudder

I don't have access to the 03 fuel pressures but they sound about right, if my memory is serves me right. Have you had the codes checked. There could be a code that doesn't turn the light on but will send you in the right direction. Autozone will check for free.
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Old 08-15-2009, 08:40   #3 (permalink)
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Re: 2003 P71 with stumble/shudder

thanks rtg, i never thought to ask if autozone can read codes that don't trigger the c.e.l. i have an actron OBD2 scanner and no codes are tripped, but the actron is no genesis scanner, i'll have to ask autozone if their scanner reads beyond the actron. thanks for the tip!
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Old 08-15-2009, 21:00   #4 (permalink)
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Re: 2003 P71 with stumble/shudder

Don't know if this will help

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Old 08-16-2009, 07:59   #5 (permalink)
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Re: 2003 P71 with stumble/shudder

jwko- thanks! i appreciate that, i hadn't found that info yet. it seems my fuel pressure is on the low side at 28-32psi compared to 35-45psi. i've been told that my problem is transmission related, on a 100k mile car that is a possibility. but, more and more i'm thinking it is a fuel delivery problem, or ignition. as i mentioned, changing out the throttle position sensor made a big improvment. that is the problem with modern cars, there are so many sensors, that they mask the simplicity of the old days when either your problems were, fuel, spark, or transmission.
and, i did go to autozone, they are not able to read any codes that don't throw the c.e.l., it was worth a try though.
thanks for all replies!
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