99 p71 take forever to accelerate...

07-16-2011, 11:22 AM
Hi, my names Adam and i've had a lot of success reading from these threads! I have a 99 p71 for 6 years now and i've only had the car running great once... Alright here's the problem.. I go out and fire her up, she's starts and idles like a kitten! As soon as I go to get on the highway I hit the throttle to half and she revs up (really slowly) to about 30 mphs then shifts to second gear! The whole time you can feel the engine rev up slowly and she barely even touches the power band... She will go at full throttle but it takes her a while as it feels like she is being flooded the whole time? Here's the things I did as a backyard mechanic... Fuel pump, IAC motor, tps sensor, mass air flow sensor, installed k&n fipk air cleaner system, changed all o2 sensors, replaced intake manifold three years ago with aftermarket, coolant temp sensor, fuel filter, I did almost all of the front suspension and steering! These are things I replaced over the 6 years I had the car! I also had the exhaust checked 1 year ago and the guy said it was perfect! I love this car and I want it to run like a p71 not a turtle! There is no MIL light! I know theres someone smart enough out there and can lead me on the right path! PLEASE HELP MY TURTLE P71 RUN LIKE A COP CAR!!!!!!!!!

07-17-2011, 04:40 PM
With the car in park, when you hit the accelerator does the engine rev up normally or is it also slow?

It could be so many things. I suggest you get the ECU scanned for codes even if the MIL is not lit. Could be a soft code of some sort.

07-17-2011, 05:30 PM
Need alot of Air, fuel, and exhaust for horse power.

Air - Air filter, MAF/IAT, or unmetered air leaks
Fuel - Bad fuel filter, fuel pump, fuel regulator, or relay.
Exhaust - Plugged catalytic converters, or exhaust stream.

I have seen K&N filters cause random misfires on jaguars, also a slow
or slugish MAF/IAT sensor.

If the MAF/IAT, or Air filter is contaminated with too much oil, it could cause the same problem.

07-18-2011, 10:42 AM
With the car in park if I rev the engine it will rev up with a second delay when you first hit the gas. I had the car scanned at napa auto care center, and the guy couldnt even tell me that my o2 was bad as the numbers were steady for the o2... I had to ask him if the o2 sensor should be a steady reading then he told me that it was bad... Theres a soft code for the evap system, I believe it p0455 or something like that. I was told that the evap system has no control over engine management! Here's something interesting... When I disconnect the battery for a half hour, then connect it back, the car seems to have more power with slightly high shifts, but only for a day or two????

07-18-2011, 03:07 PM
A flat voltage on an upstream (front) HO2 sensor would indicate a failed sensor putting the engine/transmission into a failsafe mode. It will not run with normal performance. Replace the bad HO2. If it is a downstream (rear) O2 sensors, it will just set a code and MIL, and not cause the ECU to enter a failsafe mode.

Since when you disconnect the battery you reset the ECU's learned fuel trims, shift points, and spark tables, it defaults to factory defined tables until they can be relearned.

Also, try resetting the ECU again by pulling the battery for a while again and disconnect the MAF sensor. Leave the MAF sensor disconnected. You will get an MIL and the engine will remain in open-loop mode, using only factory defined tables to maintain safe operation. Do not do this for an extended period of time (I've done it for about 20 miles before with no problem before I realized I forgot to reconnect it). Power should not drop off during this time.

I'm not sure exactly where based on the information given, but you have a sensor issue somewhere causing this problem.

08-17-2011, 11:30 AM
I'm going outside now to disconnect the battery and maf sensor. I'm going to leave the maf sensor for a few miles and try that! My cousin has a memo scan tool, which I can see 2 o2 sensors but they are not labeled... on of them fluctuates through a wide range while the other one barely moves up and down by about 100.... I have good power up until half throttle. When I give it full throttle it bogs down a tiny bit from what it was at half throttle...

10-29-2011, 10:47 AM
So After disconnecting the battery and mass air flow sensor the car has more power... but only up to half throttle... When I put the accelerator down to WOT it bogs down a little from half throttle... It downshifts just fine but half throttle gives me more speed than full throttle? I replaced the maf sensor about a year ago brand new from oreillys. Could it be the wrong maf sensor? It fits a regular crown vic?

10-29-2011, 08:28 PM
It could be a bad Throttle Position Sensor (TPS). These are also cheap and easily replaced parts. You can test it with a multimeter. Measure the resistance. Resistance should (I want to say decrease) as you increase the throttle. If it goes the opposite direction or has a "dead spot" on it, the TPS is bad.

11-28-2011, 09:25 AM
The tps is new and that gave me a different problem.. What I have found out with my cousins scan tool is that the (LTFT) always is at 0. If I kick it down or leave it idle the LTFT doesn't move past 0? The (STFT) is going within it's range, + and -. WHY IS THE LONG TERM FUEL TRIM NEVER ADJUSTING?????

11-29-2011, 09:45 PM
LTFT On both banks are staying at 0? They will stay at 0 if you are in open loop mode (car is not up to operating temperature).

When scanning the LTFT on bank 1 and 2 are you sure you are actually reading that PID? What scan tool are you using?

12-19-2011, 10:25 AM
I'm using my cousins scan tool which was like a hundred online. It's a MEMOSCAN! The LTFT is at 0 when I start the car and after 2 and a half hours it still reads 0 on both banks... It says in the monitor status that the 0xygen sensor monitor, and the heated o2 monitor and both reading N/A. It idles fine but accelerates like a turtle. My gas mileage on the interstate only hit about 17 mpg driving more than an hour one way and driving it like a grandpa... I have heard about the DPFE sensor, but have little knowledge on it... I still have no MIL light... Please someone help me before I get sick and tired of it and put her down... lol

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