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#4071638 - 07/23/20 12:01 PM RPM surging: the saga continues
GMUE03 Offline
n00b

Registered: 12/23/18
Posts: 47
Loc: Florida
Hello all, for a while now my car has been doing an odd thing. If in drive or reverse, below 5 MPH, the RPMs will die and the car will shudder if I make quick steering inputs (like maneuvering into a parking spot). It gets to the point that the battery light will come on briefly when it happens (battery runs at 13.4V at idle, so I don’t think it’s my battery). I can also replicate the symptom if I coast at low speed and bring the vehicle to a stop briefly (like creeping up in traffic). This issue is only apparent at low speeds. I’m at a complete loss. Scanner tells me I have no codes. I’ve replaced everything that I can think of that would cause this issue.
•new hitachi MAF
•new motorcraft IAC valve
•motorcraft fuel filter
•all new motorcraft plugs and coils

Can anybody point me in the right direction on this? Maybe my IAC is defective in some way?


Edited by GMUE03 (07/23/20 12:03 PM)
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2003 Mercury Grand Marquis LS Ultimate Edition- 90K


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#4071644 - 07/23/20 01:33 PM Re: RPM surging: the saga continues [Re: GMUE03]
2007CrownVic Offline
Over the Hill

Registered: 11/19/11
Posts: 2976
Loc: Canada
Did you clean the throttle body? New fuel filter?

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#4071664 - 07/23/20 03:27 PM Re: RPM surging: the saga continues [Re: GMUE03]
RF_Overlord Offline

Poobah

Registered: 12/14/02
Posts: 7121
Loc: MA
There's a switch in the power steering hard-line that loops around in front of the A/C compressor. The purpose of that switch is to signal the PCM to increase RPM when steering effort gets high at low speed, such as your symptoms describe. Had a bad one in my ex's '03 Marauder. You can test the switch itself with an ohmmeter while a friend saws the steering wheel back and forth.

There are 2 different ones used, one with a square connector and one with a round connector. Rock Auto had the wrong one listed and I found the right one under the Crown Vic section.


Edited by RF_Overlord (07/23/20 03:59 PM)
_________________________
'03 Mercury Marauder (The Blackbird)
Trilogy Motorsports supercharged #61
Too many mods to list / Driveway Queen

'04 Grand Marquis LS Limited Edition (Spruce Green)
Daily Driver (Thanks, Adam!)

'00 Grand Marquis GS (Silver)
Rotted frame and broken transmission crossmember
Being resurrected...slowly.

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#4071676 - 07/23/20 05:12 PM Re: RPM surging: the saga continues [Re: RF_Overlord]
GMUE03 Offline
n00b

Registered: 12/23/18
Posts: 47
Loc: Florida
Good to know, I’ll test it and let you know what the results are. What kind of symptoms did you experience when it went bad?
_________________________
2003 Mercury Grand Marquis LS Ultimate Edition- 90K


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#4071682 - 07/23/20 05:35 PM Re: RPM surging: the saga continues [Re: GMUE03]
RF_Overlord Offline

Poobah

Registered: 12/14/02
Posts: 7121
Loc: MA
increased steering effort when making low-speed turns, like parking.
_________________________
'03 Mercury Marauder (The Blackbird)
Trilogy Motorsports supercharged #61
Too many mods to list / Driveway Queen

'04 Grand Marquis LS Limited Edition (Spruce Green)
Daily Driver (Thanks, Adam!)

'00 Grand Marquis GS (Silver)
Rotted frame and broken transmission crossmember
Being resurrected...slowly.

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#4071926 - 07/25/20 10:38 PM Re: RPM surging: the saga continues [Re: GMUE03]
GMUE03 Offline
n00b

Registered: 12/23/18
Posts: 47
Loc: Florida
Wasn’t able to check the switch today because I didn’t have a second person but I did realize that when I turn the whee the RPMs do raise like they’re supposed to but once I stop giving steering input the RPMs drop to the verge of stalling
_________________________
2003 Mercury Grand Marquis LS Ultimate Edition- 90K


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#4072096 - 07/27/20 09:42 PM Re: RPM surging: the saga continues [Re: 2007CrownVic]
GMUE03 Offline
n00b

Registered: 12/23/18
Posts: 47
Loc: Florida
Throttle plate and body are clean
_________________________
2003 Mercury Grand Marquis LS Ultimate Edition- 90K


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#4072592 - 08/01/20 11:46 AM Re: RPM surging: the saga continues [Re: GMUE03]
speedfreak Offline
Member

Registered: 08/13/06
Posts: 169
Loc: Massachusetts,USA
How did you check voltage? Have you checked the engine grounds? I put a PI alternator in my Sport and it puts out just over 14V according to my meter and my stereo display. What your actual idle RPM? Have you checked all the accessory pulleys for tightness? I'd also check the tps signal. I think I remember something about they have a wide acceptable range and can be easily modified to get some adjustment to get it in a better area of that range. If it's off it can cause a lower, but acceptable to the ecm, idle.
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2006 LX Sport: enlarged Air Box intake tube to 4" and sealed to radiator support, stock "Sport" front spring/ arnott HD rear air bags, KYB PI spec gas-a-justs all around, 28.5mm front sway bar, 21mm rear sway bar (both with poly bushing), 3:27 locker rear, Heinous rear control arms, Metco watts link, dual 2.25 cat back w/ stainless no-name mufflers, 20% tinted windows, Powerslot rotors, black AMR 19" staggered rims, SVT badge on decklid, Sony head unit, kenwood [email protected] 45watts, jbl 12" sub @500W


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#4073150 - 08/05/20 01:27 PM Re: RPM surging: the saga continues [Re: GMUE03]
2008interceptor Offline
Over the Hill

Registered: 09/02/02
Posts: 3130
Loc: Pennsylvania
What is the level of the power steering fluid? I had an issue almost similar to a bind feeling. Someone in here told me that is an issue certain years. The pump gets overwhelmed I don't know if it is known to cause a stall. Though I don't see why not the fix was using the later pumps with increased capacity 09+.


Edited by 2008interceptor (08/05/20 01:30 PM)
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2008 Ford Crown Victoria Police Interceptor P71 with street appearance package.

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#4073278 - 08/06/20 12:17 PM Re: RPM surging: the saga continues [Re: speedfreak]
GMUE03 Offline
n00b

Registered: 12/23/18
Posts: 47
Loc: Florida
I checked my battery voltage on the terminals with a multimeter. With the car off the battery read 12.6V. With it at a warm idle it read 13.4V. I don’t have a tach but according to my scanner it read ~700 rpm iirc at a warm idle. (Id have to check again). All the pulleys don’t have any play, I put in a new tensioner and idler pulley not too long ago. I replaced the TPS with a motorcraft unit, it reads 20% at closed throttle.
_________________________
2003 Mercury Grand Marquis LS Ultimate Edition- 90K


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#4073282 - 08/06/20 12:18 PM Re: RPM surging: the saga continues [Re: 2008interceptor]
GMUE03 Offline
n00b

Registered: 12/23/18
Posts: 47
Loc: Florida
Level is within the minimum margin, fluid was flushed via the syringe method (did it about 5 times) last year with Mercon V.


Edited by GMUE03 (08/06/20 01:43 PM)
_________________________
2003 Mercury Grand Marquis LS Ultimate Edition- 90K


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