1997 Lincoln Town Car: engine surges

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The Derfer - 29 Oct 2006 21:16 GMT

I've got a 1997 Lincoln Town Car, Cartier Series.
I notice that when idling in the Drive Gear, the car sometimes
surges ahead, occasionally with force a bit stronger than
the force with which I've got the brakes holding it back.
And sometimes, the engine dips really low, almost to the
point where it seems like it's going to stall, which
thankfully it doesn't.

One other pattern: the car only does this when I've got
the heater or A/C on.

What could this be and how might I repair it? I took it to
Midas and they adjusted the idle, which helped but didn't
ultimately solve the problem.
TIA.

-The Derfer

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Backyard Mechanic - 29 Oct 2006 23:14 GMT

> I've got a 1997 Lincoln Town Car, Cartier Series.
> I notice that when idling in the Drive Gear, the car sometimes
[quoted text clipped - 11 lines]
> ultimately solve the problem.
> TIA.

There IS no adjustment to the Idle Air control. What they PROBABLY did
is either adjust the throttle stop screw... a NO-NO.. or spray some
intake cleaner in the IAC.

NEVER LET THOSE MONKEYS under your hood.

If you have some metric wrenches, you can go to NAPA, get the part and
replace it yourself. I dont recommend cleaning it. Effect wont last
long.

While you are at it, you might google on how to clean your Mass Air Flow
sensor. Needs done periodically, never mind what Ford says.

Signature

Yeh, I'm a Krusty old Geezer, putting up with my 'smartass' is the price
you pay..DEAL with it!

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tomasz.kk@gmail.com - 30 Oct 2006 01:21 GMT

> One other pattern: the car only does this when I've got
> the heater or A/C on.

maybe its related to A/C compressor which obviously takes some power
from the engine.
mine 4.6 does the same, its normal i guess. Without A/C it idles
fine, i have new ignition wires, new spark plugs and MAF cleaned,
and air filter new too.
Dont know what else could affect the idle speed, its controlled
electronically, no any adjustments,

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lugnut - 30 Oct 2006 02:36 GMT

>> One other pattern: the car only does this when I've got
>> the heater or A/C on.
[quoted text clipped - 6 lines]
>Dont know what else could affect the idle speed, its controlled
>electronically, no any adjustments,

As is the case with the OP, your problem is also likely an
IAC problem. If the IAC is working properly, you will have
to pay very close attention to ever know when the a/c
comprerssor is in or out. Many times, the IAC can be
cleaned by soaking the valve end overnite in a good solvent.
You can also just bolt in a new one from a dealer for about
$80 or aftermarket for about $50. Either way, the IAC is
the likely problem. You should never adjust the idle stop
screw. That controll the engine base idle. If you adjust
it to cover up an IAC problem, the IAC will not be able to
properly control the idle even if it is replaced. Setting
the base idle must be done "by the book".

Lugnut

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zwsdotcom@gmail.com - 30 Oct 2006 02:58 GMT

> it to cover up an IAC problem, the IAC will not be able to
> properly control the idle even if it is replaced. Setting
> the base idle must be done "by the book".

Isn't it necessary to recalibrate this after replacing the IAC valve
anyway?

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Backyard Mechanic - 30 Oct 2006 19:28 GMT

>> it to cover up an IAC problem, the IAC will not be able to
>> properly control the idle even if it is replaced. Setting
>> the base idle must be done "by the book".
>
> Isn't it necessary to recalibrate this after replacing the IAC valve
> anyway?

No... has nothing to do with the IAC, except to keep IAC air control
within proper range.
If they adjusted the stop screw to increase idle speed, the IAC might hit
the internal end of travel when starting in very cold weather. With
resulting hard to start symptom.

Once IAC is replaced, get a tach and check for approx 550-600 rpm when
engine is up to temp and IAC connecter off. If higher than that, adj to
550 rpm or the rpm stated in book.
That rpm is for v-8 only.

Signature

Yeh, I'm a Krusty old Geezer, putting up with my 'smartass' is the price
you pay..DEAL with it!

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lugnut - 30 Oct 2006 19:38 GMT

>> it to cover up an IAC problem, the IAC will not be able to
>> properly control the idle even if it is replaced. Setting
>> the base idle must be done "by the book".
>
>Isn't it necessary to recalibrate this after replacing the IAC valve
>anyway?

Not unless someone has already screwed around with the idle
stop. Idle stop adjustment also changes the base for the
TPS. The only thing you need to do in a routine replacement
of the IAC is make sure the throttle body is clean. You can
get the procedure for a good service manual- you may find
one at your local library. The MAF also needs to be cleaned
occasionally - this is a good time for that maintenance.
Once you do this, the codes need to be cleared. A scanner
is the best way to do that but, disconnecting the neg
battery cable for 10-15 minutes will also clear it. If you
clear the codes this way, start the engine with all
accessories "off" and don't touch a thing other than the
starter. Let the engine idle til warm and move it among
each of the trans selector positions several times allowing
time for it to stabilize in each. Drive the car around
normally for a few miles to allow the PCM to relearn the
engine operating parameters. You should be good to go at
that point.

Lugnut

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Sharon Cooke - 30 Oct 2006 14:33 GMT

> I've got a 1997 Lincoln Town Car, Cartier Series.
> I notice that when idling in the Drive Gear, the car sometimes
[quoted text clipped - 13 lines]
>
> -The Derfer

Clean or replace IAC valve. Take it to someplace like AutoZone where
they'll pull the engine trouble codes, for free (except Caifornia).

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