01 DOHC (AX4N) RPM bounce + AC on - Taurus Car Club of America : Ford Taurus Forum
Reply
 
LinkBack Thread Tools
post #1 of 17 (permalink) Old 09-10-2016, 03:28 AM Thread Starter
Member
 
Join Date: Aug 2012
Location: Los Angeles
Chapter: West Coast
Year: 2001
Model: Ford Taurus
Engine: 3.0L 24v Duratec V6
Posts: 123
Rep Power: 10
 
Trader Score: 0 reviews
01 DOHC (AX4N) RPM bounce + AC on

Hi, I have two perfectly identical 01 Ford Taurus (SEL DOHC AX4N)

both are regularly serviced with OEM fluids and filters

one has 100K on the ODO <--------- This one has steady RPM no matter AC on /off (and clutch engage), and always sitting on 600-650 IDLE no bouncing

the other has 35K on the ODO<----- here I got a 100-200RPM boost / bounce every time the AC clutch engage, nothing major but its cycling like this every 5-7 seconds. other than that the RPM are sheer steady, (till the clutch cycle again) read on the forum - its just the PCM compensate for loss of power by the AC compressor

which one acts normal ?

Thank yall!
DarronSEL is offline  
Sponsored Links
Advertisement
 
post #2 of 17 (permalink) Old 09-10-2016, 07:12 AM
Crazy Devoted Member
 
Join Date: May 2011
Location: NY State
Chapter: Northeast
Year: 2003
Model: Mercury Sable
Engine: 3.0L 24v Duratec V6
Posts: 7,535
Rep Power: 85
      
Garage
Trader Score: 0 reviews
Quote:
Originally Posted by DarronSEL View Post
Hi, I have two perfectly identical 01 Ford Taurus (SEL DOHC AX4N)

both are regularly serviced with OEM fluids and filters

one has 100K on the ODO <--------- This one has steady RPM no matter AC on /off (and clutch engage), and always sitting on 600-650 IDLE no bouncing

the other has 35K on the ODO<----- here I got a 100-200RPM boost / bounce every time the AC clutch engage, nothing major but its cycling like this every 5-7 seconds. other than that the RPM are sheer steady, (till the clutch cycle again) read on the forum - its just the PCM compensate for loss of power by the AC compressor

which one acts normal ?

Thank yall!
Your PCM is a flip phone technology, not a 'smart' phone. It gets inputs from various load expectations and adds IAC to match the load and keep the rpm steady. The tranny, PS and A/C are rpm matched. If the load is less than expected the rpm will increase. My '01 did that a while before I sold it. It means the A/C is not up to par. My '03's (wagon and sedan DOHCs) are within a needle width.

If the IAC is draggy, the RPM will drop with each of the key inputs. Put in gear and the rpm will drop. And all of them will be off. Only the A/C and it is the A/C at fault.

(I miss my flip phone)

-chart-
chartmaker is online now  
post #3 of 17 (permalink) Old 09-10-2016, 07:37 AM Thread Starter
Member
 
Join Date: Aug 2012
Location: Los Angeles
Chapter: West Coast
Year: 2001
Model: Ford Taurus
Engine: 3.0L 24v Duratec V6
Posts: 123
Rep Power: 10
 
Trader Score: 0 reviews
Ah! Replaced the IAC with OEM motorcraft, not even a slight change ..
What's up with m AC compressor?!
If it's not "satisfying" the PCM should it be replaced ? (It works perfectly though ..)
DarronSEL is offline  
 
post #4 of 17 (permalink) Old 09-10-2016, 07:56 AM
Devoted Member
 
repairman54's Avatar
 
Join Date: Aug 2003
Location: Montague NJ
Chapter: Northeast
Year: 2003
Model: Mercury Sable
Engine: 3.0L 24v Duratec V6
Posts: 1,142
Rep Power: 35
 
Trader Score: 0 reviews
A/C is cycling frequently? Only 2 things cause that. Undercharged or Overcharged refrigerant.
In isolated cases other components but low on 134a is the most common.
RPM bounce is normal, tachs in these cars can vary, not exactly precision gauges.
As chart said rapid cycling of a/c and flip phone PCM results in a system lag so it may not be getting a chance to "settle" in.

John
"Some suffer from insanity, I choose to enjoy it"
'11 Tahoe
'09 Malilbu LS
'03 Sable LS 24v
'05 Sable 24v son's
'01 FLHR
Ski Doo's Sea Doo
Previously enjoyed vehicles
'07 Mustang GT 3 pedals
'88 Bull 170k rust & trans = junked
'94 Bull 160k sold while still running
'00 Sable wagon 24v 212k sold running fine
'89 S10 Blazer 4x4
'79 Dodge Van period customized
'75 Cordoba
'68 GTO
'68 Chrysler Newport 2dr
'67 Chevy Caprice 2dr
'67 Chevelle
'65 Bonneville
'65 Chevelle
'64 Olds Jetstar 88
repairman54 is offline  
post #5 of 17 (permalink) Old 09-10-2016, 09:04 AM
Crazy Devoted Member
 
Join Date: May 2011
Location: NY State
Chapter: Northeast
Year: 2003
Model: Mercury Sable
Engine: 3.0L 24v Duratec V6
Posts: 7,535
Rep Power: 85
      
Garage
Trader Score: 0 reviews
Quote:
Originally Posted by repairman54 View Post
A/C is cycling frequently? Only 2 things cause that. Undercharged or Overcharged refrigerant.
In isolated cases other components but low on 134a is the most common.
RPM bounce is normal, tachs in these cars can vary, not exactly precision gauges.
As chart said rapid cycling of a/c and flip phone PCM results in a system lag so it may not be getting a chance to "settle" in.
Good call on 'short cycling'. Your car is talking, asking for HELP!

I took my IAC (looks clean) out and wiped the shaft where it goes through the seal at the solenoid end with a Q-Tip, drop of light oil, move the piston with a Q-tip and then wipe off the excess oil. Made a difference. I think mine is a close to perfect as it gets. But I am paranoid. If a few minutes effort make it better, why not?

And the PCV makes a difference, only OEM, and the elbow. PCV can cause low or high idle. Been there.
-chart-
chartmaker is online now  
post #6 of 17 (permalink) Old 09-10-2016, 09:18 AM Thread Starter
Member
 
Join Date: Aug 2012
Location: Los Angeles
Chapter: West Coast
Year: 2001
Model: Ford Taurus
Engine: 3.0L 24v Duratec V6
Posts: 123
Rep Power: 10
 
Trader Score: 0 reviews
That's interesting, the entire IAC area is really nice and smooth + brand new OEM IAC in place, PCV was never replaced in 16 years, but one would think if malfunction should through a cel code or act funny no matter AC on / off ..
Would you replace it ?
DarronSEL is offline  
post #7 of 17 (permalink) Old 09-10-2016, 09:27 AM
Crazy Devoted Member
 
Join Date: Dec 2006
Chapter: Midwest
Year: 1998
Model: Mercury Sable
Engine: 3.0L 24v Duratec V6
Posts: 18,811
Rep Power: 99
     
Trader Score: 1 reviews
Yes, if 16 yrs. old, lol. Get a Motorcraft pcv valve from Rockauto online. Preventive maintenance. Carefully inspect pcv hose/elbow assy. when replacing. Idle may still fluctuate if a/c issues are present.

Last edited by sheila; 09-10-2016 at 09:30 AM.
sheila is online now  
post #8 of 17 (permalink) Old 09-10-2016, 02:01 PM Thread Starter
Member
 
Join Date: Aug 2012
Location: Los Angeles
Chapter: West Coast
Year: 2001
Model: Ford Taurus
Engine: 3.0L 24v Duratec V6
Posts: 123
Rep Power: 10
 
Trader Score: 0 reviews
Quote:
Originally Posted by sheila View Post
Yes, if 16 yrs. old, lol. Get a Motorcraft pcv valve from Rockauto online. Preventive maintenance. Carefully inspect pcv hose/elbow assy. when replacing. Idle may still fluctuate if a/c issues are present.
Hi Thanks, will do!

as a side note my Idle RPM doesn't fluctuate nor bouncing etc ..
its very steady, then the AC clutch kickin in and the Idle raise about 100-200 rpm on top of normal idle speed of 600
and so on every 5-7 seconds ..

needless to say none of this happen when AC is off ..

any idea what could it be ?
just lack (=or too much) of 134a could in theory cause this ?
DarronSEL is offline  
post #9 of 17 (permalink) Old 09-10-2016, 02:29 PM
Devoted Member
 
repairman54's Avatar
 
Join Date: Aug 2003
Location: Montague NJ
Chapter: Northeast
Year: 2003
Model: Mercury Sable
Engine: 3.0L 24v Duratec V6
Posts: 1,142
Rep Power: 35
 
Trader Score: 0 reviews
Rapid cycling of the a/c is the issue. Most common is lack of or low 134a. Compressor cycles on low pressure cutoff switch. It's function is to protect the compressor from lack of refrigerant.
Cutoff is on low pressure side of the system, usually shuts off compressor when low side pressure drops below 20 psi. .
System needs to be checked and on a 15 yr old car it's normal to have a miniscule leak and loose some over all this time.
IMO your system is cycling on the low pressure cut off. When compressor starts it draws down the equalized system pressure to the cutoff limit stopping compressor, then pressure will rise back up and trigger the cutoff to restart compressor and back down it goes again to the low limit cutoff. That's why it keeps starting and stopping endlessly and too quickly, PCM is not designed for this scenario, on a hot day compressor will run endlessly to provide cooling.
System pressures need to be checked first before wasting money on other engine components.
Money spent on a IAC would get a set of A/C gauges at Harbor Fright, about $50

John
"Some suffer from insanity, I choose to enjoy it"
'11 Tahoe
'09 Malilbu LS
'03 Sable LS 24v
'05 Sable 24v son's
'01 FLHR
Ski Doo's Sea Doo
Previously enjoyed vehicles
'07 Mustang GT 3 pedals
'88 Bull 170k rust & trans = junked
'94 Bull 160k sold while still running
'00 Sable wagon 24v 212k sold running fine
'89 S10 Blazer 4x4
'79 Dodge Van period customized
'75 Cordoba
'68 GTO
'68 Chrysler Newport 2dr
'67 Chevy Caprice 2dr
'67 Chevelle
'65 Bonneville
'65 Chevelle
'64 Olds Jetstar 88
repairman54 is offline  
post #10 of 17 (permalink) Old 09-10-2016, 02:34 PM
Member
 
Join Date: Jun 2010
Location: CA
Chapter: West Coast
Year: 2004
Model: Ford Taurus
Engine: 3.0L 24v Duratec V6
Posts: 435
Rep Power: 15
 
Trader Score: 0 reviews
Have you reset and let the PCM relearn it's idle strategy since all the maintenance you've done? And was this problem there or different before you did the maintenance?

There's a separate idle strategy with and without AC.
rjacket is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Taurus Car Club of America : Ford Taurus Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Similar Threads
Thread Thread Starter Forum Replies Last Post
AX4S/AX4N Bellhousing differences >> Hoping to bolt up my 3.8 + AX4N. DMX Engine and Drivetrain 8 10-12-2015 05:23 PM
Vulcan to DOHC swap gen 4 engine to gen 1 car ZAFH Engine and Drivetrain 21 11-22-2014 08:12 AM
AX4N HELP Dbhill42 Engine and Drivetrain 24 09-02-2014 09:31 PM
Will my tranny bolt up? AX4N... help...please? taurusflip Maintenance and Repair 17 11-24-2013 09:27 AM
DOHC for Vulcan swap unclejunk Maintenance and Repair 21 04-27-2013 07:52 AM

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome