IAC error code problem

[rvbuilder2002]

Hi.
I am a long time lurker making first post.

I have a 98 Ranger with 2.5L with 200,000 miles, with a P1504 code (it has actually had the problem for a long time but I have been unable to resolve it)

I originally replaced the IAC with a new after market (made no difference).
I have done a lot of checking for vacuum leaks and can't find any.

Unplugging the IAC causes no change in idle speed.

There is no voltage at the IAC connector plug when checked with a meter between the two wires.

The idle speed screw on the throttle body was already adjusted out as far as it can be (unscrew any more and throttle plate sticks).

Could this actually be related to the TPS being bad?

Any other ideas or checks I should make?

Other than this one problem, the truck runs great and has good power. The idle is even pretty smooth, just a bit fast but not severely.

Thanks

 

[swetrid]

Here is atsb that might pertain to your problem.
Printable View (4 KB)
TSB
00-3-5 HIGH IDLE - TAURUS WITH 3.4L SHO AND RANGER WITH 2.5L AND MANUAL TRANSMISSION

Publication Date: JANUARY 31, 2000

FORD: 1998-1999 TAURUS SHO
1998-2000 RANGER


ISSUE:
A high idle may occur on some vehicles. This may be caused by a poor electrical connection at the wire harness (-12B637-) to Throttle Position Sensor (TPS).

ACTION:
Splice into wire harness (-12B637-) just after the TPS with TPS Connector High Idle Service Kit. Refer to the following Service Procedure for details.

SERVICE PROCEDURE

Verify the concern vehicle exhibits a "high idle" condition when depressing the clutch or shifting between gears for the Ranger or when shifting between Park and/or Neutral for Taurus SHO. If high idle condition is not exhibited, proceed with other driveability diagnostic fix procedures. If condition is present, obtain a High Idle Service Kit (XF1Z-15K607-AA) and proceed by following the instructions found within the service kit.

PART NUMBER PART NAME
XF1Z-15K607-AA High Idle Service Kit



OTHER APPLICABLE ARTICLES:
NONE

WARRANTY STATUS:
Eligible Under The Provisions Of Bumper To Bumper Warranty Coverage And Emission Warranty Coverage

OPERATION DESCRIPTION TIME
000305A Install High Idle Service Kit (Ranger) 0.6 Hr.
000305B Install High Idle Service Kit (Taurus SHO) 0.7 Hr.

DEALER CODING
BASIC PART NO. CONDITION CODE
12B637 30

OASIS CODES:
203200, 617400, 619400


--------------------------------------------------------------------------------

Copyright © 2000 Ford Motor Company

 

[rvbuilder2002]

Thanks,

I will check that out.