High idle problem.

[marknbacon]

How are ya'll doing. I recently bought a (used, salvaged title, beater.) 2003 Focus ZX5 with 215k miles, rebuilt title, what looks to be a replacement motor, as well as a few misc. problems. Changed the oil and filter, trans fluid and filter, and the trans mount.

Since I got the car, it had an extremely low idle (500-700 rpm, it died often before we changed fluids and filters)and continued to run slow until my mechanic cleaned up the throttle body and intake with some carb cleaner as it had some buildup around the valve. After that, the car wants to idle (and continue to run) at 3k-4k rpm. I can keep it down by stopping the car and holding it with the brake, but it really really wants to accelerate by itself. Once I get it up to speed, I usually don't have to touch the accelerator to keep it at speed.

Also, if I'm driving it and it's in 3rd gear, it acts like it jumps into neutral, but if I accelerate, it'll drop it's RPMs and shift into 4th.

I've check codes on it, I get p0122 (TPS sensor) and p0755 (SSB, or "shifting solenoid position 2").

Personally, my suspicion is the TPS is bad, and causing a high idle and every time I mess with it, it changes the position and idles a little slower. I'm not too concerned with the p0755 code right now.

Does anyone have any other ideas what the problem is with the idle is, or maybe a confirmation on if the TPS is the problem?

Much appreciated.

[Sponsor]

[BC_ZX3]

Check the wiring as indicated by the DTC code defintion below. On a rebuilt or swapped motor salvage vehicle, I'd re-check all the wiring harness connectors and the wiring integrity as a first step.

P0122 - Throttle Position (TP) Circuit Low Input
The TP sensor circuit is monitored by the PCM for a low TP rotation angle (or voltage) input through the comprehensive component monitor (CCM). If during key ON engine OFF or key ON engine running the TP rotation angle (or voltage) changes below a minimum calibrated limit, the test fails.
Causes:
TP sensor not seated properly
TP circuit open to PCM
VREF open to TP sensor
TP circuit short to GND
Damaged TP sensor
Damaged PCM
A TP PID (TP V PID) reading less than 3.42% (0.17 volt) in key ON engine OFF, continuous memory or key ON engine running indicates a hard fault.

Try http://fordfuelinjection.com/?p=30 for some background info.

On the Focus, the TPS has three wires: brown, white and yellow.
Yellow is VRef (5V)
White is TPS
Brown is Signal Return

With a voltmeter, you need to the read the voltage between the TPS and SIG RTN pins as you rotate the throttle open with ignition on. Use the chart at the bottom of the article for approximate voltages. Look for a steady increase in voltage from 1V to 5V, closed to open.

[marknbacon]

Ok, the sensor might not be seated properly, do is there a how-to somewhere on how to do that? Also, I'll have to check on the voltages when I go to work tomorrow as my multimeter's leads got damaged during my last PCS move.

Also, to re-check the the wiring integrity (continuity check) I need to know where those wires go, and I'm a little too cheap to buy the wiring manual on that. Do you (or someone else) know what connector and pins those wires go to?

Thanks.

[marknbacon]

Also, is the sensor supposed to spring back into position? Because it isn't.