Hi! Engine runs great, starts great, but at stop lights/signs when first heading to work as engine warms..... engine hits about 135F to 140F and the idle wants to surge up and down between 600-750 rpm. Idle is rock solid when under 135F +/- and over 140F +/-. Weird? I just put the new RiffRaff CPS in and it ran fine for a few weeks, but now the surge? any ideas? Check pigtail and connection on CPS? Also installed new Motorcraft ICP too. Engine ran great with new sensors when first installed, It doesn't stall, just irritating for a few minutes on my daily commute. As soon as engine hits 140-145 it goes away.

 

Any way to scan codes? Could be air temp sensor giving wonky signal causing PCM to bounce between high and low idle. Just a guess without any data to go on.

 

Where are you watching the engine temp? Through a scanner, dash or a mechanical gauge?

 

Will scan again with OBDII, nothing popped up last scan.

 

Glow Shift Coolant Temp gauge... I ran the Forscan app on OBDII last week, Oil Temp & Coolant Temp basically mirrored each other as engine warmed up.

Any idea why the idle would fluctuate for only a 5 degree +/- change in Engine temp? Maybe the viscosity change at 135F is messing with the ICP to IPR to PCM? I'll try unplugging the ICP right when it starts fluctuating at 135F and see if the idle stabilizes.

 

I'd recommend starting FORScan and capturing a log of the drive through this warmup period. Include all of the PIDs below. Post the CSV file and/or chart the file using the PID charting tool. Let's see if any of these parameters are moving strangely, to give us a clue.

https://www.ford-trucks.com/forums/1...d-q-and-a.html

RPM(1/min) – Engine revolutions per minute

IPR% - IPR duty cycle percentage

ICP(psi) – Injector Control Pressure (select ICP, not ICPV, as seen in the image below)

VSS(mph) Vehicle speed sensor

FUELPW(ms) – Fuel injector pulse width

MFDES(mg) – Mass fuel desired

EBP_A(psi) – Exhaust back pressure (select the EBP_A and not EBP)

MAP(psi) – Manifold air pressure

IAT(A°F) – Intake air temperature

MAT(A°F) – Manifold air temperature

EOT(A°F) – Engine oil temperature (select EOT, not EOTV)

MGP(psi) – Manifold gauge pressure (boost)

ECT(A°F) – Engine coolant temperature (only available on ZF6)

TFT(A°F) – Transmission fluid temperature (only available on 4R100)

VPWR(V) – Vehicle battery power

TC_SLIPACT(1/min) – Torque converter (only available on 4R100)

BAROV - Barometric pressure (select PSI instead of the default volts)

APP - Accelerator Pedal Position

 

Thank you Jeff, I'll try to get all that data soon, Very generous of you to analyze it.

I bought the "Motorcraft" ICP from Auto Parts Wholesale on Amazon....instead of Riff Raff, just to save $30 (what a dumb ***)....I pulled the ICP sensor plug and it was oily, It's only been 45 days since install??? WTF...Counterfeit? or Motorcraft made in Wuhan now?