My engine started to race up to 1600 rpm after varying amounts of running. It's a little disturbing sometimes, when you apply the brakes to slow down or stop, and then the engine suddenly decides to rev up all by itself.

I ran the KOEO test, and it showed a code of 24, which according to my old EEC-IV code chart shows ACT voltage out of range. I can't remember where the ACT sensor is on a 1990 4 liter v6; can anyone remind me?

It also showed a stored code of 14, which my chart says is intermittent PIP, and to check the TFI module. Does an engine with EDIS have a TFI module?

 

our aero's have vacuum assisted brake boosters ya? is it a possibility that the booster went bad causing an intermittent vacuum leak when the pedal is applied, which causes the rise in rpms? just a thought... that's how it works on my civic any ways... lol

 

i'm with dcrb on this one air leak in the brake booster.

clear the codes and see if they come back with the symtoms of racing idle
intermittent ACT might cause the symtom, if the sensor wire was intermittently shorting out from vibration.
also could be the IAC, the PCM keeps it wide open with max. pulses as long as in cruise mode and TPS is above min. acts as dashpot if TPS input suddenly goes to 0. may be sticking open at times.

ACT
Ford Fuel Injection Air Charge Temperature (ACT)
top driver side of intake plenum behind the IAC


yes there is PIP on a 4L EDIS system

created in the Ign.ControlModule comes out on pin 1, goes to pin 56 on the PCM
there is an NC pushbutton switch in the PIP line used for testing, can't remember where it is located, may be open. test continuity from pin1 of the ICM to p56 of the PCM, disconnect both before testing.
should also be able to see PIP signal on line with scope.



DTC 14/211 indicates two successive erratic Profile Ignition Pickup (PIP) pulses occurred, resulting in a possible engine miss or stall.

Possible causes:

-- Loose wires/connectors.

-- Arcing secondary ignition components (coil, cap, rotor, wires, plugs, etc.).

-- On-board transmitter (2-way radio).*

l Verify all radio and condenser installations. Carefully follow manufacturer's installation instructions regarding the routing of antenna and power leads.
------------------
System Description

The 4.0L EI (High Data Rate) Ignition System consists of a CKP (variable reluctance) sensor, an Ignition Control Module (ICM), Powertrain Control Module (PCM) and one 6-Tower Coil Pack.

The EI (High Data Rate) System operates by sending crankshaft position information from the CKP sensor to the ICM. The module generates a PIP signal and sends it to the PCM. The PCM responds with a SPOUT signal containing advance or retard timing information that is sent back to the ICM. The module processes the CKP and SPOUT signals and decides which coils to fire. In addition, the module generates an Ignition Diagnostic Monitor (IDM) signal to the PCM which is used to indicate a failure mode and also provide a tach output signal.
-----------------------

ICM

The ICM is a microprocessor-based device with coil drivers which make decisions about spark timing and coil firing. The module turns the coils on and off at the correct time and in the proper sequence based on information from the CKP sensor and a pulse width modulated signal (SPOUT) generated from the PCM. The module receives CKPS and SPOUT signals and produces PIP and IDM output signals which are sent to the PCM.

 

Thanks guys. (96, I will repeat what others have said: You are a fount of information!)

I haven't had a high powered transmitter in the car for many years, just the cell phone, so that can't be disrupting the PIP. I have no aftermarket radios installed. So I'm going to look for possible bad grounding of one or more of the ignition components.

I'm almost sure that the immediate cause of the higher idle speed is due to the IAC, but commanded by the EEC; it stops doing it after a restart, so the IAC is probably not sticking open. But it would come on randomly, whether I'm applying the brakes or not, but looks like only after the engine has warmed up. And in the past, when I've had less severe vacuum leaks than from the brake booster (a small hose popped off of the rear vacuum tree), the engine would barely idle, and the EEC lit up the CEL. That's not happening now.

We did a quick test with a restart (reset) after a high idle occurrence by idling down the street. It cruised along at about 12 mph for a while, and then suddenly jumped up to 25 mph all by itself. Putting the transmission in neutral, the idle was definitely up. I'm going to check the ACT sensor. What are the correct voltages for hot and cold?

 

ACT info:
Ford Fuel Injection Air Charge Temperature (ACT)

However for the engine to race IAC is more likely the culprit.

 

Sorry, I missed the ACT link in 96's message.

The page says that it's less likely for the ACT to fail than for something else. Is this true even if the EEC reports out of range voltage readings during the KOEO test? It was above 50F when I ran the test, as suggested by that page.

Just to cover everything, I'll try to clean out the IAC tomorrow.

 

Racing Engine - I thought this thread was going to be about a supercharged Aerostar or something.
Yep, you guys know your stuff!

 

Sorry VanGo, I realized it was a poor choice of words when I first saw my post show up. The first thing that came to my mind was probably the same as you. But I think it is the way a lot of mechanics describe an engine that revs up and down, either manually or on its own.

 

you guys crack me up.
i came to the end of this tread thinking i was going to read something about xlt finding his Aero's problem.
that's great, nothing like in the middle of the a long wet dark winter turning a headache into a good laugh.

Racing Aerostar, are those synonyms or a diabolic semantically use of words.

 

Well, it's not the IAC; it moves just fine, and the idle speed changes with unplugging/plugging the connector.

There's also no obvious vacuum leaks in the brake booster or line. I tried tugging on the lines with no affect on the idle. If I pull any lines while idling, it does as I expected: the engine starts to buck, and the CEL comes on again. Just for completeness, I ran KOEO again, and it kicked out code 91. My chart says bank 2 always lean, look for a vacuum leak.

I found the ACT, from inside the cabin through the dog house opening. It's more to the rear than the front, and nearly impossible to reach. It doesn't look like the wiring is damaged; it's wrapped up into a bigger bundle pretty quickly after leaving the intake.

I'm going to have to hold off on getting any further on this for a couple months as it will require movements from me that I can't do right now due to health issues.

 

can of carb cleaner with spray tube to pinpoint leaker?

can't think of any location to measure ACT voltage except at the sensor, pain.

saying a prayer for you healing fast
have a Merry Christmas with your family

 

Thanks for the suggestions and good wishes. And Merry Christmas to you and all.