EEC IV technician (high idle)

[lonestar]

Hopefully someone here can help, given all the useful threads I have found in the past. I need some advice for an erractic high idle on a 88 Escort. I have checked the engine codes as follows
KOEO
73 refers to TPS (throttle pos.)
34 EGR not responding, suggest EVP (valve pos.) or PFE (press. feedback)

Memory
23 TPS out of range
32 EGR not respond, similair to 34

KOER
99 ECA has not learned to control idle

Now comes the weird part. I can quickly turn the ignition off and on and the idle usually returns to normal, indicating a electrical problem, rather than mechanical such as a stuck EGR. Then the high idle returns if revved above 2000-2500 RPM. Mant places suggest if you get a 73 code replace the TPS and test again. I replaced the TPS a year ago for the same problem, but no luck, so I just lived with it. Not sure about the calibration part. It appeared to have no way of calibrating it, just a little slot to catch the butterfly shaft. I'm thinking of also replacing the PFE, but it didn't cause an high idle in my mothers 91 Taurus.
The 99 code threw me. I was thinking maybe my ECA (computer) may be fried and I could pick oine up at a junk yard.

Now that I have my X to drive, I can work this so I can sell it, or drive it to work.

 

[Guy Groves]

My 2 cents....

Go buy this book:
How to understand, service, and modify Ford Fuel Injection & Electronic Engine Control, by Charles O. Probst, SAE (List $30)

This covers 1988 - 1993 Ford fuel injection / EEC IV

Observation:
Erratic high idle

1) Code 73 - KOEO: Insufficient throttle position CHANGE
The TPS is NOT adjustable.

2) Code 34 - KOEO: EGR - Insufficient EGR Flow / excessive exhaust backpressure; or EVP voltage above closed limit (SONIC)/PFE sensor voltage high or out-of-range.

3) Code 23 - KOEO: TP out of self test range

4) Code 32 - KOEO: EVP voltage below closed limit (SONIC) / EPT circuit volyage low (PFE)


5) Code 99 - KOER: Ignore for now, assume casacaded error code due to other codes. With EGHR and TPS error codes the ECC can not learn how to idle properly.

What to check:
I would not expect the sensors to be bad. I would first look at the connectors and the mechanical working of the EGR, and installation of the TPS.

TPS:
Are you sure you got the TPS on correctly? Make sure the shaft from the throttle valve fits into the sensor correctly so that it works (rotates the sensor with the shaft).

Connectors:
Are the harness connectors on properly (TPS, EVP, PFE)? - If you cleaned the "grease" out of the connectors this could be a problem. You may now have a connection problem, the grease is an eltrolitic / oxidation inhibitor grease for electrical connection. Without this grease you may simply have bad contacts and could be the simple solution for the problem.

EGR:
Have you changed, cleaned, or otherwise played with your EGR? The 34 & 32 codes indicate that you should check out your EGR.
a) The valve that controls the exhaust flow into the manifold must be clean. They are often "gunked up". If you clean it, it MUST be clean all the way around or it will not seat properly and there will be a leak. The intake hole must also be cleaned of any carbon deposits.
b) check connectors
c) test voltage levels (see reference)
d) If you removed your EGR did you replace the gasget? you may have a leak there.

 

[lonestar]

Thanks for the info, thats alot for 2 cents.

I fooled with it yesterday and tested some things

TPS tests fine, varies resistance as throttle opens (about a year old)

ISC tests fine, nose switch opens and closes (about 2 years old)

EGR closed

I was also suspecting the PFE. I guess that acts as a EGR position sensor. If signaling open EGR the computer may be compensating by holding the throttle open. But, when I knew the EGR was closed and reconnected it, I disconnected the vacuum line so it wouldn't open and disconnected the PFE so no signal would be sent and and still got an high idle. I have had a EGR vavle stuck open before on a 83 LTD and it caused a rought idle or it died, not a high idel. This is why I tend not to blame the EGR, but that system may not of had a EGR position sensor to compensate for a open EGR.

Also I made sure the TPS was installed conrectly by loosening the bolts and turning the throttle to see the TPS twist a little. Suspected the connections, disconnected the TPS and it would not start. All connections have dieletric grease and terminals are clean.

ISC is a little confusing. The actual component test fine, if done correctly. Two terminal have constant continuity, and the other two seem have continiuty at open throttle and discontinuity at closed throttle. Then I tested the signal voltage, two terminals were 10V and the other 2 were 8V. ???????

I guess their could be a wire shorted out somewhere, who know's where, causing a signal to be misread. I know my fuel injector wires were shorted out once, the insulation rubbed off where they came out of the hard ribbed protection sleeve. Took forever to find, all I knew was no fuel, changed filter and pump before tracing down the wires.

So I guess I'll replace the PFE and see what happens. This did not seem to affect my mothers 91 Taurus though, it just caused the ENGINE light to come on. Oh well, maybe at least I can get rid of two of the trouble codes.

Thanks again, I may look for that book

 

[Guy Groves]

Maby we should step back and take a clearer look at things .... Often times when I do this the answer is right in front of my nose, and I just keep missing it.

LOOK FOR THE MOST SIMPLE AND OBVIOUS ANSWER, THAT'S USUALLY IT.

Occam's Razor - in a nut shell...
"when you have two competing theories which make exactly the same predictions, the one that is simpler is the better."

So here are my thoughts, you may have tried them already. Sometimes a second opinion helps, these are simple minded so please don't be offended. I check things in this order, looking at the simple answer first.

Inspect wire harnesses first. Check to see that none of the harneses have rested against a hot component of the engine or exhaust. Look for melted jackets / wire insulation.

1) Has the idle adjust screw been moved or adjusted , or has anything been done near the idle adjust screw that could have unsettled it.

If so, re-adjusting the idle to see if you get proper idle conditions. You may also need to adjust the engine advance.

2) Have you inspected the throttle cable? is it kinked or stuck, not settling down to a full rest (idle) position?

3) I was going to mention the ISC last time and forgot. This is a simple little solenoid device. Internally it can become gunked up quite badly.

First: While engine is at high idle after a minute or two (when it should be at low idle). Disconnect the ISC. If the idle drops or engine stalls the selonoid may be faulty. Typically the ISC needs to be cleaned. My experience is that it is usually not an electrical problem.

You can remove ISC and clean it. A good grease cleaner is required. I clean mine with grease off using an old tooth brush and stiff bristle pipe cleaners, then brake kleen, and blow it out with compressed air.

Second: Perform eletrical connection tests. There is both a voltage and Ohm test. (Check out the previous reference book for details) There should only be a two wire connection. The connector nearest the keyway is the ISC circut, the other is the VPWR circut. The VPWR typically has two wires a the connection as it serves voltage to many instruments.


3) Check the air intake system:
a) Check Air tube for leaks. Make sure the hose connectors at the MAS and TB ar tight (no leaks there).
b) Check the Mass air sensor meter - (Clean the vane airflow sensor - carefully using a non-depositing spray cleaner) This is known to solve many problems.
c) Check Manifold gaskets (all of them)
- Throttle body to elbow
- Elbow to upper intake (I have experienced a problem here, but it usually results in rough idle (up and down), not fast idle).
- Upper to lower intake (have you added a phoenelic spacer? could be an air leak there.
- Fuel injector O rings
- Lower intake to heads


4) Check all vacume lines for leaks. Are the vacume lines to the EGR connected properly. It sounds like you already checked for leaks.


5) Air Conditioning IS the AC system working properly? AC demand causes the EEC to increase idle speed, faulty A/C clutch can do the same, or simply a cycling pressure switch.


good luck

 

[lonestar]

"when you have two competing theories which make exactly the same predictions, the one that is simpler is the better."

KISS Theory - Keep It Simple Stupid

I little more background,
No AC, disconnected several years back. Replaced ISC about 2-3 years ago. One day started getting high idles. Replaced TPS about a year ago. Still high idle, could flick ignition switch and idled normal until next stop (not always, intermittent), so I lived with it.
New idnition module 2 weeks ago, but with a little story. Decided to take the old car for a drive, and it died after it got good and hot. Wouldn't start, suspected ignition module, tested ok at Autozone, reinstalled ignition module and it started no problem. Suspected electronics went bad when hot, so decided to replace anyway. Autozone catogorizes ignition module by throttle body or fuel injection, which I thought was weird because throttle body is fuel injection (should ask Throttle body or Multiport). Mine is CFI so I stated throttle body which was a WELLS F126. Lifetime warranty, stated I bought the bad one about 5 years ago, looked it up for my warranty. I had purchased a WELLS F121 then. Turns out the F121 is for the fuel injection and the F126 is for the throttle body. So what to do, the F121 had ran fine for the past 5 years so I said just give what I had. Off with the F121 I went and it still seems to start and run fine, still with high idle..........
Took off air box to inspect every thing (TPS, ISC, EGR). Although it seems they are funtioning properly and idles fine, when goosed, the computer is still opening the ISC to run at high idle (3000rpm or so) Sometimes it slowly returns to idle others I just flick the switch a couple of times. The only thing I can imagine is the PFE is signaling a wide open EGR and the computer is compensating rather than return to idle, but I did disconnect the PFE and got the same response. It appears to be getting a false signal from somewhere.

So for now, I have disconnected the ISC at idle speed and it runs fine.

Oh well, it's an ongoing saga. I plan to replace the PFE when it returns from the dealer. I am finally taking Ford up on that 5 year old igntion switch recall. It seems all that switch flicking wore it out.

It seems you have experience in this area.
Thanks for all the advice.

 

[lonestar]

Got my recall ignition and replaced the PFE. Got rid of the EGR related codes, but still have the high idle and code 73.

In a nutshell
new PFE , fairly new TPS and ISC, looked at the schematic last night and a few other sensors are are connected through a commmon ground or ref signal. These include :
Air Charge Sensor
Coolant Temp Sensor
MAP Sensor

Anyone heard of any of these causing an high idle or tripping a code 73.

All connetions and vacuum line appear to be fine. Idles fine until I touch the throttle. Then the ISC extends and keeps the throttle at that position.

The Never Ending Story..........

 

[lonestar]

OK Yesterday I unplugged both the MAP and Air Charge sensor and looked at all the wires for some short where the insulation may have rubbed off. Started it. Reconnected all sensors. Started it again, and now it runs fine. Occcasionally it will take a second to return to normal idle, but it does not stick at 3000 rpm. And I still get that Code 73.

What's going on?

 

[lonestar]

Bump, it's been awhile, since I messed with it, but I still have a problem

 

[Guy Groves]

That pesky code 73...

You mentioned that the idle does return to normal, but slowly. This sounds OK, when my vehicle goes from high idle to normal it takes 3-5 seconds for the idle to slow down.

The high idle isn't as high as 3000 RPM?

wait a minute...
I just looked back at the thread and have two suggestions:

1) Regarding electrical connections. You are putting dielectric grease on the connections. This is very important and can be the cause of numerous random electrical problems.

2) It sounds like the the throttle body shaft may be bent or otherwise damaged causing it to stick, or some other part of the linkage is binding. I would also check and make sure the throttle and cruise control cables are not sticking, and the linkage connections are not binding.

You've replaced the TPS. All I can say is to check that it is installed properly, I don't think there is any real adjustment on your system.

Guy

 

[dogfriend]

I have two thoughts:

1. Wiring problem with the TPS. Either corroded terminals or partially broken wire. Check voltage at TPS and check return voltage at the computer if possible.

2. It is possible that the TPS could be bad even though you replaced it. Test it by reading resistance while moving slowly thru the range of motion.

 

[lonestar]

WOW, it's been awhile. I haven't messed with it, but I drove it last night and I still have the prob.

A little overview:
Intermittant High Idle (3000 or so RPM) at stop Can flick ignition off and on and it returns to idle, so I suspect electrical sensor prob. Rev up and high idle again. From what I can tell the computer is getting some type of false code and holds the ISC open, but it returns to idle position after flicking ignition.

ISC replaced before prob
TPS replaced after prob
PFE replaced after prob

Sensors and wiring seem to checkout.
TPS resitance varies as throttle opens.

Now I am up in the air for what to do next. I may just clean all the terminals and pull evertyhing apart, inspect, reconnect it and see what happens. Or I may go get a Motorcraft ISC and TPS from a junkyard, unless I can get a new one under warranty from Auto Zone. I really don't want to spend another $100 on a $400 car, I'm trying to sell it. I even thought about taking it to the junkyard, but I hate to see it junked, it still runs good, new tires, clutch and brakes.

Thanks

 

[MrShorty]

Have you checked for vacuum leaks? You mentioned a MAP sensor which indicates that you have a speed density system as opposed to the mass air system that's on explorers. A high idle is a common symptom of a vacuum leak on a speed density system.

 

[Guy Groves]

Mabe it is simpler than we are making it?

My bets are on a vacume leak, mall adjusted idle set screw, or the throttle cable itself is sticking or improperly adjusted.

1) Was other work done prior to all the problems? Does it ever idle properly?

If it never idles properly I would simply check:
a) Throttle cable operation,does it return to full "low" position?
b) Adjust the idle adjust screw to reset the idle to 1000 rpm.

If you have cruise control also check that cable, that it returns to low position when off.

If other ignition work has been done check the advance as well as the idle adjust. (reset the timing - set idle to 1000 (idle adjust screw), set timing to 10degree BTDC, spark order, plugs, bla bla bla.

2) Clear the EEC memory, disconnect battery for at least 20 minutes. What codes do you get?

From earlier info if you still get EGR code 34, or other device running on vacume, I would suspect a vacume leak. Check ALL vacume connections and lines.

If you still get TP codes (73, 23, 32) Then you are back to the TP sensor. It could be the sensor, or the idle adjust screw setting,or cables as mentioned first.

 

[lonestar]

Thanks for all the input, but I really think it is something electrical.

It idles fine, until I rev it up. Then it sticks at a high idle. All I do is flick the switch and it returns to normal.

There is no idle screw. It's a CFI with a ISC, idle speed control solenoid. When it is cold the ISC sticks out a little farther, and idles down as it warms up. Then when I give it gas, the ISC sticks out and doesn't return causing the high idle, flick the switch and the ISC returns to idle postion. The nose switch in the ISC to sense when the throttle is open or closed works.

I would suspect mechanical problems such as a stuck EGR, vacuum leak, idle screw, or throttle cable if it idled and ran rough all the time, or did not return to idle by the simple flick of the switch. It's almost like it has a short or bad ground.

THE EGR code dissappered when I replaced the PFE.

I need to mess with it some more to see if I can find something new.

 

[Runnin'OnEmpty]

Lonestar, have you taken a voltage reading from the TPS? I don't know exactly what your application calls for, but it should read somewhere betweeen .8v and 1v on the signal wire (KOEO).

Do you have a throttle blade stop screw, or an ISC adjustment? If the TPS voltage is off drastically, maybe you can make your own adjustment to get it back in range, , by bending mounting brackets or elongating mounting holes.......?

EDIT: Maybe it's simply a weak throttle return spring. The ISC needs a certain amount of pressure to return to it's rest (curb idle) position.......? Just some thoughts, for what they're worth.

 

[lonestar]

Ok, did some more research.....

Found a TSB cmentioning the IAC (idle air control), which I assume replaced the ISC (idle speed control) on earlier cars like mine, it's replaced, and seems to check fine.

Other suggestions. MAP (manifold air pressure), temp sensor, or O2 oxygen sensor. I do believe my thermostat has been stuck open for several years, no heat. This may cause it to run rich, foul out the O2 sensor, and now causing the high idle. The high idle has also been around for a couple of years too, coincidence. Not sure, but that's what I'm going to start looking at.

 

[Glacier991]

Based on a net article I posted here, you might try unplugging the suspect sensors, and make the computer "invent" signals. I'd start with the IAC, and go from there. A vacuum leak, while plausible doesn't explain the 3000 rpm. This is where a scanner would be really nice (if only the car was newer). Look PAST the trouble codes. They can often be symptoms, instead of causes. Also, rare as it is, PCM's DO go bad. This IS a curious one. Let us know what you find.

Happy Exploring

Chris

 

[lonestar]

Alright, this is what I did tonight.
Disconnected battery to clear codes, Drove until high idle occured, whipped out code scanner and this is what I got, repeatedly.

73 - insufficient throttle change
23 - TPS voltage out of self-test range
33 - EGR or PFE signal out of range
99 - ECA has not learned to dontrol idle

once, I believe
68 - Vane Air temp signal voltage, Idle tracking failure

Tested sensors.

TPS
tested fine, 5 volt ref voltage, signal voltage varied from 0.5 - 4.0 volts, closed-open throttle

ICS
4 wire, 2 for stepper motor, 2 for nose switch. Continuity opened and closed in nose switch, stepper motor opened and closed throttle. One weird thing, is it had 2 10v ref voltages. could disconnect so it wouldn't hold open throttle, but would cause hesitation during heavy accel.

O2
3 wire, ground, 12v ref, signal voltage varied from 0.1-0.9. Dropped to 0.1 when forced lean (created vacuum leak. Seemed it may have a discontiniuty in the ground wire at the harness. car side continuous with ground and sensor side, but sensor side not continuous with ground. ??

MAP
Really didn't have time the time or tools to test. 3 wires. ground, 5v, 5v. Neither 5v wire changed when vacuum tube was removed or vacuum increased.

I also ran across another sensor, ACT, Air Charge Temp. Didn't seem to make much diff if it was connected or not

I am really tired of chasing this thing down and am considering trying to get a new ECA (computer) from a junkyard, or just junking the whole thing.

 

[dogfriend]

Originally posted by lonestar

MAP
Really didn't have time the time or tools to test. 3 wires. ground, 5v, 5v. Neither 5v wire changed when vacuum tube was removed or vacuum increased.

They may be able to test this at Autozone or Napa.

The center terminal should be the MAP/BP signal - it should vary in frequency (you need a frequency counter), decreasing as vacuum increases.

 

[lonestar]

Tested MAP. Brought it to school and put it on a oscilloscope. Seems fine. 158 Hz - 0 vacuum and decreases HZ as vacumm increases.

TPS, ISC, O2 and MAP all seem to test fine.

Only thing left to test is
ACT (air charge temp, disconnecting doesn;t make a diff
ECT (engine coolant temp) temp guage reads
PFE, replaced

I guess I should start looking for a ECM.

I may not have fixed the problem, but I''m learning how to test sensors.