Calling all 8691V ECU Tester Gurus. High Idle/Tool Readings

[metropoj]

Digifant 86 2.1L, 290,000 miles on motor.

Symptom: Idle high after warmup just started a few weeks ago out of the blue. Idled fine at start cold, then slowly increases to around 1400rpm once warmed up.

8691V Shoebox ECU Monitor hooked up. First time using it so bear with me.

What is done so far:

1. Throttle Position Switch working fine.

2. I swapped out the Aux Air Regulator, made no difference. Cleaned up old one and reinstalled. BTW, should I be able to blow air through one of these things ? I have one that I can blow air through and one that I can't. Both seem to run when plugged in.

3. Temp Sensor on coolant tower Ohms seemed to be OK.

4. EVAP system seems to be holding vacuum as per Bentley tests.

ECU Monitor hooked up and I observe the following values.

1. COolant temp, Air, Temp, O2, O2 ground all are within acceptable limits and very rock solid.

2. Voltage readings VERY HIGH, anywhere from 15.9V up to 18V. I swapped in another voltage regulator but no change at all. Suggestions what's next ? According to docs it shouldn't be more around 13.5 and steady.

1. AFM Voltage reading VERY HIGH at idle cold. readings should be <.25 cold, mine reads 1.73V cold idle ! Once I get to WARM, 30MPH and 60 MPH, the values are in acceptable range.


My concerns are with the High AFM and Voltage readings, and the fact that the air bypass screw on the throttle body is turned all the way in and it still idles around 1k-1200 RPM.

What is left to do yet:


1. Check again for vacuum leaks. Will try the propane hooked to hose method.

2. I have not checked timing nor sure yet how to do that. I'm sure something on line here will help.

3. I hesitate breaking into the AFM as the original owner had it replaced a few years back, doesn't mean anything but I can try and swap in the old one and see if it is any different.


4. Check the power steering pressure sensor. What is the test for this ? I haven't found anything online yet on how to see if one is working or not.

What other things can cause a high idle like that ? I just read this morning about the breather tower diaphragm as a possible issue too .

[crazyvwvanman]

First step, get a voltmeter. Then measure the voltage on your battery with the KEY ON engine off. Then again with the engine running. Should be about 12.5v key on engine off, 14v engine running. Compare that to what the diagnostic tool says at the same times. What did you get?

For working out the high idle, idle the van, verify it is too high, then reach down and unplug the wiring connector from the idle air valve. Does the idle change? In what way?

Mark

[crazyvwvanman]

You misread the manual on this. Your AFM readings are what the manual says to expect. It is not written as clearly as it could be but the first column where it says "Cold (key on)' it also means ENGINE OFF, key ON.

Mark

[metropoj]

You are totally correct, I read that wrong as key on (and running) cold values as you suggested

I will take the VM and measure across the battery now for the comparison.

I'll try the idle air valve too. I wasn't too sure to unplug it when running for fear of damage and report back what I find out ...

[crazyvwvanman]

I unplug them all the time with engine running but I DON'T plug them back until the key is off.

The idle controller gone bad is a very common cause of sudden high idle. That is what we are checking for.

Mark

[borninabus]

[metropoj]

After reading more posts on the subject, I went hunting and pulled the ICM.

Cracked it open and yeah, it's shot. The transistor on the board is all cooked.

I found a non burned up up replacement ICM in my bin of spare parts but first I'll have to figure out why the old one died in the first place.


I have 3 Idle Air Control Valves. The one on the motor I can blow air through. My 2 spares I found in the box I cannot blow air through.

Should I be able to blow air through one of these ?

UPDATE: I was just reading up and found out that, no, I shouldn't be able to blow through these. Maybe why the ICM is blown in the first place.

Now, onto the high voltage readings by measuring at the battery to see what's up with that.

[metropoj]

Cleaned all terminals on replacement ICM, contact cleaner, Installed used Control Valve as well and backed out my idle screw, run very well now.

As far as my 8691V Voltage readings on the tool, I see 13.5V at the battery while the unit reads about 4-4.5V higher than at the battery, very odd indeed.

But at least i know I'm not cooking my battery !

Thanks for the help guys ...

[crazyvwvanman]

Sounds like you are getting there.

When the engine is running the ECU gets its voltage from the alternator. When the key is on but engine not running the ECU gets voltage from the battery. Do you see those same way too high voltages with key on and engine not running? If so, suspect the 8691v to have a fault.

Mark

[metropoj]

I went ahead and cleaned all grounds incl fuel pump after I started a hiccup on a routine drive yesterday. I noticed the Fuel Pump circuit would blip when it stuttered. Now it runs quite well at the moment.

So here is the thing on the High Voltage readings .....

1. Turn on ignition, no start, Voltage starts to read at 13.6V and keeps climbing on the tool by itself until it gets up to 16+ V.

I decided to start the motor and run as I didn't want to possibly damage my ignition system while sitting in the 'start' mode.

I have seen readings as high as 19+ V on the tool during driving !

Very strange stuff.

The van however is running super at the moment. The idle hunting that the PO had and vacuum signature rocking back and forth every 2 seconds or so has pretty well completely disappeared, and for good reason. The ICV / ICM issue surely must have caused fuel mixture problems...

I would be lying by saying the high V reported at key on and running isn't a concern to me.......

[bluebus86]

some of the ecu testers had a 9 volt internal battery, later superseded to not have a 9 volt internal battery.

if yours has the 9 volt internal battery, suggest you replace it, that could be why the readings are off. finally if that aint it, email shoebox electronics about the issue. you may have a valibration issue, unless of course you have confirmed by a seperate lnown good voltmeter the problem of high voltage is real.

so open the tester up and see if a battery is inside.


good luck
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