idle problem solved - strange EHA cruuent remains

[ThomH]

Hi!

Finally I seem to have found the major problem. I opened the OVP and found a broken solder joint. Actually it looked as if half of its connection would be intact. However, after soldering on the pin again, my idle was much smoother. Before, I had no ABS light on and I could measure the EHA current fluctuating, hence no hints towards a broken OVP.

Anyhow, I still have this issue with my EHA current during KonEoff. And it becomes even more strange. These were my readings so far:

day <10-20s >10-20s remarks
. 1 . 10 .... 20
. 2 . 10 .... 20 ... with eng off for a while
. 2 . 10 .... -7 ... eng off but directly after eng on
. 3 .. 6.5 .. 13 ... today
. 3 .. 6.5 .. -5 ... eng off but directly after eng on

10-20s means the current is different the first 10-20s after turning the key from thereafter. Day 1-3 are the different days I measured the current. Day 1 and 3, I used the same multimeter. I assume it to still work correctly as I measured a control current of -4 to +2mA during idle, today . The resistance of the EHA is a perfect 19.5 Ohm (as the reference).

So my idle has quite improved (econometer rotates about 5 DEG from time to time but the sparks are also not perfect) although I have an EHA current of only 13mA.

This leaves a few questions open:
1)Is it normal to have this step in the KonEoff EHA current at 10-20s?
2)What does it mean when the KonEoff EHA current behaves different when the engine ran directly before?
3)Is it critical to have only 13mA KonEoff?

AND
Steve got me so much into this closed loop thing that I wonder why my sparks have black sediments.
4)Is this only from the time when the O2 sensor is still too cold?
I would assume that in a warm system the KE should adjust the mixture in such a way that my sparks should stay clean.

5)If I got Steve right, all it takes to adjust the mixture is to receive an EHA current that equably fluctuates around 0mA and which should stay within +-3mA?!
6)In case I would have a different current at a stable 2000rpm and at idle, then I would have to search for an error in the system like an air leak, right?

Best, and thanks a lot
Tom

[psfred]

Tom:

Check the duty cycle and report back -- if it wanders around KonEoff, probably have a computer problem.

13mA EHA current at idle hot is way too high -- check the duty cycle and try to set it to 50%, and see it the EHA current drops to around 0mA.

Your plugs are black because you are running very rich -- duty cycle is probably something like 35%. (or 75%, I cannot remember which way is rich.

Fixes are:

Correct mixture (fix any vac leaks first)

New O2 sensor -- bad one causes all sort of problems

ECU checkout and replacement if bad

Fuel distributor problem, causing excess fuel delivery (usually requires new fuel distributor).

Bad pressure regulator -- replace if leaking.

Peter

[ThomH]

Peter

sorry, 13mA was always meant engine off (should actually be 20mA)

If my O2 sensor readings vary between 0.02 and 0.95V (applying 1V to / grounding of the KE side of the unplugged sensor connection), the O2 sensor should be ok, right?

I want to test my injection valves first and then I will reset the mixture according to duty cycle (measured by average volts) and EHA current.

However, I still wonder if I should do something about the low KonEoff EHA current of 13mA?! I don't see a deterioration when the engine is running now. Actually it is the opposite way as I fixed the bad OVP during the time when the decline of EHA current (KonEoff) occured (happened just before I fixed it, hence it's no result of this repair).

Tom

[psfred]

Tom:

Something wrong with the EHA current in startup state would indicate a bad computer, it's not getting any data (rpm, etc) from the engine. Unless a bad temp sensor or grounded or open wire can do this (stevebfl or someone else with far more expertise will have to tell you, I don't know), the ECU is sick. If it is, won't matter what else is going on, the mixture will wander around.

I assume that you have gotten the ignition system in tip-top shape as well -- misfire will cause black sparkplugs, too! Since you've been chasing an idle problem, I'd guess you've fixed this.

There have been several posts about curing rough idle problems with new injectors -- if they are not delivering the same amount of fuel each, the mixture will be off for at least one of them (some rich, some lean, etc) and you will get loping idle and constant EHA current variations as the ECU attempts to get the O2 correct -- since some cylinders are richer than others, too much O2 gets by on the lean ones, so the ECU richens up the mix to get rid of theO2, the rich cylinders get richer and the O2 drops too far, the ECU leans the mix back out, the lean cylinders go too lean and misfire, the O2 goes way up, and the cycle repeats. The missfire makes the engine run rough, and the rich cylinders end up with soot on the sparkplugs. the soot will burn off at highway speeds and re-appear at idle.

Peter

[ctaylor738]

Thom -

What is your engine number? I just looked on the CD, and depending on what engine version you have, the KOEO spec could be either 10 or 20 mA - entschuldigen Sie, bitte, if you have already checked this.

[ThomH]

Hey, can we switch languages ;-)

According to my EPC, the engine # is 12002422.
However, I assume it to have 20mA, as this is the current I measured first. But if you could verify this, I didn't see any such table in my CDs.

Cheers
Tom

PS: I bought a new fuel filter to have one item less that could impair my valve testing. If it only wouldn't get as cold the next days...

[ctaylor738]

Ich brauche der 103.9xx Teil!

Der Tisch ist bei der Seite 13 im "KE Injection Tests " am CD.

Besser mit mir im Englisch!

[ThomH]

I found the table (the wooden table is a Tisch, the table on a sheet is a Tabelle, however), I must have overread this one all the time. 20mA is the correct reference.

I guess, I will have Bosch to test my ECU.

Tom

[ctaylor738]

Personally, if the car is starting easily, running well and getting normal readings while driving (close to 0 at steady RPM, moderate enrichment on acceleration, enrichment on warm-up, etc.) like im Tabelle auf Seite 13, then I would not worry too much about the KOEOff readings.

BTW - "overlooked" nicht "overread" :-)

[ThomH]

As it got a bit warmer (therefore started raining) today I had another look at my idle system.

I discovered by eye a small rift at the joint section of the hose ICV > bend. In order to check if it is a leak I used brake cleaner. Nothing happend. This time (once I already checked all hoses with a flammable fluid without "success") I sprayed the brake cleaner directly into the air flow meter to test what happens: nothing. How can this be?

My EHA current still fluctuates around 0mA for 1s and then up to -8mA for another 1-2s. Hence I do not believe that my mixture is this rich that further richening (with brake cleaner) would show no impact.

On the other hand, when I unplug the ICV my rpm goes down (not up). This already encouraged me in the past to search a leak.

Anyone with an explanation for this?

Cheers Tom