Mercedes-Benz Forum banner

1 - 20 of 23 Posts

·
Registered
Joined
·
30 Posts
Discussion Starter #1
my iacv is malfunctioning.....it opens with ign on for a few seconds then closes.....its not voltage supply problem from the ovp or wiring...its been tested.... the wire going back to #3 on the ecu is good but theres no completion of the circuit in the ecu....i dont know if the ecu is bad or if theres another factor in why the ecu kills the circuit....p.s. ive tested with a/c off and shifter in park....any help?....thanks
 

·
Registered
'01 SLK230,'93 190E 2.3, 1971 LS5 Corvette Convertible
Joined
·
2,172 Posts
my iacv is malfunctioning.....it opens with ign on for a few seconds then closes.....its not voltage supply problem from the ovp or wiring...its been tested.... the wire going back to #3 on the ecu is good but theres no completion of the circuit in the ecu....i dont know if the ecu is bad or if theres another factor in why the ecu kills the circuit....p.s. ive tested with a/c off and shifter in park....any help?....thanks
Welcome to BW. Well, since this is your first post, we don't know what's been done to your car before this problem started. You might want to complete your profile so we'll know your year and engine information.

I had the same problem after I replaced the head gasket on my '93 2.3...the ICV would operate when the ignition was turned on and then close after 10 seconds. I did the same thing as you and checked the ICV circuit to pin 3 on the 25 pin connector at the CFI Control Module. That was good.
Next, I built an LED tester and checked for DTC's. I had a DTC 4 code: Air Flow sensor potentiometer.

I checked continuity on the Air Flow Potentiometer Sensor Connector going to the Control Module. No continuity on the 3 wires....it turned out that I had inadvertently switched that connector with the Throttle Position Sensor Connector when I was putting things back together after a head gasket job.
They are close together and use the same type of connector. After switching the connectors, the car started up and idled at 900-1000 and then went to 700 after 28 seconds.
 

·
Registered
Joined
·
30 Posts
Discussion Starter #3
thanks for the reply...ive had this issue on 190 rev forum and cant get any responses.....anyway....its a 1988 190e 2.3 8v.......i bought it for $200 with blown headgasket....got that fixed.. although ill never feel right about those damn stretchbolts....my condition is that it will surge and stall when cold,,,but gets better as it warms...still idle is a little rough warmed up and will stall at lights if not careful...ive replaced 3 iacv's....3 potentiometers....2 fuel distributors w/eha's....all coolant sensors even though the old ones tested good
all fuel injectors...adjusted zero on afm plate...wires.. plugs[bosch h8dc]...cap/rotor......other problems that might be related but doubt it are...... no power to my magnetic cooling fan yet i have voltage at temp sensor......and a voltage draw that drains the battery every couple days
 

·
Registered
'01 SLK230,'93 190E 2.3, 1971 LS5 Corvette Convertible
Joined
·
2,172 Posts
thanks for the reply...ive had this issue on 190 rev forum and cant get any responses.....anyway....its a 1988 190e 2.3 8v.......i bought it for $200 with blown headgasket....got that fixed.. although ill never feel right about those damn stretchbolts....my condition is that it will surge and stall when cold,,,but gets better as it warms...still idle is a little rough warmed up and will stall at lights if not careful...ive replaced 3 iacv's....3 potentiometers....2 fuel distributors w/eha's....all coolant sensors even though the old ones tested good
all fuel injectors...adjusted zero on afm plate...wires.. plugs[bosch h8dc]...cap/rotor......other problems that might be related but doubt it are...... no power to my magnetic cooling fan yet i have voltage at temp sensor......and a voltage draw that drains the battery every couple days
OK....looks like you've done a lot to your engine.

1. Stretch Bolts: yeah, different than other types that get torqued, but that's German engineering.

2. I'm assuming you replaced the ICV hoses on both sides and they are tightly connected and not leaking.

3. How about your duty cycle reading, have you checked?

4. What's your idle (rpms) at start-up and warm?

5. When it's running, if you unplug the ICV do the rpms increase?
 

·
Registered
Joined
·
30 Posts
Discussion Starter #5
all new iacv hoses from autohuas....i dont understand "duty cycle" tests..i dont have any of the "special tools" like socket box or lambda tester etc.....just a multimeter and also this is a cal. car with its own diag. set up.....it doesnt idle till its warm and when it does.. that could be at 1000rpm or 700 but rough at both and nothing in between....the valve is closed at that default 2mm open all the time except those first few seconds....but ive unplugged every thing else just to see if anything will change and it doesnt...also all vacuum leaks were eliminated but they effected anything..... anyways i double checked what was plugged into what.. but its all good...the afm pot and throttle sensor plugs wont interchange on my harness anyways....is there a way to do those socket box tests with a multimeter?

'








'
 

·
Registered
'01 SLK230,'93 190E 2.3, 1971 LS5 Corvette Convertible
Joined
·
2,172 Posts
Since you have a California car, have you checked for trouble codes (flashes)at the built in LED tester by the battery? Mine had 4 flashes....that's what led me to the Air Flow Potentiometer Sensor.

For 'duty cycle' reading and adjustments, I use a Craftsman 82139 volt ohm meter that has duty cycle capabilities. For this, you read across pins 2 & 3 at the round diagnostic port (x11) by the Ignition Control Module on the drivers side fender well.

Is your fuel adjustment tower still factory sealed, or has it been removed/altered?

Have you downloaded the online manual or do you have one that covers testing?
 

·
Registered
Joined
·
30 Posts
Discussion Starter #7
ive checked for trouble codes with my x11 with red lite and button.....no codes for a while...but had some when i swapped components..then cleared them afterwards.............my tower is still untouched....and i have 3 manuals all of them crap...i ordered the one from mercedes dealer and it was the same as the free online one......the problem i have with the manual is the constant use of "special tools" and wiring diagrams that are so poor ,i dont know what im reading or what model they're for....yet ive narrowed it down quite a bit now....id like to know more about the duty cycles...i have two highend meters. one from fluke and other from beckman...as well as an old craftsman engine analyzer with tach/dwell/volts/amps/alt/.....thanks
 

·
Registered
'01 SLK230,'93 190E 2.3, 1971 LS5 Corvette Convertible
Joined
·
2,172 Posts
ive checked for trouble codes with my x11 with red lite and button.....no codes for a while...but had some when i swapped components..then cleared them afterwards.............my tower is still untouched....and i have 3 manuals all of them crap...i ordered the one from mercedes dealer and it was the same as the free online one......the problem i have with the manual is the constant use of "special tools" and wiring diagrams that are so poor ,i dont know what im reading or what model they're for....yet ive narrowed it down quite a bit now....id like to know more about the duty cycles...i have two highend meters. one from fluke and other from beckman...as well as an old craftsman engine analyzer with tach/dwell/volts/amps/alt/.....thanks
No codes, that's good. You stated that your ICV opens at start-up the closes to the default 2mm opening. Is your ICV 2 pin or 3 pin style?

I wouldn't worry about special tools. I also have a Fluke meter and some others, but I purchased the one from Sears due to the duty cycle feature. It sounds like you're from the old school like me...you can use a dwell meter to check duty cycle. Here's what you're looking for at the x11 connector on pins 2&3 with a dwell meter, this is from one of my old threads:

"One more piece of information, during my research I found out that you can also use a dwell meter to read duty cycle. I still have one that I use to adjust the points on my Corvette. Sure enough, I put it on pins 2 & 3 when I finished using my Sears meter and it fluctuated between 44 & 46 degrees, just like the information stated:

45 degrees = 50 % duty cycle
<45 degrees/50% = running rich
>45 degrees/50% = running lean"


You really need to read up on duty cycle information. It should fluctuate when taking the reading, if it doesn't then there is a fault in the system like the manual states. If your adjustment tower is still factory sealed, then you'll need to gain access to use an allen wrench to make adjustments. I cut mine off with a hack saw just below the ball bearing.
 

·
Registered
Joined
·
30 Posts
Discussion Starter #9
ok..this looks like a new way to go now....on the "duty cycle"..does the engine need to be running?.....also all the tests i want to get access to are done with a "socket box"......is there an alternative to this?...thanks for all your help
 

·
Registered
Joined
·
30 Posts
Discussion Starter #10
i also bought a master fuel inj. kit and tested all the components...and have gone thru the "probst bosch fuel inj." book....good stuff but not much help on a mercedes ke3 system
 

·
Registered
'01 SLK230,'93 190E 2.3, 1971 LS5 Corvette Convertible
Joined
·
2,172 Posts
ok..this looks like a new way to go now....on the "duty cycle"..does the engine need to be running?.....also all the tests i want to get access to are done with a "socket box"......is there an alternative to this?...thanks for all your help
Yes, check it with the engine running at warm-up temp. I wouldn't worry about the socket box at this point, just see what your duty cycle shows at pins 2&3 at the x11 diagnostic connector on the fender well.
My '93 has to be put into diagnostic mode to read duty cycle...not sure about yours.

Here's a link to duty cycle information:
http://www.landiss.com/mixture.htm
 

·
Registered
Joined
·
30 Posts
Discussion Starter #12
looks like my dwell meter is missing leads...so its back to multimeter....ive been reading all over about on/off ratios and cant find anything solid..i have to press x11 button to get there.....and i get 2.12 volts steady....then i messed with mixture tower and it settled at 2.60 v...only after dropping from 6.53v...is this a california result?
 

·
Registered
'01 SLK230,'93 190E 2.3, 1971 LS5 Corvette Convertible
Joined
·
2,172 Posts
looks like my dwell meter is missing leads...so its back to multimeter....ive been reading all over about on/off ratios and cant find anything solid..i have to press x11 button to get there.....and i get 2.12 volts steady....then i messed with mixture tower and it settled at 2.60 v...only after dropping from 6.53v...is this a california result?
You shouldn't get a steady voltage reading due to the O2 sensor doing its thing.
If you do have a steady voltage, then you probably have an issue somewhere...that's where the on/off ration chart comes in handy. That's how I found my Air Flow Sensor problem, the reading was a steady 40%.
I try to get a copy and post.
 

Attachments

·
Registered
Joined
·
30 Posts
Discussion Starter #16
in the manual it says 80% is barometric sensor or wiring so i checked that and its ok...this just gets stranger everyday
 

·
Registered
Joined
·
30 Posts
Discussion Starter #17
i reset x92 or x11/4
[the california tester} and got 50 which is o2 sensor....i thought that was ok
 

·
Registered
Joined
·
30 Posts
Discussion Starter #18
could a bad o2 sensor create such extreme problems??....ive never had a bad one do that on any other car/truck ive had
 

·
Registered
'01 SLK230,'93 190E 2.3, 1971 LS5 Corvette Convertible
Joined
·
2,172 Posts
could a bad o2 sensor create such extreme problems??....ive never had a bad one do that on any other car/truck ive had
Yes, if it's putting out too high of a voltage.
If yours is a California model, the O2 Sensors are supposed to be replaced every 60,000 miles.

when i got the 50% it was fluctuating between 6.6 and 6.9 volts....is that enough fluctuation?
I would think so, if I get a chance I'll check mine tomorrow with my duty cycle meter and dc meter.
 
1 - 20 of 23 Posts
Top