IACV Observation (kills engine) - PeachParts Mercedes-Benz Forum

Unleashed · #1 10-26-2006, 03:23 PM

Since I got my 16v, the IACV has been unplugged. As soon as I plug it in, the engine won't hold an idle. If it's idling and I plug it in, it just shuts off.
So, to investigate, I took the airbox off and watched the AFM plate. As soon as the IACV was plugged in, it closed, cutting the air from the mixture, and obviously killing the engine.
I've taken the IACV out and cleaned it thoroughly, and tested it by running voltage to the poles - it opens and closes fine.
How can I stop it doing this?! I'm thinking vacuum leak somewhere? I changed the moulded rubber hoses to it (they had got old and gone hard), but no difference.
Help! This is driving me nuts!

1989 190E 2.5-16.

mbdoc · #2 10-26-2006, 06:02 PM

You might try the search feature here for air flow position sensor.

IF the air flow position sensor sends bad info to the CIS-E computer, that computer can cause those idle problems.

Unleashed · #3 10-26-2006, 06:23 PM

Well the car runs fine at all other times, it has no spluttering, bogging down or other running issues. It's just that is unplugged, so obviously cold starts are a bit of a pain. It starts okay, but idles very, very low and if it IS cold (heading into winter, so far 7 degrees C was the lowest) it stalls if you aren't careful - just until it's warmed up, in which case it's fine.

dkveuro · #4 10-26-2006, 06:37 PM

Quote:

Originally Posted by Unleashed

Since I got my 16v, the IACV has been unplugged. As soon as I plug it in, the engine won't hold an idle. If it's idling and I plug it in, it just shuts off.
So, to investigate, I took the airbox off and watched the AFM plate. As soon as the IACV was plugged in, it closed, cutting the air from the mixture, and obviously killing the engine.
I've taken the IACV out and cleaned it thoroughly, and tested it by running voltage to the poles - it opens and closes fine.
How can I stop it doing this?! I'm thinking vacuum leak somewhere? I changed the moulded rubber hoses to it (they had got old and gone hard), but no difference.
Help! This is driving me nuts!

1989 190E 2.5-16.

Plugging or unplugging a device while powered is never a good idea.
On VW's and Audi's this blows the driver in the power control .

Check the basics... The closed throttle contacts in the air
flow position indicator (on the throttle housing) can have high
resistance. The control module not seeing a closed/open/part
throttle and therefore will not adjust idle speed. This switch
is no longer available separately from MB and requires
replacement of the entire throttle housing.

Check your OVPR too.

The voltage is supposed to be ......( Shopkey calls for 4.6-5.1vdc.) on the air flow meter . With this reference voltage different the system will not set idle correctly.

.

dkveuro · #5 10-26-2006, 11:15 PM

Quote:

Originally Posted by Unleashed

...............................
So, to investigate, I took the airbox off and watched the AFM plate. As soon as the IACV was plugged in, it closed, cutting the air from the mixture, and obviously killing the engine...............

1989 190E 2.5-16.

Being as the afp snaps closed, it would seem the computer is seeing an engine speed above idle target and shuts off fuel for a 'coast down' or closed throttle condition.

This system shuts off fuel when the engine speed is above 1200 pm and the throttle switch is closed.

Need to check the TPS to see if it is operating/set correctly.

.