Troubleshooting Rough Idle on 89 iX - Has wierd coolant sensor and extra fog relay??

[Andrew325is]

My 89 325iX I bought in April idles rough when you first start it up and then mostly smooths out when it warms up. I began troubleshooting by replacing some of the vacuum hoses such as breather hose and intake boot. The throttle body switch didn't have continuity when in closed position, so we took it out and cleaned it and it works now. The ICV seems okay. Since that didnt fix anything I thought I'd check the coolant temp sensor that sends input to the dme/injectors. What I discovered is a 3 pin sensor with wires going to an extra relay. The relay has a wire going to the selonoid on the starter and another wire which appears to go to the fogs. What is this for? Why would a fog relay be connected to the coolant temp sensor? I don't know where to find a 3 pin coolant sensor so should I take all that extra stuff out and replace the plug on the injector wires so that I can replace the sensor with the OEM 2 pin version?

The wierd 3 pin coolant temp sensor (black) below the temp gauge sensor (brown/orange):





Wires going to relay:




Relay:



Wire from relay to starter selonoid (small red):



Wire from relay to fogs? (brown):



I disconned the extra relay and the car seems to start better. I'm going to take it for a test drive. If the temp sensor isn't the problem maybe I've overlooked another vacuum leak. It's giving me a head ache! I'll probably take it to a shop on monday.

[jeff_b]

I would inspect that connection from the temp sensor harness to see if it's been hacked up. One pic shows what appears to be electrical tape on the harness after the branch.

That shit looks like someone either:

a. ran a 12v switched source to feed the fogs' relay (for fogs on / headlights off)
b. spliced in another 12v source for the temp sensor for some reason

The extra wire/relay load may drop the applied voltage to the temp sensor, causing it to not operate properly.

Just my .02

[Andrew325is]

It's definitely been hacked up. The wires have electrical tape around them going to the relay. It's just so weird someone would do that. I wonder where they got the sensor and the plug for it, some other car I would imagine. So I should probably cut all that out. I'm going to trace the wires a little more. The car is running much better with that relay removed. Also, before, when I turned on the fogs it'd blow the driver side fuse. Now I just replaced the fuse without the relay and the fuse didn't blow.

[ZM Blue Devil]

we have 3 ix for parting right now at the shop, if you need wiring/harness from and ix let me know via pm.