Idle Temp Sensor? 84 533i

[Werkaholic]

Can someone tell me which one of these numbered sensors is the idle temp sensor? I've seen other pics on here but the arrangement all seem a bit different. So, which one is it?

Thanks all for your help.

[demetk]

Coolant temp sensor would be 5. Thermo-time switch would be 4. Coolant temp sender for temp gauge would be 2 if it has one wire. Idle control temp switch looks to be 1 & 3. Either 1 or 3 is redundant.

[NINA85]

I have an 04/83 533i. The thermostat housing has all the same sensors as yours, MINUS the #3 in your photo. There is a blank in that position. I have seen it used in my 85 535i for the vacuum switch that controls the charcoal canister evaporative purge valve. Its usually a green sensor with two spouts. Anyway I believe 5 is your Coolant Temperature Sensor. 4 is your Thermo-Time Switch. 2 is your Coolant Temperature Sender and 1 is your Idle Control Temp. I usually have trouble with that but once I figured it out with the bentley I drew a diagram and labeled it so I didn't have to ask anymore.

[bavarianautowrks]

#1 is the idle temp sensor. New sensors are garbage and you can jump those two leads to stop the constant high idle of around 1k rpm.

[Sean335]

I have a high idle (1100rpm) on my 1984 533i
I am replacing the 4 or 6 coolant switches/sensors because it putters out once the engine warms up.
If the new idle control sensors that are out there are crap, how can I jump the two leads to stop the high idle?
thank you

[willyv124]

See my post here for options. https://www.mye28.com/viewtopic.php?p=1510096#p1510096

I ordered #5 and am waiting for it to arrive.

In the mean time did you try shorting the two connectors of #1 in the first picture of the OP in this thread to confirm that is your issue?

[Sean335]

I did not jump the leads. But that idle control temp switch has rabbit ears that came off and the epoxy that holds the switch in the brass is crumbling. so I figured to replace it- should be here tomorrow.

Right now the car starts, runs for 2 minutes and stalls out. no start until the engine is cold. Past work includes, engine /trans mounts and a valve adjustment (last year when replaced the busted open oil pan from driving over railroad tracks) and a new oil pan shield by Red46/Catuned) the car ran like it did before-so happy. I put the car on stands sprayed down and cleaned the engine bay, low pressure air dried thee compartment, painted the car, and drove it. about two weeks later it dies when it warms up.

So now, one by one, I replaced sensors on the coolant thermostat housing (except the engine idle temp control switch), and no luck, the distro-cap and rotor (was so ate up when i opened it), ignition coil and still no luck, and I checked the DME and little green computer box next to it and they both get 11.5v. checked and cleaned the spark plug they're 2yrs recent and clean (not driving the car)

I started switching out relays 1 by 1 and starting the car in between. when I switch out what I think was the fuel pump relay and started after several jumps and light grayish blue smoke out the tail. I drove around the block twice, then took it on the freeway and 700ft later I felt a kick/bump and the car stalled out and had it towed back home.

I thought I threw a rod so I visually check the engine and no rods protruding so I jumped it and it started but stalled in 2mins. when it got warm.
what now? cant remember If replaced the alternator though (I remember cleaning it/adjusting tensioner/fixing that weak crappy bracket) I'm going to start it and pull the battery and see what happens.

Gents please let me now if you have any thoughts about this e28 journey.

[Sean335]

So I started it and disconnected the battery. it ran for 1min. then dies.
Started a 2nd time, right away, and ran for one mins again the dies. now no start.
what gives?

[Mike W.]

Off the top of my head, green doesn't seem right for the FI temp input sensor, #5 in your pic. IIRC there have been posts about it needing to be a specific one, probably white. The closest thing to a problem with it I've ever had was on an old L jet car when the wiring harness had a break in a wire leading to it and the car wouldn't run when it was open. So since you said you replaced all the sensors, I'd go back to the old one there and see what happens.

I have had problems on a -33 with a bad switch, #1 in your pic. But it ran ok, it was an issue going into closed loop and maybe idle, but would definitely run.

You mentioned problems after replacing the fuel pump relay, you think... That suggests a problem there, although it's a pretty basic relay. However, the main relay is problematic and a very special relay. It had to have either 87 and 87 (the same) pins, or 87 and 87b pins. If it has an 87a it's the wrong one and the car won't run. Big deal, it's bitten many over the years, it's a very specific relay. You've changed so much stuff at this point you may need to verify by wire color what relay is what so you don't have them mixed up, especially the main.

Lastly and 533s and 535s are really quite different, I did have a 535 parts car one time that would start, seem to run ok for about 30 seconds, about, then die and not restart for a while. It was the ECU. Popped a spare in and it started up and ran like a champ. Yes, the symptoms do match, but I think it's very unlikely to be the problem. I mention it because it is so similar, but I really don't think it's your problem. 059/535 ECUs seem to be more problematic than 008/533 ECUs.

[Sean335]

you gave me something to consider. im going to read your reply a couple more time after I get off the phone (sourcing a replacement DME to compare against and see what happens) just in case, thanks.