Transmission on 1989 420 SEL

[Cigar Havana]

I sucked some ATF fluid out my 1989 420 SEL (230,000 KM), after only 14,000 KM and it looks a cloudy red, not like new ATF, so I think it is best to change it. Anybody know why it is getting so cloudy so quickly?

Also, I notice that when in 'D' traveling about 50 KHP, on a slight downhill, if I take my foot off the gas, the engine seems to slowdown the car. If I shift it into neutral, the car coasts faster. Is this normal, or is this a symptom of some other problem?

[86560SEL]

Perhaps the car is not shifting into 4th? What are the RPMs at 55MPH?

[Cigar Havana]

I think it is shifting into 4th. The RPMs at 100 KPH is 2000 RPM. 100 KPH is about 62 MPH.

I changed the fluid and the filter. I put in Walmart synthetic transmission fluid, and a Febi filter and gasket. Drained the pan and torque converter. I couldn't get the plug out of the pan, must have put 100 NM onto the plug. I didn't want to put more in case the hex key started to strip. Any ideas on how to get the plug out next time?

That throttle position switch, does it have another name too? Where exactly is the switch located?

[Cigar Havana]

Could I just spray some carb cleaner or wd40 at the switch and get it freed up? Any other possible causes for not coasting well?

[Inthemedia]

Yes, testing the TPS is very easy. With engine off, disconnect the TPS 3-prong connector (just behind and to the right of the Cold Start Injector (CSI)). You will be testing the connector that remains stationary with the engine (not the end that was unplugged). With a Ohmmeter, make sure you have continunity between the middle pin and the pin furthest away from the CSI. This is the "Idle" sensing position of the switch. If you don't have continuity then the switch is bad. Another symptom of a bad switch is your idle speed will be around 1200-1400 in Park if this switch goes bad.

Next have an assistant push the accelerator down. Make sure you have continunity between the middle pin and the pin closest to the CSI. If you don't then switch is bad and indicates that it is dirty and needs to be cleaned or replaced, misadjusted, or defective.

Let us know what you find out.

T.C. Mann (aka TechMann)

[Will_w202]

I thought the slow-down was normal in the older (pre-98?) cars. My 97 C230 does this and I thought it was just a sign of good compression

Either way, it saves me from having to use the brakes on off-ramps

[Cigar Havana]

Well, I just tested the throttle position switch (TPS), following inthemedia's excellent directions. The engine does not have a high idle. In neutral, it idles about 600-650 warm, and warm in drive, 500 RPM.

The ignition was off for the following tests. The test between centre and the pin furthest away from the cold start injector (CSI), was continuous, it was a closed circuit. Between centre and the nearest pin to the CSI, it was wide open. Hooked up some aligator clips to the pin and put the meter near the windshield, as I pressed down on the accelerator peddle, all the the way down, no change. I used a digital multimeter, and made several tries, once on the 200, 2K, 200k and 2M ohm scales, not even a twitch.

I guess the verdict is the switch needs to be replaced? Any opinions?

Should I have tested with the iginition on, but the engine off?

Is this a DIY job? As bribenz indicated, I guess there are a few gaskets and seals that will need to be replaced when putting things back. How many hours? Any complications?

[Cigar Havana]

OK, I bought a new switch. I was surprised that the part was not named a throttle valve switch as it is called on the service CD. The label on the switch says it is a 'switch overload protect' 201 540 56 45.

I though I would also replace the intake manifold gaskets and O rings. Has any DIYer done job 14-450? How long does it take?

[Cigar Havana]

Well I finally replaced the throttle position switch (TPS). Replaced the 3 vacuum lines and 4 rubber fittings, and the TPS gasket, along with throttle spring. Setup the TPS as per the service manual, 0 ohms at idle, as soon as the plate moves 0.2mm, idle circuit goes to infinity.

Now I have a high idle in neutral. It starts out at about 800 RPM and slowly creeps up to 1000 rpm and stays there. But as soon as I put it into drive, RPMs drop to 500-550, which is normal.

I retested the TPS once installed, and all tests results are correct. I double checked the new vacuum lines. Lower port on TPS goes to Black and white vacuum valve switch/sensor. Top vacuum lines goes to red sensor, then to EGR valve. The fat lines goes to the purge valve.

I must say, that I did get ambition and thought I would try to replace the intake manifold o-rings and gaskets, since I was half way there already. After pulling all of the bolts, draining the coolant, etc. I realized the manifold wasn't coming out without block and tackle or an engine lifter. So put all of bolts back, and replaced the control linkage, etc.

Any ideas on the high idle? From past posts, it could be:

1. Temperature switch. Which one? I have 3. the blue one with 2 terminals, or one with 1, which is the one that shows on the dash, or is it the green one, with 2 terminals?

2. Idle control module. I have a new one. Is there anything else that needs to be done other than pull the old, and put in the new?

3. Idle control valve, or slide valve. Maybe I have have hooked this up wrong come to think of it. Should the wires to the plug come out of the bottom or the top?








I checked the lambda, and it is around 45-50%.

[ericgr]

Verify the connection to your idle control valve. The connectors on mine were very brittle. You can tell if the connection is good or not by disconnecting the leads to the idle control valve. If the car idles the same (high) then either the connectors/connection is bad or the unit is bad (unlikely because yours seemed to have worked before). I made new connectors by using standard crimp connectors from the electronics or auto parts store. strip the old connector off, crimo ine end, and pick a connector that, on the other end, fits nicely onto the valve