300E Cold start issues
 

OK. So I bought this car the other day, and it runs great, except for one problem. Upon cold start, it runs really rough, and if I so much as touch the gas pedal, it stalls. It takes several cranks, and then stutters like all hell. Once it warms up, it's fine. This is a completely different beast to me (coming from a W123 diesel), and I can't seem to find another post that matches my symptoms (if I'm missing something on this board, please let me know). Also, possibly related, the previous owner mentioned that the idle had been turned up a bit (warm idle @ ~2k) to compensate for a crack in the insulation of a wire going to an injector. I've ordered a part to fix that (a little replacement boot). I also plan on checking into the OVP this weekend, as the ABS light is on, and I've heard that relay can do stange things when it goes south. Let me know what you folks think. Thanks!

By the way, this is the part I ordered for the injector:

Well, first off....that part you ordered does not exist on the 1989 300E.....might as well return it.

The injectors are completely mechanical, no wires exist. Only the cold start injector has a wire, and I doubt it has any issues. The issue you are describing is caused by a faulty engine temperature sensor (at the far back of the drivers side of the engine with a big connector plugged into it) and possibly a stuck or gunked up idle control valve.

Since your ABS light is on, I'd replace the OVP relay before anything else, it could very likely be the cause of all your issues.

Your seller was feeding you stories....you can't "turn up" the idle on these cars, it is computer controlled. The whole problem is that the electronic injection and idle control system is not operating....and it is running on mechanical injection. Idle speed on mechanical injection is about 500rpm, if the electronic idle system is working then in park it should be around 700-800, and 600 in drive or reverse. And it should go to around 1100 when first started cold, then drop down after a few minutes of warmup.

So maybe I should also be looking at an engine temperature sensor and maybe a Idle Air/Speed Control Valve . Is there anyway to test any of these parts?

Yes, put a multimeter that does ohm readings on the pins of the temp sensor (test the 4 pins 2 at a time, criss cross....there are two identical sensors in there for two different computers)

The idle valve can be tested just by giving it 12 volts, if it clanks and moves the little valve in the opening, it works. It'd be good to drown it in brake cleaner to get all the gunk out of it. The hoses connected between the idle valve and engine/intake are also likely hard and need to be replaced to prevent vac leaks (which might explain your 2000rpm idle)....lots of rubber parts under there, as many should be replaced as possible. Gassers are sensative to vac leaks.

Where does you economy gauge sit while in park and drive without pressing the pedal? In park with the A/C off it should be essentially pegged in the black, in drive it should move a couple need widths off the peg. With the A/C on it should move over towards the red a bit more. If its near or in the red all the time then you have some big vacuum leaks.

Economy guage sits in the black at idle. I noticed that the parts page shows two different temp control sensors, the one described above, and one at the air filter housing. Could that by chance be the one missing in this picture? Could this be part of the problem? Thanks.

I don't believe a 1989 model has that sensor....your intake tube may have been replaced at some point, and the later ones have a sensor there (mine does)....thus the hole. If it is not dangling around below there then I doubt yours has one. The sensor at the back of the engine is most important to the computer to run the engine properly. It needs a 22mm deep socket to be removed, and you need a proper inch-pounds torque wrench to put it in to the right torque (not much) so you don't damage anything.

Also, would vac leaks cause a higher or lower idle. I do notice that the transmission is shifting a bit firm...

The transmission should shift pretty firm, firm is better than soft. Vac leaks will raise the idle. On a throttled engine (gas) the more air it gets the higher it rev's.....that's why they have a throttle plate, it restricts air to the engine....the result is a vacuum in the intake....which is what the "economy gauge" is looking it, its essentially just showing the level of vacuum in the intake, black = high vacuum/low throttle, thus less fuel consumption, red is low vacuum/high throttle, lots of fuel consumption. :D

You can test for leaks by spritzing starter fluid around various spots on the engine while its running....if the rpms go up when you spray somewhere, there's a leak.

OK. I found the temp sensor, but it looks a bit different from anything I'm finding here (let me know if I am in error). The part that I thought I found is in the picture below (the attachment, which looks like what most other folks have). However, mine looks different. Mine looks like this:

http://catalog.peachparts.com/ShopByVehicle.epc?q=1989-Mercedes--Benz-300e-Cooling--System&yearid=1989%40%401989&makeid=63%40%40MERCEDES+BENZ%40%40X&modelid=6201%3AMBC|1507%3AED|100000 13%40%40300E&catid=240909%40%40Cooling+System&subcatid=241011@@Engine+Temp.+Sensor&mode=PA

...however, it only has 2 poles instead of 3. What am I missing? All the replacements I see have 3 poles...:confused: Anyone know where I can get this little bastard?

This will be the component. It's usually installed in the earlier variants of the M103. Or the non cat models. It's a standard part.
Search Fast Lane - here's there part number Manufacturer: BOSCH Part Number: W0133-1615795
What's your location?

http://farm3.static.flickr.com/2306/...a6d37628_o.jpg

The bosch book lists these as the causes of cold start issues on continous fuel injection systems:

cold start valve
fuel pump not running
air flow sensor plate rest postion incorrect
fuel pressure incorrect
coolant temp sensor or wiring faulty

http://www.bentleypublishers.com/mercedesbenz/300e-4matic/Mercedes-W124-85-95-Workshop-Man.html

http://www.bentleypublishers.com/isbn/9780837603001/index.html

Nope, that sensor is the one for the gauge on the dash. The one posted with the 4 pins is the engine computer temp sensor. It is available, its also known as the Water Temp Sensor on Fastlane:

http://catalog.peachparts.com/ShopByVehicle.epc?q=&yearid=1989%40%401989&makeid=63%40%40MERCEDES+BENZ%40%40X&modelid=6201%3AMBC|15 07%3AED|10000013%40%40300E&keyword=sensor&subcatid=P:240675@@Water+Temp.+Sensor&mode=PA

A pic:

http://img.eautopartscatalog.com/hir...300&height=300

Sorry pawoSD, Incorrect.

Two pin version in earlier M103's. Four pin in later M103's.
Two pin version is in Non cat versions of M103. - Can use leaded and unleaded fuel.
The OP has stated that he has the two pin variety. The temp gauge sensor is a one pin in that version.
I'd be interested to know the O.P.'s location

The OP is double posting. Go to this thread
http://www.peachparts.com/shopforum/showthread.php?p=2240340&posted=1#post2240340

Sorry to double-post. I've updated my profile with my location. From here on out, I will post only to this thread, as it wil probably be more widely searched. Does anyone know what the torque specs should be for tightening? Thanks.