M103 - poor idle/start help - PeachParts Mercedes-Benz Forum

Hit Man X · #1 10-06-2006, 01:22 PM

So far on my chum's 300E ('87) we're replaced the cap, rotor, plugs, and plug wires. This helped VASTLY. I know with the 103 this is important. We have Bosch cap/rotor as well as wires and NGK plugs.

The ignition system on there was from 1987!!!

Yes, original Mercedes star and part numbers on the parts. LOL Fuel filter is up next, along with a fan belt, aux fan switch, thermostat (more about that later), and a diff service.

Anyway, what else should I look at for a poor idle? I'm considering a set of new brass injectors. Could the fuel be off in the distributor? Maybe the fuel pump relay? Idle seems to hunt some between 600-800rpm at times too.

On the thermo, should I run the 174°F or the 188°F? I'm starting to believe it's okay for these motors to run in the 100°F area... is this true?

Thanks!

gmercoleza · #2 10-06-2006, 02:59 PM

Glad to hear my cap & rotor were put to good use. For hunting idle, just clean the TPS. Do a search here - basically you spray carb cleaner on it, then WD40 to lube. My 300E had a horrible up/down 500/1500 idle and this solved it. A couple months ago it started to return somewhat, and I cleaned the TPS again and all is smooth as silk once more.

Don't be so quick to replace the injectors. In this order, I would do the following:

1. Run Techron through the tank at 2x the dilution recommended on the bottle. Do this 2 or 3 times, then change the oil.
2. Look for and fix vacuum leaks.
3. Look for and fix injector seal leaks.
4. Inspect ICV hoses and replace if brittle.
5. Clean ICV with carb cleaner, then follow up with WD40.
6. Turn EHA adjustment screw 1/4 turn clockwise - this made an INCREDIBLE difference for me.

That's all I can think of. For the record, my 300E now idles like glass and is a pleasure to drive. I did all the above after idle quality began deteriorating a few months ago. Now that it's fixed, it just sits in the garage and gets waxed every now and then...

Hit Man X · #3 10-06-2006, 03:13 PM

Yup, finally got around to putting it on... I can't believe the car had the original ones. LOL I have some spare brass injectors here so I figured I'd install them. They have about 40K on them? Something like that.

The E drives well once moving, just the idle is somewhat poor. I'll eye the TPS next time I get the chance. I did clean the ICV a while back, let it soak in a tank of B12 overnight.

On the EHA, yeah I know these cars run lean at WOT for whatever reason. Emissions I guess. I need to get a dwell meter so I can adjust the CO too. The breather to the valve cover from the air cleaner is cracked too.

I may get lucky and get this car, my bud now wants a 300TD

gmercoleza · #4 10-06-2006, 03:36 PM

FWIW, I just sent mine through the TX inspection a couple of weeks ago, and it passed with no problem - wasn't even close. So if you're scared to enrich, don't be. I don't think 1/4 turn or even 1/2 turn will cause any problems.

Hit Man X · #5 10-06-2006, 03:37 PM

Currently I can smell some unburned fuel, so I'm not sure what the issue is with it. We got it inspected anyway... I have another nine months to play before the inspection becomes an issue again.

gmercoleza · #6 10-06-2006, 03:43 PM

This might be a no-brainer, but...

Have you checked the air filter? Also, is the gas smell from the tailpipe or is it under the hood? Those green o-rings on the EHA tend to seep, and just a few molecules of fuel can somehow magnify to create the aroma of gallons of gushing gasoline.

Hit Man X · #7 10-06-2006, 03:46 PM

Just replaced it again, did it when he first got the car. About 14 months ago?

Ya know, I don't recall if it was out the tailpipe or not. I'll huff some next time.