Unknown Idle,start-up problem. Take A look, I Need All TheHelp I Can Get... - PeachParts Mercedes-Benz Forum

86 300E · #1 09-01-2010, 12:48 AM

Recently replaced the OVP and ran a 2 91 Octane tanks with Seafoam treatment. This helped a little but the problem still exists.

Run Down:

I start the car in the morning around 5am it takes 2 long crankes and it normally starts.

Upon start up, she idles real rough and I need to press the accelerater pedal to keep her running.

After i push just a little gas, she picks up and the idle clears up after a few mins... almost perfect very very slight miss.

(All of this these steps she is in park)

If i sit there for another 2 mins in park the rpms will very slowly creep up to around 1500.

I push the accelerator pedal to the floor and the RPMs stay the same. (sometimes they decrease to slightly under 1000)

Then I put the car in either Drive or Reverse the RPM's lower down to 600-800 rpms and idles with a slight miss.

Anyone have an Idea of what I should look at for?

Gilly · #2 09-01-2010, 04:54 AM

Valve stem seals

86 300E · #3 09-01-2010, 05:25 AM

http://www.peachparts.com/Wikka/M103ValveSeals

86 300E · #4 09-01-2010, 05:32 AM

ive been reading some of the forms wouldnt i see a use of oil and blue smoke on a start up if the valve seals where the case?

mbzman · #5 09-01-2010, 02:05 PM

Have you checked for vacuum leaks?

Gilly · #6 09-01-2010, 05:12 PM

You'd see yellowish or tannish deposits on the spark plugs, more so than smokey starts. Check them all.

Gilly · #7 09-01-2010, 05:16 PM

A check for a vacuum leak is never a bad idea. If the engine does run OK after a minute or two, I'd think it's not caused by a vacuum leak though, because if it was causing these problems, it would never really clear up. Unless it's just leaking vac when the engine is cold.

However, one thing I just thought of, is that a bad OVP or even just a blown OVP fuse causes bad cold starts. Not as bad when warmed up, but they do start and run poorly when cold with an non-functioning OVP.
Gilly

ps2cho · #8 09-01-2010, 09:46 PM

Check that the idle control valve is functioning along with no vacuum leaks of the attached hoses. You can remove it via the two bolts and shoot it clean using carb cleaner if you wish also.

Use the X11 connector to read the mixture % and make sure there are no errors or a completely out of whack reading. Use this site as reference:
http://www.landiss.com/mixture.htm

86 300E · #9 09-02-2010, 03:02 AM

how do i get the reading off of this?

Cal Learner · #10 09-02-2010, 05:49 AM

Check out the Landiss link if you haven't already done so. The test with voltmeter is at pins 2 and 3. Pin 3 is the signal pin; pin 2 is ground. Then apply the formula to calculate duty cycle. Easy and quick to do.

mak · #11 09-02-2010, 10:43 AM

Quote:

Originally Posted by Gilly

Valve stem seals

could it also be valve guides ,or then we would have additional symptoms of start up smoke?
mak

Gilly · #12 09-02-2010, 05:05 PM

"typically" you will be able to do the seals once, then the next time it will need guides. So it depends on if it's had seals done before on if I'd expect it to need guides. Round numbers would be 100,000 to 150,000 it will need seals, then maybe 200,000 to 250,000 miles it'll need the guides.
Gilly