1998 e300 rough idle - PeachParts Mercedes-Benz Forum

Nicks1 · #1 05-31-2007, 11:46 AM

I had the O rings and copper seals replaced on my IP. The engine was running perfectly prior to this maintenance; now the engine has a rough idle, but only after it warms up. The rough idle goes away if I turn on the A/C or place the car in drive. Someone suggested it might be a sticking idle air by-pass valve. (I don’t know where that is)

Also, does anyone know where to find schematics, technical and training information for the Injector Pump

Any help would be appreciated.

TMAllison · #2 05-31-2007, 12:02 PM

If by rough idle you are refering to knocking/nailing at idle this often occurs after replacing the delivery valve seals. Typically lessens with time. Performing a diesel purge (2 cans) helps to get rid of minute particles of contaminates that are flushed into the injectors after replacing the seals.

Mine quieted back down after 2 purges and ~2k miles.

Nicks1 · #3 05-31-2007, 01:53 PM

Thanks for your reply,

The engine seems to "mis",(for lack of a better description) every few seconds.

I'll try the purge again and keep my fingers crossed that it will "fix itself" in 2k .

Nick

1998 E300 TD
155k miles

aklim · #4 05-31-2007, 05:11 PM

If you have enough miles, spring for a injector testing. That will remove any debris in the injectors and will definitely make sure that the injectors are firing like they should. I did mine at 120K and it works fine.

Parrot of Doom · #5 05-31-2007, 07:05 PM

Rough idle is quite likely to be a weak spring on the EGR valve.

aklim · #6 05-31-2007, 08:06 PM

Wife said the car smoothed out once we cleaned the injectors and found one with poor spray pattern and low pop off pressure

Nicks1 · #7 06-02-2007, 04:34 PM

I ran two cans of Diesel Purge. It still idles rough unless I turn on the A/C or place it in drive. Now I have all sorts of air bubbles though the fuel lines, even after driving it for 200 miles. Is this normal after a purge.? Is there any way to bleed the air out?

Nick
1998 E300 TD
160K miles

nhdoc · #8 06-02-2007, 05:18 PM

If you have air bubbles I'd bet the o-ring on your prefilter is leaking. Check that first thing...did you happen to replace the prefilter recently? The o-ring is sold separately and is often overlooked or develop leaks that cause rough idle.

aklim · #9 06-02-2007, 07:05 PM

Quote:

Originally Posted by Nicks1

I ran two cans of Diesel Purge. It still idles rough unless I turn on the A/C or place it in drive. Now I have all sorts of air bubbles though the fuel lines, even after driving it for 200 miles. Is this normal after a purge.? Is there any way to bleed the air out?

Nick
1998 E300 TD
160K miles

If it is the prefilter or any of the O-rings in the lines you need to change them. Start with the prefilter. Driving the car will bleed out the air. I would think a few miles should do it.

TMAllison · #10 06-02-2007, 08:33 PM

Was the air there before your DP?

Nicks1 · #11 06-02-2007, 10:40 PM

I had no air bubbles at all in the fuel lines at all before the purge so I am guessing that the O rings in the fittings I pulled off need replacing. I''m also going to replace the plastic fuel line clip that's underneath the intake manifold.

Nick
1998 E300 TD
160K miles

TMAllison · #12 06-02-2007, 10:53 PM

As Marty said, if no air prior to the DP, you should first look at the pre-filter o-ring (check the bolt and washer/hold down and make certain its tight) and also the o-ring on the fuel line that enters the pre-filter. Both can be difficult to get sealed again. A dab of silicone grease can be helpful if they refuse to seal as can crimping the washer to create more downward pressure on the pre-filter.

All the lil white horseshoe clips on the ends of the fuel lines should be loose and floppy when properly installed. They are pushed closed (eg: make a ringer) for removal.

aklim · #13 06-03-2007, 01:19 AM

Change all the lines or at least the O-rings of the lines you disturb. You might have to change them all

nhdoc · #14 06-03-2007, 05:17 AM

Quote:

Originally Posted by aklim

Change all the lines or at least the O-rings of the lines you disturb. You might have to change them all

That's where I'd start...any time you disturb the lines there's a chance you break open one of those dopey seals. If your fuel lines are dark, replace them all and if they aren't replace all the o-rings at the end-joints and see if that doesn't help your idle problem out.

Nicks1 · #15 06-03-2007, 10:30 AM

Thanks you all for your help. I'll let you know how things work out after changing the O rings and fuel lines.

Nick
1998 E300 TD
160K miles