380SE runs Bad heres my spark plug ????? - PeachParts Mercedes-Benz Forum

barndoor · #1 09-20-2003, 09:23 PM

I have a '85 380 SE.
It starts right up,but Idles rough and is not running (on all 8?) correctly.I just pulled the spark plugs,the right side looks good the left side #s 5-8 looks like this one,the tip is very clean,with a color from being hot.These plugs are new (Bosch Super W9DC) but have only about 10 minutes on them,(not really driving just around the property "limping"
anyone have any ideas?

psfred · #2 09-20-2003, 09:26 PM

Barndoor:

No pic, didn't come through. What color is "from being too hot"?

Dark color at the base would indicate rich rather than lean running.

Bright white with blisters on the ceramic or fused on crud indicates lean running (vac leak).

Peter

barndoor · #3 09-20-2003, 10:00 PM

ceramic is white,some crud on metal.Electrode and Tip are VERY clean.

psfred · #4 09-20-2003, 10:45 PM

Looks fine at the tip, but I cannot see down to the base of the insulator -- is it white all the way down?

If so, I'd expect an overlean condition. This could easily be a vac leak on this car, often around the injector seals (although they don't leak like Volvo seals do).

Do the plugs on the other side look the same or different?

Peter

barndoor · #5 09-20-2003, 11:07 PM

The plugs on the "other" side look good.The "other" side has new injector seals.This car developed a head gasket leak on the right side (1-4) (leaking only oil) on a long trip to california(limped it home).I removed the head had it rebuilt,(only did the one because the left side had been done just before I bought the car),new head gasket set,new cam,followers,and rails.
Ever since I have had this problem,Its been two years!I have started and run the car to operating temp about once a month since,and along the way replaced plug wires,fuel pump/filter,some vacuum lines,injector seals on right side,some rubber hoses going under the manifold and a couple other parts.It still has the same problem since the head was removed.(it ran great even with the leaking head gasket).I am not getting any fluctuation of the economy gauge at any RPM.It feels like a vacuum leak,but ???
I am about to take it to a shop.Living in so. oregon our Mercedes shops are Rare.But we have a couple choices,none of which I am excited about,plus I always do all my own auto repairs and have never taken a car to a shop in 21 years of ONLY german car ownership.

psfred · #6 09-20-2003, 11:19 PM

Could be a couple things.

First, check the seals on the left side. Spray some carb cleaner or brake parts cleaner on the injector seals at idle. You don't need much. If the idle changes, they are leaking, replace. You may want to replace them on principle.

Next, if the K-Jet has the split manifold like the D-jet does, you need to check the seals between the top and bottom halves. Same drill, but aim at the seals. If those leak, pull the manifold and replace them.

Did you put a new gasket on the left manifold? I's assume so.

If that isn't it, check the valve timing on both sides. I don't think you would run with the left side a whole tooth off, but hey, anything is possible, and that would affect all the plugs on that side.

Make sure you don't' have an idle hose leaking, I'm not sure what the setup is on the K-jet, but the D-jet has one for each side. A leak will screw you here.

Make sure all the vac taps are OK, and that nothing is leaking vac on one side -- use a vac pump (MitiVac -- I should charge them for advertizing! -- works well). If you have a vac servo or door locks, etc leaking into one side you can get lean running over there.

The key, I think, is that all four plugs look different than the other side, has to be something that affects all four equally.

Peter

barndoor · #7 09-20-2003, 11:36 PM

ok first,
I removed ,& installed the right head without taking off the manifold,and without replacing left head gasket.Right head gasket slipped in and I torqed it down.(I researched this way of doing it before I did it and found that is what the dealer would of done in this case,although I always felt guilty about it)and this may be the problem.
I have also thought maybe I screwed up on the timing chain,but I was very careful with markings and Maybe someone could verify if it is possible that it would run this good off a tooth?I can change left side injector seals no problem.
what is the idle hose?
(I have a '75 450 sel w/D jet also for comparison)
all door locks work well,also Vac Taps? what are they?
this MitiVac,does this detect vacuum leak?
would a Tech be able to easily detect vacuum leak?
sorry for calling you fred Peter,and I really appreciate your help.
mark

psfred · #8 09-21-2003, 11:29 AM

Mark:

A MitiVac is a hand powered vacuum pump. Very useful for finding leaks, as it has a vac gauge on it. To find a leak, you would unplug the vac line in question from the manifold, then hook up the Mitivac and see if the line hods vac. If not, you can then trace back and see what is leaking. By this time, most of the vac servos and switchover valves/vac amplifiers will be going, the rubber diaphrams split.

Sucking a bunch of air down the left side will cause it to run lean.

I'd certainly check the left side manifold gasket for leaks, ditto for the seal. Very easy and cheap.

On the D-Jet there is a Y shaped hose from the idle valve to the manifold. One leg of the Y goes to each side of the lower manifold chamber, so if the left one was cracked, that side would run leaner thant eh other. Don't remember if the K-jet engine has the same setup or not.

I think it you have the cam one tooth fast you might be OK, don't know about one tooth late. Easy enough to check, just pull the valve covers and align the cam mark with the cam tower mark on the right side and see where the crank pointer and the cam mark on the left side is.

Peter