'91 190E 2.3 lumpy start
 

Our '91 190E has a problem which occurs on starting. The severity is proportional to the length of time between starts, and is not noticeable on restarts the same day, and usually not after a 24 hr rest. After a 2-day rest, though, the symptoms occur: starting is immediate, but the symptom is running on less than all 4 cylinders and threatening to stall. This persists usually until starting to drive down the street, or for a couple of minutes, then all is fine.

So far, after a 2-day rest, I removed the plugs. All appear fine and similar in appearance, with no raw fuel smell. Started up then for just a few revolutions, then turned off. Still no raw fuel smell on any plugs, even though symptom was present. I do detect a possible slight hint of dampness of some sort on plug #4 threads.

Since coolant level goes down over time, and most external leaks have been corrected, I believe, my first thought is a gasket leak, even though the head gasket was previously replaced about 40k ago. Anyone have thoughts of other possible issues?

Thanks, Steve

Check the distributor cap and rotor if you haven't already done so to see if they are pitted. If the head gasket was replaced 40K miles ago it's unlikely that it needs to be replaced so soon. One of the classic signs of a blown head gasket is oil in the coolant reservoir.

You may also wish to consider replacing the fuel filter if it has been awhile since it was last changed.

No oil in the coolant reservoir, no water in the oil. From this I deduce any leakage (if it exists) to be extremely small. Yet if so, why the first-start issue? I have checked the ignition components, and see nothing there that would likely cause this symptom. The plug wires are fairly new, good integrity, and were previously working fine. I will have someone start the engine in the dark and look for signs of arc-over, though. Thanks, and any other thoughts?

Steve

Well, never solved the problem, but.... it went away on its own. Of all the possible causes, I have no clue what would cause such a symptom except possibly a temporary clog at an injector..

Steve