190E 2.3 running rough
 

I have a 1985 190E 2.3 and it has been having a weird problem

it starts ok, but when I let it idle, it miss fires every once and again. now, that in and of itself wouldnt irritate me, but when the car is standing at a stop light in drive, the engine miss fires and stumbles so much that the engine actually died once.

I have hooked my vac gauge up to the engine and it all seems withing spec, but I keep having a feeling its vacuum related.

worked perfectly one day, miss firing the next.

any ideas guys?

would hate to have to sell the car.

Does it have the correct Bosch Super Plus Non-resistor copper core spark plugs in it? And how new is the distributor cap/rotor/wires/coil?

its had the same plugs in it since I bought it (duno what kind) but it ran perfect before

the wires are brand new, dist cap is a couple years old - coil, no idea

I didnt think it was the distributor since it runs absolutely perfect on the highway

pull a plug out and check it. Also check your Lambda setting, it might need some adjustment.

am I just looking for spark?

lambda setting?

no check the condition of the spark plug. The lambda is the fuel/air mixture, it can cause your car to run rough.

plugs, I can do - where is the lambda adjustment or w/e?

I would just check the plugs before going to anything fuel system related. It may have run fine for "a while" on the wrong kind of plug....and only now is showing problems.

I'll check em' just seems weird that it would start out of the blue, and so severely

also, where do I buy those special plugs other than a MB dealer?

cranks a ton before it starts when its cold, idles great till it gets a bit warmer (probably above 40*c) then it runs like trash again

if I hot start it, it'll crank and fire right up but it dies in a second or two unless I press on the gas pedal a little bit, after 5 seconds of that, it will idle, but really rough.

when the motor is at operating temp, the car barely runs in drive below 1,500rpm

haven't had time to pull the plugs yet, still working on finding a socket thats the right size.

At the dealer....they are about $3.50-4 each. You have a 4cyl. Thats like $15-16....

fair enough, I guess thats not too bad

Intermittent problem could be humidity related. As mentioned above...a cracked/leaking dist. cap, or bad plug wires will cause misfiring due to shorting from humidity...work ok on a clear dry day, and be a bear when things become damp.

Also

Verify engine temp sensor...little one with two vaccuum lines located at the front of the head above and to the left (looking from the front of the engine compartment)...the sensors go bad regularily (plastic body can break free from the brass housing causing air leakage, or the vacuum lines get cracked netting a bad temp signal). This is the sensor that tells the ezl/cpu what temp range your engine is running in, and can definitely affect timing and fuel feed.

Check also that your crank sensor is not loose or does not have a damaged/broken wire.

Would check these things out before ever touching the lambda adjustment....if you do want to play with it...make sure it's only done with diagnostics, and with someone who knows what they are doign around. Using a digiatal Volt meter, you can monitor the O2 changes, and make sure that they oscillate equally above and below .5V when under different loads, or use the diagnostic pins and a repair manual to verify voltages when running..To me the O2 method is more reliable, because certain other unrelated fault codes will cause a bad read at the diagnostic pins. Better to have someone knowledgeable around when doing this...the lambda adjustments are super sensitive and should never really be done by "ear".

I have a distro cap and stuff from my old 88 M102 in the garage, that motor always ran perfect - are they the same 85-88?

is the vacuum sensor the one with 3 openings on it?