Rough Idle
 

Hi All,

I have an 88 190E 2.3. It has developed a rough idle problem. When it is idling hot or cold it seems to be running on three cylinders, however when I get to about 2000 RPM it seems to smooth out. Also I noticed when I checked the distributor cap that it seems to be arching (cap and rotor only have about 1,000 miles on it). Could this be a distributor problem or????? Any help on where to start would help.

Thanks in Advance,
Merpar
:)

Did you see arcing, or only what seems to be the results of arcing?

Steve

checked your plugs lately?

Hi,

I don't see any signs of arching on the engine; just on the inside of the distributor cap and some burn marks on the rotor. This was also the case on the one this replaced about 1,000 miles ago, but the idle was fine at that time. Just thought this may be a sign of a distributor problem???

Merpar

RE: rough idle
 

I had a similar problem on my 87 300E. I did a tune up; cap, rotor, plugs and wires. The plugs were backordered from the website I ordered the parts from and I only recieved three. Replaced them and the problem improved a little. Got tired of waiting for the other three plugs, and found that Napa sells the "Bosch Super" plugs (for about $1.09 ea) I was using. Replaced the last three, and it runs smoothe for the first time since I purchased the car.

After talking to a few people, I've discovered that the Bosch Platinum plugs are the worst to use as they have more resistance, confusing the computer, resulting in rough idle and hesitation starting from a stop light. I'm no mechanic, and this is about as technical as I can get, but it helped my situation, hopefully it might help yours. Good luck.

Had the same 'running on three cylinders' with ours last month. Also signs of arcing and wear inside distributor cap, on rotor, and to HV terminal of coil. Additionally, one plug wire resistor end was crushed - felt like gravel. I replaced ALL those items - no change.

On the advice of some folks on this group, I pulled the coil wire and spun the engine a few times. Then, quickly as possible I removed and sniffed each spark plug. Hard to tell, but some gas smell evident on plugs 2,3,4, never on #1. I repeated the test several times - same result. I had a spare set of used injectors, so I swapped out the #1 injector. It ran fine after that.

I have been running a lot of Techron in my tank since then, 'cause smog test due before the end of the month. I SHOULD have been using it more frequently before. That #1 injector I replaced was less than 1 yr old.

Steve