MB 190E missfire when half warm.

[mb201]

Its a 89mod 2.0l, never have problems when cold or hot, when half warm it sometimes blow the hoses out from idle regulator with a bang. Any good suggestion what i can try to change to fix this? or is it maybe lean on mixture?

[Hirnbeiss]

Sounds like you have backfiring through the intake. The first steps for this are ensuring the mixture is correct, checking/replacing the distributor cap, and replacing the plug wires (which lead a hard life, baking away on the cylinder head) as well.
The theory is that you have to get a spark in a cylinder when its intake valve is open and when the mixture is too lean. This usually only happens by "crossfiring", when the wrong cylinder gets a a spark.

[mb201]

Thanks, yes i have checked and replaced electric + distributor. How to adjust the mixture on this and how much do you adjust the screw?

[Hirnbeiss]

I wouldn't recommend adjusting the mixture unless you can measure the results, like with an exhaust sniffer. I would look for a good independendent shop to do that.
How old are your plug wires?

[mb201]

Ok, i dont know, i changed them from another 190. Same problem when changing them, i would think problem would be there all the time if it was wires. This problem only happens now and then when car is stopped for a couple off hours,