strange engine problem

[Guy911]

hello , can anyone help out ?

3.2 86 engine does strange things :

when cold and idling , the engine is going up and down from 0 RPM to 2000 RPM and eventualy stops running.
when I take the oil filling cap of , the engine is running perfect !


when hot, engine is idling on +/- 1000 RPM and no possibility to lower down , or same strange thing occurs .

somebody had the same problem ?
what to do ?

any advise is welcome !

thanks

[buster73]

When you remove the oil filler cap the mixture will lean out. Sounds your injection setup might be off. Try a search on this issue in this forum.

[Guy911]

thanks buster73

i've done that, but can not realy find the cause , or the way to fix it.

seems that removing the cap leans out the mixure, but what to
replace ?

car has just got his big maintenance job , and before it did not suffer of this. before the engine was getting a lot of air through false places.

or is putting a K&N airfilter on the cap a "allowed" solution ?

[PorscheG]

Disconnect your O2 sensor, and see if that makes any difference.
It should richen up the mixture and settle things down. You may have a bad O2 sensor that sends false signals to the DME, which in turn will adjust the mixture to compensate.

[buster73]

Take it back to where you had the maintenance job done and have them check the mixture. probably they sealed off some air leaks without re-adjusting the mixture. Hopefuly it is just an adjustment and no hardware issue.

[Guy911]

yep , will do that (taking back to shop)

I hope they will find the problem soon , did not hear a solution so far from them

thanks for the reply's !

bye bye