740 GLE Running Rough
 

could someone give me an opinion: volvo 740 2.3 16v engine code B234F 155bhp, the car came to head gasket change, before and after words it didn't run well and died, but when it runs it detonates(shoots) in the inlet manifold on quick accelerator pushing.
timing belt marks are good checked.
throttle position sensor changed
idle air control valve works checked
spark plugs and wires ok
distributor changed
ignition control unit changed
still doesn't run
what could be the problem?

Sounds as if timing is not correct. Re-check your timing and also the distributor installation.

fault code 3-1-2 is also displayed

Here is an article that may help a bit...
RWD -