944 running problems

[malpaslane]

hi everyone, i,ve just got a 944 on the road for my daily drive , which is starting to have some running problems,. when i first got the car,it ran fine ,but needed a clutch plate and had viabations on start up which went away went engine warmed up , i,ve changed the plate and the belts (which i found someone in the past had set up the balance shafts wrong) and cleaned the thottle body out, car started and ran fine ,except now i have viabation at around 2k rpm and car doesn,t want to idle when cold untill i hold the revs for afew seconds and then it,s ok,but also doesn,t fire up on the button when warm if i,ve let it sit for around 15 to 30 mins, viabation i put down to engine mount before belt change, but now not sure , it seems worst when i lift off accelerator,bad idle in mornings i think is some thing to do with voltage, as when i start the car the volt gauge shows under 12 volts and when i rev the engine the volts go up and i can hear the pump in tank kick in, but the car was fine before the belts were done. can anyone help as i have a long drive coming up very soon and haven,t got time to do alot of checking, cheers

[Razorback1980]

If the volts are showing low, one of two things are happening there. Either there is a battery drain somewhere or there is a bad ground. Both happen often with these cars. Does the battery sound low on voltage while cranking in the morning? If so, then there is something draining the battery down over night and the car MAY not be running correctly because of lack of voltage. The other thing to do is put an ohm meter between the negative battery terminal and a metal piece on the engine. Should read zero ohms. If not, clean the ground cable going to the back of the engine. It would also be a good idea to measure the voltage on the battery and then measure the voltage on the main starter post. Make sure those are the same or you need to find a dirty battery cable connection from between the battery and the starter post. As for not idling when cold, there are a number of things to look for on that. Check for any vacuum leaks, these engines are sensitive to those. I am not sure if ROW cars have oxygen sensors or not but if so, then disconnect it before starting the motor one morning and see if it runs better..if so, replace the oxygen sensor. What that does is when the oxygen sensor is disconnected, the computer will richen the air/fuel mixture and if your car runs better, then the oxygen sensor is not adjusting the air/fuel mixture properly. The vibration around 2K puzzles me unless the balance shaft belts are still not on correctly. Maybe double check them.