Hi guys, new hereI own a 1989 Volvo 740 estate with the B230E engine and 4 speed auto. Bit rough but running condition and I'm fixing it up as I go. It idles a bit rough in neutral, the rpm fluctuates but is normally below 800rpm, but it is even worse when stopped and in drive. Rpm drops and engine starts vibrating alot, so I have to put it into neutral when stopped in traffic.

The inner and outer injector seals have been replaced as iv heard this is a common problem, the seals where rock hard but replacing them doesn't seem to have had an effect, iv had a look round for air leaks and can't find any. Also it's had a full service recently, including gearbox fluid and filter, but still no change. Could it be HT leads and distributer cap? As I haven't changed those yet

Im hoping there's nothing terminal with the gearbox
Thanks guys

 

Start with the easy stuff . Clean the throttle body and the idle air control valve. Then reset the idle per the recommended method. Also you might want to replace the plastic hose from the MAF to the throttle body. This will eliminate any air leaks. Check and clean the dist. cap and rotor and if bad replace. Also check compression and see if you can find out when the valves were adjusted. Good luck.

 

And your low idle has nothing to do with the gearbox...
You may want to take a compression test for starters to eliminate the possibility of a bad valve, worst case scenario, before putting money into parts.