Recently bought a 1988 740 wagon with the 2 litre non turbo engine with 128,000 miles. Has an occasional problem starting when hot or warm. Cranks over for maybe 30 seconds before firing up then runs rough on 2 or 3 pots for a few seconds. Once running she's fine. Does it perhaps one start in five, otherwise starts OK. Starts from cold OK. Injectors seem OK, fitted new leads, distributor & rotor arm. No flywheel sensor at this age so not that. I'm at a loss as to what it might be. Any guidance much appreciated.