Troubleshooting with Steve Rothwell
PORSCHE 924 ROUGH RUNNING
QI have a 1980 Porsche 924 which is being restored. It had a failed head gasket and I have had the cylinder head professionally overhauled, including the fitting of a new camshaft. After rebuilding the engine, it starts and runs, but not very evenly. It has an erratic idle speed which alters by around 200rpm, and when accelerating the engine hesitates and misfires at around 2500rpm. I used a strobe light to check the timing, but the marks on the flywheel seem to jump around.
The problems only show up on the engine when it is hot, and it starts from cold easily. I have replaced the HT leads and spark plugs as well as the distributor cap and rotor arm, but none of this has made a difference. I did try using a mobile mechanic who suggested the problem may be an air leak, but spraying carb cleaner around the manifold made no difference to the engine note. The exhaust system is a genuine Porsche unit and new so I wouldn’t expect any problems in that direction. I was wondering if the injectors were at fault, but the mobile mechanic’s analyser said emissions were OK. Any thoughts?
Joseph Steel
The one
