This LRO reader emailed LRO.firstname.lastname@example.org to ask our experts for suggestions on what may be causing his 2.25 Series III to burn oil.
My Series III 2.25 petrol has no chance of passing the local traffic department emissions test due to exhaust smoke; it’s blue/white and smells of petrol. A compression test revealed all four cylinders are reading 142psi. It rattles at idle and on hard throttle, so the ignition timing isn’t right.
The mechanic says it’s due to oil control rings, but the compression test results seem to contradict that. I think it may be a cracked valve stem seal. Would it help to carry out a cylinder leakage test? What about using more viscous engine oil or a product called Restore? Does any of the above give an indication of what might be at fault? Any suggestions are welcome.
Robin Cury, Dubai, UAE
The blue/white smoke indicates burning oil, but I’d also be concerned about the smell of petrol – either there’s far too much petrol going into the engine or the petrol is not getting burnt properly. A 142psi compression test would indicate an engine in generally good condition, but I can’t remember the last time I did a compression test on a 2.25 engine and had the exact same reading on all four cylinders!
Before any further diagnostics, make sure the timing and fuelling is correct; if the carburettor is completely worn out, the engine will be smoky as the excess fuel is not getting burnt and also will be washing the oil from the cylinder bores and stopping the piston rings doing their job properly. It’s worth doing a cylinder leakage test, but it’s not always successful on the 2.25 engines due to their fairly agricultural tolerances.
If setting the running of the engine does not cure the fault, I’d be tempted to do a decoke (head gasket and valve stem oil seal change and cleaning of cylinder head and valves) and to fit new rings. I would not recommend thicker oil, and products such as Restore are, at best, a temporary solution.
This workshop advice appeared in the February 2016 issue of LRO. Back issues are available to download on digital devices here.