I have a 4g92 SOHC 1.6l engine that is not doing anything particularly bad but is just running really rough and blowing a bit of ugly smoke, especially when it is cold. Plugs, oil and air/oil filter have all been recently replaced and fluid levels are all good. Any suggestions, whether simple tweaks or recommended upgrades are appreciated Cheers Jeremy
How old is the car? What colour is the smoke? By cold do you mean the ambient temp or the car temp?
its a 1994, a whitish smoke and tends to be when engine is cold but also slightly present when ambident is cold and engine has warmed up. Its done 139000km
Whitish smoke implies water getting into the combustion chamber. That could be a head gasket. However, the colour is often very hard to discern from inside a vehicle. Since you mention that you aren't loosing fluids, I would lean toward oil-based smoke. Just a few drops of oil make a lot of smoke. The smell would actually tell you more.
If it is oil, I would suspect valve stem seals before rings. The primary reason is that it is occurring after the car has sat long enough to cool down. This is when a drop or two drips down into the combustion chamber. When you start the car this is quickly burnt up and, in the process, is fouling your plugs some. That will clear up as the oil is burnt off and then the car will run fine again. As the seals get worse, the quantity of oil will increase and, eventually, the oil will completely foul the plugs out. At that point, the car may not start until the plugs are cleaned/changed (I know from personal experience).
I would suggest you do a compression test and possibly buy a kit to test for combustion gasses in the coolant. Regardless, the standard repair calls for pulling the head and that means you should replace stem seals and the head gasket at the same time. You can do the stem seals with the head on, but that requires an air compressor and may require a special tool to compress the springs. If your timing belt and water pump are fairly new, I would try it with the head still on. If they need replacing, it's really fairly simple to pull the head on a 4 cylinder.
stem seals--compression test will not show the failure but is a good thing to do to see if there are "other problems"
two options---compression test ok---head off --reset reseat valves-replace stem seals---while you are there (not sure of your engine) replace (if applicable) lifter/cam(ok check for wear but why not upgrade?) pushrods??---change cam belt/chain and replace oill pump and drive as you already have easy access to it compression test not ok----look forward to either bent or valves that do not seat correctly or in the worst case worn bores/bust rings/holed or cracked piston. From what you describe it is the stem seals----but do the other work while you are there as it is false economy not to just my 0.2 Timberwolf
Thanks heaps guys, I know it takes time to reply and its appreciated. Your advice has given me much to get on with, I will report back on my progress. Cheers again
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