98 1.25 Zetec Smoky engine - therealrem

I picked up a car for my other half at the weekend which (for £800 at least) is in pretty good condition.

The only issue is when warm and you rev the engine - not hard necessarily, just to 4000 or so when stopped and in neutral or when pulling in 1st, 2nd or 3rd you get a small amount of black smoke from the exhaust.

I suspect that the engine is running rich so have changed the air filter (it was filthy and the crank case breather connection onto the filter box was a bit dirty.) This reduced the amount of smoke. The breather pipe itself was clear and unblocked.

When its not as cold as it is tonight I'll have a look at the lambda sensors as I suspect they are original and the car has done 100,000 miles (with full ford service history). Has anyone any hints and tips for what other fuelling things would be straight forward to check. A guy at work suggested a can of redex injector cleaner.

Other points to note:
- Passed MOT in Nov and emissions were fine
- Exhaust needs looking at. Don't think its blowing but it's a bit loose and needs mounting correctly
- It's not used any noticable amount of oil in the 200 or so miles I've driven
- It's been filled with fully synthetic 5W/40 for the last few years
- Car is a mid-1998 1.25 16v Fiesta Zetec
- I've got another 1997 1.25 Fiesta LX that runs perfect I could swap parts from to try

Cheers, it's cold so I'll stay inside and plan my next move...

Edited by Pugugly {P} on 02/01/2008 at 19:19

98 1.25 Zetec Smoky engine - Screwloose

The only thing you need to check is the voltage on the black wire from the oxy sensor when the engine is fast-idling at full temp.

It should be sweeping between 0.2 and 0.8 volts. If it isn't; don't automatically assume that it's the sensor - it could be telling the truth.

Ask Honest John

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