Why diesel engine has a smelly exhaust at idle

More information please. What year is this vehicle? Is this a constant high rev or is it surging high then low and back again? Are you sure it is oil from the exhaust? Using a pair of rubber gloves, rub some of this 'oil' between your finger tips, oil will feel greasy. Sometime soot can form in the exhaust, especially on diesels, and when this mixes with water it can look like oil.
This 'Air Noise'. Is it a whoosh, whistle. hiss? This information can give clues as to where the problem is. Air noises, over rev and oil from the exhaust could be more than one problem. Get a Good mechanic to look at this and to check the Turbo and all the pipes for issues.

Check the level of coolant

I suggest you have your car checked as soon as possible - while a rattling exhaust isn't desperately urgent it could be the cat breaking up which might later restrict the flow of gases. Most importantly excessively loose timing belts or chains tend to make most noise when the engine is idling. If the noise is being caused by this delay could be very expensive.

If you have to replace them frequently look for some emission/ dirty exhaust problems.

(which engine. ?????)_
as always check all fuses. and scan the ECU for DTCs. first.
there is no need to fix OBD2 cars like 1980 cars (hard rows to hoe)
it can be 2 problems this......
lets fix the easy one first. idle. (and hope for moving issues to fix for free) it idle car is parked, so is 100% safe tests. (not moving)

so it surges at idle.
questions.?
1: hot or cold or both.?
2: low extreme RPM and high at idle.
400 to 800 RPM? surge.
1000 to 2000. what? numbers tell the tale.

first off, idle is the last thing to work right on any engine.

there are many ways to find what is wrong.
fix idle surge way.
i make sure that the engine holds closed LOOP status.
hot idle, if not , i fix that first.
keep in mind if not in closes loop and lean
all lean engine surge and guess what the ISC will add to the surge
because idle is way too slow, so the ECU open the ISC wider
and wider and its still too slow, so the ECU resets the ISC
this cause a worst hunt (surge)
the ECU adjust spark time and the ISC to get 800 rpm. (spec. look up yours)
so say , i see closed loop failed, OBD2 scan page 1
i look at the O2 sensor an its stuck lean.
if stuck lean and it really is (o2 bad?) then its lean and it will surge
.
examples.
1: i find 02 sensor bad, (only effects idle and light steady cruise)
2: i find fuel pressure at 15PSI , hopeless low .
3: i find all injectors clogged. and lean.
4: with MAF EFI, ( i find maf reading too low, (dirty) causing lean.
5: if MAP car, i find the MAP stuck hard high vacuum causing lean.
not knowing what engine you have or the idle hot surge range,
i can not go farther.

the driving bog tells me,
1: scan the ecu ,get DTCs; do that first.
2: clean MAF if car has one, ask how..
3: check fuel pressure.


my guess is engine is lean. and starving for fuel all the time.
cept WOT.

MAF cars starve for fuel if there are any vacuum leaks.
MAP cars do opposite, they race fast with 100% full power.
MAF is air density EFI
MAP is speed density EFI.
apples and oranges diffr. so what engine.

to me it sounds like your just about to put water down your exhaust mate or your rings are binding up. I recon dump your oil and run diesel oil from now on and reset your timing belt before those new spark plugs end up in your lap.

Just an idea but the Ford Mondeo ( european car ) from which I believe your engine
is taken has a habit of splitting a low pressure tube at the back
of the engine this is a relatively
cheap, easy fix. The other symptom this used to throw up was a
little more black smoke from the exhaust and a pacing/ surging from
the engine.

Engine also smokes when car driving if turbocharger still faulty. Did you change the engine timing belt (the timing belt kit) meantime? What about engine oil consumption? When engine glow plugs (one or more) burnt then engine exhausts white smoke at idling. Also white smoke at engine idling when water is still present in diesel fuel.

sounds like an Idle air control valve or a positive crankcase ventalation valve(or pcv valve). use some intake cleaner in the air intake and take the pcv valve out and shake it it should rattle and move freely. mike