Smoke from exhaust, running rich?

Pulseammo

Pulseammo

Pulseammo

Associate
Joined
10 Jan 2006
Posts
1,449
Location
Scotland
Hello all, you may remember me from other fun threads such as "Is my timing out enough to cause no start?", but I am back once again to terrorise the motors forum and pick your collective brains. :D

I'm having some further problems with my C3 Picasso, namely:
- Smoke from the exhaust when pulling away from lights / after idle.
- Not really any smoke when idle or at constant cruising speed. But pressing accelerator after idle causes it, pulling from lights, junctions, etc.
- Yesterday the car started to stall near idle revs (pulled up at lights and stalled by the time I came to a stop, couldn't get her started again).
- When the car did start again (after being pushed into a side street), it wanted to stall unless the accelerator was pressed slightly (1.5k RPM).
- When the car would not start it would crank and make a kind of "whoomp" noise at the end of cranking, sometimes it will make this sound when pushing smoke out, I think it may be misfiring.
- After a couple of minutes holding the throttle at 1.5k I was able to release it without stalling.
- Smoke in my opinion is a brown / grey, maybe a hint of blue though.
- Idle in general doesn't seem rough?

(Photos taken at idle, but after giving the accelerator a quick press to make smoke appear)






From what I can tell the problem gets worse once the engine gets to temperature AND driving around - for instance it can sit idle on the drive without stalling for 10+ minutes.

So far:
- I've replaced the PCV valve in case it was stuck open, no change. (Valve cover gasket also done before.)
- Checked PCV has negative pressure at valve cover, it does. Checked for cracks in PCV hose, don't think there is any.
- I've compression tested the cylinders to try and rule out worn piston rings, 175PSI every cylinder, dry test.
- Air filter hasn't been changed in 3 years but only has 15k on it, looks fine to me.

Questions:
- I've pulled my spark plugs and found that I appear to be running rich, can anyone confirm this is dry carbon deposits near the end of the threads?
- Also looking at this video you can see that there is a lighter portion on each insulator tip, is this bad spray pattern from injectors?








A couple of weeks ago this car wouldn't start because I believe the cylinders got washed with fuel, when I pulled the plugs diagnosing that problem they looked like better than now, no black carbon around the end of the threads (please ignore the oil deposits on these older photos, valve cover gaskets needed done and have now been done). But the smoky exhaust has gotten worse over the last two weeks. I am wondering if a rich condition existed before which caused my cylinder wash out a few weeks back.

So I'm lost as to where to go with this. I've taken some live data, short term fuel trim is 0% at idle (when there is no smoke), but ranges heavily between +/- 20% depending on throttle. I'll see if I can export the graph to a better format.

Anyone know what diagnostics I should be carrying out for all banks apparently running rich?
- Lack of airflow?
- Oxygen Sensors?
- Fuel Pressure Regulator?

Thank you!
 
Yes, I have P1676 pending and P0014 pending, no engine management light though.

I'm ruling out P1676 to have anything to do with it - it's alternator related and the alternator was replaced a couple of years ago, it's giving off good voltage and I never get the battery warning light.

(I tried to clear codes, but even without restarting the engine they come right back).

P0014 on the other hand is interesting, exhaust cam is too advanced, the engine also has variable valve timing (VVT, VANOS). I may pull the exhaust VANOS solenoid to inspect (that'll be a joy since it's down the back of the engine a bit). Edit: The exhaust VANOS solenoid is actually the one at the front, happy days.

O2 Sensor:
Also run a bunch of live data, the pre-cat wideband O2 sensor seems to be alright, it reports readings as an AFR wandering mostly between 14.65 and 14.75, some slight peaks at 14.6 and 14.85. It reacts to pumping brakes to create a lean condition as well as start spray for a rich condition, so I think it is operating correctly.

Fuel Trims:
Engine doesn't seem to be adding or removing fuel... it does if I get on the pedal (O2 sensor goes lean to 14:1 for a moment then fuel trims hammer in +14%, settle back down to +6% with revs held at 1.6k). So in short even though I'm seeing carbon on the plugs and smoke in the exhaust, the wideband doesn't seem to reckon there's a rich condition - yet it can see it if I spray ether. Don't know what to make of that.

I've noticed it will smoke at idle now as well once the car is up to full temperature, and continue to smoke. Strangely turning the engine off and restarting 30mins later resulted in very little smoke at idle... here's a video when it got bad at idle. The smoke smells acrid, like a bonfire, also smells a bit of petrol, the patch on the cardboard is water though:

 
Last edited:
Removed the exhaust vanos solenoid, clean as a whistle, almost no debris at all on the filter screen - so clearly I'm looking after the ungrateful heap of junk with its oil changes.

Honestly I've never really read live data but this all looks fine to me also, car isn't adding or removing fuel in reaction to the smoking exhaust as far as I can tell. Sensors seem to be reacting normally.

Completely stumped. I removed the air filter and allowed the car to idle for a bit - no change, so intake filter is clean enough.

I don't feel a huge amount of air rushing into the intake, but covering it with my hand you can feel a suction start to build up. To be honest if I had a restricted intake I'd be expecting the fuel trim to be subtracting a ton, and it's not.

Edit: Also tasted that liquid coming off the exhaust (it's fine, relax, I'm Scottish), just tastes like clean water - no sweetness in it at all, not taste at all in fact - not sure if there would be if it was coolant after it's been through an exhaust though.











 
Last edited:
Pulseammo said:
- Yesterday the car started to stall near idle revs (pulled up at lights and stalled by the time I came to a stop, couldn't get her started again).
- When the car did start again (after being pushed into a side street), it wanted to stall unless the accelerator was pressed slightly (1.5k RPM).
Click to expand...
that's reminiscent of what happened when my 3er cam position sensor went bad.. but maybe you'd have a code on a modern car,
mine became especially temperamental especially on warm restarts (it is dictasting when the injectors operate I thought)
 
JonRGV250 said:
Is it using excess oil? (ie burning it)
When did it last pass an MOT emissions check?
Click to expand...

It always has since I've owned it, it uses something in the region of 1litre per 1500 miles - the owners manual has a warning in it saying this is normal. A bit of internet research over the years has shown other people complaining about that too. It also had a leaking valve cover gasket which I've now recently resolved, which could have been contributing.

Last MOT was November, only advisory was the brakes.

Sometimes the smoke does have a vaguely blue-ish gray to it, which lead me to the PCV system, I felt there was too much valve cover vacuum pressure and thought perhaps the PCV valve was open when it shouldn't be - but I replaced that and it's made no difference. I can only see about half the hose which goes back to the intake manifold, so I may pull the airbox and anything else I need to out tomorrow to try and confirm that hose is intact, I did have it pulled aside to do the valve cover gasket.
 
jpaul said:
that's reminiscent of what happened when my 3er cam position sensor went bad.. but maybe you'd have a code on a modern car,
mine became especially temperamental especially on warm restarts (it is dictasting when the injectors operate I thought)
Click to expand...
Interesting... it has two cam sensors, exhaust and intake, I have a multimeter so I may try to test them, I think it's just a hall effect sensor so I should be able to pass them by some metal, or magnet.

Honestly my scanner is one of those ELM bluetooth dongles, it's prolly not very good, but the scanner app does have specific settings for my ECU and does seem to manage to show the basic codes at least.
 
Sinbad2000 said:
Oil smoke after idling could strongly indicate valve stem seals leaking.
Click to expand...
I'll see if I'm getting smoke immediately on start up, I've not done that test yet. My understanding was that valve stem seals tended to be a cold engine problem though and tended to alleviate once at temperature.

I do wonder though if fixing the rocker cover gasket has increased the vacuum in the rocker cover and is therefore pulling oil past... Edit: Actually that makes no sense because the vacuum source is the PCV crank case breather hose in my case, so the vacuum is from the intake manifold. More likely would have been a stuck closed PCV valve causing high pressure forcing it past the seals.

Another thought was my oil control rings but there's basically no way to test for that afaik.
 
Last edited:
The vacuum source is actually the "suck" stroke of the combustion cycle. With throttle closed (at idle) you get strong vacuum at the valve bodies as the valves open which can suck oil past the stem seals
 
Easy way to check valve seals is go for a drive, find a long downhill section and go ndown it just using the engine has a brake when you get to the point of slowing down to much acclerate and look to see at the back if you have a trail of Blue smoke. Piston rings, you will know if they are worn by the amount of smoke in normal driving conditions. Personally I would check all the breather pipes, remove the throttle body and clean making sure all the small srilling and pipes are clean.
 
So as it happens I did spend yesterday tearing down the intake, sadly though I didn't actually get the manifold off, just the airbox and throttle. (I honestly don't think the manifold would get out the engine bay of this car, hence I stopped).

There was oily residue on the walls of the intake manifold, and the backside of the throttle. More concerning was the sludge leaking from the PCV hose. There were no real oil puddles though and I've read that misting of the intake can be normal from the PCV system.

Cleaned the PCV hose through with brake cleaner and attached a shopvac to it to suck all the sludge out, before / after:







Also checked both vanos solenoids while I was at it, exhaust solenoid had an almost completely clean filter mesh. Intake was more dirty, slightly low resistance reading on that one too but still actuated fine testing with a battery.





So after all that the car does have less smoke now at idle and had reverted to it's original "smoke on pedal from idle"... but even then it doesn't seem to be as much. I really don't feel like I've fixed anything or improved anything, I think the fault is just intermittently worse or better.

Didn't have time to check the cam sensors. Haven't looked at fuel rail pressure either.

I've done some preliminary valve stem seal tests:
  • Starting the car - no puff of smoke, no smoke at all in fact until after about 60 seconds and only very light smoke. Smoke here seems to actually be a lot better in general right now even when pumping the pedal (it still gives a puff but not as much as my earlier video by far).
  • I took up second gear and went down a hill for maybe a 10 - 15 second stretch, not sure on my exact engine revs but I must have been about 1.5k? Throttle fully closed, literally zero smoke. Took it round the block and got a small amount when pulling out of a junction... I'll need to do more testing.
 
Today is the first day I've been able to test the car properly, took it to the local shops, then next town over, 60mph roads.

Zero smoke, not at idle, not after idle, not at 60mph, checked on start up as well, zero. Also no sign of it wanting to stall either.

Also went down a very steep but long hill in the area, 3rd gear all the way off the throttle. Nothing. Back on the gas at the bottom, no smoke.

I refuse to believe that I've fixed anything. I'm sure it must be intermittent. And I doubt oil smoke would be affected by the slightly warmer weather today, infact hotter oil would surely go past a seal easier.

Collected a ton of live data linked to GPS so I'll have a sift through that later when I can.

So I guess the thread is on hold until it decides to conk out again. Thanks for all the help and suggestions so far, they are much appreciated, I am checking as many of them as I can.
 
You must log in or register to reply here.
Back
Top Bottom