Intermitant Heavy smoking on tickover

Craig · Post by **Craig** » 22 Sep 2003, 16:21

Can anybody help me with a persistant problem, every few months my car develops a nasty bug. On tickover it will struggle to mantain the revs and usually idle around 500 -600 rpm, also it will chuck loads of black smoke out of the exhaust.As I pull away the smoke thins out and the car drives ok, but the fuel consumption is bloody awfull.This is the third time it has done this and the problem only seems to go away if you rev the proverbials out of the car whilst driving!.The last time this happened my local garage said it was the oil that had gotten sludged up and was blocking the oil control rings on the pistons, so they changed the oil and took the car for a good run again reving the knackers off it.This fix has only lasted about a month or so and it's back to smoking again.I know this must be a straightforward fix but I'm stuffed if I can work out what it is can anyone help or should I burn the damn thing!!.

Tsquared · Post by **Tsquared** » 22 Sep 2003, 18:41

are you burnign any oil or is there any oil blow-by? Are you using a high detergent oil or a synthetic oil? How many miles/KM are on the engine?

If it is a sludge build up a top cylendar lubricant may help (in the states we have a product call Marvel Mystery Oil). Or a product like BG oil additive may clear up some of the oil issues.

Worse case you may need a ring job/overhaul.

T

Guest · Post by **Guest** » 23 Sep 2003, 07:21

Could be 5 reasons.

1) Throttle body = Need to clean throttle body. (black smoke, struggle to maintain revs)

2) Oil blow by = ring job (black smoke)

3) Valve not seated properly = change oil (garage could manage to solve it with new oil, need to use fully synthetic oil)

4) Clogged air filter = change air filter (black smoke, poor fuel consumption)

5) Did not reach operating temp, engine not hot enough = run engine at least 30 minutes each trip (every few months develop nasty bug)

Hope this helps. Thats why you need to tell long story. How u drive the car. where u go. etc etc more clues = easier detective work

Craig · Post by **Craig** » 23 Sep 2003, 17:36

The car has 177,000 on the clock and does not behave badly at any other time besides when this fault occurs.On a previous garage's instructions I have removed and cleaned the throttlebody and the o2 sensor.Neither of these made any impact on the problem at all,the car has had fully synthetic oil put in less than two months ago and ran ok up until a few days ago when the fault reappeared.Yeah the car doesnt do a great deal of mileage each day and is only run for a maximum of about 30 - 60 minutes before being put away again.Earlier this year I went on a long run and got stuck in stop start traffic for about an hour and a half , the check engine light came on and it started to smoke realy badly but once out on the motorway again it cleared up. I got the garage to inspect the car the next day but they couldnt find any thing wrong after resetting the engine warning light. This is driving me daft and if I dont solve it soon I may have to sell the blody thing and buy something else!!.PLEASE HELP!

Tsquared · Post by **Tsquared** » 23 Sep 2003, 17:49

Engine Warning Light??? There should have been a fault code that the parts changer at the garage could have gotten.

A faulty O2 sensor could also cause a sooty exhaust. With 177,000KM that is about 110,000 Miles. Unless it has been run very hard and not maintained at all the rings should be good for quite some time. Intermittant smoke leads me to believe a sensor or some electronics that may be fading in and out.

Guest · Post by **Guest** » 23 Sep 2003, 19:51

Stop/Start traffic = high temp.

High temp => connectors expand and or get oxidized => check engine light and black smoke => O2 sensor coz of connectors.

O2 sensor maybe ok but problem lies in connectors, make sure connectors are real tight. If O2 connectors are frayed you can cut bloody connector off and solder wire to another connector or buy another O2 sensor.

Check Mass Air Flow Connector too.

Unplug ECUs, wipe the connectors with cloth wet with WD40, (better not spray, hmmph...) and plug back the ECUs.

If 1993 850 you need to remove the ECU filter to prevent ECU overheating in traffic jam. (no need to use, I have added an extra 12V fan where the filter was)

MJJ · Post by **MJJ** » 23 Sep 2003, 20:55

If memory serves correctly, oil produces voluminous blue smoke, while a rich mix causes black. I'd focus my troubleshooting on the fuel system. Revving the bejesus out of an engine never cured it of anything.

Guest · Post by **Guest** » 24 Sep 2003, 07:15

well a cheap solution is to put in a bottle of fuel injector cleaner. (since revving engine clears injectors...............) its worth a try........

Craig · Post by **Craig** » 24 Sep 2003, 13:28

Thanks for all youre responses.

The car has 177,000 miles on it not km but because its ex-police its been very well serviced. In between these bouts of crap running the car runs fine- no smoke, be it blue black or grey.So I would not think it's the rings otherwise it would be belching oily smoke all the time.The injector cleaner may be an idea because I find that on start up from cold the car goes upto about 2,000 rpm for a few seconds before settling back down to a normal idle. but I'm not sure what bearing blocked injectors would have on the smoking problem.
Is it possible to have an intermitant o2 sensor or do they just fail?. There are no bad connections on the o2 sensor and I dont want the expense of changing it if I'm not certain as they're expensive.
I know what youre saying about reving the buggery out of the engine to clear the fault, but it seems to be the only thing that cures it at the moment and I would sooner risk that, than drive around looking like an extra from a bond film!
Cheers to you all for helping me try and sort this out it would probably cost me an arm and a leg to take it to a dealer!!

Volvord · Post by **Volvord** » 24 Sep 2003, 16:45

Check all your air intake hoses carefully for cracks, cuts, or leaks. Any leak between the MASS and throttle body will effect mixture. The MASS are also known to cause problems, they are expensive but this could be the cause. The O2 sensor could also be your problem but they do not usually cause as rich a mixture as you identify when they fail.