Black Smoke in Volvo 740 Turbo?

Question

I have a 1988 Volvo 740 turbo that has recently begun spewing black smoke. White smoke I understand happens when the turbo begins to go. Black smoke I understand to be oil. I just drove the thing and it does do the white smoke thing. Drives consistent with the turbo going out as in it looses power when the turbo meter goes into yellow/active. If I keep it out of the yellow/active range there is less smoke and it just drives like a 4-cyl. Any ideas about the black smoke? Drives fine otherwise...my own hunch is that it spews black smoke because it doesn't like how my sweetheart drives it. Her history is that she's driven numerous other cars into death.

Answer 1

Black smoke indicates a rich fuel mixture. Causes of excessive fuel mixture is, faulty oxygen sensor, faulty fuel pressure regulator, faulty coolant temp. sensor, or faulty air mass flow meter...the easiest thing to check is disconnecting the O2 sensor at the green wire....test drive it and observe performance difference and black smoke improvements. Also measure the voltage at the O2 sensor at the black wire. It should read approx. .700-900mv. If lower than this, ground the green wire for the O2 sensor....this forces the fuel trim to run max. rich and O2 senor should read .800-900mv. If no change, then replace it with a Bosch O2 sensor..Avoid aftermarket parts if u can...Just keep in mind that there may be multiple faulty parts and process of elimination is key to replace all faulty related part....If O2 sensor is ruled out, and u don't have a fuel pressure test gauge, one sign if it's faulty is listen to the fuel pump....it should have a steady consistant buzzing sound. Any irregular buzzing sound could indicate a fuel press. that is ristricting fuel back to fuel tank...this is a common problem...on a car with over 100kmiles and age of car...also a sign of press. reg. failing is leaking diaphram internally...just disconnect the vacuum hose at the regulator and check for any signs of fuel leaks coming out of it and look thru the hose as well....if all ok, install a good known used air flow meter and test drive....If one of these is the culprit and performance has improved and black smoke significantly less then u fixxed that problem...Next is the white smoke...check eng. oil level and remove excessive oil if overfilled...this is a good time to do oil change if due...If overfilled and oil level normal test drive or let it idle for at least 15 to 30 minutes..this gives time for the residue to burn off in the exhaust system...And another critical and most overlooked cause is the the flame trap housing, the vacuum hoses connected to it and more importantly..the vacuum hose port that is on the intake manifold...replace all dirty and clogged parts...and don't forget to clear the vacuum port with metal coat hanger or something.....Car shuts down or looses power? Inspect all vacuum hoses for the turbo wastegate....a broken vacuum hose for the wastegate causes the turbo to over boost.....and thank god the engineers designed a over boost sensor device that shuts off the engine momentarily to prevent engine damage.Check all turbo hoses to and out turbo unit all the way to the intake manifold...use your hand to feel underneath the big hoses after the turbo intercooler and feel for any hidden damage that u can't see with your eyes......I will continue with this when i get back from dinner....running really late.....bye for now.......

I'm back now! Where were we? Oh yeah...wait a minute...i believe i covered everything hear....good luck and let me know if this info. helps..

Answer 2

Black smoke sounds like you have a fuel delivery problem. Something is making it burn too much gas. Volvos are bad about leaky injectors and the fuel pressure regulator could be an issue also.

Answer 3

. recommend a fuel pressure test and vacume line inspection to the regulator and an oil change if it is found to be contaminated with gas. and while this engine does not use a flame trap the crankcase ventilation hoses and parts should be serviced and cleaned as required in addition to above i had one come in w/similer complaint and found that timing belt was about 4 teeth off loose and flapping.. after replacement the car ran perfect.

Answer 4

You can start by not DRIVING it anymore for one thing.

Black smoke means over-rich condition. White smoke is head gasket but since you've got your colors all mixed up maybe that's not your real problem.

Definitely you need to check for a fuel delivery/enrichment issue. You're going to screw up your catalytic driving like this.

Answer 5

White smoke is usually a bad head gasket. If compression in 2 adjacent cylinders is lower than the rest that is a pretty good indication of a bad gasket.

Answer 6

The piston rings are prolly goin bad, letting fuel sneak past the pistons and collectin in the crank case. Could be the valves too though.

Answer 7

Check your turbo hoses, one or more of them could have a hole or is coming apart in some other way. Just a possibility, never hurts to check.

Answer 8

Black smoke is to much gas, white smoke is water and blue smoke is oil.

Answer 9

don´t let your sweetheart drive your Volvo!!!