A few days ago, I reported clouds of black smoke upon accleration, particularly driving uphill in the mountains. The car is an '86 760T which had been running very well and on which I had put a Dawes device a couple of days before. I removed the device, but clouds of smoke continued. I read O2 sensor voltage and found a constant .87 volts at idle after I drove the car for 15-20 minutes. I thought I had poisoned the O2 with silicone I sprayed on turbo hoses to put them back on the car after some fiddling. Some at Brickboard thought the Dawes device had blown a turbo hose, but these are new and checked out OK. Last night I checked O2 voltage and it fluctuated like it should. Today, I drove the car and it ran perfectly. Is it possible O2 sensor had a mild case of silicone poisoning and has now cured itself, perhaps cleaned off by exhaust gas and heat? I have a new O2 sensor and FPR in the mail from fcpgroton. Should I install these anyhow, since most other fuel injection, ignition and fuel delivery components and sensors in the car is now new, but O2 sensor and FPR are original as far as I know? Best regards.

my favorite culprit. bolts work loose, boost is bled to atmospheric, and amm tells ecu to pour on the coal, ergo black smoke.

doesn't do the cat any good either!

Although how the compressor bypass valve would do the tighten up after leaking I haven't the foggiest.

I will check in case a bypass little loose makes little difference without G-valve, but big difference with it set around 10 psi. Thank you for your reply.

Glad to hear thing are running well, although I always wonder about it, when a prob goes away before exactly pin pointing what caused it. I'm NOT hoping it comes back! You know what I mean.
Steve
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88 765 w/2stage boost & G-valve

All I can think is that it was (mild) silicone poisoning of the O2 sensor, now more or less cleared by hot exhaust gas. I checked voltage on the O2 sensor a the time of the black smoke, and read a constant .87 volts. Now, O2 sensor voltage fluctuates again like it should. Still, it is the original O2 sensor on an '86 car with over 150,000 miles! So, it is probably time to put in a new sensor to be safe rather than sorry. Anyhow, can you think of any way that the G-valve set at around 10 psi could have caused the black smoke from running too rich? Turbo hoses are new and without holes. I checked for holes to be sure. Vacuum is tight with vacuum/boost gauge reading eight O'clock at idle in neutral, nine O'clock at idle in drive holding the car with the brake pedal. Vacuum also drops like a rock down to seven O'clock upon lifting off the gas pedal. Thank you for your reply and best regards.

Hi Rafael, I've got the original at 288K! How do you like the g-valve? I love mine and it's set to around 8 psi.
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Warren Bain - '86 744Ti M46 >285Kmi, '96 965 >99Kmi Wifemobile near Manassas Va.. I get e-mail replies to my postings.

Hello Warren:

Do you have the original O2 sensor in your car? The car was running smoothly and powerful before I put in the G-valve. After I put it in, the car ran more smoothly and powerful at all rpm, both very plesant and a bit scary because the boost needle would hit two O'clock (around 10 psi) in less than wink. There was some drivetrain rumble at 5,000-6,000 rpm, but the engine felt silky smooth. Then, I had the black smoke. Looking for a solution to the problem I temporarily disconnected the G-valve. I have a new O2 sensor and FPR in the mail (those on the car are original). When I put these on, I will put the G-valve back on. The car ran so smooth and powerful, I think it is worthwhile even to do an engine teardown and rebuild to run the G-valve at 12 psi or even 14 psi. That is, at least on a fairly new car with perfect paint and interior like a 940T. One could spend a reasonable amount of money on upgrades of suspension (IPD sway bars front and rear, Cherry Turbo upper and lower braces, urethane bushings, otherwise all new Volvo bushings, new struts and shocks), tires, brakes and headlights and have a very desirable road car for not much money. Best regards.

I have too many original pieces on my car right now. I need to exchange some of them. It's cold here right now, a condition about which you know far too little .
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Warren Bain - '86 744Ti M46 >285Kmi, '96 965 >99Kmi Wifemobile near Manassas Va.. I get e-mail replies to my postings.

God bless you, you have original pieces on your car. On mine, there are not many of those. Cold is a condition about which I can happily forget now, but I knew it well in my hometown (NYC). You are Canadian, you should be sweating in anything warmer than the Artic and all year in Virginia.

I would install the new FPR and O2 sensor. These are wear items (they just wear V-E-R-Y slowly) so in an '86 car you would be better safe than sorry to replace them. I agree that something perhaps burned off the O2 sensor, but it is still time/mileage to replace it. I figure around 125k for a sensor.

Will do! I think you are right, moreover engine management components would now nearly all be brand new. The only thing I can remember has not been changed is the coil, but I tested it with a multimeter and it checked OK. Other systems like cooling, brakes and suspension have been overhauled or are being overhauled. AT was throroughly rebuilt a year ago. All fluid have been thoroughly flushed and synthetics put in. A/C is now all new forward of the firewall plus evaporator. As I write, I am drawing a vacuum in the A/C, but the vintage pump I borrowed is drawing only 25 inches Hg after two hours. Is this enough? Should I put in R134 and see what happens? Best regards.

I probably shouldn't be sticking my nose in here but I'd say that
while meter checks on a coil are helpful, it is a high voltage component
and might have weak insulation that would short at high voltage even though
it reads OK with a meter. On the other hand, if it does, you will have
pretty clear symptoms - cutting out, maybe only when hot, or maybe not running
at all.

25" is not enough. I have an old rotary vane vacuum pump that doesn't do
any better than that dry but if I give it a shot of oil (motor oil, for
example) in the intake, the vacuum goes up to about 29" for maybe 10-15 minutes.
Some of the old vacuum pumps have an oil injector on the intake that does
this for you.
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George Downs Bartlesville, Oklahoma

Hello George:

Thank you very much indeed for sticking your nose in here. The coil has given none of those clear symptoms yet. Rather, the car had been running better than ever until the recent episode of black smoke. Today, the car ran very well again. Coil does not seem to be a problem now, but if it gives any sign of trouble I will repalce it because I prefer to be safe rather than sorry. I do not much like car maintenance, but I hate breakdowns. So I choose the lesser of two evils, so to speak.

Please, tell me more about how to inject oil and get more vacuum out of that pump!!! I have had the pump going for three hours and all I get is 25 inches Hg (60 cm). I have overhauled the A/C and I want to put R134 in and deep freeze myself. I am in the tropics where it is very hot and humid! Thank you again for your reply. Let me hear from you again.

I'm not sure what kind of pump you have but mine a an old rotary vane pump on
the end of a small electric motor. I just squirted a squirt or 2 of oil
into where it sucks. It then sucks harder for a while but after the oil
dissipates it is back to where it started.

I spent 22 years in Panama, returning to Oklahoma (retiring) in June 1998.
Most of the time I did without because it was more trouble than it was
worth and most of my trips were short. Also my 122 tended to overheat
with AC running in Panama City's heavy traffic. In the interior I drove
fast enough that I didn't need it too badly.
¿y donde estás tú?
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George Downs Bartlesville, Oklahoma

Estoy en Puerto Rico. I live at the old Army base in the mountains in Cayey. Now it is a University of Puerto Rico campus.