: Sooty Stalling 98 Deville

08-26-07, 07:12 PM
I started having problems with my 98 Deville w Northstar about 2 weeks ago. First it was hard to crank but it cranked and I had no codes. then about a week and a half ago it stalled on me and started emitting dark "smoke" out of the exhaust just once still no codes. Then a few says later it was still doing all of the above but then it threw the following codes: P300 Current- Engine Misfire detected, P1380 Current- Misfire Detected-Rough Road Data Not Available, P1599 History-Engine Stall, P0152 Current- Heated O2 Sensor Circuit High Voltage Bank 2 Sensor 1, And I also had one for the O2 Sensor Bank 2, Sensor 2. So I talked to my mechanic about changing out the O2 sensors and he told me it could all be caused by a faulty or clogged fuel filter. So I changed out the fuel filter myself and drove it for the rest of the afternoon and for awhile the codes went away. Then after a few hours the codes came back but it was only the misfire code. So I changed out the spark plugs and drove it again and it drove fine for a bit then threw out just the misfire and the O2 sensor code for the front sensor Bank 2 Sensor 1. I noticed when I took out the spark plugs that there was a black sooty residue on the plugs similar to the soot on the inside of a chimney. Today I changed out the front O2 sensor and drove it again and I am still getting the hesitation and stalling only now when I idle it is throttling itself. I also noticed the same sooty residue on the O2 sensor probe tip when I took it out. The code that is showing now is the misfire code. Any ideas would be greatly appreciated.

08-26-07, 09:01 PM
No way a fuel filter is going to cause sooty exhaust or plugs. You are running rich, not lean. Check for a leaky FPR. Easy to do, Check the Tech Tips section.

08-26-07, 11:18 PM
Thanks for the help and sorry again for the double post. I read the post and will just go ahead and replace the part just to be on the safe side but I was wondering if I should do the engine cleaning technique described in the following post after the change out in order to deal with the soot.


08-27-07, 10:02 AM
That procedure is for extreme cases of oil consumption to free stuck rings. If you do it wrong, as mentioned, you can hydrolock the engine. Then you are in deep doo doo. I'd use the WOT procedure described in the Technical Archive at the top left of this page.

08-27-07, 12:03 PM
Thanks again Ranger for all of the help. Next time I know to come here first. Maybe I would have saved myself some time, frustration and money.

09-04-07, 05:45 PM
What, other than a faulty FPR could cause the engine to run rich?

09-04-07, 06:18 PM
just about anything....

bad o2 sensor, a misfiring cylinder will make the rest of the engine run rich while the o2/computer reads lean... faulty sensors...

09-04-07, 06:47 PM
well I have a brand new o2 sensor reading faulty codes.. and im getting a pretty fuel rich exhaust, no codes about anything but the o2 sensor, very sooty inside the top of the engine.

and a wonky idle at coasting

sorry to hijack the post but maybe we both have the same issue.


09-04-07, 07:05 PM
what is the o2 sensor code? rich bank? rich both banks?

09-05-07, 11:57 AM
bank 1 sensor 2 high or intermittent voltage and heater fault. same codes that were thrown before i replaced the sensor.. so its no the sensor..

I'm going to try a TEC treatment, my mechanic thinks it could be a sticky injector or two clogged up by carbon ..

FPR is good

09-05-07, 02:26 PM
Have you checked to make sure the wiring isn't getting melted on the exhaust?

09-06-07, 04:15 PM
Everything is wrapped up tight down there, thank you for the suggestion. Any possibility I, and the previous mechanic, replaced the wrong sensor after the cat?

09-07-07, 06:34 PM
Earlier Northstars had 4 O2 sensors. At some point they switched to 3 (eliminating the pre-CAT sensor). If you have a pre-CAT sensor, that is Bank 1 Sensor 2. If not then you replaced the correct one.

09-11-07, 05:56 PM
I do have a pre-cat sensor, and that is the one I replaced.

p0141, Heater Circuit Malfunction (Bank 1, Sensor 2) is the only code that has been popping up randomly.

Oh so confused...