Seafoam is great if done properly. Trickle it into an already warmed up engine using the brake booster line, then when you get just about half a can or a little less into the engine shut it off, reconnect the brake booster line and let it sit 10-15min. It might run a bit rough at first, but normally just when the idle smooths out the white smoke with appear. I personally either rev it up, or take it for a drive to knock out as much carbon deposits as I can, then once the smoke goes away you should be good to go. Take the rest of the Seafoam and place it into the gas tank.

I had a 97 Range Rover HSE Vitesse and although it was in mint condition and ran great but whenever I went to pass someone it looked like a mini version of rolling coal. I tried several LR Fuel Treatments (got them for free from my LR buddies) and they did nothing. I knew the previous owner didn't drive it like I did so the engine was probably full of carbon deposits. I grabbed a can of Seafoam, let it suck up just under half a bottle, then I let it sit for 15min and man did it smoke. I jumped into it and of coarse everyone thought it was blowing up lol. I hit a nearby FM Road and drove it until the smoke stopped. The idle was much smoother and after that whenever I went to pass anyone I didn't see a small black cloud behind me.

I've used it on other vehicles (Non LR) and because they aren't known for running rich I never noticed a difference and they hardly ever smoked. However on LR's I've had very good results with it. I drop a bottle into the fuel at every oil change.

I've also seen O2 sensor faults that were actually caused by a bad MAF.

 

 

Yep that's it (on a D2 use the brake booster line).

 

How did you check for vacuum leaks? Basically, if it were a vacuum leak that only affected one bank of the engine...l'd be checking the lower intake manifold/valley pan gasket area on that bank. Spraying carb cleaner (which is flammable, so use caustion), preferably with a nozzle tube for directing spray in certain location better, and see if you notice any change in idle.

Also, has your engine ever been out or head gasket repair? Just wondering if maybe the engine harness got pinched? And, l know it's a son of a ***** to get a look at the connection, but can you verify that the upper plug has all of it's wires terminal ends securely in place? They can be pushed out of the plactic housing, while assembling connection...and even the smallest amount can throw off readings from sensor.

​​​​​​​ Brian.

 

 

 

No, each bank 1 or 2, sensor 1 control Short Term Fuel Trim for that bank of cylinders. When the 02 shows lean condition, fuel trim increases fuel, once the 02 sees rich, the fuel trim changes to lean. They basically flip-flop constantly. That's why the fluctuations are so quick on the front sensors, they are constantly adapting for optimum emissions and fuel mileage.

The down-stream 02's are just along for the ride, more or less, and report the condition of the cats. They have absolutely no affect on fuel trim, short or long term.

Noticed you mentioned code P0135 was frequent before. This is another code that rears its ugly head when you have a bad connection or faulty 02.

You also mention your bank 1, 02 sensor fluctuating between .7 and .1...it's strange that you never see .9 (rich condition). It's almost like the sensor is seeing lean conditions most of the time...so the short term fuel trim is going rich more than it would regularly. An exhaust leak would create this issue, too. Are you sure you don't have more than one exhaust leak, one upstream of the sensor?

I'm leaning towards exhaust leak or bad wiring harness/connection...since swapping 02's made no difference.

Brian.

P.S. l hate trying to fix vehicles over the internet...it's hard enough in person.