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Both my girlfriend's and my taxi have been intermittently running rough lately. Deb's car is stalling sometimes, and mine is having phases of a few minutes each time where it is very underpowered. I had put a new stepper motor in each car a few months ago, which was about when the problems started. So, thinking it might be a bad batch of stepper motors, I replaced them with new ones again. No change. I had the throttle body on each car cleaned by a taxi mechanic who does this stuff every day. Again, no change. The problem wasn't electrical - it was clearly some sort of fuel starvation issue. Whenever my engine ran on low power output, it still did so smoothly - there wasn't the roughness that running on four or five cylinders would produce. So, it wasn't plugs or coils. That's where I was starting to get stumped and started to do some searching through Falcon forums, and started reading threads about oxygen sensors and PCV valves. The more posts I read, the more it seemed like either one of these two was causing the problem for each car. I finally decided to replace the oxygen sensor and PCV valve on each car. The first task was to figure out what each of them was, which wasn't too hard. Ford's price for an oxygen sensor is around the $400 mark, so more searching was done to see what alternatives there are. Sure enough, Bosch make one. Bosch stuff is sold very cheaply all over Australia by a company called MTQ Engine Systems. The part number that people had posted on forums matched the part number listed in the Bosch PDF that I found. Goody. This job was going to be done today. I decided that this morning, and nothing was going to stop that. Any natural disasters, terrorist attacks or armageddons would have to bugger off and wait until at least tomorrow. Today I was going to replace the *&^%$# oxygen sensor and PCV valve on the two taxis. I had been receiving substantial whinging from both the girlfriend and my day driver, and there was a sudden development today of an urgent requirement to shut them both up. So, having figured out what oxygen sensor to buy, I made the call to MTQ. The price in their catalogue was $39.50 plus GST, which was most acceptable. But, they didn't have any in stock in Perth, and would have to get them from the eastern states. This was not compatible with my declaration that this job was going to be done today. A call to Repco confirmed that they had them available. For $111. No worries, don't call me, I'll call you. A call to another auto parts company confirmed that I could get them for a trade price of $61.55 each. But, he wanted a parts order, on a letterhead, etc. He wouldn't do them for trade price for a taxi. I gave up and rang another branch. Rod was more than happy to sell them to me for trade price, but he only had one in stock. Crap. However, he immediately solved the problem by creating an order on the computer system to be picked up at the place that had the two in stock, at trade price. Ripper, it took a few phone calls and some stuffing around, but I finally had two oxygen sensors lined up. Girlfriend was called and informed of the situation - it was her job to go and pick up the sensors (ie NOW!), whilst I moved on to organising PCV valves (including figuring out what one is first). PCV valves were easy - they came to about $11.00 each from the usual Ford dealer that I get taxi parts from, and they had plenty in stock. I got the oxygen sensor out of my car and rang girlfriend to inform her to hurry the hell up. She did this, and my car had a new oxygen sensor a few minutes later. She went off to do other stuff whilst I decided to get the Aprilia out and go pick up the PCV valves. Doing my car was easy because the engine bay was cold. Doing Deb's car was going to be a pain because she would have to drive the thing to my place (ie hot engine bay). It all worked out rather well. After fitting the new oxygen sensor and PCV valve to my car, there was the magic moment where the engine actually did start and run properly. Deb arrived some time later and we left her car in my front yard with the bonnet up for a while. Surprisingly, it cooled down fairly quick and the same job got done on her car. She left about 10 minutes ago and just rang. Bugger, a phone call so quick meant that she'd already had more grief. No, she was calling to tell me how much better the gearbox kickdown now worked. Now that I know how cheap and simple it is to do replace these two parts, I wish that I did it weeks ago. Ah well, another lesson for future reference. The photos: Here's the old one that came out of my car, next to the new Bosch one that is about to go in Deb's car. Minor differences at the sensor end, but they look like they would both do the same job. Here's a photo of the clip on the one that came out of my car. This was difficult to disconnect - it was mounted to the firewall and there were hoses blocking my view of it, so I just had to feel around and guess how to unclip it. It turned out that was doing it the right way, but the plastic wouldn't come loose until some "encouraging" words were said. I used a small flat blade screwdriver with one hand to push the clip in and yanked it in different directions with the other hand. The Ford service manual PDF that I looked through before starting this said to use Loctite 767 or similar (ie anti-seize), so I got Deb to get the smallest amount they've got. Apparently smallest and life time supply mean the same thing. A photo of the engine bay in Deb's car, showing the oxygen sensor location and the LPG hoses that I also had to deal with. You remove this heat shield. There are three bolts on the top that require a 13mm socket. There are two bolts at the bottom that require a 10mm socket. The removed heat shield - you can see where the lower bolts go. I've disconnected two hoses from the LPG converter so that I can get to the oxygen sensor. I don't know what size spanner it takes - I just used a large crescent to loosen it. Here's the new one ready to go in, with the anti-seize on the threads. The new one in place. To tighten it, I used used low to medium force with a crescent. Pretty close to spark plug tension. Now it was time to replace the PCV valve, which turns out to be a stupidly simple thing on top of the engine. I got the plastic valve and the rubber elbow, which needs to be forced onto the PCV valve. The new PCV valve in place. I always use a zip tie to tighten the hose's grip, preventing it from coming off. The finished job. New oxygen sensor and PCV valve are in place, the heat shield is back on and the hoses are connected where they are meant to be. Here's the two old oxygen sensors side by side. On the left is mine; on the right is Deb's. My car is currently up to 457,000km and I'm pretty sure that's the original one. Deb's car is up to 280,000km and I'm pretty sure that's also the original one. This is also confirmed by the fact that they look identical, apart from the colouring on the sensor ends. Photos of the parts numbers. The part number for the Bosch oxygen sensor is 0 258 986 603. As mentioned earlier, the cheapest place that I can think of to get them is MTQ Engine Systems (www.mtqes.com.au). While you're there, don't forget to get some Bosch AeroTwin wiper blades ($15.50 vs $30-35 retail), some PBR Super Dot 4 brake fluid (ie what I use for my brake fluid flushes), a set of spark plugs, an oil filter or three, a petrol filter, air filter, drive belt and maybe a spare headlight globe or two. They also have Bosch brake pads, alternators and starter motors, as well as PBR brake parts (eg disc rotors). Get a catalogue and have a look through it while you're there - if it's Bosch or PBR then they have it at much lower pricing than everywhere else. How I confirmed the part number for the Bosch oxygen sensor: It wasn't that hard - some searching on Falcon forums found it easily enough. But, to make absolutely 100% sure, I went to http://www.bosch.com.au/content/language1/html/2230.htm and clicked on Engine Management Systems. On that page (ie http://www.bosch.com.au/content/language1/html/4543.htm) there is a link for Oxygen Sensors. Clicking on that downloads a PDF. For the 2009-2010 version that I got, the listing for a BFII Falcon is at the bottom of page 57.