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Friday, September 12, 2008

Mondeo MK3 engine warning light.

Recently polybore has been involved in a bit of car diagnostic work. The engine warning light came on the dash of his 2001 MK3 V6 Mondeo. Now having had experience of paying mechanics to track down the symptoms of an engine warning light and how much this costs I thought I would at least try and identify the problem.

The car was going to the garage to get new tyres so I asked them to plug the car into the computer to get the code from the ECU. Well it turned out that the engine was running on a fuel mix that was too lean. This was resulting in a loss of power and increased fuel consumption.

First off I replaced the fuel filter then reset the ecu by disconnecting the battery for about 20mins. The warning light went out but came back on again the following day. Then I tried replacing the air filter no joy there either. The next possible cause for this error code is a vacuum leak. Sure enough when, with the engine running, I put my head under the bonnet I could hear a hiss, can't believe I had not noticed it before.

Having identified that there was a leak somewhere it was difficult to pin point it. Crawling around on top of a hot V6 with an ear to each hose was uncomfortable to say the least and I spent a frustrating time doing this. Then I found a fantastic tip online. I would love to attribute it but it came up on the google search page but I could not find the actual item at the web site.

The trick is to use a short length of hose or tubing as a sort of stethoscope. Hold one end to an ear and probe around in the engine with the other end. It works fantastically well for isolating the hiss sound of an air leak. I found the leak almost straight away even though it was an awkward place.

I sealed the leak with some insulating tape and now the car is back to full health. Now I just need to identify the part number of the t junction rubber tube that failed and get a new one. Looks like I should be able to fit it myself.