Hi folks

I have a 02 Focus 2 litre Ghia with a very annoying problem. For the past 4 or so weeks when driving I can feel a very severe lag and have a lack of power. It feels like I am being pulled back when accelorating and the car kind of judders along. Also when changing gears the engine seems to over rev. When it first happened I googled the problem and it pointed towards the MAF which I changed, however this didn't cure the problem. I have since checked for air leaks, and everything is fine there. I have changed the plugs, air and fuel filters and still no difference. I have cleaned the IAC valve also to no effect. The MIL light hasn't come on ever.

Yesterday I had the car MOT'd and it failed on emmisions. Something about lambda after 2nd fast idle????? The mechanic also ran a live scan of the engine, and said that the Lambda sensor itself was fine and switching as it should. He also checked for DTC's and it came up with fault code P1120, which points towards the TPS.

The thing is after some further googling, I am not sure that a faulty TPS could cause the symptoms I have described above as most people with a faulty TPS seem to report erratic idling, which mine dosen't do. Another thing I have read is that a P1120 code dosen't always mean a faulty TPS and it could also be a wiring problem.

My questions are, could a faulty TPS cause the above symptoms, and is there anyway I could test the TPS, wiring etc.. to narrow down the problem? If so I would appreciate it being explained in dummy terms.

Any help would be much appreciated, as I have already thrown hundreds at this problem and can't really afford to buy a TPS if it dosen't cure the problem.

cheers

Hi folks

I have a 02 Focus 2 litre Ghia with a very annoying problem. For the past 4 or so weeks when driving I can feel a very severe lag and have a lack of power. It feels like I am being pulled back when accelorating and the car kind of judders along. Also when changing gears the engine seems to over rev. When it first happened I googled the problem and it pointed towards the MAF which I changed, however this didn't cure the problem. I have since checked for air leaks, and everything is fine there. I have changed the plugs, air and fuel filters and still no difference. I have cleaned the IAC valve also to no effect. The MIL light hasn't come on ever.

Yesterday I had the car MOT'd and it failed on emmisions. Something about lambda after 2nd fast idle????? The mechanic also ran a live scan of the engine, and said that the Lambda sensor itself was fine and switching as it should. He also checked for DTC's and it came up with fault code P1120, which points towards the TPS.

The thing is after some further googling, I am not sure that a faulty TPS could cause the symptoms I have described above as most people with a faulty TPS seem to report erratic idling, which mine dosen't do. Another thing I have read is that a P1120 code dosen't always mean a faulty TPS and it could also be a wiring problem.

My questions are, could a faulty TPS cause the above symptoms, and is there anyway I could test the TPS, wiring etc.. to narrow down the problem? If so I would appreciate it being explained in dummy terms.

Any help would be much appreciated, as I have already thrown hundreds at this problem and can't really afford to buy a TPS if it dosen't cure the problem.

cheers

Without wishing to state the obvious; Sometimes throwing money at a problem using Google for recommendations is not always the most cost effective solution to repairing a fault, unless you are sure you have the skill to diagnose and repair it yourself the garage may have been a cheaper option. Good luck in getting it fixed and please keep us informed of the outcome.

You could try unplugging the TPS and see how she runs with it unplugged. I got a new TPS for £25 on ebay.

I did speak about the problem with a mechanic and he said that it was one of those symptoms that could have many causes and it was a case of replacing things one by one till the problem is solved, which I have done myself without the costly labour charges. He wanted to start by changing the CAT at a cost of £300+.

I certainly wouldn't start by changing the cat. That would be a last resort! The fault code you describe suggests 'Throttle position sensor out of range'. Try disconnecting it and see how it runs, if there is a difference then you have solved your problem. They are easy to replace.

I did speak about the problem with a mechanic and he said that it was one of those symptoms that could have many causes and it was a case of replacing things one by one till the problem is solved, which I have done myself without the costly labour charges. He wanted to start by changing the CAT at a cost of £300+.

Diagnosing faults on all modern cars is a nightmare, unfortunately gone are the days when a man with a spanner could fix anything, today you need to be a genius with a computer to find the fault, that's what a good garage should be able to do without putting a wet finger in the air and guessing at what to change, and then passing a large unnecessary bill on to you. I know my limitations and for complex faults I pass it on to a competent garage to fix.

a ford dealer can diagnose the issue and read the live data which will be cheaper than replacing random parts