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Discussion Starter · #1 ·
Hi all,
I have ran an OBD test on my mk1 and it has given two errors, P0171 and P0301.

Things I know it needs replacement:
  1. catalytic converter
  2. manifold pipe seems rusty and can even feel burnt exhaust in the car mostly in summer but also during winter though less, I presume the flex pipe is rusty and has a leakage as I can hear a leakage noise from the exhaust.

Things I have already done or checked:
  1. cleaning MAF sensor
  2. air filter is almost new (changed in this summer + oil)
  3. no crack vacuum hose
  4. no engine fault signs on the dashboard
  5. new spark plugs and cables last summer

The engine starts fine everytime, but it sometimes hesitates to accelerate specially when setting in the first gear, and sometimes even running on 50-70 miles/h, when pressing harder on the gas pedal. It seems like it is not taking enough air for a very short time, and then it starts to accelerate smoothly. Could this be due to fuel filter that is near to get clogged?

I am going to order a new catalytic converter + manifold, and wanted to hear your opinions what else could be needed to replace or what other things I should look for.

thanks in advance for any help and advice
 

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I would:

Pull spark plugs and see if they all look OK -and- if all look the same -and- check for proper gap setting on each one.

Replace the fuel filter.

The spark plug cables connect to a coil pack. That coil pack often fails (here in the USA) and develops tiny cracks that can cause (some of) similar problems that you described. -hesitation and the P0301 misfire.

What year is your car, what engine?
 

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Discussion Starter · #4 ·
Thanks for the reply Marde,
its a 1.6 zetec petrol from 1999.

could this fault be related to the flex pipe is leaking?
I believe the fuel filter is inside the tank, is there a way to get to it or does the tank needs to be replaced?

I check the coil pack to see if there is anything wrong with it.
 

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Check the OBD descriptions here:http://www.focusfanatics.com/forum/showthread.php?t=59286

There's a long list of possibilities to think about.

Fuel filters for that year should be under the car, external to the tank if done as the NA models were.

PCV hose is a common cause on our engine versions, would be worth a close look on yours.
 

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Discussion Starter · #6 ·
I have now changed the catalytic converter and ran a new obd test, this time is only showing P0301. I have checked all those causes related to this code and I assume the ignition coil might be the culprit, as I experience some hesitation in accelerating when setting the car in first gear.
Is there any way to diganose the ignition coil to be sure its functioning properly? (there are no visual signs of cracks on the body)
 

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If car even remotely running I'd be fixing that flex leak before I touched anything else. It seems somewhat misplaced to care more about the car than your own health there. Exhaust leaks can KILL you.
 

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Spray you ignition coil with water and observe any spark. Or remove and look underneath for any cracks/discolouration of the rubber material.
 

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Water spray is to help check for stray spark going to ground because of insulation problems - wires/coil. Only sparks when running, water spray can make it miss worse & sometimes even make it more visible.

If you wet a plug wire & it starts stumbling for example, you can be sure that wire is shot.

The mention of looking at the bottom of the coil (dismount to see) is because problems often show up there. We see regular running troubles when coils are cracked, it lets moisture in to cause internal shorts.
 

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Discussion Starter · #12 ·
Thanks for the tip, its a quick and useful way to check for faulty wires. I have ordered an ignition coil as I don't know when it was last replacedm, and hope it sill solve the problem now.
 
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