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Possible catalytic converter problem

Tiny
SPANGLES711
  • MEMBER
  • 2002 VOLKSWAGEN POLO
  • 1.2L
  • 3 CYL
  • 2WD
  • MANUAL
  • 93,340 MILES
Hello, recently a garage carried out an mot and repair on my vehicle, it failed its mot originally due to exhaust emissions and they suggested after checking everything over that it might be the catalytic converter and that they could take it off and possibly weld it due to it being cracked.
I went on their suggestion and went ahead with this, due to them being a garage and taking their word on it that this would fix the problem and it passed the mot after the work was carried out by them. My issue with this is now that since they have carried out this repair the car is running terribly which it was not before bringing it to them, even only one month ago when I paid over £300 for them to service the car this was not an issue then. The car is idling very low and is stalling and suffering from a loss of power when pulling off, it stalled when I was driving at 25 mph. It seems as if there is some sort of blockage or something, so I’ve checked this issue online and everything is mostly coming back as a problem with the catalytic converter being blocked or a blowing exhaust. But this was fixed By them apparently. So I don’t see how that would be an issue.
as it stands I believe that the welding that was done on this car has somehow caused the car to lose power when pulling off, causes the car to idle low and causes car to stall. This wasn’t an issue before they did their welding
Yes, it is an older car and has done nearly 94,000 miles but the car did not stall and did not suffer from a lack of power before I paid them to sort it. The work they have carried out to fix a problem has caused more of a problem.

Check engine light on now.
Any advice would be helpful.
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Wednesday, March 4th, 2020 AT 2:52 AM

20 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good morning.

It is very possible that whatever welding was done, has created a blockage in the converter.

Return to the shop and ask them to recheck there work. The converter may have originally failed from being blocked and when they welded it up, this is the result.

Can you give me the code that was set?

Roy
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Wednesday, March 4th, 2020 AT 4:45 AM
Tiny
SCGRANTURISMO
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Hello,

It is possible that when they cut the catalytic converter off they cut it off incorrectly and cut into the honeycomb inside and caused a piece to break free after it was reinstalled causing a blockage. Is your vehicle's temperature running any hotter than normal? Here is a link below, to a guide explaining how to test your vehicle's catalytic converter:

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

From the video that you sent I would also recommend checking for a vacuum leak. Here is a link to a guide below that explains how to do that:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

When your rpm's at idle are higher than they normally run or your rpm's are "searching" like your vehicle's are, this indicates a vacuum leak, which would also have all of the driveability concerns that you are expressing. Please go through this guide and get back to us with what you find out.

Thanks,
Alex
2CarPros
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Wednesday, March 4th, 2020 AT 4:50 AM
Tiny
SPANGLES711
  • MEMBER
  • 10 POSTS
After searching this online I found the same thing about the honeycomb, I’m waiting on the garage to get back to me regarding this. As to the code I’m not sure as my obd2 reader doesn’t pick up my car.
I have to drive at about 25 in 1st then change gear to 2nd otherwise it will stall I don’t know if this helps at all?
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Wednesday, March 4th, 2020 AT 5:03 AM
Tiny
ASEMASTER6371
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Ask them for the code when you talk to them.

It sounds like you are going to need the converter replaced.

https://www.2carpros.com/articles/bad-catalytic-converter-symptoms

https://www.2carpros.com/articles/catalytic-converter-replacement

Roy
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Wednesday, March 4th, 2020 AT 5:04 AM
Tiny
SPANGLES711
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  • 10 POSTS
Yeah will do, what are my rights as far as this goes? Will I have to pay more for new cat and fitment or will they have to replace it out of their own pocket due to them damaging it the first time? If this is the problem.
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Wednesday, March 4th, 2020 AT 5:07 AM
Tiny
ASEMASTER6371
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That is between you and the shop. I would at least think they would apply the repair cost they charged you against the cost of the replacement.

Roy
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Wednesday, March 4th, 2020 AT 5:11 AM
Tiny
SPANGLES711
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Yeah this was  242 including mot cost they said cat and fitment was  275 I think so hopefully they can sort this. I’ll send the code through if they give me it.
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Wednesday, March 4th, 2020 AT 5:13 AM
Tiny
ASEMASTER6371
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Sounds like a plan.

Roy
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Wednesday, March 4th, 2020 AT 5:19 AM
Tiny
SPANGLES711
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The garage has got back to me they said this:

As discussed, the weld repair would allow it to pass the MOT test emissions that it was failing on. If you'd like to drop it round tomorrow we can take a look for you and go from there?

So my problem here is that during the discussion with the garage not at one point did they say it would pass the emissions but deem the car Undriveable if they went ahead with this.
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Wednesday, March 4th, 2020 AT 7:56 AM
Tiny
ASEMASTER6371
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I do not think they even thought that at the time of the repair.

There repair caused the issue because the leak was allowing the motor to breathe. With that repair, it may have passed your inspection but it blocked the exhaust not allowing the engine to breathe.

Roy
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Wednesday, March 4th, 2020 AT 8:01 AM
Tiny
SPANGLES711
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They have said there was a misfire in cylinder 2 and are claiming there weld was nowhere near the honeycomb on the catalytic converter so they are going to look at it tomorrow.
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Wednesday, March 4th, 2020 AT 8:40 AM
Tiny
ASEMASTER6371
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Okay, let them come back to you with there findings.

Roy
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Wednesday, March 4th, 2020 AT 9:44 AM
Tiny
SPANGLES711
  • MEMBER
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Quick update:

Garage has had car all day, said the problem was that the throttle body was blocked up they cleaned this out and it was still doing it. They then unplugged the EGR valve so that it would run and it does, they said the fact that the cat has now been welded means that the EGR valve was not performing as it was meant to or something. This is what they have claimed the problem was but won’t the EGR valve being unplugged cause a problem for the mot at a later date?
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Thursday, March 5th, 2020 AT 8:50 AM
Tiny
SCGRANTURISMO
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Hello,

No, the EGR valve is supposed to be not clogged. This is how your vehicle reburns a portion of the exhaust to make sure all of the hydrocarbons are being burnt up in the engines combustion process. Since exhaust gas is being diverted back into the throttle body, EGR valves get soot built up in them that periodically needs to be cleaned up otherwise they will plug causing them to fail.

Thanks,
Alex
2CarPros
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Thursday, March 5th, 2020 AT 1:04 PM
Tiny
SPANGLES711
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The EGR is disconnected now and it runs fine.
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Thursday, March 5th, 2020 AT 2:03 PM
Tiny
ASEMASTER6371
  • MECHANIC
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Just to add what Alex has posted, and I agree, if the cat is clogged and it opens, it is a way for the engine to breathe when the cat is clogged.

Is this a vacuum control for the valve or electric?

Roy
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Thursday, March 5th, 2020 AT 6:01 PM
Tiny
SPANGLES711
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Not sure what it is. The garage has said they unplugged the EGR valve and now it runs doesn’t stall and doesn’t search for its rpm.
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Friday, March 6th, 2020 AT 12:24 AM
Tiny
ASEMASTER6371
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Give it some time and see if the issue comes back.

Roy
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Friday, March 6th, 2020 AT 5:13 AM
Tiny
SPANGLES711
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Okay, thanks for the advice. I appreciate it.
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Friday, March 6th, 2020 AT 7:27 AM
Tiny
ASEMASTER6371
  • MECHANIC
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You are welcome.

We are always glad to help.

Roy
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Friday, March 6th, 2020 AT 7:31 AM

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