Afternoon all.

Wondering if anyone could shine some light on an issue I’ve had with my car for what seems like years, and is now almost coming to a critical point… almost 😉

Before I start, this is proper bangernomics. Car is twenty years old, I’ve had it for nearly half that time and it cost me £350. So my plan is to run it forever or until it presents me with a job I can’t do myself or is too expensive to have repaired at a garage.

So the long-term issue is rough running, seems to be almost random but getting generally worse with the odd period of running ok. Always assumed it was fuel related, dirty injectors, rubbish supermarket fuel etc etc. So when it was working ok I’d assume it was due to some Redex, or premium fuel I’d added. Starting to think that was a blind alley and the issue is more likely to be electrical-based.

Just recently it’s been getting really bad and I’ve kind of gotten used to it because I drove a friends car the other day and realised my car is definitely in trouble. No performance, Struggling to get out at roundabouts/away from lights, up hills etc. I live and work in a city so can get pretty stressful thinking it’s going to conk out all the time. Yesterday I had the window open and noticed a sound like a blowing exhaust, so I stopped somewhere, looked underneath the car and the back half of the catalytic converter is glowing red! Now driving around in a rubbish car is one thing but I don’t want to spontaneously combust!

So I left it to cool down, then drove the couple of miles back home. Same rubbish performance setting off through the gears, blowing sound, and now a new sound like something is broken, like I’m dragging a load of metal along the road. Got out quick to check, can’t see anything so just drove it home as is. The sounds seem like they’re coming from the gearbox area, but it still shfts as normal. The sounds also seem to stop when I start to brake or put it in neutral (I think).

So, any ideas? I realise there may be two or more problems here that may or may not be related. My own thinking is along the lines of something causing it to not be firing on all cylinders, causing fuel to be burnt in the cat, which may or may not have melted and destroyed itself – hence the noises. I service the car once a year, and most recently in March – oil and oil/air filters only. The sparkplugs were probably last changed a few years back. The HT Leads and coil pack have never been changed to my knowledge. So planning to put new coil pack and leads on it. New cat too? Any tips or ideas about how best to diagnose the problem?

A glowing cat is a sign of a car running very lean – which indicates a fuel issue

This was more prominent on the first cars with cats in the early 90s. Newer engine management stopped them running so lean in the mid-90s

I am a fellow banganomic fan who drives a 21 year old car 🙂

What car is it?

It’s a VW Polo.

It’s been great to be fair. No issues at all apart from the perennial and intermittent rough running. A no-frills/low-stress cheap runaround. It bombs around the city all its life, rarely getting a good run which probably adds to its woes.

Possibly clean the MAF with brake cleaner. Also check for hose leaks. The glowing cat could also be an issue with the exhaust. My car’s 18 years old, and I’ve had it 17 of those. Mine had a cat about 10 years ago – it was OK but would occasionally throw a warning light, so got it changed at my local garage for £450.

Sounds like your about to play a mass of parts darts. (And expensive parts no less)

Even more so with not only your suggestions but those of the forum .

Without seeing the car we will never know

There are many things it could be from your description.

agree trail rat

If i’d had 10 years from a £350 car, i wouldn’t be throwing parts or labour at it

Its had a hell of a life. Let it die with dignity 🙂

I don’t know, I like it. Parts are cheap and usually easy to fit. And most importantly, I know it. A new banger would come with its own set of unknown issues. Plus, I do find it interesting fetling with it and learning how things work. I’ve done loads of things on it myself that I’d never done before. Why not just keep it going?

Although, saying that, there’s a limit…

To be clear I’m not saying don’t fix it I’m just saying get someone who knows how to diagnose rather than guessing.

The internet can’t help with descriptions such as above as it actually sounds like you have a few different faults that could be caused by quite a number of different causes. Some cheap to fix and some spendy. And throwing parts at it is rarely the best way to diagnose .

I had an old bangernomics A3 that made a horrendous rattling sound. Bit like ball bearings in a tin, was the cat breaking down. Also blowing wher it joined the downpipe, fell off one day. Had it replaced and it was a very different car.

Sounds like yours could be a similar issue. Knackered exhausts cause all sorts of performance problems and poor gas flow might account for the glow. Collapsed cat blocking the gasses in making the heat build up.

How many miles?
Town life is really hard on engine/exhaust.
Does it make the new noise when the car is not moving?
(If it only rattles when moving then that may point at the drivetrain)

Damaged baffle in the cat/exhaust?

Just remembered: I replaced the exhaust two years ago and noticed an improvement. This was the mid and back box only (from the cat back)

I might throw a cat, some HT leads and a coilpack at it. All of which I can fit myself and can be had for less than £150. Although after the last time I swore I’d never fit another exhaust again. Contorted under a ton of metal wielding an angle grinder wasn’t much fun in hindsight.

HOW DO YOU QUOTE SOMEONE?

<quote>How many miles?
Town life is really hard on engine/exhaust.
Does it make the new noise when the car is not moving?
(If it only rattles when moving then that may point at the drivetrain)

Damaged baffle in the cat/exhaust?</quote>

About 80k
Yeah, it’s lived in cities its whole life.

The noise is not present when stationary. It sounds like I’m dragging a load of broken iron bits. Starts after a while, upon changing gear then dies down a bit after I get up to speed. Braking seems to stop the sound. So ‘only under load’ it seems. I’m thinking maybe I’ve properly borked something by having to thrash it all the time due to the under-performance.

If it were mine I’d take a look at the spark plugs first. Should show what the combustion is like.
Does it have an odb port? If it’s been misfiring it may well log it in the ECU.

If it’s got a cat, it’ll have a lambda sensor to ensure correct mixture. No idea about the Polo but on our elderly Astra G, if the sensor goes out of spec it’ll throw a check engine light.

Not a mechanic but my money would be on a clogged cat but it’s all just guessing as stated above.

Check the engine mounts aren’t shot, if they are it could explain why it’s mainly noisy when under load (a normal gearbox and engine touching the exhaust will make a lot of horrible noise).
Blocked cat will cause exhaust to blow out of the damaged flexi caused by the flopping engine… maybe 🙂

Looking at the condition of the spark plugs will tell you a lot about how the engine is running – you can tell if one cylinder is not getting a good spark, or a wrong fuel mix. If you have a Haynes manual there’s usually a chart in it.

Sounds like you have a Schrödinger’s cat – it might be dead, or it might not be!

I had a 98 polo 1.4. I once got a noise that i thought was blown exhaust that turned out to be a rear wheel bearing. Another time it was misfiring/ running on 3 cylinders that turned out to be one of the leads from the coil pack to the spark plug. This caused my cat to glow red too (failed subsequent MOT on emissions as it had destroyed the cat). I am no mechanic but might be worth checking these?

Thanks Greybeard. I’ve got the grubby Haynes manual, and I’m at a loose end tomorrow so will get it up on ramps and have a proper poke around. Will give the cat a bash and see if I can hear anything loose. Will have the plugs out and test the cables for continuity.

Could be that the cat is breaking down and is restricting exhaust flow.

Happened to my Wife’s 308 and caused it to run terribly, until it stopped at the side of a busy dual carriageway.

Don’t just bloody guess and replace parts. That’s a really bad idea. Get a diagnostic tool, preferably VCDS. If you want to play bangernomics, I’d say VCDS (and subsequently sticking to VAG cars) is essential.

{makes mental note to not buy a used car from Jambourgie}

I’m actually a fan of parts dart when diagnosing older cars – to me the only reason to scrap a car is terminal rust until then replacing a whole swathe of parts isn’t a bad thing when talking about old/higher mileage cars. I actively target areas of our Volvo and replace surrounding parts when I’m doing work on a particular component.

A 20 year old car that you’ve had ten years out of and cost you 350 sheckels in the first place, that you’ve no idea what’s wrong with it despite your claim to “knowing” the car? Stop being stubborn and weigh it in for steel, you’ve gone from bangernomics to daft. It owes you nowt. There’s an argument of “it’s just a tool” but when it ceases to be a reliable tool then it’s not “just a tool” any more, it’s a boat anchor.

My first car cost me £300 quid. It was 13 years old when I got it and I got 3-4 years out of it, I considered that amazing value in 1990 back when I was a povvy student.

I’d be with the OP, it’s obviously got some sentimental value. Checking the cat hasn’t imploded should be fairly easy before spending cash, if there is still a noise once the running issues are sorted that can be tackled 2nd

Well done for keeping it going.dont scrap it.

but when it ceases to be a reliable tool

When did it stop being reliable.

From what the op has posted it needs a repair.

As above, probably best to scrap it, it’s unlikely to be economical to fix.

If I were trying to fix it, I would pull the plugs first and run a compression check. It’s possible it has a burnt exhaust valve and fuel is burning in the exhaust. If a cylinder has lost compression, scrap it. Following that, remove the exhaust and see if it runs properly without it. If it does, then replace the exhaust system.

Otherwise, new plugs and ignition leads are generally first thing to try. Depending on the specifics of the ignition system, it might need ignition coils replaced. Problem is, replacing all those is really just wasting money you could spend on a better car, so taking it to a mechanic and having it diagnosed properly will probably be cheaper than just randomly throwing parts at it.

The sentimental value thing is for losers, unless it’s actually a classic car that will be worth maintaining. If it’s just a standard shitbox, scrap it and get a better shitbox.

I’d take the cat off and look inside.

Chances are its blocked.

Sounds to me like the supports for the catalytic converter matrix have corroded and the matrix has partially collapsed. If you can get a 2nd hand one from a scrappy then maybe. Parts roulette is not a good way to go for any old car. Trade it in for a 1.6 petrol Focus.

Classics can be any car of certain age.i would personally just get a garage to guide you.when an ignition module in my car died it would only just drive.if you want to do the repairs yourself then in addition to here join an owners club and get advice as someone is bound to know what is wrong with it knowing the model inside out

Let it die.

You need a minimum of a new cat, which has been melted by burning fuel in it, and you still need to sort the misfire.

Could have potentially been addressed cheaply earlier on as the misfire is unlikely to be complex, but by running it with a misfire you’ve made the problem worse.

Those saying scrap it…. Have you looked at the cost of a replacement car.

The current market makes repairing it look like chicken feed money.

Currently Absolute shitboxes that look like they scraped an MOT by way of a couple of 50s the ashtray are going for north of 1k .

I suspect it’s due to lots of folk thinking they are being original like the thread by funky dunk getting rid of the expensive rental to get solid cheap transport paid for in cash driving prices of lower end up

I forgot to say owners clubs are also great for getting good condition second hand spare parts often with people knowing what will fit your car as well as cheap upgrade sh deals on things like suitable alloys.

If it costs a few hundred to fix, that’s the repayment on a newer vehicle for a couple of months, then add depreciation.

Might be a simple fix, but I’d say the cat has gone. My cat was a big job for the garage as it’s up near the manifold, so all sorts of gubbins had to come out the local garage did it.

I run a 19 year old car I’ve had from 10 months old. I do, however, check any issues out before they are a problem – that’s where OP pushed it a bit. I’d not be running a car that wasn’t delivering on power and running rough.

I’ve just replaced my back box – 19 years ain’t bad. The worse part of the job, getting the rubbers to break free from the three rusted hooks on the old back box. Fitting the new back box was a doddle.

Maybe drop it in to a local garage and ask their opinion. If the cost is massive, then maybe time to change.

Running a ‘well maintained’ car (note the “well maintained”) is better for the environment than buying new cars every 3-5 years given lifetime polution etc.

Just don’t buy a JRL car.

I’d be with the OP, it’s obviously got some sentimental value.

I’m sure that’ll be a great consolation when the OP is standing behind the Armco on the M6 in a blizzard.

I’m sure that’ll be a great consolation when the OP is standing behind the Armco on the M6 in a blizzard.

You don’t really understand cars do you.

I’m sure that’ll be a great consolation when the OP is standing behind the Armco on the M6 in a blizzard.

A 20 year old fixed car you know is better than a 10 year old replacement banger thats probably been sold as the previous owner also got to the same stage in terms of what was considered a worthwhile repair.

And…

It bombs around the city all its life, rarely getting a good run

I’m sure that’ll be a great consolation when the OP is standing behind the Armco on the M6 in a blizzard stuck in the wilds of a Tesco carpark in the drizzle waiting for a jump start.

i would personally just get a garage to guide you

Thats just a way of letting someone else play parts roulette whilst they guess how much cash is in your wallet…if you can wield a few spanners its much better to do some research on owners forums and not cough up for someone else’s labour! You don’t end up running old bangers if you pony up to a garage every time something goes wrong unless you are in the rare position of truly being able to trust your local. Especially if they have a forecourt of slighter shinier cars…they’ll soon convince you to trade-in!

I’m with hols2, compression test and/or exhaust off completely and see if that sorts it. Probably the other way round as the exhaust experiment is free.
Love the expression parts darts, that’s all that modern day vehicle repairs are a lot of the time.

With regards to garages it’s best to go to a local independent who are trustworthy.owners club would be the first port of call though.

The only time I’ve seen an overheating cat (it was flowing orange at the time, unburnt fuel igniting in the exhaust headers down to the cat) the cause was a faulty coil pack. I’d be looking at plugs and coil pack first.

The trick to fixing modern cars is to read the codes and then really understand what they mean and which is the root cause. Because some codes are knock-on effects from others.

But you need a decent code reader, and for VAG preferably a VCDS not a cheapo, as you get way more information from it. If you’re near South Wales I can help you out.

Op here. Thanks everyone!

Yes, my plan is to throw some leads and a coil pack at it. Hardly ‘parts darts’, they’ve not been replaced for at least ten years. I’ll probably replace the cat, maybe just cut it out and bin it 😉

For all those saying ‘get a new car’ etc. I’d want exactly the same make model and year anyway as it fits my needs perfectly, so it’d be a load of ballache finding one, collecting it, paperwork etc. It’s not about being sentimental, I just have some experience on working on this car, and thus confidence. I fitted a new cambelt and water pump last year which was a major job for me. It goes through the MOT every year with no issues… basically, I’m gonna run it for as long as possible.

Good call on the diagnostics VAG thing, been meaning to get one for years but never really had reason to buy one as there’s been no issues.

Molgrips – thanks mate, I’m up in Sheffield.