Popping noise in exhaust in idle

[GTi-Tecnix]

Does any have this issue with their MK5 gti? When the car is running stationary I hear some pops in exhaust sometims. Is this unusual? I recently had a misfire issue with coil in cylinder 2 but that's now soreted but the popping has been consistent since I bought car a year ago. It pops sometimes but always there when stationary intermittently.

[AJP]

Quite common. The odd pop isn't too much to worry about - for now. If and when it gets progressively worse and it idles like a bag of sh*t, then you might be looking at pulling the injectors before too long, assuming plugs and coils are good.

Also keep an eye on any misfires under load.

How often does it misfire on idle?

[GTi-Tecnix]

Quite common. The odd pop isn't too much to worry about - for now. If and when it gets progressively worse and it idles like a bag of sh*t, then you might be looking at pulling the injectors before too long, assuming plugs and coils are good.

Also keep an eye on any misfires under load.

How often does it misfire on idle?

misfire on underload?

It just jerks slightly not that often I'd say. I hear the popping every now and then. Sometimes I dont hear it. Intermittent for now.

Going to use the injector cleaner as noticed spark plugs been toasted recently. What's the opinion of sea foam?

[AJP]

Quite common. The odd pop isn't too much to worry about - for now. If and when it gets progressively worse and it idles like a bag of sh*t, then you might be looking at pulling the injectors before too long, assuming plugs and coils are good.

Also keep an eye on any misfires under load.

How often does it misfire on idle?

misfire on underload?

It just jerks slightly not that often I'd say. I hear the popping every now and then. Sometimes I dont hear it. Intermittent for now.

Going to use the injector cleaner as noticed spark plugs been toasted recently. What's the opinion of sea foam?

Under load. When you're flooring it in 3rd at 40mph for example; the engine is under load.

Can you be more specific? Is the misfire on idle every 20 seconds? Once a day, week, month?

When you say the plugs are toasted, can you describe the colour, and any deposits? A pic would paint a thousand words.

I can't vouch for anything like sea foam.

[pudding]

If you're not a VCDS guru, you can throw some parts at it.

In order of cost, cheapest first:-

Spark plugs - dealer NGKs, or NGK BKR7EIX.  Both the same heat grade and gap, but these TFSIs seem to like the Iridiums.

Coils - A set of red ones from AKS are <£100.  Dealer black ones are ~£40 each.  Both the same.  Reds just cheaper.

Injectors - Do all 4.  It's a waste of time pulling the intake off to replace only 1.  The other 3 will follow suit soon after.

If you do have access to VCDS, a persistent misfire will be fault coded if the detection count meets or exceeds it's limit.  Or you can fire up the live counter channels 1 - 4.  If the ECU detects a cylinder not contributing (crank speed not increasing on the power stroke) it will flag it.

Generally with injectors, idle and part throttle can feel lumpy but smoothes out under acceleration.

With dying coils, it usually misses under load, usually from cold at 1/2 throttle.   When gone completely, the miss will be permanent.

If none of the above, compression test it.  You should see ~14 bar across all 4 on a healthy engine.   If one cylinder is much less than the other 3, there's your problem.  Busted ring land or a burned out exhaust valve.  Usually the former on remapped engines.

Seafoam and other spray in snake oils do absolutely nothing on old engines, let alone modern DI engines.

[AJP]

If you're not a VCDS guru, you can throw some parts at it.

In order of cost, cheapest first:-

Spark plugs - dealer NGKs, or NGK BKR7EIX.  Both the same heat grade and gap, but these TFSIs seem to like the Iridiums.

Coils - A set of red ones from AKS are <£100.  Dealer black ones are ~£40 each.  Both the same.  Reds just cheaper.

Injectors - Do all 4.  It's a waste of time pulling the intake off to replace only 1.  The other 3 will follow suit soon after.

If you do have access to VCDS, a persistent misfire will be fault coded if the detection count meets or exceeds it's limit.  Or you can fire up the live counter channels 1 - 4.  If the ECU detects a cylinder not contributing (crank speed not increasing on the power stroke) it will flag it.

Generally with injectors, idle and part throttle can feel lumpy but smoothes out under acceleration.

With dying coils, it usually misses under load, usually from cold at 1/2 throttle.   When gone completely, the miss will be permanent.

If none of the above, compression test it.  You should see ~14 bar across all 4 on a healthy engine.   If one cylinder is much less than the other 3, there's your problem.  Busted ring land or a burned out exhaust valve.  Usually the former on remapped engines.

Seafoam and other spray in snake oils do absolutely nothing on old engines, let alone modern DI engines.

All accurate and excellent advice as usual Kev, however it's worth noting I had two completely different symptoms from two separate injector failures.

One on cyl 4 gave the horrid spluttery idle, but fine under load, just as you describe.

Then one on cyl 2 was fine on idle but huge misfires under load. You'll remember that thread!

Totally agree about getting all 4 done. I should have done so when the first (idle) misfire reared its head. After the cyl 2 drama I got all 4 refurbed by Mr Injector (google it).

Steve @ Statller was rather impressed with the level of work - I get the impression he's used the same guy since.

[pudding]

Yeah that was a bit of a nightmare!

I'm not normally an advocate of just throwing parts at a problem, but it seems with these engines it's a necessity to fix misfires.

[AJP]

Yeah that was a bit of a nightmare!

I'm not normally an advocate of just throwing parts at a problem, but it seems with these engines it's a necessity to fix misfires.

Yep, it makes sense to do the old plugs>coils>injectors sequence of troubleshooting in any case. If those are eliminated, like you mention it's a matter of looking deeper for internal issues. Not cheap.

[GTi-Tecnix]

If you're not a VCDS guru, you can throw some parts at it.

In order of cost, cheapest first:-

Spark plugs - dealer NGKs, or NGK BKR7EIX.  Both the same heat grade and gap, but these TFSIs seem to like the Iridiums.

Coils - A set of red ones from AKS are <£100.  Dealer black ones are ~£40 each.  Both the same.  Reds just cheaper.

Injectors - Do all 4.  It's a waste of time pulling the intake off to replace only 1.  The other 3 will follow suit soon after.

If you do have access to VCDS, a persistent misfire will be fault coded if the detection count meets or exceeds it's limit.  Or you can fire up the live counter channels 1 - 4.  If the ECU detects a cylinder not contributing (crank speed not increasing on the power stroke) it will flag it.

Generally with injectors, idle and part throttle can feel lumpy but smoothes out under acceleration.

With dying coils, it usually misses under load, usually from cold at 1/2 throttle.   When gone completely, the miss will be permanent.

If none of the above, compression test it.  You should see ~14 bar across all 4 on a healthy engine.   If one cylinder is much less than the other 3, there's your problem.  Busted ring land or a burned out exhaust valve.  Usually the former on remapped engines.

Seafoam and other spray in snake oils do absolutely nothing on old engines, let alone modern DI engines.

Hi Pudding, thanks for this. I already have the red Audi R8 coils and the ngk iridium spark plugs in my car as you mentioned. But the popping seems to start sometimes when I start the car up or I'm about to switch engine off on idle. I think you've hit the nail about lumpy idle as it does smooth out when acceleration and the car in general drives and pulls fine.  Can you give me an idea as to how much work goes into injector removing, cleaning etc?

Also, on a seperate note, I am thinking of changing the stock air intake to a k&n or a ramair intake, any tips and advice on this please? My MK5 DSG has a dump valve that hisses every time you accelerate of changing gears, that was installed by the previous owner for some reason. Will an air intake affect the dump valve or mass air flow system? Thanks in advance.

[pudding]

I would leave the factory airbox in place until you've got to the bottom of the rough idle first, and get rid of that after market dump valve and put the OEM one back on.  I wouldn't be surprised if that is partially the cause of your problem.

They do pop a lot when warming up because they run very rich with heavily retared ignition to heat the cats up.    Remappers really should code out the warm up routines for cars with aftermarket downpipes, but I don't think any of them do.   It should be smooth when up to temperature, but again, depending on what's been messed with / modified by the previous owner.
 

[GTi-Tecnix]

How do I remove the dump valve? Is the dump valve popping then? I don't know my car has been remapped or not, how do I find out! I wouldn't say the idle is rough just that I hear pops out the exhaust intermittently. When I first bough car I filled up full tank and was driving really rough and wasn't accelerating very quick and I had to press really hard on gass, even then it wasn't a smooth 200 miles drive home with the new car! The EM light flashed. This was straight after I bought the car. When I got back my mechanic took two spark plugs and saw they were really black covered in carbon. He cleaned them and cleared the engine management light on dash and was driving as it should. I then changed coils to red Audi R8 and used denso iridium spark plugs as some retard on eBay suggested it was for MK5 Golf Gti, and it totally drove like a 1.0L slow coach, wasn't driving smoothly or accelarting at all! Was definitely lagging. I then changed them to the NGK iridium BKR7EIX 2667 plugs and that sorted that problem out. Sent the denso's and got a full refund.
Only recently cylinder two had failed as I it caused misfire. I've now changed the coil which has fixed the issue of misfie. I just want to know why my exhaust does popping sometimes in my car? I've used ignitioin cleaner but will that fix dirty injectors? I very much doubt as I've seen the process to clean an injector on a MK5 GTI takes time so how can injector cleaner do all that job of what a rebuild would and give same results?? I does not add up.
I have only recently considered changing the air intake to an induction kit. But the dump valve was there for a purpose but do not know as to why?? Does this affect the air intake induction replacement?


I would leave the factory airbox in place until you've got to the bottom of the rough idle first, and get rid of that after market dump valve and put the OEM one back on.  I wouldn't be surprised if that is partially the cause of your problem.

They do pop a lot when warming up because they run very rich with heavily retared ignition to heat the cats up.    Remappers really should code out the warm up routines for cars with aftermarket downpipes, but I don't think any of them do.   It should be smooth when up to temperature, but again, depending on what's been messed with / modified by the previous owner.

[pudding]

Popping in the exhaust is a misfire.  You may not feel it, but it's still a misfire.

To find out if it's mapped, you need VCDS.   Engine module, Advanced ID, then look at the Flash count.  It should be 0 if it's standard and never had any dealer updates. 1 or more, it's very likely remapped, but you can confirm by logging the requested boost pressure channel.  If 1.5 bar (2500 millibar) or more is requested.....definitely remapped.

The dump valve should be the factory one.  Bolted to the turbo on the GTI, and remoted mounted in front of the inlet manifold on ED30/Pirelli.   Crappy aftermarket ones with vacuum lines running to it should be removed immediately.

If I were you, I would put as much as possible back to standard and go from there.  What about the exhaust and downpipe? Are they standard?

People don't usually want to hear this, but popping / misfiring not cured by replacing parts is usually always a mechanical problem.  Exhaust valve or more likely a broken piston because the top piston ring has overheated and butted together.   A compression test will confirm that.

[GTi-Tecnix]

So I've made some enquiries with previous owner and this is the feedback I've received from them:

"Dump valve is a standard unit but fitted on a spacer plate to make it louder, never had it remapped so should be standard. No idea why the coil pack packed up but they are serviceable part. Ideally wouod need plugging in to determine why its popping on tick-over?"

I've also been advised a proper cold induction kit for the air intake would sound and go a bit better!

Also when I say dump valve I mean diverter valve, so the spacer makes it louder why he installed it!

[AJP]

So I've made some enquiries with previous owner and this is the feedback I've received from them:

"Dump valve is a standard unit but fitted on a spacer plate to make it louder, never had it remapped so should be standard. No idea why the coil pack packed up but they are serviceable part. Ideally wouod need plugging in to determine why its popping on tick-over?"

I've also been advised a proper cold induction kit for the air intake would sound and go a bit better!

Also when I say dump valve I mean diverter valve, so the spacer makes it louder why he installed it!

Mate, I'd really recommend taking Pudding's advice here. Don't even think about things like intakes until the car is running properly.

Maybe think about giving the car to a respected specialist. They'll tell you what Pudding told you, if you really need to hear it twice.

[GTi-Tecnix]

The car is running fine. There is a slight vibration underneath when stationary and car is pulling as it should do; in terms of performance I can't complain really. All the down pipes and exhaust are standard nothing modified. The spark plug that I referred to earlier as being "toast" was due to black carbon. At the back tips of my exhaust there is black smoke carbon.

I heard that popping in exhaust can be caused by unburnt fuel being ignitied in the hot exhaust.