[Closed] Engine hiccups

It’ll make no difference IMHO. I’d try and work out a pattern to the stutter, then when you can reproduce it on demand show the garage.

My guess would be a damaged coil
Pack.

I can make it do it on demand but the garage is saying its normal. Automatic preparing for a gear change but does it in manual, D, and S.

If it was a damaged coil wouldn't it have an error code? I don't really know how these things work.

Seems low mileage for a coil pack, but sounds similar to symptoms my car exhibited recently. £99 for 6 packs and an easy fit in 1 hour, just with some pipework to remove. (BMW).
BMW dealer quoted £1113 for an in-tank fuel pump which is still absolutely fine and wouldn't have fixed the issue.....

More likely a coked up lamba

But it's a guess.

Or they might all do that

Is the Lambda the mass air flow sensor?

I’m wondering if this caused the engine to run slightly rich for a while

That won't happen if the blockage is before the MAF sensor, cos the car knows how much air is going in. If the petrol engine even uses a MAF sensor - I think traditionally they measured oxygen content in the exhaust (lambda sensor) to get the mixture right. But that engine is turbo and fancy pants FSI so maybe it does have one.

As for 'engine preparing to change gear' that's bobbins. I've been in enough VW taxis to know that the new ones are utterly seamless at all times; even my old high mileage one is smooth when accelerating briskly - it only has a slight back-off when accelerating slowly. You can eliminate that theory by leaving it in gear and accelerating through 3k.

I have experience of Lambda sensors on a V6 Honda outboard engine and doubt this is the cause. As said, it measures the O2 in the exhaust flow and adjusts the fuel mixture accordingly - when it fails I'm pretty sure there would be an error code and the engine would simply revert to a 'safe' fueling mixture that's a bit richer than optimum.
Don't think it would cause a very short lived hiccup - I these are more likely to be caused by an electrical anomaly.

It's the coil breaking down, I had the same symptoms in a petrol car I drove recently.

You said this only happens when COLD.

When the engine is cold it will be running with Low Temp' Fuel Enrichment enabled - like the old fashioned 'Choke' pulled out. This enrichment can lead to slight spluttering and in my opinion is not unusual.

When the engine is cold it will be running with Low Temp’ Fuel Enrichment enabled – like the old fashioned ‘Choke’ pulled out. This enrichment can lead to slight spluttering and in my opinion is not unusual.

It shouldn't happen with a modern engine. The old fashioned 'choke' was just richer or leaner as you adjusted the knob. A modern engine is always measuring how much air and fuel are going in and how much is burning, so there should never be an issue.

I had an older VW 1.8t that hiccupped when cold. After replacing the MAF and various other random "fixes" I cleaned the throttle body. It didn't look dirty - just a smear of oily deposit round the butterfly, but it totally fixed the problem and transformed the car (back to normal).

I'd have thought the coil packs would be worse when warm, if anything.

I had a similar problem but with a turbo diesel engine in a Mondeo.A sudden hiccup going up an incline when the throttle was pressed.
Gradually got worse until the car started going into limp mode.Ford dealer diagnosed faulty injector.Car had only 30k miles on it. New injector didn't solve the problem.
Poking about on the internet I found that in the turbo area is some sort of impeller that kicks in when extra boost is required and this can get gummed up causing the hiccup.Never explored it as I got rid of the car.

I had similar, along with sometimes a bit of a struggle to start when cold (VW 1.2 TSI). The car's about 5 years old, done 50k miles or so.

I put some redex through with a tank of fuel, and it's been fine ever since (fingers crossed)

edit - no warning light or anything, so I doubt OBD would have anything flagged up. I did suspect plugs and/or leads, but it's now pulling smoother through 2500-3000rpm than it did as well as not having any issues when cold (it only happened twice, once only a couple of seconds turning over rather than an instant catch).

A modern engine is always measuring how much air and fuel are going in

This is true - but it uses that info' to make the mix richer than stoichiometric when the Low Temp’ Fuel Enrichment is active. No engine likes to run rich and coughing or slight mis-fire is not unusual.

Would it not cough/mis-fire all the time though rather than just at 3000rpm when being pushed? A 1.2L petrol should be up to temperature easily within 10 mins (so no fuel enrichment) let alone 15-20 mins.

A 1.2L petrol should be up to temperature easily within 10 mins

Kinda depends on how it's being driven - so maybe or maybe not.

A 1.2L petrol should be up to temperature easily within 10 mins

Kinda depends on how it’s being driven – so maybe or maybe not.

Yeah, also, displayed water temperature != actual water temperature != oil temperature. So "warmed up" is a difficult term to define unless you have additional readings (and nobody gives you oil temp on a 1.2 TSI, even though the ECU will undoubtedly monitor it.)

Would it not cough/mis-fire all the time though rather than just at 3000rpm when being pushed?

Also, different running conditions can bring out different issues - partly from being able to notice it, partly you might for example (if it was a spark problem) have a weak spark that can light the mixture some of the time if everything's getting mixed well (high revs perhaps) or is inhibited when the cylinder has more or less fuel in the mix.

Similarly a blocked injector nozzle might still allow adequate burn a lot of the time but under certain demands might not - particularly on a lean burn engine.

i hate threads like this....

a lamba if out of spec will not always give an error code. nor will a MAF as the error code needs a reading to be out of spec. used to be a very common issue on low mileage short trip micra's when I worked at Nissan.

Lamba and Maf are different. MAF measures physical volume of air being ingested by the engine.

Lamba "sniffs" the exhaust and senses the oxygen and alters the fuelling. they work together

so if a sensor is dirty. or has a poor connection it doesn't always follow an error code will be generated.

could be anything. its like me saying I have a bit of a cough, could be anything from a cough to FBA

You could try inspecting the spark plugs just to look for any evidence of an ignition problem on one of the cylinders - could point to a dodgy plug, coil or wiring.

Best bet is registering on a dedicated forum for that Marque and searching for other owners having similar issues.

With our fiesta the coil pack deteriorated to the point the car would barely run, still no error codes. Even the lambda looked normal on the obd2.

If the petrol engine even uses a MAF sensor

The lambda just trims the fueling a few percent either way over the long term.

The MAF is what the ecu uses to work out how much petrol is needed.

There might also be throttle position sensors and air pressure (ambient and manifold) in the equation but it's the maf that provides the main input.

I'll check all the air flow pipes first then.

Does anyone know where the MAF sensor would be? I don't really know what I'm looking for, but happy to try cleaning it if it's easily accessible.

thisisnotaspoon

Member

With our fiesta the coil pack deteriorated to the point the car would barely run, still no error codes. Even the lambda looked normal on the obd2.

This. My Focus felt like it had completely lost a cylinder yet no engine light or codes present. Prior to that it did feel like it had an occasional misfire.

The MAF sensor will probably be after/next to the air-filter. On the 1.8T it's easy enough to get off, then you spray it with electrically contact cleaner while it is in a plastic bag. Shake it around the let it dry. I did all that with no benefit to my problem, but it only took half an hour or so and cost the price of a can of electrical cleaner.

Cleaning the throttle body took a similar amount of time/effort and cost a few quid for a new throttle body gasket. I already had carb cleaner (from the days when my car had a carb!). It was the throttle body that was the problem (see previous post).

I'd expect a breakdown of electrics such as coils to get worse with temperature rather than at specific revs.

I had a problem with my engine reporting lean running when a pipe split, but it didn't noticeably effect performance.

Look for youtube videos for help in doing any of these things. They can be effing brilliant.

My SMax used to have a small stutter or hiccup under power. Never correlated it to the engine being hot or cold but thinking about it it was probably more likely when it was cold as I usually only noticed it on a slip road not far after leaving the in laws house so the engine wouldn’t have had time to warm up properly. But it never got worse and I determined it was the climate control as it didn’t do it when the climate control was off, so just assumed it was the transition in power demand when the a/c compressor was kicking in or off via the compressor clutch. Noticed it a few times but didn’t seem to be an issue. So has your car got a/c or climate control?

It does have climate control so I'll try turning that off tomorrow morning and see what happens. How can that be linked to the engine?

I had a good look for the MAF sensor while replacing the air filter this afternoon and could see it. Maybe it doesn't have one? Unless it's buried down by the throttle body.

I did buy some injection cleaner but then someone on a Skoda forum said don't use it. I don't know why but haven't used it anyway.

I went for a long drive after changing the air filter (it was pretty filthy) and it did stutter/jump/hesitate as usual but only for the first 5 mins. It was a hot afternoon so guess that made things warm up quicker. I filled the tank with some premium fuel to see if that makes any difference.

It does have climate control so I’ll try turning that off tomorrow morning and see what happens. How can that be linked to the engine?

The compressor puts a lot of load on the engine so with climate control it will kick in and out according to the climate control system cold air demand. There is a clutch on the compressor so when cold air is demanded the clutch engages and the compressor is then driven by the engine. This sudden load on the engine was what I determined to be causing the momentary stutter of power delivery. The engine ECU is programmed to compensate for the additional load but if the engine is cold then maybe it just causes a small stutter in power delivery. A long shot but I was convinced that was what was going on with my car so worth checking out before you go investing any money in mechanics trying to troubleshoot. If it is this then just ignore it, it never got any worse in my case and though I did notice it a few times it mostly happened on the drive from my in laws as I was accelerating down a slip road.

I'll give it a go tomorrow.

Really hoping it's nothing much or is a genuine 'feature' of that engine. Just hope it won't be much worse during winter.

I really like the car and can live with it if it's nothing to worry about. But If going to be a long term battle with the manufacture I'll just sell it and get something different.

Well I'm glad Duncan came along and said what I was about to say.

You'd have spent a fortune if you followed all the "it's definantly this I had it on xyZ in 1934 "

Parts darts/crystal ball at its finest.

One thing I would check before throwing money at anything is that it's soft ware is up to date. A colleague had a specialist playing parts darts and go round replacing all the ignition coils and plugs etc trying to cure a stutter

They stuck it into the local dealer who said straight away "oh this hasn't had the latest software update" and it was grand from then on. -that was a very low milage 1.4tsi

It was at my dealers for a week and they confirmed everything was up to date. Though it wuldnt hurt to try a different dealer to get a 2nd confirmation.

I'm hoping its something dirty inside the engine; the car had one previous owner from new doing very short journeys.

Another thing i did notice is when the engine is cold (left over night) the starter motor will turn over 4 or 5 times before the engine starts. Its the same whether the ambient temperature is 7 or 18. I'm a geek and keep notes on things like that!

I'm reluctant to add any ignition cleaner after someone said don't. Maybe a tank of higher octain fuel will clean it?

The fact that your "dealer" had the car for a week and supplied it with a filthy air filter ,
and leaf debris in the intake means that they have done almost nothing.
i would get a second dealer to look at it as well as contact the manufacturer to make a complaint - it is still under manufacturere warranty and it clearly has not even been inspected/serviced.
Did you take a photo of the intake/filter ? I would have left it all in place and shown them in person.

Edit - > dont mess about with it - the MAF is delicate and you could easily damage something - this car is under warranty still ?

You’d have spent a fortune if you followed all the “it’s definantly this I had it on xyZ in 1934 ”

Parts darts/crystal ball at its finest.

Unfortunately if the professionals have given up there isn't much else you can do once you've done the logical things (like turn off the aircon if you think that's a possiblity). I put up with a misfire for over a year before stumbling on the solution. It wasn't exactly stumbling as it was one of several suggestions on various forums, but it just seemed to me like an unlikely one. In the end I wasted the cost of a MAF (£70 ish)* on "parts darts" which in the grand scheme of keeping a VAG on the road isn't much.

* and a bottle of injector cleaner which did no harm, but no good either.

Given what you've said there about taking some cranking to get it going, have a look at the fuel pump. My Seat Exeo 2.0 TDI started to do that when it was cold or left for a few days. It turned out the high pressure pump driven by the timing belt was starting to fail and when left the fuel pressure would drop and require some extra cranking to get it going. That being said its unlikely to cause your stuttering as once pressurised it was fine. Could be worht popping the timeing belt cover at the top and have a look to see if you can see any fuel leaking

Injector Cleaner added to fuel is fine. Worth a go, won't cause any harm. Certainly worth squirting the throttle butterfly flap with some carb cleaner - be aware it may run very badly on start up due to residue from the cleaner

The strange thing is that it happens at a very specific RPM and only when the engine is cold. In my mind that rules out a lot of the usual electrical/fuel supply problems as you'd have the issue more consistently.

Maybe go onto Ebay and get one of those USB dongle things you can plug into the ODB plug in your car that tracks all the engine parameters and drive it for a few days and have a look at what's going on. You never know you might see some specific parameter getting its knickers into a twist at that point. Wont tell you why but will at least give you an idea where to be focusing your troubleshooting efforts.

It is still under warranty. The problem is the dealer just says they can't replicate the fault. If you're very light on the throttle I'd won't do it but does when you accelerate quite hard out a roundabout on a dual carriageway for example.

I've been in touch with the manufacture but they dit want to know.

If the premium fuel makes no difference after half a tank I'll put some injection cleaner in.

Why can't they accompany you on a drive?

Definitely try a different specialist or dealer. I once had a 'specialist' try to convince me I my DMF had failed, when it was actually the springs that had broken, slightly lowered the ride height, mucked up the suspension geometry and the inner edge of the rear tyres had developed a sawtooth.

Why can’t they accompany you on a drive?

They did but just said they couldn't feel anything. Then said its normal for that engine and gearbox.

Do you think the mileage is genuine ? 9K miles and a filthy air filter doesn't sound right.

It could have been parked right up where loads of leaves collect on a regular basis.

The cars in pretty much new condition and that model was often available on mobility so could have been a households second car for short runs.

Only guessing though.

Testing it out again today, once warmed up it was perfectly smooth in every gear. Just 3rd gear when cold is a bit hesitant under load.

Given the specific speed it happens at, I'd hazard a guess it's a point at which the engine changes running modes.

I rarely deal with petrol cars, and certainly even less VWs, but I'm aware quite a lot of these smaller petrols switch between stratified (aka lean burn), and stoichiometric (aka conventional burn) depending on speed/engine load. A suitably knowledgeable VW tech should know what happens at 3000rpm, but sadly, suitably knowledgeable seems to be a dying thing in the motor trade.

As a technician, it's the kind of fault I could spend a lot of time trying to find the exact cause of, and never find it. Plus it's time the manufacturer is unlikely to pay for, which is why lots of dealers are very reluctant to spend time trying to diagnose minor faults under warranty. However given it's not that new an engine, I would of thought any reasonable sized dealer will be aware of any common issues by now.

As for the air filter, you'd be surprised just how dirty they have to be to cause issues. I've seen filters black with dirt, and starting to collapse, yet engines have still ran fine.

However given it’s not that new an engine, I would of thought any reasonable sized dealer will be aware of any common issues by now.

Apparently stretched timing chains have been a problem with that type of engine.

The symptoms you suggest sound a lot like LSPI (low speed pre ignition). The engine is not supposed to do it, but its a sympton a number of new small capacity highly compressed engines have experienced (I work in this industry) . There are various reasons why this happens, some is down to lubricant, some is fuel quality and some is engine Configuration. I'd go with what has already been suggested and get the software checked this could well resolve the issue, if it's happening. If someone is able to take a cylinder out, it will have small pitting. Hopefully it's not this, and just some sensor issues, but all oems have suffered the effect and it would be surprising if any garage had ever heard of it in order to diagnose it..

The symptoms you suggest sound a lot like LSPI (low speed pre ignition).

If it is that and is just a feature of the engine do you think it will get worse? The garage confirmed it has the latest software so all I'm trying now is better quality fuel.

If it is (big if) unfortunately yes it will get worse when you'll get 1 or 2 instances of mega knock and the piston will shatter. Like I said it's a big if, but on your side it is well known and you would be unlikely to be out of pocket. Unfortunately as I said, it's very hard to diagnose unless it goes and has some rather expensive kit hooked up to it. The Ford ecoboost has the same problem, some engine configurations can remove the instance, but the engines are normally designed with parts and timing maps to counter it as mu h as possible.

However that said, you said you've tried different fuel types, have you run Shell Nitro and experienced the same thing, the burning characteristics of different fuels can sometimes mitigate against it, it's more interesting to know as it would not be a viable "fix".

If you've got a bit of a geeky mind google Infineum LSPI effects, it's a good eye-opener to the phenomenon.

Let's hope for sensor issues though!

Sui..

So we are now back with engines that pink?

Funny, I was just thinking that.

Pre-ignition is something that should quite quickly be picked up by the knock sensor and corrected though, and it probably is. The big question is why it would be a problem at a specific engine speed.
My guess is it'll be something like the fuel injection drops an injection stage, but the switchover isn't handled smoothly.

Duncan, yes unfortunately so. The drive to downsizing and highly boosted engines is throwing up all manner of issues. Knock sensors will only operate within a specific range, and LSPI is not something they can dwal with too well. The problem is more persistent at cold Temps under load, think car shuttling at ports.. Part of the problems come from ring packs letting too much lube through as part of the design, leading to heavy hydrocarbons being part of the fuel mix or Injector deigns causing wall wetting within the cylinder with the heavier aromatic ends in the fuel igniting at different points.. Its a very complex issue that designers are still trying to get to grips with.

To be fair high boost lean burn it's almost inevitable.

I'm a long time out of the car trade and I'm glad!

So a combination of design of low resistance/wall pressure rings and extremely thin oils 0-20w typically , is causing the inevitable problems, oil usage with some modern engines is a big problem leading to oil starvation impacting the cam chains too ..

Any ideas what I could do to fix it? I noticed today driving home from work that the 'hiccups' occurred even if I was very light on the throttle. Only in 3rd gear. Flooring it in second was fine.

So confusing!

Or if anyone has recommendations for a replacement for a Skoda Yeti? I'm very tempted to sell and move onto something more reliable. Really miss my old Fiat 500. That was a great car.