Mk5 golf gti tfsi hesitation

[Mackenzie79]

Hi, please help.. I have a mk5 2.0 tfsi The car has no fault codes, and has had various parts changed; PVC, spark plugs, temp sensor and fuel filter changed, still no joy.
If the car has been left for a few hours it hesitates when pulling off like it's getting no fuel. This is very brief and after runs perfectly. I have been told that this is 'choke mode' and this is supposed to happen?! I'm lost as never heard of this or had this issue before. Should these cars hold back when cold?.

[titchy]

there is fuel enrichment which is a form of choke have you checked the air filter enrichment is controlled by ecu via temp sensor is the temp getting to normal 90c when hot could be stat

[Mackenzie79]

I've had it on live data at my local garage. I replaced the coolant temp sensor. It wasn't a vw part though and it came up that the sensor was faulty. He said everything else seemed normal and changed the sensor for a geniune one. Still no joy. The temp dial appears to work it reaches 90and stays there. Once I reach the end of my road all is good no issues. Its just when I start from cold and fisrt pull off for a second or two there is nothing, hard to explain just feels like it has no power. If I keep my foot down it just crawls along briefly then slightly judders into life. I guess I can live with it, it's just really bugging me. How do I check the air filter enrichment?

[muff1991]

Try disconnecting the MAF sensor then drive away, see what happens?


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[Mackenzie79]

I have cleaned the Maf sensor although could still be an issue. What should happen? If the MAF was faulty would it cause this problem just on startup from cold and then be OK?

[muff1991]

Hi mate, I too have been suffering with cold start issues.. except my issue only happens when cold outside not just cold engine. If the weather is 8-10 degrees upwards.. cars fine!!! I have various threads about this forum but not a simple answer it seems. Either that or overlooking the easy stuff lol. I have searched and replaced almost all the common stuff and I still can’t figure it out. If the air temperature is below freezing (0 degrees) the car will start on the button and then cut out after 10 seconds or so.. the engine just slowly dies/stalls. But let’s say it’s 5 degrees outside, my car starts and runs, I pull away and the throttle is ridiculously laggy. Until around 2.5k and then the power kicks back in. So weird and the laggy throttle (hesitation) is defo sounding similar to your issue. Keep an eye on colder temps as they come to see if it gets worse. And if you find a fix please let me know. The only one thing I did and thought I nailed it... was one cold morning I started the car and it cut out (-1 I think it was) so I disconnected the intake air temperature sensor just above the throttle body and hey presto.. the car ran perfect, no cutting out, no laggy throttle and most of all.. no power cuts at 4K. Only when colder I get power cuts at 4000rpm, the engine just cuts all power! This disappears too with the IAT sensor disconnected. So what I would recommend to you, if your problem could be the same or similar to mine, disconnect MAF sensor and see what happens, If it’s worse then that’s a good thing! If better then your MAF is goosed! But if all is ok with that... then connect it back up and then Disconnect the IAT sensor. Then let me know what happens after a drive. Cheers. Muff.


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[Mackenzie79]

Thanks I will try disconnecting the maf and see what happens. If your issues disappear when you disconnect the iat sensor surely it can't stay disconnected I mean it must serve a purpose? Would replacing this sensor solve your prob? I've not had mine long so not experienced a winter yet. So far not had any idling/cutting out issues. Starts straight away and runs perfectly besides the initial issues I'm having. If it does get worse in the cold I will try as you've suggested though, fingers crossed it don't though. If I find a fix I'll let you know.. Thanks

[muff1991]

I've only given you a percentage of the story as its very long lol
But yes, its a fairly vital sensor for the management and I don't leave it disconnected forever.. I have replaced it yes but it didn't cure it. I've checked wiring to and from ECU to Sensor Plug and all good, I'm fairly stumped tbh.
If your hesitation is happening every cold start then try disconnecting the IAT then, it might get worse as the cold weather arrives, if it does then you'll have a head start. By disconnecting mine, It instantly fixes all those problems above. Once the day warms up a bit the car will run fine with the sensor connected again. it is literally only Cold Air Temperature related. I can only put it down to the Software (maybe a rubbish or corrupted remap) or another sensor. mechanically the car is fine. its 100% electrical I just don't know what - YET!
I'm not saying you have the same issue as me, but certainly sounds similar. I have found old posts from people in the past but no answers :(

[Mackenzie79]

I had a look at the iat sensor just, took it off and sprayed it with MAF cleaner. Noticed when I took it out, it had a bit of oil on the plastic. I assume this isn't normal? Figured cleaning it couldn't hurt. Disconnected the battery and took the sensor out with the plug attached. If it does get worse when colder I've got no hope of getting those vw plugs off lol nightmare don't wanna break it and it don't wanna budge

[muff1991]

yes, you will always get a bit of "blow by" oil in your intake.. and then hitting the sensor. My sensor was oily too.

not teaching you how to suck eggs, but the key to these VAG electrical connectors is to push the plug towards the sensor (so imagine compressing the sensor pins into the connector pins) then pull on the plastic tab, then slide the connector off. real easy but even some of them can still be a pain, especially if you have crud on a connector.

[Mackenzie79]

Thanks will give it another go.. Was looking through the paperwork I got with the car earlier and noticed its had a turbo act valve in the past. Is this another name for a DV valve? . Keep reading maybe this could be an issue but maybe not if it's the same thing. Also found paperwork for 'vehicle on board diagnostics' and on the last page is states that one malfunction was detected and lists, fuel pressure regulation valve below lower control limit intermittent. Could this be causing my problems? The paperwork has no date on it and obviously don't know if this issue has been addressed. Is this something that can be easily replaced?

[Mark_DF05]

I'd check the map sensor too, mine was damaged when I had the thermostat changed and gave similar symptoms. I've read of them not being properly connected or wires snapped a few times so worth a look.

[muff1991]

funny you should mention the MAP sensor as that is next to clean/replace on my list. If that doesn't do it, I'll be flashing a stock file onto it.
cold weathers coming and this morning it was 8 degrees, I was getting power cuts around 4000rpm. bring on the cold weather!

@Mackenzie79 the valve they're referring to is more than likely the Diverter Valve yes, never a bad thing putting a new one of those on, could be part of the issue. As for the diagnostics, It might be worth having a scan done with VCDS to see if anything comes up.

[Mackenzie79]

Hi again.. Had a scan done with Vagcom at the lion garage today and diagnosed two faults. Turbo over boost fault and number 2 misfire injector is at fault. They said the "built in dv valve on the turbo" was sticking when cold and was causing the fault and quoted over £2000 to fit a new turbo and injector. Is their a built in dv valve that can't be replaced I'm confused. I thought this was a sepearte thing?! My local garage disagrees saying that I could just clean the turbo and the misfire could be historic. The car runs perfectly after the initial stumble and there are no warning lights on the dash. Any advice would be appreciated thanks

[pudding]

They probably mean the wastegate is jammed and not opening, hence the over-boost faults.  DVs normally cause under-boost faults. The DV is replacable, but the wastegate is indeed part of the turbo. You might be able to replace the actuator assembly and see if that helps, but if the penny valve in the turbo is shot, you will indeed need a new turbo.  Approx £1000 inc VAT from the aftermarket, or £1000+VAT from VW.

Clear the fault codes and see if either come back.  Persistent misfire is usually always a bad injector. £100 for the part and a few hours labour, so you might as well replace all 4.

These engines aren't the most responsive during warm up anyway, some kind of warm up routine restricting power a bit, but yours sounds like the ECU is slamming the anvil down on the power.......which it would do if it's over boosting, for engine protection.