[Markie]

Hi, been running an I30 1.6 diesel for over a year in the UK. It's an ex police car and has had no problems, it's been well looked after. Love the car, spent hardly anything on parts. I've just completed my second service myself which was easy as modern cars go. But I do have an annoying problem. When the car is warm and the ambient air temperature is over 16 degrees there is a slight hesitation on acceleration. I've plugged in am obd reader and the readings look ok. I know it's due a fuel filter replacement in 5000 miles. Can anyone suggest what the problem could be? The engine runs quiet and smooth majority of the time; I'm a little miffed.  Thanks Mark

[Dazzler]

Welcome Mark,

Don't be too "miffed" you have a 7 year old car with a bit of history, it is allowed to have the odd hiccup! 

Could be the fuel filter or even dodgy fuel/ fuel bug. Could also be something electrical/electronic.

Always hard to diagnose by remote control, but fortunately we have some members who are a lot better at it than me.

BTW what sort of mileage has it done, and is the turbo noisy (whistle with the window down) Thinking the Turbo might be getting tired and this is showing up in warmer weather. I could be miles away from the truth (Oh hang on .. I am) 

[Shambles]

Hiya Markie.

You could have used your existing forum account rather than creating a new one . There's a "forgotten password" link on the login page

[Bogdan1986]

Hey Marky.
I have been struggling with a similar issue this year, in my 2012 diesel i30. I also get a P0404 trouble code, though. I changed the EGR valve and other parts, cleaned a lot of other things, but the problem persists. I now suspect either the lambda sensor, the ECU or some other kind of electrical issue.
The ELM 327 bluetooth I own at the moment is not powerful enough to help me diagnose issues like these. I did order a VCI clone which should arrive within the next couple of days, though.
Bottom line: intermitent issues like these are difficult to diagnose, especially if you don't have the right tools.

[Markie]

Hi, thanks for the reply. It's done 110k. The cops put a new turbo on at 78k.  Tbh, it's a very quiet smooth engine. It was cheap being an ex police car but they've looked after it. I was thinking it might be fuel filter.

[Markie]

Haha, thanks. How did you know it was me?  I can't get into my old email account either to except the reset password!

[Markie]

Hey Marky.
I have been struggling with a similar issue this year, in my 2012 diesel i30. I also get a P0404 trouble code, though. I changed the EGR valve and other parts, cleaned a lot of other things, but the problem persists. I now suspect either the lambda sensor, the ECU or some other kind of electrical issue.
The ELM 327 bluetooth I own at the moment is not powerful enough to help me diagnose issues like these. I did order a VCI clone which should arrive within the next couple of days, though.
Bottom line: intermitent issues like these are difficult to diagnose, especially if you don't have the right tools.

I bought an ELM too, the fuel rail and air intake pressure and temps looked ok. Thinking of waiting for a hot day and sitting in the car with the ELM for an hour lol

[Bogdan1986]

I bought an ELM too, the fuel rail and air intake pressure and temps looked ok. Thinking of waiting for a hot day and sitting in the car with the ELM for an hour lol

I did that a few times this summer. Turbo pressure and fuel pressure looked fine, but when it was 25C outside, the intake temperature showed 45C while driving on the motorway, 50 in city traffic. When temps are under 18C, this temperature doesn't go over 25C.
What could help a lot would be if you could see fuel trims, but the elm 327 can't read that for my i30, at least.

[Markie]

I bought an ELM too, the fuel rail and air intake pressure and temps looked ok. Thinking of waiting for a hot day and sitting in the car with the ELM for an hour lol

I did that a few times this summer. Turbo pressure and fuel pressure looked fine, but when it was 25C outside, the intake temperature showed 45C while driving on the motorway, 50 in city traffic. When temps are under 18C, this temperature doesn't go over 25C.
What could help a lot would be if you could see fuel trims, but the elm 327 can't read that for my i30, at least.

Is there only the temperature/flow taken at air inlet, or some where else too. My friend has a Ford which has two sensors, one at inlet the other at the throttle body

[Bogdan1986]

There's one intake temperature sensor in the MAF sensor, right after the air filter housing. There's one more in the boost pressure sensor, located on the intercooler.
My elm only reads the one on the intercooler... I checked by having the key on but with the engine off, and disconnecting the sensors one by one. When I disconnected the BPS, the value of the intake air temperature read by elm dropped to -40. It didn't change when I disconnected the MAF.

[Shambles]

Haha, thanks. How did you know it was me?  I can't get into my old email account either to except the reset password!

Lol. There's a few of us who read and remember all that goes on in here, especially about members who drive ex police cars.  I'll sort your old account and get back to you.

[nzenigma]

Haha, thanks. How did you know it was me?  I can't get into my old email account either to except the reset password!

Lol. There's a few of us who read and remember all that goes on in here, especially about members who drive ex police cars.  I'll sort your old account and get back to you.

Good, don't lose him Shambles, this is an interesting conversation.

Im just an observer here, but have you checked that the new turbo is the correct one? VNT actuator correctly adjusted?
Is your lag is due to slow turbo boost?...for what ever reason?

[Shambles]

@Markie please use the forgotten password link on the login page to reset your original "Markie" password (gmail account).

[nzenigma]

I checked by having the key on but with the engine off, and disconnecting the sensors one by one. When I disconnected the BPS, the value of the intake air temperature read by elm dropped to -40. It didn't change when I disconnected the MAF.

 This may be a quirk of the circuit. Did you also notice the ambient temp displayed on the radio unit? With radio 'c' plug removed it will show -40.