[christian1402]

My mk4 r32 has been struggling to start when cold recently. It will crank over loads, eventually fire bit run very lumpy at around 400rpm. As soon as I go near the throttle the car just dies. When I go to fire it up again it will start first time no problem. Again once the car is warm it starts first time no problem. No other running issues at all.

I've scanned the car and surprisingly its come up with no fault codes at all, I've even done a throttle body adaptation, again no change.

Has anyone ever come accross this before? If so does anyone have any suggestions?

Cheers.

 

[Johnboy2110]

Did you clean the TB? I had a similar issue but after cleaning the TB it sorted it and starts perfect now.

 

[PaulW]

400rpm? The car wouldn't run at all at that revs?

 

[christian1402]

Did you clean the TB? I had a similar issue but after cleaning the TB it sorted it and starts perfect now.

I havent, but I will try that this afternoon.

 

[christian1402]

400rpm? The car wouldn't run at all at that revs?

thats the point mate the car barely runs at all, very very lumpy and hardly ticks over. It shows around 400rpm on the rev counter

 

[Johnboy2110]

I havent, but I will try that this afternoon.

There is a guide on here somewhere on how to do it if you dont already know.

 

[christian1402]

I'll have a look, thanks

 

[christian1402]

ok heres a thought, the fuel pump should prime when the door is opend yes? does the fuel pump still prime when the ignition is put to on?

My drivrs door locking moduale gave up last week and hasnt been telling the car when the door is open, so im thinking because of that, the fuel pump isnt priming, and its strugging to start? makes sense to me, as the second time the car is fired up it fires up no problem, and same when its warm (there will still be fuel pressure in the pipes)

 

[JamesBaby]

ok heres a thought, the fuel pump should prime when the door is opend yes? does the fuel pump still prime when the ignition is put to on?

My drivrs door locking moduale gave up last week and hasnt been telling the car when the door is open, so im thinking because of that, the fuel pump isnt priming, and its strugging to start? makes sense to me, as the second time the car is fired up it fires up no problem, and same when its warm (there will still be fuel pressure in the pipes)

Yeah that sounds like your problem.

 

[christian1402]

my olny concern with that is - if the fuel pump should prime with ignition on, then the problem is still there, as i have left the ignition on for around 10 seconds before cranking it over and it still struggled to start

 

[CorradoR32]

The main prime is via the door switch. When you turn the ignition on, you can hear a very quick pulse from the pump then it stops. Then the fuel pump only pumps during cranking and engine running.

TBH I have my doubts as to whether a bit of dirt on the throttle blade can stop it idling properly. The return spring and the DC motor that moves the blade are very strong. I can't believe VW would produce a car where a dirty throttle blade can stop it functioning correctly. I used to have a Polo 1.8T (DBW) and the throttle wasn't cleaned once in the 60K we had it. Idle was always perfect.

 

[christian1402]

The main prime is via the door switch. When you turn the ignition on, you can hear a very quick pulse from the pump then it stops. Then the fuel pump only pumps during cranking and engine running.

TBH I have my doubts as to whether a bit of dirt on the throttle blade can stop it idling properly. The return spring and the DC motor that moves the blade are very strong. I can't believe VW would produce a car where a dirty throttle blade can stop it functioning correctly. I used to have a Polo 1.8T (DBW) and the throttle wasn't cleaned once in the 60K we had it. Idle was always perfect.

In that case, i suspect it is definatly the door switch.

My next question, does anyone know weather 3 and 5 door locking modules are the same?

 

[CorradoR32]

When it starts and runs at 400rpm, does it eventually clear itself or do you always have to stop and restart it to get it to idle properly?

By the time the engine starts, the fuel pressure should be enough. When was the filter last changed?

I replaced mine a couple of weekends ago and the stuff coming out of the pump end of it was black with dirt. Might not help but no harm in doing it anyway.