Hi nerdz. I am working on a VW golf. I don't have much experience with VWs, so I needed to know if this is a problem or not.

The client called me in to find out why it intermittently stalls on acceleration. When she took me on a test drive to duplicate the problem, the symptoms were when you punch it to the floor, it surges 3 - 5 times (almost like injectors turning on and off) then the car stalls. When it stalls, it is a no start for the first couple of cranks.

When we drove back to her house, I put a scanner on it. No codes. Pulled live data then tried to duplicate the problem, but as it usually goes, the car refused to act up with me there. Everything on live data seemed to be OK, EXCEPT I noticed the ignition timing at idle was reading 12 degrees ATDC. I thought, NO, impossible! I've never seen any car fire after top dead center and run as well as this car is running. So I decided to take a pressure transducer reading in order to verify if the computer is lying or telling the truth. Sure enough, the capture below shows indeed the computer is telling the truth (ch1 - Ignition signal for coil #1, ch 2 - pressure transducer in cylinder #1).

I have to go back and look at the car when it acts up again, but I cannot get the timing out of my head. This is the VW 2.0l FSI engine. There is no published data on ignition timing from VW for this engine. Has anyone ever experienced this? This car has no running issues - no popping, rough idling or anything.

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direct injection?

Yes, it's direct injection.

K-Mech wrote on Oct 21^st, 2018 at 1:18am:

Yes, it's direct injection.

may I suggest you get your engine oil tested for fuel dilution?

Logic wrote on Oct 21^st, 2018 at 1:45am:

may I suggest you get your engine oil tested for fuel dilution?

OK.... I can organize that. But, if you don't mind, could you please explain the Logic... [err.. pardon me  ;)] behind that?

What year is the Golf?

It's a 2005. Please find the specific vehicle data and the engine material I got from VW below.

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K-Mech wrote on Oct 21^st, 2018 at 2:45am:

Logic wrote on Oct 21st, 2018 at 1:45am: may I suggest you get your engine oil tested for fuel dilution? OK.... I can organize that. But, if you don't mind, could you please explain the Logic... [err.. pardon me  ;)] behind that?

You may have a leaking HP pump dumping fuel into the sump.

Oil test will show will show any fuel in the oil.

I see. And you infer this from the timing retard? If so, why would the PCM do this?

It was this that caused me to persue this line


K-Mech wrote on Oct 20^th, 2018 at 9:47pm:

The client called me in to find out why it intermittently stalls on acceleration

I have asked nothing about the following..........as yet


K-Mech wrote on Oct 20^th, 2018 at 9:47pm:

When we drove back to her house

;D

If you have a scantool, see about monitoring oil pressure for that when it happens, is there a PID for pressure for that? Also monitor position of cam phaser.

Logic wrote on Oct 22^nd, 2018 at 2:21am:

have asked nothing about the following..........as yet

He he he! What happens at the diagnosis, stays at the diagnosis!  ;D

fisher wrote on Oct 22^nd, 2018 at 7:01am:

If you have a scantool, see about monitoring oil pressure for that when it happens, is there a PID for pressure for that? Also monitor position of cam phaser.

I am going back there tomorrow. I was going to monitor fuel pressure, cam, crank, oil pressure and iGN and injector pulse.

I still am worried about the timing retard. I have the sinking feeling that this is an unrelated problem to the surging at acceleration. I hope I can get the car to act up.

K-Mech wrote on Oct 22^nd, 2018 at 9:48am:

Logic wrote on Oct 22nd, 2018 at 2:21am: have asked nothing about the following..........as yet He he he! What happens at the diagnosis, stays at the diagnosis!  ;D

Like backprobing and such...

Steve J wrote on Oct 24^th, 2018 at 5:31am:

Like backprobing and such...

;D

I got the car to act up. When probing the low and high-pressure fuel sensors, I found that during the surging, I was losing fuel pressure first on the low side followed by the high side. There was no data PID so I used the scope directly on the sensors.

This pointed me to the fuel pump. I went to the pump and heard it running with a whine, sounding like it's speeding up and slowing down. I probed it and found out that the fuel pump control module was giving erratic power pulsations to it, sometimes dropping out entirely. Power feed to the module was fine, as well as the ground. The module is going bad, but, the pump sounds bad as well, it's noisy, so I don't know whether the pump damaged the module or the module damaged the pump. Since the parts have to be imported from UK, I will call both the pump and module. I don't want to call a module then find out we have to order a pump as well.

I really still don't like the timing retard on this thing. Does anyone here have a hold of a VW FSI engine who can quickly check if this is a normal running condition at idle? Its odd that VW dont publish the ignition timing data.