Egr Valve - Low Flow, 1.4 Petrol

Hi Guys,

I'm really desperate for some expert help here and I'm hoping I am not on my own with this one. I bought a 2001 Golf 1.4 (AXP) last October and driving home the EM light came on. In fact it has come on pretty much every day since then and usually under the same conditions, which is on light throttle (50mph in 5th) or on overrun.

Strangely, it happens about 10 minutes into a second journey. Eg., I can drive 30 minutes to work without problem but the light will usually come on early into the return run. If it is a first journey after erasing the fault, the light doesn't come on at all, even on a long trip. However, after switching off the ignition for a period from 15 minutes up to a week or more, after restarting, the fault will reoccur just after the car has reached normal operating temperature.

The fault shown is always EGR valve - low flow and between the VW main dealer and an electrical diagnostic workshop, half the value of the car has now been spent with still no cure or hint of a solution.

Here's a shortened resume of what's been done so far:

1. New EGR valve. ( Poor deluded fool that I am - I thought this would fix it!). VW carried out adaption but ECU showed sporadic low voltage and temp fault which they said could show up as the EGR fault.
2. New coolant sensor and 407 relay - still same problem, and still EGR fault.
3. All engine earths checked and cleaned.
4. VW Software update carried out.
5. New busbar/relays fitted (starting to melt due to poor main feed connection).
6. Connections and wiring to and from ECU and EGR valve checked, all OK.
7. MAF replaced, EGR pipe and inlet manifold thoroughly cleaned for the third time.
8. EGR valve apears to work but ECU would not perform test correctly.
9. ECU replaced by VW and EGR tested OK.

VW now saying that their next course of action involves me leaving the car with them while they try to reproduce the symptom under test conditions. As well as not wanting to pay £90ph for however long, the fault only occurs when driving, so it seems quite unlikely they will find the answer this way.

I really like the car but I'm fed up driving it half the time in limp home mode and I just cannot afford throw any more money at what appears to be a unique problem. Short of a match and a petrol soaked rag - any ideas please? Can the EGR be bypassed without any side effects?

Sorry my first post is so dull, I promise I'll liven up later!

Normally this is just the pipe from the EGR valve to the inlet manifold becoming blocked, on your car this is part number 036131521AC and cost £26.33 inc. VAT but you also need gasket 036 131 547 F and gasket 036 131 550 A. I have seen a couple of cars like this where a new EGR valve has been fitted back to front; the ports are offset so this completely blocks the flow. Deleting the EGR will give the same effect as a low flow fault.

Hi Crasher,

Thanks for your input. Sadly for me, the pipe is clear and the EGR valve has been checked several times now. The ECU's self testing of the valve shows that it is working correctly too but at the time of the test, I suppose it would.

I did one last week. It had a used EGR valve fitted by someone else and still came up low flow and so we fitted a new valve, still low flow. The pipe had been blown though and pronounced clear, I found it was partially blocked; the diameter reduced by only about 20% and that was enough. I cleaned out the pipe (a new one was on back order to Germany, such is the regularity of this problem) and that cured it. Another I had turned out to be a faulty manifold Thrust (MAP) sensor, it was incorrectly detecting the EGR flow. Alos a dirty throttle body can cause this.

Thanks Crasher,

I'll definitely check the pipe again and whilst the VW agent said that they'd already checked the throttle body, I'll look at that too. They are suggesting that the fault must be some elusive intermittent electrical problem causing the voltage signal from the EGR to drop but there appears to be no evidence for this apart from the fact that they think they have eliminated all other possibilities.

If the pipe or the throttle body is the answer, I'll be highly relieved but cheesed off that the agent didn't sort the problem months (and £££'s) ago.

Thanks again, I'll let you know the result during the week.

The saga continues........

Today, I renewed the EGR pipe and gaskets and cleaned out the throttle body which had been done before recently and was pretty good. The MAF sensor is new so I left that alone.

Went on a test drive and the EM light came on after 10 minutes with the low flow fault again. Immediately reset the ECU and light stayed off (until the next trip).

Two things I did notice were:

1.The air filter housing had a some oil inside coming from the engine breather pipe and a little oil was finding its way down the throttle body - is this normal (car has done 88k)?.

2.There is a thin rubber pipe coming off the EGR valve that runs towards the inlet manifold and has a 2cm diameter cylindrical grey plastic container on the end. It has small holes on top and looks like some kind of vent or valve. Could this be connected with the low flow problem?

Any help gratefully received :1zhelp:

Low flow means exactly that, the ECU is not detecting the correct flow. If you fit a new EGR valve it has to be adapted or else it will not work. Did you adapt it in Basic Settings? The vent pipe is never a problem.

It does not have a MAF, it is a combined MAP/IAT called a Thrust sensor.

Hi ,

I have a 2000 VW Golf 1.4 16 V Engine code AXP. I have the exact same problem with the Engine Warning Light giving the error P0401 EGR Insufficient Flow. I have replaced the Electric Pierburg EGR valve and stripped and cleaned the entire EGR system . Every time I clear the fault code it comes back after about 200 miles.

I am pulling my hair out with this , can't think what else to try ??

Thanks. Yes, the new EGR valve has been adapted and VW said they were trying a new MAF but I do remember now that they later said it didn't have one and that it was a thrust sensor they replaced.

I don't have an invoice for it as they tried the new unit which didn't cure the problem but as they had mistakenly thrown the original unit away they had to leave the new one on FOC.

If it is adapted, the only solution now is to strip it all down and make sure all the ports and pipes are clear.