Need help with engine problem.

Car: 2001 Golf TDI Automatic (ALH)

Problem: Car always starts very easily but surges when at idle
Until at full operating temperature then only does it some time.

CEL light comes on sometimes, usually within 2 minutes
of starting, if cleared does not come on again sometimes
for days.

Code on CEL is P1562 "Quantity adjuster upper limit reached"

What I've done: Ran 1 can of diesel purge straight through engine

Reset timing on timing belt (was off just a little)

Checked injection timing and it was accurate.

Cleaned out intake manifold and reinstalled

Removed cat.

None of the things I have done so far have made the problem any better or worse. The intake cleaning improved power and performance quite alot.
Still no improvement on the surging and CEL. Car runs ok other than the surging at idle when cold, sometimes surges when at operating temps but very rarely.

Does anyone have a direction to point me in? What to look for or what could possibly be wrong.

Have you tried adjusting the injected quantity at idle? What is it at now?

A few things to check:

- Fuel filter due for replacement?
- Fuel pickup in the tank obstructed?
- IQ (measuring block 15), if below 3 try bumping it up to around 4
- Fuel temperature sensor (block 7) reads reasonable values?
- Idle compensation (block 13) within specifications?
- Actual timing advance matches requested (block 4)?

With any luck one of those will shed some light

Simon

Fuel filter was replaced less than 3k miles ago

It ran great for 3 months and then this started

I am quite new to vagcom and have not tried adjusting anything yet

correct me if I am wrong IQ level should be between 3 and 4?

what are reasonable values for fuel temp, idle compensation, and actual timing advance?

The specification for IQ is 2.5 to 9, and yes, it's normally between 3 and 4 on a stock engine.

Reported fuel temperature should be close to ambient when the engine is cold.

VAG-COM will display specified values for idle compensation and timing.

Simon

Here are the numbers I got from Vag Com.

These numbers were on my 2001 Golf TDI ALH at normal operating temperature:

modulating sensor: .74 volts actual, .5 to .97 volts normal

piston sensor: 3.88 volts actual, 4.15 to 4.74 volts normal

Injected quantity: 3.4 to 4.4, fluctuates a little at idle but normaly stays around 3.4

fuel temp sensor: 36 deg C with engine at operating temp and outside temp 70 deg F

idle compensation: fluctuates from .7 to 2.0 usualy 1.4, should be between -2 to +2

timing advance: 2.0 actual, 1.3 requested. on the timing graph it is just below the upper line and does not go above it.

I replaced the fuel filter 3k miles ago, could I have some kind of air leak causing this problem?

I have not checked the fuel pickup screen in the tank but actual injected quantity and requested match all the way past 3k rpm.

The car still surges at idle and it does not clear up until the engine is at operating temperature. and it still throws a P1562 code.

Any help is greatly appreciated.

After looking at the numbers a little closer the specified maf reading was around 300 at idle and reading around 500 actual.

I bought the car with a bad transmission, used, and have never driven a "top notch" TDI yet so I have nothing to compare to.

I unplugged the maf and it does not run any different than with it plugged in. If the MAF is bad and telling the ECU that there is a larger quantity of air entering the engine would the ECU try to compensate by adding more fuel? If this is the case could it be the reason the injector pump is reaching its upper limit at idle?

If the MAF on my car was good, how noticable would the difference be when I unplugged it?

The MAF could have been bad since I bought the car and I would not know the difference.

BTW the car has 130000 miles.

The gold standard test of a MAF is that the car should run better with it than without it. If the difference is unnoticeable then a new one might be better.

Runs the same or better with MAF unplugged means it is bad. If it runs worst then it is Good.

I checked and cleaned the wiring harness going to the injector pump and the number 3 injector, removed the ECU and inspected and cleaned the wiring harness connectors. cleaned the ground wires near the ECU. It runs better but still throws code.

Everything seems to be within spec except for two things:

"quantity adjustment piston displacement sensor" group. Under this group the voltage for the "piston sensor" should be 4.150 to 4.740 and it is reading 3.920.

The maf is reading much higher actual than specified. At idle specified is around 360 while actual is around 520 at 3000 rpm under load it gets closer but never matches.

the mod piston disp. reading was .740 volts and should have been 1.45 to 2.00 volts. after cleaning / inspecting the harnesses and cleaning the ECU grounds it went to 1.700 volts which is within spec. but did not fix the problem.

Anyone have any ideas on the quantity adjuster piston sensor voltage being low?

Does this car need a hammer adjustment?

Or (unlikely, but it's a good thing to check anyway) could the pressure relief piston have fallen out?

Ruled out the maf being bad, at 3000 rpm under load it was over 800 and 1000 on vag com. specified had a small flat spot up near 900 or so.

how do I check the pressure relief piston?

how do I clean the quantity adjuster?

In this picture:



you can see where the return line from the pump to the filter curves around to the bottom of the picture. Right at the apex of that curve you see a gold colored "nut" with orange paint on it. It is round with two flats on it. clean the area of dirt, then use a 10MM open end wrench to remove that fitting. It should come out as one piece. If it doesn't, just get a magnet and fish it all out of there. install the spring, then the plunger, then the retainer, putting the retainer flush with the end of the fitting.

If it is all together but the retainer isn't flush, tap it back in to flush and reinstall.

Removed the pressure relief piston fitting and it was all together.

The small clip in the end of it was sticking out half way so I pressed it in flush and reinstalled.

The car ran good with no CEL for about 2 miles and then the light came back on.

That is the longest it has stayed off in a long time.

I adjusted my injection quantity up from 3.0 to about 5.2 and then tried it then all the way down to 2.4. None of these settings helped at all with the CEL.

I have never seen black smoke coming out of my tailpipe in the 6 months I have owned the car.

Any ideas on what to try next?

Everytime I remove the pressure relief piston and put it back in I get about 2 to 3 minutes of running with no check engine light.

I can adjust the injection quantity with vagcam from around 6 down to about 2.8. I have also tried the hammer mod and tried settings from 15 down to 1.8 and none of them has helped with the check engine light.

With the IQ set at 1.8 to 2.2 it has a much quicker throttle response and revs up twice as fast as the standard setting. but still throws a CEL. At this setting with the transmission in park I dont see any black smoke when I rev it all the way to redline which confuses me.

I can not clear the code without it coming right back most times, even with the engine turned off.

If the engine was turned off but the ignition is turned to the on position how would the computer know if it had reached its injection quantity upper limit. If i erase it with the engine not running it still reappears almost instantly.

I am starting to think ECU or quantity adjuster. I have tried looking it up here but did not find anything that was of any help. Can anyone tell me how to replace or inspect and clean the quantity adjuster?

The fuel filter only has 3k miles on it but I am going to replace it tomorrow and see what it does. The pickup screen in the tank could also be an area to inspect but I have a full tank and I was told not to mess with it until the tank was closer to empty.

kbrenny said:

After looking at the numbers a little closer the specified maf reading was around 300 at idle and reading around 500 actual.

I bought the car with a bad transmission, used, and have never driven a "top notch" TDI yet so I have nothing to compare to.

I unplugged the maf and it does not run any different than with it plugged in. If the MAF is bad and telling the ECU that there is a larger quantity of air entering the engine would the ECU try to compensate by adding more fuel? If this is the case could it be the reason the injector pump is reaching its upper limit at idle?

If the MAF on my car was good, how noticable would the difference be when I unplugged it?

The MAF could have been bad since I bought the car and I would not know the difference.

Click to expand...

Those MAF numbers are exactly what you might expect if your EGR valve was not opening. If you want a safe and easy way to reduce the MAF numbers try my MAF Twist mod (link below).

As far as weather your MAF is good I would say definelty yes it is from your numbers at WOT. There is only a difference in the upper end when unplugged since when unplugged the ECU will insert a constant value of "550". The car should feel kindof limp after 2500 rpm like you've reached some kind of power limit with the MAF unplugged.
I have never touched the pump side of things... they scare me , hopefully someone here can help.

If this would have any effect on the problem I am having, I have an egr block off plate and no cat in the exhaust system.

I am having trouble understanding this problem. If my computer is telling me that the injection pump has reached it's highest limit and can not deliver more fuel (IQ set at 3 to 4) then why would it have better power when the IQ is set at 2 meaning more fuel(correct?).

It may be a bad connection in the closed loop circuit of the quantity adjuster.

I am guessing that the quantity adjuster is inside the IP. How do I get to it to inspect it and would cleaning it possibly help?

I checked the fuel line going to the IP last night with my mighty vac. I dont see any fuel until I get a vaccum past 7" hg. Above 7" vaccum it will pull fuel but once it drops to 7" or lower no more fuel and it will hold at 7".

Should this be of any concern?

Checked the strainer in the fuel tank today and it was clean.

Replaced fuel filter and it made no difference with the problem.

whitedog, where is the "closed loop circuit of the quantity adjuster" and can it be inspected and/or repaired?

I will be at the TDI GTG in Ft. Worth tomorrow and hope someone there can shed some light on my problem.

Got in the car this morning, idles rough for about 30 seconds, then the check engine light came on. I cleared the check engine light and drove 50 miles to the TDI GTG in Ft Worth at 80 mph the whole way (no CEL). Drove back 50 miles at 80 mph the whole way with no check engine light the whole trip. Got home pulled into the garage and turned the car off. Decided to start it again , just to see, and as soon as I did the check engine light came on. Maybee my car just hates my garage?

In vag com under measuring blocks is the injection quantity number directly related to the amount of fuel? IE: the higher the number the more fuel?, or is it the opposite?

There is not any noticeable difference if I run the IQ at 2.0 or 12.8. the car seems to run almost exactly the same.

I met up with Alphasenoir today and he swapped my quantity adjuster and housing for a used one that was known to be good.

It fixed the problem 100%, The car idles smoother than it ever has, has more power and smoother more uniform acceleration.

One sign that I did not pay any attention to, because this is my first TDI and I did not know it was unusual, was the irratic IQ readings.

My IQ readings would jump around alot and not in sequence but at random. For example: at idle reading would go like 1.8, 4.0, 2.1, 3.0, 4.0.

Never more than a 2.5 rang but very unstable. The new QA reads very steady at 3.0 to 3.2.