VW Golf Mk4 16V 1.6 petrol AZD CFL and Engine light on

Hi everyone,

Car has been running very well for the last few months. Took it out on the usual drive to work on the motorway a few days ago and CFL and Engine light came on - car went into limp mode. When I pulled over into the hard shoulder, revs at idle were hunting around the 1000-1200 rpm mark.

Took key out of ignition, waited about 2 mins, put key back in and car restarted. CFL light out, Engine light remained. I drove on without car going into limp mode.

On the way home, after about 20 miles on the motorway, CFL light came on again. Engine light remained. Limp mode again. Restarted car - same thing as previous.

Scanned car when I got home:

Here are the recurring fault codes from my car.

• 17961 - Barometric / Manifold Pressure Signals

P1553 - 35-10 - Implausible Correlation – Intermittent

17912 - Intake Air System

• P1504 - 35-10 - Leak Detected – Intermittent

I have checked all air pipes doing the propane test and can’t find anything amiss apart from a slight crack on the oil breather pipe where it fits on to the crankcase. I really don’t think this would cause an air intake leak fault.

MAP sensor has been replaced with a new a few days ago, with a non-genuine one. I have put the old one back in (which never previously had a problem until I assumed it did when MAP code appeared) and the same faults occur. I don’t think fitting yet another MAP will solve anything.

I can clear the codes on VAGCOM and re-adapt throttle body and EGR. However, once I set off driving the next morning, they occur again after about 20 miles of motorway driving. Limp mode is activated and then EPC and Engine light appears on the dash. If I then pull over, turn car off and then re-start, EPC light goes out but Engine light remains. I can usually drive on for about another 20 miles or so and then the EPC light and Engine light comes on again.

I strongly suspect the throttle body is on the way out as the EGR valve is relatively new (about 9 months old) and no other faults are being detected. The throttle body would probably give rise to these errors if it wasn’t working correctly. Throttle body is suspected as being the original one so if that’s right – its done 194,000 miles. I expect the servos are dying in there by now!
I'm going to give it a clean - though to be honest, it isn't very dirty in there really.
MPG is pretty good on the car. I have measured it at pretty much 38-40mpg which is spot on for this car considering its age. No cylinder misfires are being detected on VAGCOM either so it doesn’t look like the engine is in bad shape.

I have noticed that since owning the car for just over a year, that sometimes there are some slight flat spots when accelerating at low revs. Sometimes when reversing at full lock, the car stalls. It seems like the throttle body is not responding correctly to the signals from the ECU to increase the revs when the power steering is engaged at full lock.

Coolant temp sensor is absolutely fine. Apart from the heater giving a low temperature (I'm flusing the core out this weekend), and the odd bit of minor rust, there is nothing else wrong with the car. It's very reliable considering how many miles it has done.

Any ideas? I'm thinking a new genuine throttle body might be in order if the clean cannot clear these codes - as I can't risk a used one considering how many miles this car does.


Cheers,


Luke

looking at your post, I would get a genuine Mass Air Flow meter and stick it in. New one maybe faulty

As for full lock on steering, just don't do it. Keep the steering wheel away from full lock and avoid the change of note in engine when doing it. It will damage your seals.

With mileage of car, are the vacuum pipes split due to the pipes going hard ?

Thanks for the advice re: steering - I will remember that in future. Since I posted, I did a complete throttle body clean on 15th Jan by removing it and thoroughly (and carefully!) cleaning butterfly valve and the inside of the body. I also renewed the vacuum hose which connects to where the MAP sensor is and something on the side of the engine block (not sure what it is exactly). I then used VCDS to clear learned values from throttle body several times. After this, I then re-adapted the throttle body. Car has been running perfectly since then with no return of limp mode or warning lights.

It appears that a dirty throttle body can certainly be a cause of several "false positive" fault codes. I'm now going to aim to routinely clean my throttle body about every 10,000 to 20,000 miles.

I might leave flushing the heater core out until this very cold weather has gone away. Messing about with water when its this cold is not my idea of fun!

One thing VCDS did find was an EGR error. I suspect this might be the non-genuine EGR valve failing after I fitted it about 30,000 miles ago. I have since bought a genuine one which I will be putting on the car tomorrow and also getting a refund on the duff one :-0)

Sometimes buying genuine makes sense - especially if your car does lots of miles per year.