Hi,

Think i may have an injector either leaking or on its way out, as car has developed a slight "lumpyness" when accelerating, not throwing up any error codes. Before spending money at local diesel specilaist. Would like to check out with VCDS.

Now I know that I'll need to go into "Engine", and choose "Advanced Measuring Blocks", as the protocol is UDS, there are loads of options all begining "IDE00xxxxx".

Which of these options are required to check the Fuel rail pressure, and the Injectors.

Have read a couple of articles, where to check the fuel rail pressure, you need to get the engine temperature to >80c, turn off  the engine. Then via VCDS you can see if the pressure in the fuel rail increase over a number of minutes due to the residue heat in the engine heating the fuel in the fuel rail, if it doesn't increase it points to a "leak" . What I've read doesn't say wether this test applies to deisel or petrol?

So question is what UDS "IDE options" to use, and does the pressure increase in a diesel fuel rail increase once the engine is turned off due to residual heating from the engine?

I'm sure others will find the answer of great interest.

Thanks in advance

I know this isn't the answer you want! But I'm not sure if you did or could use VCDS to measure each injectors performance you'd get a definitive answer?

 

1st thing I would be inclined to do is to remove the throttle body and check it's clean as it's a cause of lumpy tick over on these engines. 

 

I bought my 180,000 high mileage 170bhp MK2 Superb with a declared engine fault. The tick over was quite lumpy. Though it was a couple of weeks before it started going into limp mode and throwing up warning lights. VCDS gave error codes P0121 Throttle Position Sensor and P1065 Regulation Discrepancy which was low pressure in the fuel rail. There were no injector related error codes. I came to the conclusion there were 3 likely possible reasons for the low fuel pressure.

 

1) The Fuel Pressure Regulator. This is quick and easy to access so I bought a cheap pattern one off Ebay for £18 though it didn't resolve the issue.

2) The fuel pump. The bearings in the pump can break up and then deposit metal filings through out the fuel system. You can check in the top of the pump by removing the FPR. Also check inside the fuel filter for metal fillings

3) Injectors these commonly fail on these engines and are expensive! 

 

On speaking to my local diesel specialist they said that the only way to check ( though they would wouldn't they! ) for the cause of low fuel pressure would be to remove and test the injectors and high pressure fuel pump off the vehicle. They suggested it would be easier to remove and test the injectors to start with. It cost me £25 + VAT to test each injector to be told they were all knackered! They were all leaking back far beyond permissible limits causing the fuel rail pressure to drop.

 

can

 

Re-manufactured injectors cost me £840 and that resolved the low fuel rail pressure. I suspect the injectors had been changed before because the injector seats had chatter marks indicating that seats had previously be re-cut.

 

The car then no longer went into limp mode and the engine management light wasn't coming on but the tick over was still lumpy and I still had the error code P0121 Throttle Position Sensor. On removing the throttle body I found it was filthy, apparently it's a common issue and cause of P0121 by not letting the throttle flap close. I cleaned the throttle body and refitted it and the lumpy tick over still remained for a few days. I've since read that the throttle body will try and self learn and calibrate if it's usual operating parameters change. What I should have done was use VCDS to restore the factory settings for the throttle body. So the lumpy tick over took a few days to go while the throttle body re-calibrated itself.

 

 

 

 

 

 

I have had a sort of vibration during acceleration, don't know if that is the same sort of thing as lumpiness.

 

It wasn't always there but could be felt throughout the car intermittently.

 

I had the bottom dogbone engine mount changed.

 

The rubber bush had deteriated ( car has covered  just over 200k miles so not surprising ) which allowed the engine to shunt back & forth too much.

 

Only £16 for a new one & solved the problem.