Could it be electrical? Perhaps the fuel pressure sensor, its wiring, has an intermittent open condition. At 70, the car would see more vibrations and that could wiggle a bad wire to drop signal.

What does VCDS say about the injector flow?

 

Injector flow, if you mean standard deviations and such, no more than 1.5 difference among all 4. In fact, very close. Not getting fault codes for intermittent conditions for fuel pressure sensor

 

Upon further research, and given all material componenets have been replaced: there is the possibiloty of a worn out camshaft??? my understanding there are componenents (lobes) that play a part on fuel injectors' firing as they should?? Any comments?

 

The camshaft does have lobes for the injectors on early TDI.

 

You can you elaborate or point me to a resource that explains a bit further as far as the relationship between lobes and injectors. I have been able to find info about this relationship on Pump Duse systems, I believe there is a auxiliary pump involved , but nothing on this system, 2.0 TDI Passat B7 generation, CKRA engine model. The hpfp pump is driven by timing belt. The hpfp has its own lobe internally and it's up and down movement pushes on a spring causing pump action. Most importantly it has a fuel rail which supplies fuel to each injector. Injectors are the solenoid type. Not sure how all these involves injectors and cam lobes. Thanks

 

2.0L TDI w/ HPFP systems (aka common rail) don’t have injector lobes on camshaft.
The earlier 1.9L TDI does have lobes on the camshaft.

 

Yes, thank you. So just wanted to make sure there is no possibility that worn out cam lobe was being cause of low fuel pressure. Only thing left to replace is the ECU. But before that I would like to check the fuel supply line from tank (pump) to filter. Maybe a very tiny hole there , so small that there is no visible leak but at higher load losing pressure. There is a diesel odor inside car so thinking there must be a leak somewhere unless the smell is from previous smell left behind during intank pump replacement maybe little diesel spillage though was very careful. Are these hoses, supply and return, replaceable and how would one get access to it? They get lost along the subframe and under cover

 

Would lose stretch bolts cause low fuel pressure? Can pressure escape out the combustion chamber, I guess is what i'm asking? The bolts I'm referring to are the stretch bolts holding down the injector brackets, which are holding the injectors down. I noticed those brackets come loose. More recently, i torqued them down and seems the low fuel rail pressure code (P0087) has not reared its ugly head.

 

Not sure how a stretch bolt would loosen? It’s a one time use bolt. Take it out? Throw it away, replace and torque to yield (TTY). Reading the rest of your post, you should replace those injector bracket stretch bolts. They should not loosen over time, period.

Can pressure escape from the combustion chamber? Yes. A leak is possible. Blow-by oil is just that. Oil, blowing by/past the piston rings. Valves can also leak pressure along with injector seals and glow plugs…

Two tests are available for this.
A compression test.
This test the total pressure a cylinder can make, dry and wet. A dry test, followed by a wet test (adding a tablespoon of engine oil to the cylinder) can determine if the cylinder walls are scored (deep scratch’s). The normal pressure would go up wet, because the oil is temporarily filling in the scores.
NOTE: a gasoline engine compression gauge won’t work on a diesel engine.

A leak down test.
This test uses two gages and shop air. Air is pushed into the cylinder to 100 PSI, depending on the gauge set. The other gauge is how much is “leaking down”. Normal test could yield an acceptable 100PSI into the cylinder and 85PSI leak down. 15% and less is leak down is considered acceptable.

 

I have replaced the bolts and TTY. I have not had the P0087 code return now for over a week. This is a bit bizarre. I struggled with this code for almost two years replacing pumps, injectors, etc. So, here is how the fix came about:

Mechanic did his diagnostics. He plugged scanner and decided there was something off on the fuel pressure regulator. The regulator is/was new. It came with brand new OEM entire fuel rail assembly. He installed one of the ones I had already tried, maybe even the original one. Test drove it. He said no more glow plug flashing, no more limp mode. I go pick it up.

Drove it home and I find glow plug cable to #4 cylinder was not plugged. Also noticed the injector's brackets are bouncing around. By this time there is good amount of oil around the valve cover rubbers where Injector's body go into the ports. I plug cable, I torque stretch bolts ( now replaced). I test drive it and limp mode again, low fuel pressure code P0087 again. It's the weekend so won't see mechanic for few days.

Meantime, i wipe all the oil and clean valve cover. I replace stretch bolts. Since then, no more oil
I decided to go to basic settings on VCDS and reset/relearn everything there is that I could, I think it included the throttle position sensor relearn among others.

Monday morning, memorial day, i go for test drive in the morning. I get up to 80 mph going uphill. Usually, car woould go into limp mode under this load. I keep driving putting it under more and more load. Eventually I get open highway up to 100 mph, up and down hills, and no glow plug flashing, no P0087. I don't reallly know what fixed it.

Could it be that indeed it was the fuel pressure regulator and the replacement was the fix. However, it took the car to be driven enough miles for computer to get used to the new regulator's adaptations? I don't know. Or could it be the regulator was previously installed incorrectly? Is there a specific was the regulator has to be oriented in order to function like it should? Coould the VCDS resets/relearn been the fix? Maybe a combination of these things?

Another theory is the strecth bolts were the culprit. The only thing with this is that when mechanic went to test drive it, those bolts were so loose that brackets were dancing around. If it was the loose bolts, I don't think he would have gotten very far before limp mode again. He said he went up a big hill at 80 mph.

This P0087 has been haunting many in the VW TDI community, including me of course. Hopefully this information is helpful. Though not quite clear yet as to what was the fix, all I know is that the P0087 is NO MORE!

 

Glad you got that cleared up!