Okay it took a bit but I finally got a fuel pressure gauge . Found at idle I'm at 2.5 bar , and when driving with some throttle it will go up to about a little over 3 bar and does not fluctuate even when the engine is acting up . So I think my problem is not fuel .
Fuel Pressure: Pressure, Vacuum and Temperature Specifications
Specification: Approx. 2.5 bar
With Hose to Regulator Connected
approx. 2.5 bar
With Hose to Regulator Disconnected
approx. 3.0 bar
After 10 minutes there must be a residual pressure of at least 2.0 bar
The factory VW testing procedures; go over more, then just the typical fuel pressure specs @ idle. We have seen, where the pressure at idle was fine BUT other tests, showed, the pump was failing and could NOT maintain adequate fuel pressure, volume, under load...... then, other tests failed! The classic one, that I have seen; is under load, the fuel volume couldn't be maintained and the check valve failing, so the residual pressure, would immediately go to ZERO, when the engine was turned off.
Here is the service manual; for the various testing procedures (pressure @ idle, removing the vac hose to fuel pressure regulator, fuel volume, isolating various parts of the fuel system, etc.).
There are quite a few pages; that go over, all the testing, the manual covers, so keep clicking "next" to see them all:
I got one off of Amazon , not sure of the make .
So the latest now , I had some coils left over from my GTI so I installed them to see what they would do . The car ran great for about 20 mins then really started to misfire . So I decided to get some new coils . Installed them and the car ran great for about 30 minutes . It's been acting up again but not to where it was before . I went out with my scan tool , and found I had multiple misfire codes and a lean code . Cleared codes and went for a test drive . Found the CEL lamp will intermittently flash but so far hasn't thrown a code . Also found my Long Term fuel trim is up to 24% , Short Term is around -3 to +2 . Can definitely feel some hesitation . Coolant temp won't go over 90°C . What is really throwing me for a loop is how it seems when I do something the car runs good for a bit then reverts back to running like crap .
Ross tech quote: “
In general, an out-of-spec value in the first field (Additive) indicates a vacuum leak since it is mostly present at idle, when vacuum is highest. An out-of-spec value in the second field (Multiplicative) indicates a fault at higher RPM, and may point to a faulty MAF.”
If you have done all the fuel pump test and feel it is ok; based upon the ross tech long term fuel trim info, the maf could be a issue?
I bought a new MAF sensor for the car (unfortunately not Bosch , can't afford it right now) . Installed it , cleared the codes and reset the fuel trims . And it barely ran . But as it got going and relearned fuel trims it got better . But it still did nothing for the issue . So I previously checked for vacuum leaks with some propane around the lines on a running engine but none found . This time I decided to smoke the system . And still no vacuum leaks present . I removed the fuel rail and cleaned them with a homemade system I made that I could control the injector to open and close while running a cleaner through it . The injectors were not that bad . So after running the car for a bit it seems like it's getting worse . The car runs fine on cold start up and for a little while until it fully reaches operating temps . Then when stopped at a light at idle it misfires and runs rough . Just off idle it smooths out but the runs bad if you accelerate a little bit harder . I scanned it again today and had the same misfire codes and the lean codes but also had a new code - P 1137 , rich code . At this point I'm now suspecting an O2 sensor . Checking the readings at idle the downstream is reading around .6-.7 volts , but I am not getting an upstream reading . My scan tool is a little older and doesn't have European on it so I am using the generic OBD2 function . If the car runs fine in open loop , but not in closed loop , it seems like I could have a bad sensor . I'm surprised it's not setting a code but I know it won't always . Let me know if this seems logical or am I missing something .
What brand maf and part number did you buy/install? Did you test the maf readings; before and after the install of the new one with live data? Solid testing and verified data results; are needed to evaluate whats going on and to do a proper, process of elimination.