Really need help with troubleshooting: ECU adding fuel

If anyone is willing to help out with this I'd be super grateful... The car has been a bag of problems since day one and I thought I was getting close to having things sorted when, just before Christmas, my fuel trims all peg positive rather suddenly. I think to myself "Okay, vacuum leak, I got this". Hook up the pressure test rig, get my bottle of soapy water, and start spraying. A few hours later I've found and fixed a few small pinhole leaks that would have probly accumulated to a large one and pat myself on the back for fixing things. Reset the ECU and fire up the car. No dice; trims are still pegged.

Then I think back to when I did the fuel filter replacement. "Wasn't there only one o-ring on the connector for the fuel pump?". I contact Deatchworks and they confirm there should be two. Order the installation kit and put in the missing o-ring. Maybe it wasn't getting sufficient fuel pressure? Reset the ECU and get the same result.

Now I'm left wondering what could possibly be the issue... Boost leak test holds fine so it's got to be underfueling somehow, right?

The only only thing left that I can think of has to do with the way my fuel rail is arranged (which requires a little explanation). When I was building the motor I was able to convert to top-feed injectors by putting in a 2008 WRX fuel rail and TGV assembly. Doing this meant that I needed to remove the dampener and regulator assembly from the firewall so I had some fuel lines made and ran them from the firewall to the connectors on the intake plenum. Those lines rotted quickly so the company I purchased them from remade them with some kind of truck-grade, heavy duty, steel reinforced lines with the promise they'd never go bad. With the extra reinforcement came a clicking sound in the cabin: hydraulic hammering. To eBay I went a-shopping and found fuel line dampeners for a 2004 STi. Get them installed and the clicking is gone but I'm left wondering if the hammering somehow blew out the pressure regulator?

I'm stumped at this point and any sort of help would be hugely appreciated. I'm about ready to pay someone to figure this out but my local dealership is worthless with modified cars and there's not really anyone good local to me. Anyone have any thoughts?

The possibilities are endless...too much air, not enough fuel, timing, sensors...are you getting any CEL’s?

At idle and warmed for 10 min what are:

MAF?

Manifold vacuum?

Throttle position?

Equivalence ratio? Phi or lambda?

A/F sensor?

Fuel pressure?

Thanks for the reply aj_mariner

No trouble codes

MAF: 3.58-3.69 g/s

Manifold Vacuum: 21 inHg (boost gauge)

4.74-4.80 psi

Throttle Position: 2.4%

Equivalence Ratio: -not sure where to find this one-

A/F Sensor: 14.24-14.36 (Access Port)

14.6 (wideband gauge)

Fuel Pressure: 37 psi

A learned value snapshot from BtSsm or FreeSSM would be great. Otherwise, what are the fuel trims in the A-D ranges?

Is the 37 PSI fuel pressure with vacuum applied or no? What is the other reading?

Learning A-C are all +15, D is zero.

37 PSI with vacuum applied, ~45 with vacuum removed. Fuel pressure rises with boost pressure.

So your currently running a top feed conversion on a side feed car but still running the stock injector correct?

 

The scaling/latency is different for the side feed vs top feed setups in the stock ecu depending on the year so its possible that could be a cause. I have never tuned for that change with a stock sized injector on these cars as most times people are running an upgraded injector when they go topfeed so I have to rescale them anyway.

 

Just a thought if you cant find anything mechanically wrong otherwise.

 

Dave

Have you tried cleaning the maf sensor? What are the fuel trims while you're driving?

Hey cryo, thanks for the input but I'm running ID1000s. Btw, I'm your new customer from Oklahoma, just coming here for the opinions of the masses ;-)

 

08SpecB_DE,

I've not cleaned the MAF but I've swapped it with a spare I have and hitting changed. Fuel trims don't change when I'm driving.

ah ok!

 

well then we will/are already discussing the issue via email.

 

Thanks

 

Dave

Something I should probably add: the car is currently running hybrid speed density so the A-C learning ranges are very narrow. I don't think any of them are used above atmospheric pressure.

Okay, I've replaced all my crappy spaghetti vacuum lines with silicone jobs and tested my fuel pressure regulator. Fuel pressures look good and fuel trims still indicate there's a vacuum leak. WTF?!?

Do you have a vacuum leak tester? Like an OTC 5163? Also...what is the MAP sensor reading at idle? Not your separate boost gage.

I don't have a vacuum leak tester but I have a pressure tester of my own design:

 

Inserted images won't play nice...

 

Used like so:

 

Not sure why these linked images don't work

 

MAP sensor reads around 5.5 PSI at idle.

That should be fine...but just as a double check, does it read 14.7 with the engine off?

Just thinking out loud:

Your sensors seem fine and within a normal range...except the TPS. That is low compared to mine which is open 14.5-14.9% at idle. But at the same time your MAF is reading within range at idle...so possibly no issue with the Throttle position being that low. My LGT is stock. Have you sprayed carb cleaner around intake gaskets to look for engine surge? You will see Fuel trims dip if there is a leak around the throttle body seal, and TGV seals in and out.

A vacuum tester will show you if your engine has a mechanical issue. The gage needle should be solid, if it flutters then you have a mechanical issue.

Also: Possible fuel quality issue.

I had my wife watch the access port for changes in AF Correction 1 while I sprayed around with a can of carb cleaner. That number didn't change no matter where I sprayed. There's something wonky going on...

I've been through a couple tanks of gas now too so unless someone filled my tank with sugar I would expect that to have give away by now.

Test your vacuum with the homemade tester then and make sure the needle is solid. The bigger the gauge the better.

How can I be sure one of the pistons isn't in such a position that the intake and exhaust valves are open (thus letting air pressure into the exhaust)?

Vacuum tester gets hooked to a vacuum hose. Easiest place to connect would be off the bypass valve after the intercooler.

 

The video starts out very basic, but gets better.

I'll give it a try and report back.

Any news? I am still wondering if your MAP reads 14.7psi with the engine off.

Hey, sorry, I forgot to reply to that bit of info. MAP reads 14.3 PSI with the car off (which about matches up with the 600 feet above sea level where I live). I've also built a smoke tester over the weekend and tested the system under ~6 PSI of pressure. I can see a trail of vapor rising up between the intake plenum and the intercooler but can't find the source for the life of me. I'm taking it to a mechanic in another town over the weekend for him to find what's wrong with it. I think whatever is going on is either a leak at a gasket somewhere like the throttle body or something more serious... hoping for just a gasket leak... *crosses fingers*

10-4. Good to hear the smoke tester found a problem.