Need some help diagnosing this. Fuel Cut?

[guybo]

After looking at the STFT, the fuel trims are going nuts- from near normal to very high to very low. It happens quickly and sporadically. In file 2016 12-10-37.csv the LTFT is 0, I assume you just disconnected the battery- that may be why the LTFT aren't whacko yet. In the other file the LTFT starts to go negative (it takes a few miles for the LTFT to settle in). But your STFT are all over the place- if you reset the ECU by disconnecting the battery, watch the STFT not the LTFT until you have 100 miles or so on the car. Judging from those fuel trims, it won't go 100 miles though.

http://www.easterncatalytic.com/educ...agnostic-tool/ some info on fuel trims. I would not try to drive this car, if it is running as lean as the fuel trims make it look, you are very close to granading that engine.

Check thoroughly for leaks in the PCV or vacuum lines. Also inspect your exhaust around the header. Make sure the basics are OK, check all the wiring for the turbo set up (like the MAP sensor and whatnot). I could see a severely cracked vacuum line causing this as the engine flexes and the crack in the line opens

FYI- you can open those log files with Google Docs (google drive)

[guybo]

https://drive.google.com/file/d/0B6p...ew?usp=sharing

https://drive.google.com/file/d/0B6p...ew?usp=sharing

these are publicly shared- his data logs in a spreadsheet

[humfrz]

Originally Posted by Ultramaroon

That's logged.

Oh, thanks, I reckon I should either learn to read the logs ...... or keep ma hands off the keyboard .......

This story is for @Cole ; brings to mind the time that a divorced neighbor lady, back in Connecticut (a very pretty/sexy lady), had an MGB that wouldn't rev over 2,000 rpms. Since I had an MG, she asked me if I would take a look at it.

Well, of course I took a look at it .......one never knows what kind of "compensation" might be in store for me, if I fixed it.

I noticed that very little exhaust was coming out the tail pipe (you see, young-ens, back then, we could tell a lot about how an engine was running by looking at and listening to, the exhaust coming out of the tail pipe).

When I disconnected the exhaust pipe from the exhaust manifold, the engine ran fine. The insides of the catalytic converter had all come unglued and was clogging up the exhaust system.

Damn, she was a good looken woman .....


humfrz

[guybo]

Do you have a separate AFR gauge? I'm looking at the AFR and it is scary high- actual AFR at 4030 RPM is at over 19, which is dangerously high. But if that primary o2 sensor is bad, that reading is false- that said, it's rare for an O2 sensor to go bad.

The question is, what's causing that AFR to be so crazy? That's certainly causing the fuel trims to be like they are.

[Spartarus]

Could only download that last log.

Something is up with the Direct injection in that log. Fortunately, the port duty cycle is 0 throughout, so I can look straight at the problem.

The thing that jumps right out at me is that Final injection time Literally drops to zero whe you hit your mysterious "Fuel Cut"

You said you were hitting a fuel cut, and that's exactly what's happening.

Fuel rail pressure takes an unexpected dip immediately before it happens, and is otherwise normal throughout the log.

Redo that log with fuel pressure target value logged.

[Kiske]

Originally Posted by guybo

Check thoroughly for leaks in the PCV or vacuum lines. Also inspect your exhaust around the header. Make sure the basics are OK, check all the wiring for the turbo set up (like the MAP sensor and whatnot). I could see a severely cracked vacuum line causing this as the engine flexes and the crack in the line opens

Correct. I did do a hard battery reset. I did a smoke test, and boost leak test of the intake and exhaust. I found a tiny pinhole around the MAF letting air get by and fixed that (new O-ring.) I also found a leak at the exhaust flange just in front of the B1S1 oxygen sensor. I was sure that, that was the cause of my fuel trim swinging. Got it all sealed up with a new gasket last night and retested. No improvement. I then swapped out the B1S1 oxygen (a/f sensor) with new oem replacement to eliminate a fouled sensor being the cause. Same with the MAF and MAP sensors. With no changes there I did a hard reset overnight thinking the car just might need to relearn fuel trims.

If the car was constantly leaning one way or the other I might have a clue which direction I need to take but, it swings depending on when and how much if has been ran. Tomorrow morning I will start it and the first 10-15min of driving will be great minus some whacked stft at idle. Because of this it's really frustrating me. If it was a constant failure I'd be able to pinpoint it much faster.


I'm using a P3 gauge which is using the ecu to read afr, same as the log files.

Originally Posted by Spartarus

Could only download that last log.

Something is up with the Direct injection in that log. Fortunately, the port duty cycle is 0 throughout, so I can look straight at the problem.

The thing that jumps right out at me is that Final injection time Literally drops to zero when you hit your mysterious "Fuel Cut"

You said you were hitting a fuel cut, and that's exactly what's happening.

Fuel rail pressure takes an unexpected dip immediately before it happens, and is otherwise normal throughout the log.

Redo that log with fuel pressure target value logged.

Idling, then reved up and held at 2500ish, no fuel cut. Let it idle again and repeated. The second time I rev'ed it up I hit the fuel cut. When reducing the rpm afterwards it stalled. I logged the fpr target value.

http://s000.tinyupload.com/index.php...03595844939359

[guybo]

Originally Posted by Kiske

I'm using a P3 gauge which is using the ecu to read afr

So that means that you are using the car's O2 sensor for AFR readings?

[Kiske]

Originally Posted by guybo

So that means that you are using the car's O2 sensor for AFR readings?

Correct, it does has a seperate analog input for a proper wideband but, I haven't done it yet because I would need to remove and tap my exhaust for another bung. Eventually if the car gets back to running and after the holidays when money allows the exhaust is getting redone with a reccirculating setup. A proper wideband/failsafe will be installed.

[Spartarus]

Originally Posted by Kiske

I'm using a P3 gauge which is using the ecu to read afr.




Idling, then reved up and held at 2500ish, no fuel cut. Let it idle again and repeated. The second time I rev'ed it up I hit the fuel cut. When reducing the rpm afterwards it stalled. I logged the fpr target value.

http://s000.tinyupload.com/index.php...03595844939359

Thanks.

I attached the image where it happened, and highlighted the suspect line.

In both instances, you hit a complete DI fuel cut. The rev limit and the stall.

The log resolution isn't spectacular, but in those few frames you see a spike in fuel pump duty, a spike in commanded rail pressure, and a fuel cut. It looks like momentary fuel starvation, but I can only speculate as to why. In both instances, there is a spike in FPDC exactly 0.3 seconds before injection cut.

For some reason, the ECU sees fit to cut fuel completely, and there is a definite reason why.

Time to start troubleshooting, from tank to injector. The problem is in the fuel system, but I don't know if it's a physical or electrical problem from just the logs yet.

My initial suspicion is your Walbro in-tank pump is failing.

All the other parameters look fine.

God I hate direct injection.

Just kidding... Look at that Manifold pressure... Something very wrong there.

[Kiske]

Originally Posted by Spartarus

Thanks.

The log resolution isn't spectacular, but in those few frames you see a spike in fuel pump duty, a spike in commanded rail pressure, and a fuel cut. It looks like momentary fuel starvation, but I can only speculate as to why. In both instances, there is a spike in FPDC exactly 0.3 seconds before injection cut.

For some reason, the ECU sees fit to cut fuel completely, and there is a definite reason why.

Time to start troubleshooting, from tank to injector. The problem is in the fuel system, but I don't know if it's a physical or electrical problem from just the logs yet.

My initial suspicion is your Walbro in-tank pump is failing.

All the other parameters look fine. Every other logged parameter is nominal.

God I hate direct injection.

Since it's showing fuel rail pressure through out the cut, wouldn't that indicate the fuel pump is fine and the issue might be with the high pressure fuel pump? Just speculating. I can see the FPDC spike to 71% but, I don't really see the pressure spike until after the direct injection is getting cutoff.

[Ultramaroon]

Originally Posted by Kiske

Since it's showing fuel rail pressure through out the cut, wouldn't that indicate the fuel pump is fine and the issue might be with the high pressure fuel pump? Just speculating. I can see the FPDC spike to 71% but, I don't really see the pressure spike until after the direct injection is getting cutoff.

HP fuel rail pressure is regulated. That last log was good. Take another like that but like @Spartarus said, log target rail pressure. Also, try climbing up on the throttle more gradually.

If rail pressure follows target pressure we can eliminate the regulator and your supply pressure as the cause.

We would then have to look elsewhere.

As a side note, Techstream has a diagnostic mode to vary rail pressure manually. Pretty slick.

edit: NVM. I'm waaay behind you guys. Thanks, Spartarus.

[Spartarus]

Originally Posted by Kiske

Since it's showing fuel rail pressure through out the cut, wouldn't that indicate the fuel pump is fine and the issue might be with the high pressure fuel pump? Just speculating. I can see the FPDC spike to 71% but, I don't really see the pressure spike until after the direct injection is getting cutoff.

Problem is, throughout the log, rail pressure and commanded pressure are always close and following.

My suspicion with the CP and FPDC jumping at the same time was that the HPFP suddenly lost supply pressure, pointing to the in-tank pump cutting out.

Forgot to clarify, that's HP rail pressure. The LP rail doesnt have a sensor.

[guybo]

Originally Posted by Kiske

Correct. I did do a hard battery reset. I did a smoke test, and boost leak test of the intake and exhaust. I found a tiny pinhole around the MAF letting air get by and fixed that (new O-ring.) I also found a leak at the exhaust flange just in front of the B1S1 oxygen sensor. I was sure that, that was the cause of my fuel trim swinging. Got it all sealed up with a new gasket last night and retested. No improvement. I then swapped out the B1S1 oxygen (a/f sensor) with new oem replacement to eliminate a fouled sensor being the cause. Same with the MAF and MAP sensors. With no changes there I did a hard reset overnight thinking the car just might need to relearn fuel trims.

If the car was constantly leaning one way or the other I might have a clue which direction I need to take but, it swings depending on when and how much if has been ran. Tomorrow morning I will start it and the first 10-15min of driving will be great minus some whacked stft at idle. Because of this it's really frustrating me. If it was a constant failure I'd be able to pinpoint it much faster.


I'm using a P3 gauge which is using the ecu to read afr, same as the log files.




Idling, then reved up and held at 2500ish, no fuel cut. Let it idle again and repeated. The second time I rev'ed it up I hit the fuel cut. When reducing the rpm afterwards it stalled. I logged the fpr target value.

http://s000.tinyupload.com/index.php...03595844939359

the problem with changing out components is that you are going to run up a big bill fast and it's really only random chance that you'll find the issue. It's not uncommon to replace a good working component with a component that is bad out of the box then you've compounded the issue. If you don't have the equipment to test the components that you are replacing you're really just costing yourself more money IMHO. You'll run out of money before you run out of parts.

Put the old components back on. Bring the car to a garage you trust and you'll save money.

[Ultramaroon]

Originally Posted by Spartarus

Problem is, throughout the log, rail pressure and commanded pressure are always close and following.

My suspicion with the CP and FPDC jumping at the same time was that the HPFP suddenly lost supply pressure, pointing to the in-tank pump cutting out.

Forgot to clarify, that's HP rail pressure. The LP rail doesnt have a sensor.

Here. I uploaded his log to datazap.

http://datazap.me/u/ultramaroon/log-...g=0&data=15-40