Over run fuel Cut diognostic help

[Hotrock]

Hi

I have an evo 6 which has been running fine at 580bhp until recently I have started to experience boost cut/fuel cut. My tuner is very busy at the moment and so i have started to try and solve the problem myself. At first I found the tps sensor was faulty and had left errors on the ECU, so i changed it and recalibrated, but still getting boost cut although errors are gone. I then checked for boost leaks and found a few minor leaks around the BOV and one of the boost hoses. These are now fixed but I am still getting fuel cut.  I have a separate boost greddy b spec 2 boost controller and CAN lambda installed.

Is there any way to tell from the ecu what the problem is? I have recorded a log file while the fault occurs and it flashes on Limits flags word and over run fuel cut when the fault occurs. There are no ECU fault codes. Can any one help. Do I need to post my map or is the error log enough?

Thanks for anyone who has the time to help..

Log 2020-02-10 6;12;55 pm.llg

[Adamw]

I think you might be mixing up a couple of things.  Over-run fuel cut only occurs when you lift-off/coast with the throttle closed to save fuel.  This occurs regularly in your log but only with the throttle closed and will never never happen on boost.

This is not a boost cut or any other limiter action showing in your log.

What is the actual problem that you are experiencing?

[Hotrock]

2 hours ago, Adamw said:

I think you might be mixing up a couple of things.  Over-run fuel cut only occurs when you lift-off/coast with the throttle closed to save fuel.  This occurs regularly in your log but only with the throttle closed and will never never happen on boost.

This is not a boost cut or any other limiter action showing in your log.

What is the actual problem that you are experiencing?

Hi Adam,

What I'm getting is immediate loss of power when I put my foot down. The waste gate is opening early which cuts the boost and feels like I hit a wall. Trying to work out what is causing it and if the ECU has any data that could help diagnose it.

When I only put my put down half way the car boosts as normal, it's only on full full boost it sounds like the wastegate opening. Could be a faulty waste gate I guess. Just wondering if that would be confirmed in any way on the ECU? Thanks again...

 

 

[Hotrock]

Btw It's in the first minute of my log file, you will see fuel/ boost cut 3 times. My foot is to the floor but the car goes no where....

 

[Adamw]

There is no boost cut in your log.  There is only one area in the first 1 minute when you have 100% throttle (for only 0.5seconds), in that area it reaches 5700RPM and 28psi boost so it appears to be doing everything it should be.  

Are you sure you are looking at the same log file?

[Hotrock]

1 hour ago, Adamw said:

There is no boost cut in your log.  There is only one area in the first 1 minute when you have 100% throttle (for only 0.5seconds), in that area it reaches 5700RPM and 28psi boost so it appears to be doing everything it should be.  

Are you sure you are looking at the same log file?

Hi Adam,

Thanks for looking, as you can probably tell a complete beginner at this. One thing is for sure, the car definitely cuts boost or fuel on its own and this definitely occurs at just before 30 seconds, then again just after 30 seconds, and then lastly at just before 40 seconds. It can be seen as a drop in rpm on the engine speed navigator window, and also as described above.

I'm sure I uploaded the correct log, should be just over 3 mins long.

That's all I know. If it's not the ECU that is cutting boost, I guess it must be a faulty part such as waste gate or boost controller?

Thanks again for your help..

[Adamw]

Sorry Im not seeing it.  Below is the first 40 odd seconds, RPM green, Throttle dark blue.  Your RPM seems to follow exactly what your foot is doing, the only time RPM drops is when your throttle is closed.

If you feels like you have a cut then it sounds more like a misfire issue as I dont see any cuts at all in this log.

[cj]

Do you mean this bit here just after you get back on the accelerator? Can you describe a bit more what you were doing when this problem happened so we have something to correlate with the log file. Eg was it just before or just after you changed gear? was it immediately after you pressed the gas pedal or was it a a few seconds later? 

Did you have your foot hard to the floor when this problem happened or only 1/3 ish. 

 

[Babych44]

Your clutch is slipping? I had this in Impreza, first it did it only when boost was kicking in

[Hotrock]

Hi CJ,

Thanks for looking. So what's happening is the wastegate sounds like it is opening early and the car looses power immediately. When this happens my reaction is to take my foot off the throttle as it feels like something has gone wrong with the engine. The boost will come back on almost immediately and the car will start to pull again until again it reaches a certain level of boost and then the same will happen.  To make this happen I have to put my foot too the floor or 3/4 way down and it happen a second or so later.

On the bit you highlighted it has already occured just before.

In the graph above the boost cut is felt at 27, 32, and 38 seconds approx ( at the peak on the green rpm graph). I did it three times on purpose to record a log. As soon as it happens I probable also released the throttle. If I keep my foot to the floor the boost would surge off and on violently and does not feel good for the engine and this is not shown on the log.

I have a separate boost controller with solenoid, I'm now wondering if that could be the problem or a worn waste gate?

Thanks again

 

 

 

On 2/11/2020 at 7:28 PM, Adamw said:

There is no boost cut in your log.  There is only one area in the first 1 minute when you have 100% throttle (for only 0.5seconds), in that area it reaches 5700RPM and 28psi boost so it appears to be doing everything it should be.  

Are you sure you are looking at the same log file?

 

5 hours ago, cj said:

Do you mean this bit here just after you get back on the accelerator? Can you describe a bit more what you were doing when this problem happened so we have something to correlate with the log file. Eg was it just before or just after you changed gear? was it immediately after you pressed the gas pedal or was it a a few seconds later? 

Did you have your foot hard to the floor when this problem happened or only 1/3 ish. 

 

 

Thanks, it's not the clutch. Just had it replaced and know exactly what you mean by slipping clutch. It has a brand new twin plate in it. You can here the waste gate chatter and the boost cut when it happens...

The same happens when it hits the map limit set at 8000rpm, it just cuts to prevent damage.

[cj]

So at 27 seconds and at 38 seconds you are only at about 40% throttle. Does that line up? You mention replacing the TPS, and we do see some points of 100% TPS in your log, but its worth asking. If you were foot on the floor, the ECU isnt seeing that.

What does the config on your boost controller look like? Does it have any logs? The only point in the log where there *might* be signs of power loss before you get off the gas pedal is at about 31.5 seconds. I say might, because boost drops off at the same data point where the TPS drops from 100% to 99%. Normally this would just be noise and suggest boost dropped before the throttle, but you go right to 0% tps after this, and its only recording every 0.1 ish of a second so we cant see which came first very definitively.

[Hotrock]

Hi CJ

I will run the test again tomorrow and post up the log. This time I will hold my foot flat to the floor for 5 seconds and then release. I'm sure that will then show the power loss I am experiencing with the throttle at 100% TPS.

Unfortunately the boost controller is a greddy bspec 2 and does not record logs.

Thanks for your help..

2 hours ago, cj said:

So at 27 seconds and at 38 seconds you are only at about 40% throttle. Does that line up? You mention replacing the TPS, and we do see some points of 100% TPS in your log, but its worth asking. If you were foot on the floor, the ECU isnt seeing that.

What does the config on your boost controller look like? Does it have any logs? The only point in the log where there *might* be signs of power loss before you get off the gas pedal is at about 31.5 seconds. I say might, because boost drops off at the same data point where the TPS drops from 100% to 99%. Normally this would just be noise and suggest boost dropped before the throttle, but you go right to 0% tps after this, and its only recording every 0.1 ish of a second so we cant see which came first very definitively.

2/13/2020 at 3:42 PM, Babych44 said:

 

 

[Hotrock]

On 2/14/2020 at 9:42 PM, cj said:

So at 27 seconds and at 38 seconds you are only at about 40% throttle. Does that line up? You mention replacing the TPS, and we do see some points of 100% TPS in your log, but its worth asking. If you were foot on the floor, the ECU isnt seeing that.

What does the config on your boost controller look like? Does it have any logs? The only point in the log where there *might* be signs of power loss before you get off the gas pedal is at about 31.5 seconds. I say might, because boost drops off at the same data point where the TPS drops from 100% to 99%. Normally this would just be noise and suggest boost dropped before the throttle, but you go right to 0% tps after this, and its only recording every 0.1 ish of a second so we cant see which came first very definitively.

Hi CJ

Here is a new log. Put my foot full to the floor for about 2 seconds, really worried about damaging the turbo or engine. This time it still does not boost properly, just seems to surge a bit. I also have the video from inside the car so I will post this up as well. The main event happens at between 3.40 and 3.50. Can you tell anything from the log?

Thanks again.

Log 2020-02-18 10;40;32 pm.llg

[Hotrock]

Here is the video of the same log.

[Monsterbishi]

Looks like it's blowing out the candles, as it were - what happens when you dial the boost down?

[Adamw]

What you have is a misfire.  I dont see any clues in the log that the ECU is causing it. 

You are probably going to have to visit a tuner for some diagnosis, Your lambda is not working so there are not many clues for us to help from.  It could be fuel related or ignition related but that covers a huge range of possibilities, so you really need someone with some experience and test gear to eliminate some of these possibilities and narrow it down.

Have you done the basics such as pulled the plugs out to check all electrodes are still there?  Fuel pressure?  Reduce plug gap?

[Hotrock]

5 hours ago, Monsterbishi said:

Looks like it's blowing out the candles, as it were - what happens when you dial the boost down?

It runs fine if I put the boost on low! I have new plugs but not coil packs. One other thing I have just noticed is it does not fire on all cylinders when I first start the engine, but a minute later its working fine. This has only happened twice so far.

Thanks for your help..

3 hours ago, Adamw said:

What you have is a misfire.  I dont see any clues in the log that the ECU is causing it. 

You are probably going to have to visit a tuner for some diagnosis, Your lambda is not working so there are not many clues for us to help from.  It could be fuel related or ignition related but that covers a huge range of possibilities, so you really need someone with some experience and test gear to eliminate some of these possibilities and narrow it down.

Have you done the basics such as pulled the plugs out to check all electrodes are still there?  Fuel pressure?  Reduce plug gap?

I changed the plugs recently, but not pulled them to check, will do today. I do not know how to measure fuel pressure, never done this before. I will certainly check the gapping on the plugs though and thinking of getting some new coil packs?

Thanks

Rob

[Monsterbishi]

I'd look at the plug gap first, what did you gap them to when you installed them?

There are a lot of parts manuals out there that wrongly specify a plug that has a 1.1mm/0.043" gap - it should be between 0.7mm/0.028" to 0.8mm/0.032"

We used to run 29psi through our 4g63 powered Mirage with a 0.8mm gap.

[Hotrock]

2 hours ago, Monsterbishi said:

I'd look at the plug gap first, what did you gap them to when you installed them?

There are a lot of parts manuals out there that wrongly specify a plug that has a 1.1mm/0.043" gap - it should be between 0.7mm/0.028" to 0.8mm/0.032"

We used to run 29psi through our 4g63 powered Mirage with a 0.8mm gap.

New plugs put in gapped to. 0.5mm as specified by the tuner. Unfortunately still getting same problem. Car is running just under 600bhp when it works.

What to try next, could it be coil packs? Here's another video of the error. The boost controller is hard to read (bouncy recording) but it looks like it is not holding boost and jumping erraticly. Thanks for your help.

 

[Monsterbishi]

There's not much point in even looking at what your boost controller is showing until you sort out where the misfire is coming from, test all the ignition components and then work from there, have you determined whether it is one specific cylinder that is misfiring?

 

[Hotrock]

You sound very certain it's a misfire! So far I have replaced the spark plugs, tomorrow I need to buy new coil packs at a cost of £100. If it's not the coil packs or spark plugs what next?

24 minutes ago, Monsterbishi said:

There's not much point in even looking at what your boost controller is showing until you sort out where the misfire is coming from, test all the ignition components and then work from there, have you determined whether it is one specific cylinder that is misfiring?

 

 

[Monsterbishi]

The first order of business is to test the components you have, there's no point in getting out the Visa card until you know whether something actually needs replacing.

What is the Wideband/Lambda value doing immediately prior to when the issue presents itself?

[Hotrock]

6 minutes ago, Monsterbishi said:

The first order of business is to test the components you have, there's no point in getting out the Visa card until you know whether something actually needs replacing.

What is the Wideband/Lambda value doing immediately prior to when the issue presents itself?

Im not sure how to check that?  But looking to learn how to diagnose the fault. My tuner is busy until the end of April so I'm attempting to fix it myself. I have no previous experience with with looking at. ECU logs, which is why I posted up my log file here to see if anyone can help me read them. I just had Can lambda fitted last year, and car has been running very smooth until now. Can you take a look at my logs as I do not have a clue what I'm looking for?

Many thanks...

[remski2]

Your map voltage jumps in volts.. This being it only shows 1 digit instead of 3.

There is no 1.05 or 2.55.. its just either 1, 2, 3, 4 or 5

 

 

Next.. your voltage drops from 14 to 13v multiple times.. 

Is your electrical system OK ? 

[Hotrock]

Thanks for looking. I see what you are saying. As far as I know the electrical system works fine but I'm up for checking everything!

Recently I have replaced the coil packs and plugs ( just to be sure), and have taken apart the waste gate and rechecked for boost leaks, but all is ok.

I can hear something clicking on and off under the bonnet, I don't know what this is but comes from near the firewall and intake manifold, sounds electrical..

Could it be anything to do with a sensor?? Where should I begin to check now..

Running out of ideas. Car runs fine on low boost, it's only when pushed it gives problems (so on higher boost).

If it were electrical would this not happen all the time?

Thanks for your help...