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Over run fuel Cut diognostic help


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I see the drop but not 100% sure what it is. When driving with the air-conditioning on every so often I feel a very slight drop in power and rpm goes down just for a millisecond. As soon as I turn off the air conditioning it works fine. It's always done this since I had the Link G4 fitted.

Not sure this is the problem. How do I check map sensor?

On 2/25/2020 at 4:47 PM, remski2 said:

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

 

 

2020-02-25 11_46_21-.png

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

Is your electrical system OK ? 

2020-02-25 11_55_05-PCLink Engine Management.png

 

4 minutes ago, remski2 said:

did you look into what I said about MAP sensor ?

 

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53 minutes ago, remski2 said:

did you look into what I said about MAP sensor ?

There is nothing wrong with the MAP sensor, you need to look at the parameter “MAP”, not “AN 1 - MAP sensor V”, which is just the low res voltage.  The oscillation is due to the misfire.

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  • 1 month later...

Hi All

Still not got to see my tuner and now stuck at home with nothing to do, so trying again to fix the car.

Does anyone have any idea of how I can see the AFRs and fuels pressure on my log? I just found out the fuse had completley melted on my fuel pump relay, which is making me think my problem could be a fueling problem. I have put a new relay and fuse holder on to the 450lph hard wired walbro fuel pump, and it performs better but is still surging at higher boost. The pump is whinning (but don`t they all) a bit louder than usual since I rewired it.

 I have cured all boost leaks, changed coil packs, leads, and spark plugs. Before I order a new pump is there anything I can check on my log or activate and record a new log?  Just want to be sure before spending more money...

thanks again..

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  • 3 weeks later...

Replaced wide band lambda sensor today and recorded new log. Still getting a cut/ surge on high boost? I have attached my log file if anyone has a chance to take a look. It happens between 9.20 and 9.23. Im at 100% tps and flat out but it still cuts then comes surges back on again. Any ideas?  thanks again...

https://drive.google.com/file/d/12ES2ilp2vMEBpyVOwG07PZjBE8OVlpO4/view?usp=sharing

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If that Lambda sensor is telling the truth you would probably not expect the engine to still be in one piece. Is it wired and calibrated correctly?

What is the boost target? 300kpa? It hits 313 kpa a bit after 9.22 and cuts like an over boost protection or WG table may have been set up to do same.

If you post a calibration (tune) file there are plenty of people here that will have more chance of helping you

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I will say it again:

On 2/19/2020 at 7:57 PM, 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?

 

You could keep replacing parts until you die without finding the problem.  You need to get it to someone that has the tools and experience to diagnose in a structured way.  The fuel pressure would normally be one of the first things to check but it doesnt look like you have even done that yet.

 

3 hours ago, remski2 said:

Looking at the log you are at 29psi boost but AFRs are ~17. 

 

50 minutes ago, Rob W said:

If that Lambda sensor is telling the truth you would probably not expect the engine to still be in one piece. Is it wired and calibrated correctly?

Anytime there is a misfire a Lambda will show lean due to unburnt air going through the engine.  It is a Link CAN Lambda.

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13 minutes ago, Adamw said:

 

 

Anytime there is a misfire a Lambda will show lean due to unburnt air going through the engine.  It is a Link CAN Lambda.

Do you think it might be misfiring all the time Adam? Everytime the throttle is pressed it goes lean and ends up at 1.2Lambda at 300kpa before he has the cut.

And I agree, I'd be going to a specialist

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4 minutes ago, Rob W said:

Do you think it might be misfiring all the time Adam?

There is no way to know without being there yourself.  The original explanation of the problem was "What I'm getting is immediate loss of power when I put my foot down" so I get the feeling from that it is not just a problem at peak boost but all the way up.

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Appreciate the input and help! The car has been like this since Novemeber and when I called my tuner he got me booked in for Feb 2020. Then came covid 19.... I have spoken to him and he is hopeful for getting me in Septemeber 2020 now! I wont take it to anyone else as he bulit the car (taking it from 280bhp to just under 600bhp) and I trust him. Im a chef by trade and have no work for the forseeable future so am stuck at home working on a few projects, one of which is fixing my Evo!!  

Your right, I dont want to keep throwing money at new parts and not find the answers. After Adam mentioned the Lambda was broken and was not giving any reading I replaced it in the hope it may shed some light. Its a link Can Lambda and I could not get the same bosch sensor that came off (as it is discontinued), so I called bosch and they gave me the replacement part number which I ordered and fitted. I have not calibrated it as I beleived it was just plug and play, do I need to calibrate it? 

I am not a mechanic or tuner and this is first time I have ever even looked at an ECU log file. Never needed to before, but am learning as I go. From what you guys are saying I should give up and take it to  my tuner and tbh, I could not agree more and wish I could! ATM I have a load of free time, a garage full of tools and the ambition to learn and fix this myself . You are 100% right again, I have probably not done all the basics including a fuel pressure test. If that is the next step in diagnostic I will order a gauge and get it fitted...  Tell me what to do and ill try it, and if it turns out to be beyond my means then I will gracefully retire and wait till Septemeber.

Hell, Im happy to pay for this support if I can get to the bottom of the problem and fix it. One thing is for sure, the problem has got better since I have been tinkering about. As I said, I have replaced the plugs and gapped correctly, replaced coil packs, built a home made boost leak test kit (watching youtube) and found several boost leaks which I have fixed. One small leak on the throttle body still remains that I am waiting for a shaft seal to arrive to fix that.  I also found out I had a burnt out fuse/ relay to the hard wired fuel pump, I have also now fixed and replaced this.  The car is 100% running better now and even more so since fitting back the lambda sensor, but as you can see it still has a cut/ misfire problem (but not as bad). Low boost mode at 500bhp runs perfectly now, no cut at all. It is also cutting alot less than it was which shows I may be getting close to the issue.

I really dont think its a tuning problem, it has been running great for years and then one day this problem suddenly happened. A car does not just suddenly untune itself as far as I know, and I have not added any new parts, so I think something has just gone wrong. From what you guys are saying it appears to be running lean? This is progress and Im happy that a problem has now been highlighted. This gives me something to investigate and work with. Thanks again for taking a look and your input. Any and all ideas are welcome..  Perhhaps the throttle body boost leak seal will solve the problem when the part finally arrives lol, or may be Ill need a new fuel pump.  Either way im up for battling on a bit more, after all Novemeber is a long way away..

Thanks again..

 

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I would check the fuel pressure next, whether that be a cheap gauge on a piece of hose taped to the windscreen or a fuel press sensor connected to the ecu will be fine.  What you are looking for is the fuel pressure should increase 1:1 with boost pressure.  So, say you have 43psi fuel pressure at 0psi boost, you should see 53psi fuel pressure at 10psi boost and 63psi fuel pressure at 20psi boost.

Do that and report back.  Obviously you will have to see some boost to do this test but I would highly recommend you dont give the car a hard time until this is diagnosed.  If it doesnt increase 1:1 then there is a fuel supply problem and that could be a large range of causes which we'd then narrow down with further tests.

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Well.. one thing comes to mind if it was running correctly and seems lean besides the fuel is that you have a leak in your exhaust allowing air in and messing up your AFRs.

2nd thing I noticed is that your fuel table is stays flat during your run.

From 4900 to 6600 its pretty much flat at 51.5 - 52. 

I'd think it should increase as 4000 to 4700 there is a jump from 41 to 50.

 You injecting anything like meth ?

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7 minutes ago, remski2 said:

Well.. one thing comes to mind if it was running correctly and seems lean besides the fuel is that you have a leak in your exhaust allowing air in and messing up your AFRs.

2nd thing I noticed is that your fuel table is stays flat during your run.

From 4900 to 6600 its pretty much flat at 51.5 - 52. 

I'd think it should increase as 4000 to 4700 there is a jump from 41 to 50.

 You injecting anything like meth ?

I've just been under the car to do the lambda sensor and checked the full exhaust system which was all good with no leaks.  Not running any meth, just normal pump fuel. I have no idea about the fuel tables being flat, but am going to order a gauge and check the fuel pressure asap and report back.  Many thanks..

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