Extreme Negative Fuel Trims -35% to -40% both banks when extended hot IDLE

[Fu Manchu]

Nope. They don’t have the skills.

 

[duca1991]

@duca1991, late to the party but I’ll comment anyway

I’m always annoyed when hearing that expensive parts are changed by some mechanics using a parts canon mentality rather than actually confirming the parts themselves are defective. Seems much easier and more profitable for them to spend large chunks of their clients money only for the problem to remain (where sadly many clients simply continue to hand over more cash)

Annoyingly in this case, for the lack of correct diagnosis, there would have been cost effective petrol direct injection test services available that would have confirmed the old injectors were actually ok and minimised the need to spend larger sums on new injectors.

Regardless of what the fault is, when getting a $1000 parts estimate as an owner, I’d be asking why multiple parts would suddenly fail at the same time? Could there be some other part that‘s common to both banks of the engine that could causes the fuel trim? Could there could be a fuel contamination issue in which case other parts of the fuel system could be impacted? Are there any service bulletins that are relevant to such fault condition? etc, etc? I’d want intelligent answers back (but I’ve witnessed mechanics telling convincing lies just to make $$ and avoid warranty) so it’s a really difficult situation for many who know nothing about mechanical and/or electronic things.

Sadly in this case it seems that mechanic isn’t exhibiting top skills within his field and in future I’d be looking elsewhere for service.

But we are where we are and as already suggested by others, I’d pop the left rocker cover off ASAP and if it’s obvious fuel has washed that area clean, you know what the problem is… then just replace the high pressure injector and change the oil… Better to be sitting down when you find the price of a high pressure fuel pump for the LFX as it’s around the $500-$600 mark (I’d use genuine over after market ones even if more costly)…

This is what the high pressure fuel pump looks like..

View attachment 257017

Don’t delay resolving this issue as fuel in oil can destroy engines. Hopefully there hasn’t been too much damage already done to your engine from the fuel in your oil

Really, I always want my old removed components given to me in a box when getting mechanical work done… Why, because if the fault isn’t fixed I’ve got known good parts that have some value and it’s often easier to sell those old parts than go through the process of ACL statutory warranty claim and fighting for a refund (through VCAT where OP lives)

Such is car ownership

PS: Diagnose Dan is a great resource that in many cases highlights the importance of taking what some professionals say with a grain of salt before handing over good money.

The following example is when both a dealer and independent mechanic can’t resolve the cause of a no start which is faulty cam timing that impacting high pressure fuel injection. This isn’t related to your issue other than clueless mechanics being involved but it’s an interesting watch anyway. (in this example Id expect the engine is junked because interference fit engine and all that entails).

Wow! thanks for your reply and the big write up.
much apreciated.
Im getting the car dropped off to a electrical/mechanic with a dyno and his going to try and diagnose it.
I'll keep you updated about the finds!

 

[07GTS]

reminds me of the time my local mechanic said that an apprentice at the local holden dealer couldnt diagnose his engine issue (VS V8) so he took the vehicle to him to find the fault, turned out to be dizzy issue guess the scan tool cant tell them everything

 

[uglyoldfatbastard]

reminds me of the time my local mechanic said that an apprentice at the local holden dealer couldnt diagnose his engine issue (VS V8) so he took the vehicle to him to find the fault, turned out to be dizzy issue guess the scan tool cant tell them everything

That is because it is just a tool (the scan tool) it does not make you a mechanic just like owning $10k worth of tools does not make anyone a mechanic.

 

[duca1991]

Update:
First mechanic gave up, didnt understand the issue and moved me on (didnt charge me after feeling confident he could fix it), spoke to another mechanic he recommened me too and his ghosting me after i explained the issue.
Looks like im on my own or someone can recommend me a mechanic somewhere in Melbourne.

Luckily i bought a new car to use.

After thinking and talking to friends and mechanics over the phone.
Its believed the High pressure fuel pump is not leaking internally and the smell of fuel in the oil was caused by a leaking injector or short drives.
Changed all the injectors with new genuines.

Fuel smell hasnt come back to the oil and Whilst using my Scan Tool, i can see PSI being build up between the HPFP and the injectors when the car is OFF (fuel vapours expanding), so injectors are not leaking.

Changed MAF 2 times,, changed all PVC, hoses, spark plugs are brand new, checked intake manifold for leaks, Rich Issue still there.
1 thing i have no changed is the Coils, but i put a multimeter on them to check all there resistance and they all seem to match.
Not sure if this is a good indication of them being ok, maybe under load they act differently? not sure.
But i can get a set of Mace Coils for $200, might be worth doing to see what happens.

Now, i have messed with exhaust and changed the upstream o2's and the issue is still there but now the car acts different.
to get the o2 sensors out i had to remove the exhaust headers from the engine and remove o2 sensors from outside the car.

Iv done that job on both sides, reinstalled the headers, RESET the ECU to have everything learn agian and now the long fuel trims even worse bank to bank and car acts even more strange.
Within the ECU Reset and the car just idling for 20 minutes bank 1 is showing -22 long term, bank 2 is like -12, but the Short terms at idle are flucuating between -1 and +1 so i have no idea why the long terms are so out of wack when the short terms never went that negative?

I then thought maybe it was to do with an exhaust leak somewhere? since i removed it and put it back and the issue acted different.
I released the bolts slightly on the flange that goes to the Catalyctic converter and the Fuel trims pegged positive, so my idea about a leak causing the car to run rich went out the window.

So im back to square 1. Whatever i did with o2's and removing exhaust headers changed the cars behaviour but i think i might of added another issue and the actual issue is still there somewhere else.

I just cannot believe such a rare issue is happening with it, 0 fault codes other than the car eventually throwing code bank 1 and 2 rich.

I thought maybe its the ECU, but iv'e been told its not ECU otherwise id be experiancing alot worse issues like electical fault codes, or computer not talking to other parts of the car which i have Zero issues with.

No idea where to go from here and Im losing hope, im already 2 grand into the car without any change.

 

[burnz]

check the temp sensor if faulty the engine is overheating, without the cooling fans..
the ECU will dump extra fuel as a coolant to protect the engine..

 

[lout]

where abouts in melbourne

 

[hjtrbo]

Next mechanic will replace the HP fuel pump. You've change everything else lol. Best of luck, can be so frustrating sometimes.

 

[bionz91]

came across the same issue with no luck

 

[WitiTune]

I have had similar issues on the direct injection 3.6 engines when the purge valve is faulty. Under load and rpm the fuel trims would be fine. When left idling for a long period the long term fuel trims would climb to 25%. The past vehicle actually started out with a misfire after filling the fuel tank.

Interestingtly the purge valve did not leak when smoke testing the intake, it would try and work and get stuck, i unplugged it with engine running and plugged it back in and it kicked into life and the fuel trims returned to normal. After a few drives the issue returned, fitted a new purge valve and no more issues.