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rb25det r33 unstable idle + hesitation + black smoke / error code 54


CUR33
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Hi everyone,

I've done some searching on the forum, however couldn't find something which exactly matches my issue or has solved it.

The issue is relating to unstable idle on start up where revs fluctuate and black smoke can be seen from the exhaust with a noticeable fuel smell.

After about a minute, the revs will start to stabilize but if gas pedal is pressed it worsens the rev fluctuation. soon after plugs become sooty.

Note: I've attached a video of what happens

 

Troubleshooting I've done so far:

  • CTS replaced, tested wiring (good ground and other wire giving 5volts)
  • adjusted timing to 15 degrees
  • checked for vacuum leaks around the intercooler pipping and engine bay > measured vacuum at -17hg
  • changed plugs
  • MAF sensor tested (signal wire showing voltage change, car stalls when unplugged)
  • coils tested (engine hesitates when each one unplugged, resistance testing consistent throughout the 6)
  • tested with o2 sensor plugged and unplugged

 

Car was running fine a week ago. in some cases if i unplug the battery and clean the plugs it runs smoother.

The car is running a stock ecu and at times throwing error code 54 on the dash which is A/T Control.

It has a manual transmission but i realized the ECU is for automatic (MEC R531 A1 4225)

Could this be possibly causing the issue?

As you can see I'm currently running out of ideas looking for some possible causes/solutions.

Thanks

Ray

 

 

 


 

 

 

 

 

 

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On 9/21/2021 at 4:27 PM, CUR33 said:

It has a manual transmission but i realized the ECU is for automatic (MEC R531 A1 4225)

Could this be possibly causing the issue?

No. It'll be fine. But you should set the timing to suit the ECU, which probably wants 20°, being an auto. Not a big issue, you're just running 5° retarded.

Check your fuel pressure.

 

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On 9/21/2021 at 6:21 PM, GTSBoy said:

No. It'll be fine. But you should set the timing to suit the ECU, which probably wants 20°, being an auto. Not a big issue, you're just running 5° retarded.

That's good to know, i did end up adjusting the timing to 20° to help with idling issues.

On 9/21/2021 at 6:21 PM, GTSBoy said:

Check your fuel pressure.

I currently don't have a fuel pressure gauge to check.

But i did check that the Fuel pump primes and the pressure build up in the lines can be heard just before the pump stops.

Also when i open the filler cap it makes a 'tisss' sound.

 

The issue is:

Black smoke from exhaust

hesitation/rev fluctuation

- spark = yes

- coils = good

- FPR = untested

- Injectors = untested

- fuel filter = good

I'm started to think the issue could be relating to the injectors or fuel regulator.

more testing tomorrow to try and identify the issue..

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On 9/23/2021 at 8:32 PM, GTSBoy said:

Check that it is not too high, not that it is too low. You will need to use a gauge.

I ended up testing with a gauge. On prime fuel pressure jumps to 50psi then back to 0.

See video.

i tested with another fuel rail and the same thing happens. The pressure doesn’t hold in the lines and dropped after fuel pump stops.

After changing the rail car is not starting, when cranking I noticed the cat overheat warning light comes on. Might need to check if the Cat is blocked.

So there are the issues:

- car no longer starting

- not holding fuel pressure on prime

- cat overheat warning light (might be blocked)

274D03EB-F396-4E5E-94CC-ED6C8C4ED99E.png

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On 9/25/2021 at 10:21 AM, CUR33 said:

On prime fuel pressure jumps to 50psi

Maybe a little too high.

On 9/25/2021 at 10:21 AM, CUR33 said:

then back to 0

How fast?

On 9/25/2021 at 10:21 AM, CUR33 said:

After changing the rail car is not starting

What do you mean, "changing the rail?"

On 9/25/2021 at 10:21 AM, CUR33 said:

I noticed the cat overheat warning light comes on

Also used as CEL. Now you have a code to investigate.

On 9/25/2021 at 10:21 AM, CUR33 said:

(might be blocked)

Yeah, nah.

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On 9/25/2021 at 11:14 AM, GTSBoy said:

How fast?

Straight away (as per video)

On 9/25/2021 at 11:14 AM, GTSBoy said:

What do you mean, "changing the rail?"

i replaced the rail with another one, complete with injectors and FPR. After installing, car won’t start.

C6F1E0C0-A73E-443C-9B15-3F4E4AE98E3F.thumb.jpeg.6cb8b25d9345a9e912af28ab24959c82.jpeg

On 9/25/2021 at 11:14 AM, GTSBoy said:

Also used as CEL

By CEL do you mean relating to an ignition problem?

the ignition loom was converted from series 1 > series 2 and ignition coils changed to s2 ones with the (igniter at the top)
 

I can confirm the 1st 2nd and third plug is giving spark. (See pic)

90B27582-270A-403B-AE6F-87BB6071385E.thumb.png.fbb77ef18f882794eda45bb90c22296b.png

More checks:

- cat = removed not blocked

-  coils = Resistance test relatively consistent on all 6 

- spark good tested on cyl 1, 2, 3 (by grounding to the rocker cover) 

- still investigating why cat overheat light started turning on when cranking.. 

 

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I don't generally watch videos posted in these threads as they are almost always useless.

CEL = Check Engine Light.

 

Something you did wrt the rail swap is wrong, or the injectors or FPR are faulty. Put back the proper stuff. Don't report fuel pressure behaviour on different equipment to that which possibly caused the problem without first reporting the behaviour on the original equipment that was on the car when reporting the problem.

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Also worth noting - The videos don't seem to work (at least when I clicked on them)

Troubleshooting methodology is better than most Mr GTSBoy 😛

Generally though - Why swap a rail? How could a rail fail other than it leaking? And if it leaks with 50PSI you will absolutely note it is time to replace the rail.

Fuel pressure doesn't stay indefinitely. It also doesn't drop away straight away. I doubt we have a tunable ECU in there to see what is going on, in which case you'd better make sure you're running stock injectors, stock rail, stock FPR and basically stock everything if you're going to use the stock ECU's error codes to diagnose stuff.

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On 9/27/2021 at 9:13 AM, Kinkstaah said:

Why swap a rail?

I had access to spare rail which included the injectors and FPR. That way if the issue was relating to a leaking injector or FPR issue it would be sorted. 

However the fuel pressure it still not holding.
iv changed the FPR as well and no luck.

 

note: old fuel rail setup has Since been reverted back

We know that there is definitely a fuel pressure leak.

fuel leak down test = failed (pressure drops instantly)


The question is where is the leak occurring..

possible causes

injectors = no leak from any while priming

FPR = tried to pitch the short hose on the FPR while pump was priming and the pressure shot up to 100psi but after pumped stopped went back down to 0

F6CB4351-46B2-4FCD-A613-0BF51C8D2439.thumb.jpeg.c7c06d98046d5c6e674defe7efd88967.jpeg

In saying that iv tried another FPR with the same result.

Either the 2 FPRs I have are faulty or something else is causing the Pressure drop.

 

Fuel tank lock ring 


One other observation is that The lock ring where the fuel pump goes in the boot is split. fuel pressure might be escaping from there.

 

349AD4B7-12E7-4826-B74F-EDEFD60769E9.thumb.jpeg.b8d3a50efd19ecbc3650f8cbb0ec3c99.jpeg

 

I’ll replace this first and see if that changes anything.

 

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The pressure should drop. Maybe not instantly, but it should. It doesn't just hold the pressure indefinitely when the engine is off and the fuel is not pumping.

If it did, there would be no need to prime the fuel system... ever. If the pressure is dropping or being too high (or really, fluctuating) while the engine is running then there's an issue with the FPR.

If you have two sets of stock injectors, and two stock FPR's and two fuel rails, I wouldn't be chasing the fuel side of the engine bay at this point for your problem.

Personally I'd be re-checking that MAF (is it the same auto/manual/is it clean? did you actively clean it with MAF cleaner?)

Alternatively, anything else custom in that circuit?
You have spark, but do you know you have spark at the right time?. You've set timing to 15deg, but have you checked it with a timing light? Could it be out? Whats your CAS doing?

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On 9/27/2021 at 12:44 PM, Kinkstaah said:

Personally I'd be re-checking that MAF (is it the same auto/manual/is it clean? did you actively clean it with MAF cleaner?)

yes the MAF was cleaned, voltage was checked (12v, signal voltage and ground are good)

 

On 9/27/2021 at 3:42 PM, GTSBoy said:

Check valve. It'll be the check valve.

That's what i'm starting to think. The check valve is in the fuel pump (Walbro 255). I will be replacing the whole pump.

 

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