Running lean on boost

Discussion in 'ENGINE' started by H_D, May 7, 2019.

  1. H_D

    H_D Paid Member

    Running td04, stock ecu and 6psi boost. Afr gauge is reading between 13-14 on boost with wide open throttle so i switched it off immediately. The AFR readings are fine on startup, idle and when off boost.

    In terms of the fueling setup the follwong has been done....

    walbro pump fitted about 7 years ago, recently had the injectors rebuilt and tested, new genuine fuel filter, stock FPR.

    I have checked the map sensor and getting a solid 5V all new vacuum lines on it too.

    Also replaced the vacuum line for the FPR.

    Spark plugs also indicate its running lean

    Any suggestions???
  2. SKINY

    SKINY Registered User +

    Fuel pressure regulator and a fuel cut defender I was always told I'd need to run the TF035 kit buddy! Also try resetting your Wideband and check the sensor, I know from other folks experience these cars eat them for fun at 80£ a go, a trick I've used a good few times now on seemingly bad sensors is clean them with jiffy lemon juice, soak overnight then a good scrub and clean again
  3. H_D

    H_D Paid Member

    Im using a brand new Aem AFR gauge kit. Looking at the plugs its deffo running lean. Its running less than stock boost so no need for a fuel cut defender.
  4. Jay

    Jay Admin

    Reset ECU.
    Recalibrate lambda probe.
    Then start searching for an issue.

    If it's in the 14's stay off boost until you work it out. That's dangerous territory.

    FYI 4efte plugs always look lean unless there's a proper overfuelling condition. Only takes you to tootle about on light cruise and they are white. Wisely you have opted for a wideband so no need to guess too much :cool:
    SKINY likes this.
  5. H_D

    H_D Paid Member

  6. dac69er

    dac69er Super Moderator

    i would measure your fuel pressure.
    could be a failed fpr.

    check fuel pressure on idle with the vac hose connected then disconnected, the fuel pressure should rise when you disconnect the pipe. then put some pressure in the vac hose and see if that increases the pressure again.

    ideally you want to monitor the fuel pressure when you are driving as it could be the pump can supply the pressure at low flow, but at higher flow the pressure drops off and you go lean. 7 years for a walbro is pretty good going tbh. i change walbros when i do a oil and filter change ;)
    SWJ and H_D like this.
  7. H_D

    H_D Paid Member

    Would i need some sort of gauge to check fuel pressure?
  8. SKINY

    SKINY Registered User +

    Yea mate, you should be able to pick up a cheap enough test kit or find a nice friendly garage that has one.
    H_D likes this.
  9. H_D

    H_D Paid Member

    looks like il be heading to machine mart sometime this week to get the gauge
  10. H_D

    H_D Paid Member

  11. SKINY

    SKINY Registered User +

    Yea that would do, bear in mind you need to see the guage when your driving bud
    H_D likes this.
  12. dac69er

    dac69er Super Moderator

    That isn't really much good as you don't have test port on a standard rail.

    You will either need to make something up or find a more oldskool kit.

    If I get a chance tomorrow I will have a look for you.
    H_D likes this.
  13. SWJ

    SWJ Member

    The good news .. is you know it's running lean under boost! The bad news is you don't know why??? Back to basics, it "has" to be a vacuum leak or a fuel pressure problem, I would think??

    A fuel pressure gauge would most likely be helpful as under boost, FP should rise. That aside "under boost" vacuum lines as such, that could pass a "carb spray test" under idle, conditions conditions, might not under boost???

    I've seen that with my Porsche 951 Turbos S and came close to getting a SUV up my butt!!! From a dead stop, I pulled out on the Hwy in front of a SUV going 70+, it was closing fast but it should have been no issue?? So I pull out hit the throttle and I got nothing, WTH!!! That was uh close!!

    So I go back and trouble shoot?? I honestly have no idea how I found it?? But the big hose that goes to the intake manifold was ... slipping or collapsing under boost??
    I tightened the hell out of it but it still happened ... if I eased into the throttle it did not! So I replaced that hose and it never happened again. :)

    It might be something like that going on, but I don't know??
    H_D likes this.
  14. H_D

    H_D Paid Member

    Forgot to mention the car had been going under a major overhaul and only started it last week after 30 months being off road. Im suspecting a clogged fuel pump or failed fpr as every other fuel component is brand new. Also tested the afr sensor with brake cleaner and it went straight to 10
  15. H_D

    H_D Paid Member

    I can hear the fuel pump making a whining noise that are normal for the walbro so im guessing this rules out the relay???
  16. SWJ

    SWJ Member

    Oh no test port on the rail?? I've been out of the game ... ever since I blew up my 3ee to 5efe swap! I blame the shop but I digress. Fuel pumps are kinda noisy anyway so what it is doing while static ... won't tell you much?? If it idles and drives, you know it's getting fuel. But what is it doing under boost, that's the question??

    Plan B, ...

    I have no first hand experience with it, but when I get my crap together ... I'll need to buy one for each of my turbo cars. But to be fair it might only "confirm" what you already know, something is wrong?? If fuel pressure does not go up under boost, it could still be fuel related or a vacuum leak?? Lot's of sources for vacuum leaks on a turbo motor ... sigh.
    H_D and SKINY like this.
  17. H_D

    H_D Paid Member

    Getting 13.55v at the fuel pump when car is running
  18. SWJ

    SWJ Member

    OK well the good news is you know the pump works ... for the most part?? But your chasing tail as it were?? The car idles and drives sooo, you already knew the pump works ... to whatever degree?? Sooo, while that is interesting?? It still does not solve the "mystery??" ,

    Everything seems to turn to crap ... under boost?? So that is the problem?? And static test ... won't solve the issue?? Static test aren't gonna find the "issue" if it occurs only under "Boost??"

    I've been there done that and it did not work?? Swapping parts can get expensive and is generally a "PIA!" But you have "something" that is changing under boost, conditions most likely??

    The least expensive option .. is just to go over thing and tie wrap a zip tie over vacuum line in the engine compartment! What looks under idle "could slip under boost??" I have dealt with that and it was the hose that goes to the manifold?? It "looked tight at idle?? But under boost, it slipped??? I broke down and changed that hose and problem solved!
    Now that might not be your issue?? But zip ties are cheap. :)
  19. H_D

    H_D Paid Member

    The connections were quiet poor on the pump so i fixed that. Didnt get a proper chance to test the car last night but when i drove home i put the car in boost for abt 2 seconds and afr went down to 12. Going to take it for a longer drive down some a-roads later on today. I think the poor fuel pump connections were causing the issue
  20. SKINY

    SKINY Registered User +

    Getting somewhere then bud :) old Toyota wiring can be an utter ball ache, ive seen my fair share of it over the years and the GT is no exception:eek:
    If you can strip a bit of the sleeve off the wire at the connection it should be a nice shiny copper, if there's any signs of corrosion replace that section of the wire. A multimeter is very handy for end to end testing to pick up wiring issues too
    H_D likes this.

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