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Thread: Exhaust firing/spluttering when throttle is applied

  1. #1
    Member h0ivik's Avatar
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    Exhaust firing/spluttering when throttle is applied

    Info regarding the car:
    Stock internals
    Stage 3 Horsham chip
    GT2860RS
    444cc injectors
    Z32 AFM
    Walbro 255 fuel pump
    3 inch exhaust & apexi air filter
    FMIC
    Plugs are BCPR7ES gapped to 0.8mm
    Timing is set to 15 degrees

    I've been having this issue since I changed my AAC, back to the one that came with my car.. Tested another one since I was having troubles with idling.

    So a basic explanation of the problem: whenever I apply throttle, the exhaust goes bang. It happens 99% of the time when I let go of the throttle, and then start to accelerate again..

    Since the AAC was the only thing I changed before this started to happen, I of course suspect that it is the culprit. However, the engine is idling perfectly @ 850 (+-50), which it didn't do before.

    Another thing that happens, more randomly, is that the engine sometimes just dies, when I have to stop quickly. RPM just goes from 3k to 0. After reading a bit about that problem, it seems like the AAC valve is the cause of that issue (?).

    Any good ideas? The car is absolutely perfect to drive, except for that damn banging whenever I apply throttle...

    Johan

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    Does it hold boost fine? sounds like a boost leak to me?

    Do you have a wideband is it over fueling?

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    Member h0ivik's Avatar
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    Holds boost fine, yes. Might be a leak, I haven't checked for leaks since last year..

    I do have a wideband, it's around 14/15 when driving normally. So doesn't seem to be overfueling..

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    Member R3K1355's Avatar
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    Have you run through all the troubleshooting stuff in the Fuel Injection Manual??

    Link Here

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    Member h0ivik's Avatar
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    Quote Originally Posted by R3K1355 View Post
    Have you run through all the troubleshooting stuff in the Fuel Injection Manual??

    Link Here
    I've only checked the CTS, air regulator and AAC so far, will check the rest today.

    Thanks for the link!

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    Member R3K1355's Avatar
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    Have you checked for ECU fault codes as well?

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    Does it go rich or lean when it starts sputtering ?

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    Graphics Guru Davus200's Avatar
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    I had this issue on and off for a while.... Was convinced it was the usual boost leak, or coils but did a few tests and nothing....

    Since cleaning the AAC and TPS its completely gone!

    As the AAC was the only thing you changed sounds like thats at fault, maybe try cleaning it or trying a known working one.

    Otherwise have you tried cleaning the MAF? And is it a genuine one? The fakes are a nightmare!

  9. #9
    Member h0ivik's Avatar
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    Quote Originally Posted by R3K1355 View Post
    Have you checked for ECU fault codes as well?
    Checked ECU for fault codes last week, no problem there.

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    Member h0ivik's Avatar
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    Quote Originally Posted by autosri View Post
    Does it go rich or lean when it starts sputtering ?
    I guess sputtering was the wrong word to use, it's more pop and bang noises than sputtering. Anyways I just took a quick ride in the car and recorded.

    https://youtu.be/YONRMV-sc0M

    Recorded with my phone, sorry about the quality of the sound.. But you can at least hear the exhaust go BANG in that clip.


    https://youtu.be/sT0s-FbGoms

    This is the air fuel ratio gauge, you can hear the pops here as well, once I start accelerating again.

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    Member h0ivik's Avatar
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    Quote Originally Posted by Davus200 View Post
    I had this issue on and off for a while.... Was convinced it was the usual boost leak, or coils but did a few tests and nothing....

    Since cleaning the AAC and TPS its completely gone!

    As the AAC was the only thing you changed sounds like thats at fault, maybe try cleaning it or trying a known working one.

    Otherwise have you tried cleaning the MAF? And is it a genuine one? The fakes are a nightmare!
    I did clean my AAC before I changed it back again, but might rip it off and give it a clean again..

    Did you clean the TPS as well? Don't think I've done that, might give it a try! If that doesn't work I'll try to get a hold of a known working AAC and see what happens.

    Haven't cleaned the MAF yet, will put it on my list of things to do. Should be a genuine one, bought from a shop here in Norway (cost me 180 pounds).
    The previous Z32 MAF I had (bought a used one), was not a genuine one, didn't work good at all!

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    Member h0ivik's Avatar
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    Done some more testing today. Took off the AAC unit and gave it a clean, wasn't really dirty but.. Also cleaned the AFM.

    No changes unfortunately. But, I tested the AAC since I had it out, just to make sure everything was good. Applied 12V to it, and it clicked as it should. Measured resistance on the terminals, no problem there.
    Also checked that it was being supplied 12V from the loom, which it was.

    Can't hear it click when I plug it in and ignition is on, is that normal?

    Made no difference when I disconnected it when the car was idling either.. Does anyone know if the idle is supposed to change when you disconnect the AAC?
    I would think the idle should change, but I dunno...

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    Last edited by h0ivik; 17-05-2019 at 17:04.

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    AAC is pulse width modulated (PWM). It won't noticeably click on/off when on the car. It is held wide open on cranking and running off idle.

    There are 2 types of AAC. Early type pushes a spring loaded plunger that has a cone in a brass hole in the idle control block. Late type has a tube with a small window that a plunger closes. The early type needs the whole idle block removing to clean properly, the plunger should be quite free.

    Idle speed should drop when AAC is unplugged. Turn the hex head screw on rear of idle control, aim for 800 rpm.

    Idle speed should increase with a surge and drop back to 850 rpm when AAC is plugged back in if unplugged while idling.

    Check idle switch on front of TPS has continuity with throttle shut. Do a mode IV ECU check to verify it sees the idle switch open/close. Should open at about 1000 rpm.

    Clean the throttle body / plate.

    Try to wiggle the AFM plug, if rpm changes close down the terminals in the plug to make a better connection.

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    Member h0ivik's Avatar
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    Quote Originally Posted by skyshack View Post
    AAC is pulse width modulated (PWM). It won't noticeably click on/off when on the car. It is held wide open on cranking and running off idle.

    There are 2 types of AAC. Early type pushes a spring loaded plunger that has a cone in a brass hole in the idle control block. Late type has a tube with a small window that a plunger closes. The early type needs the whole idle block removing to clean properly, the plunger should be quite free.

    Idle speed should drop when AAC is unplugged. Turn the hex head screw on rear of idle control, aim for 800 rpm.

    Idle speed should increase with a surge and drop back to 850 rpm when AAC is plugged back in if unplugged while idling.

    Check idle switch on front of TPS has continuity with throttle shut. Do a mode IV ECU check to verify it sees the idle switch open/close. Should open at about 1000 rpm.

    Clean the throttle body / plate.

    Try to wiggle the AFM plug, if rpm changes close down the terminals in the plug to make a better connection.
    Thanks for the info!

    Looks like I have the late type. I could see the small window opening/closing when giving it 12V.

    TPS has continuity when throttle is shut, no continuity when I move the throttle. Did a mode IV check, red inspection lamp goes on when I barely touch the throttle pedal (according to the fsm I have, this should happen).

    Disconnected the AAC and set the idle to 800 rpm, plugged it back in and nothing happened. Still idling at 800 rpm. Idle doesn't change when I unplug it as well. Is my AAC bad?

    AFM plug seems to be OK, nothing happens when I wiggle it.

    Will clean throttle body/plate later today.

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    Quote Originally Posted by h0ivik View Post
    Disconnected the AAC and set the idle to 800 rpm, plugged it back in and nothing happened. Still idling at 800 rpm. Idle doesn't change when I unplug it as well. Is my AAC bad?
    As you see it move when applying power it's OK.
    Problem must be feed or ECU or loom between AAC and ECU.

    Test the system as page EF&EC-106 in the fsm.

    If you unplug the ECU, then with ign on you should have battery volts on pin 106. This battery/ign feed also powers Lambda sensor heater and fuel pressure regulator solenoid (aka hot start valve) via 10A fuse next to fuel pump fuse in engine bay fuse box. Probably won't notice if they don't have power.

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    Quote Originally Posted by skyshack View Post
    As you see it move when applying power it's OK.
    Problem must be feed or ECU or loom between AAC and ECU.

    Test the system as page EF&EC-106 in the fsm.

    If you unplug the ECU, then with ign on you should have battery volts on pin 106. This battery/ign feed also powers Lambda sensor heater and fuel pressure regulator solenoid (aka hot start valve) via 10A fuse next to fuel pump fuse in engine bay fuse box. Probably won't notice if they don't have power.
    Did the diagnostic procedure, as explained in the fsm. Warmed engine up and checked voltage between pin 106 and ground, got 12V. Dropped to 11,5V when I turned on the heater + headlights.

    When unplugging ECU and ign on, I also get 12V from pin 106.

    Checked the 10A fuse as well, working.


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    Last edited by h0ivik; 19-05-2019 at 20:33.

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    Has anyone changed the breather set up ?

    Also, check the breathers (especially the PCV valve area) for build up of gunge in the pipework.

    Check that the throttle butterfly is closing and there is no buildup of crud where it should seal against the throttle body. Also, check the seal where the operating rod for the butterfly leaves the side of the throttle body.

  18. #18
    Member h0ivik's Avatar
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    Quote Originally Posted by Jonny Wilkinson View Post
    Has anyone changed the breather set up ?

    Also, check the breathers (especially the PCV valve area) for build up of gunge in the pipework.

    Check that the throttle butterfly is closing and there is no buildup of crud where it should seal against the throttle body. Also, check the seal where the operating rod for the butterfly leaves the side of the throttle body.
    Don't think the breather set up has been changed, here's a photo of it: https://flic.kr/p/2fTxESN

    Checked for gunge in the breather hoses, there was a little in the hose going to the PCV valve, but not much.

    Throttle butterfly is closing as it should, not too much dirt in there (https://flic.kr/p/2fY9fd2). I removed the whole throttle body and cleaned it a bit today, will take a better look at it tomorrow and give it a good clean!

    I was a little unsure on how to get the operating rod out, but I've searched it up now, will check the seal tomorrow. I assume that I'll have to pull the rod out to get a good look at the seal?

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    whats your intake piping like? if its too short and straight you may be getting poor readings through the afm, ive had issues with hesitation and revs dropping at junctions and changed my intake pipe to one with more bends and an "air straightener" and it seems to have improved (ive only done a couple of miles since though so cant say its cured it)

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    Quote Originally Posted by sxbaz View Post
    whats your intake piping like? if its too short and straight you may be getting poor readings through the afm, ive had issues with hesitation and revs dropping at junctions and changed my intake pipe to one with more bends and an "air straightener" and it seems to have improved (ive only done a couple of miles since though so cant say its cured it)
    I̶t̶'̶s̶ ̶v̶e̶r̶y̶ ̶s̶i̶m̶i̶l̶a̶r̶ ̶t̶o̶ ̶t̶h̶i̶s̶ ̶o̶n̶e̶:̶ ̶h̶t̶t̶p̶s̶:̶/̶/̶r̶a̶c̶e̶s̶-̶s̶h̶o̶p̶.̶c̶o̶m̶/̶1̶2̶9̶8̶1̶4̶-̶l̶a̶r̶g̶e̶_̶d̶e̶f̶a̶u̶l̶t̶/̶p̶i̶p̶e̶-̶k̶i̶t̶-̶t̶o̶-̶i̶n̶t̶e̶r̶c̶o̶o̶l̶e̶r̶-̶f̶o̶r̶-̶n̶i̶s̶s̶a̶n̶-̶2̶0̶0̶s̶x̶-̶s̶1̶3̶-̶c̶a̶1̶8̶d̶e̶t̶-̶v̶e̶r̶2̶.̶j̶p̶g̶

    N̶o̶t̶ ̶t̶o̶o̶ ̶s̶h̶o̶r̶t̶ ̶a̶n̶d̶ ̶s̶t̶r̶a̶i̶g̶h̶t̶ ̶i̶m̶o̶ ̶:̶)̶

    Looks like I misunderstood your question, my bad!

    No pipe between AFM and filter, filter is bolted straight onto the AFM. Have had it like this for about 2 years now, since I went up to stage3. Didn't experience any issues after fitting it then, most CA engines around here that I've seen has had it the same way as I have..

    Is it normal to have a pipe between AFM and filter?

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    Last edited by h0ivik; 21-05-2019 at 06:46.

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