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Thread: Poor running need some advise

  1. #1
    mitsiboyblue's Avatar

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    Poor running need some advise

    Hi guys, well.... you need to know im getting alittle frustrated with my VR4tt (manual) at the moment. Probably cant see the wood for trees as they say . As some of you know it has undertaken some serious engine overhauling these last 12 months with a full and complete engine rebuild. piston, conrod, bearings, hybrid turbo's, head work, cooler plugs, new fuel pump, filter all new gaskets, head bolts, oils, filters etc,
    Its all running now but driving it around locally its a totally different car (Not nice at all) to drive
    Idling is perfect, light throttle is not so bad but.... if i accelerate abit harder it's hesitant, doesn't come up on boost as expected (was almost instant last time) it's jurking and holding back but doesn't feel like a misfire.
    There are no DTC's prescent and the fuel pressure regulator set to 3 bar with reference pipe disconnected and running on 99 octane.
    The electronic boost controller is set to off for the time being so its just running on wastegate pressure. Just out of curiously, If i push it through this hesitation and get it on boost over 3-4ooorpm it will take off and is still pulling a very strong boost up to 7000rpm where i eased off.
    Im pretty sure its not a mechanical issue after all the re-work but cant rule out any of the eldctrics, sensors ect.
    Has anyone experienced this or have ideas what i could check next as i feel like im just wasting time now and need a fresh head.
    Dave O



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    intake air metering issue? do you have a record of AFR's from idle thru to WOT?

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    Quote Originally Posted by Amonlym View Post
    intake air metering issue? do you have a record of AFR's from idle thru to WOT?
    No i haven't, wideband was to be one of my next investments. What is your theory?

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    It just sounds similar to (some) issues people have had with a bad MAF - not all of it however.
    Power comes from fuel and air, if you dont have a MAP sensor added as part of the work, your only indication of air volume is the maf. you can try unplugging the maf and see if it changes the behaviour.

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    Quote Originally Posted by Amonlym View Post
    It just sounds similar to (some) issues people have had with a bad MAF - not all of it however.
    Power comes from fuel and air, if you dont have a MAP sensor added as part of the work, your only indication of air volume is the maf. you can try unplugging the maf and see if it changes the behaviour.
    Ok, yes i will try this later when i get home and let you know, this will put ecu in to 'limp' and engine control settings will average out. Yes? i cant rule it out but it's very strange that last time the car used it never displayed this fault.
    I understand that with all modifications from standard there will be affects to the running and behaviour of the engine, but what ive done i wouldn't have thought it to have such a dramatic affected.
    Dave O



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    Unplugging the MAF will use a very basic TPS/RPM table for fuelling, but it should improve it if the MAF isn't working correctly

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    Quote Originally Posted by Confused View Post
    Unplugging the MAF will use a very basic TPS/RPM table for fuelling, but it should improve it if the MAF isn't working correctly
    excellent!.... i think i might have a spare MAF somewhere but not sure whether it was off a VR4 or V6 galant? Do you know is there a link to component test proceedure on CVR4?

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    All the service manuals are in the Articles Library - both European models (which are in English) and the Japanese models (which are Japanese only).

    Both use the same section numbers, and testing procedures are fairly similar between the two, so I usually find the right section in the UK ones, look it up in the Japanese one, and then do a bit of a comparison between the two, using words from one and values from the other to make sense of it all!

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    Quote Originally Posted by Confused View Post
    All the service manuals are in the Articles Library - both European models (which are in English) and the Japanese models (which are Japanese only).

    Both use the same section numbers, and testing procedures are fairly similar between the two, so I usually find the right section in the UK ones, look it up in the Japanese one, and then do a bit of a comparison between the two, using words from one and values from the other to make sense of it all!
    Helpful, thankyou

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    Quote Originally Posted by mitsiboyblue View Post
    Helpful, thankyou

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    Well.... its all come to light this evening guys....
    Disconnected MAS and took it for a spin and it was worse.
    Really no power and popping and banging from exhaust under hard acceleration and then on de-celeration popping
    But then came the clouds of smoke, got it home and
    stripped off intake pipework and found rear turbo has snapped its shaft on the compressor side. im guessing this was the lack of power the other day as only 1 turbo was boosting and this evening i think the unsupported shaft has moved and it hemeraged oil through the whole system.
    Any body got a set of turbos lying around they want to sell?
    Dave O



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    Quote Originally Posted by mitsiboyblue View Post
    Well.... its all come to light this evening guys....
    Disconnected MAS and took it for a spin and it was worse.
    Really no power and popping and banging from exhaust under hard acceleration and then on de-celeration popping
    But then came the clouds of smoke, got it home and
    stripped off intake pipework and found rear turbo has snapped its shaft on the compressor side. im guessing this was the lack of power the other day as only 1 turbo was boosting and this evening i think the unsupported shaft has moved and it hemeraged oil through the whole system.
    Any body got a set of turbos lying around they want to sell?
    Dave O



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    Here's the culprit!

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    Ouch

    And the turbos looked so pretty once they'd come back from being uprated

    Unfortunately (for me) it reinforces my viewpoint to not **** with stuff and leave everything as Mitsubishi made it...!

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    Quote Originally Posted by Confused View Post
    Ouch

    And the turbos looked so pretty once they'd come back from being uprated

    Unfortunately (for me) it reinforces my viewpoint to not **** with stuff and leave everything as Mitsubishi made it...!
    In some respects i have to agree with you but i personally think this is more to do with bad engineering practices from the turbo shop. Nut over tightened or not balanced correctly/ at all. It will be a few days now before i can strip and check out the true extent of the damage.

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    Ouch really sorry to see this.

    Other possibility is it didn't like the over-fueling and popping, but wouldn't expect it to fail like that.
    Does one turbo broken explain the hesitation / surging felt initially? perhaps if it was blocking exhaust flow on one bank until pressure got high enough to spin what was left of the turbine wheel? what condition is the rear turbo in? is it repairable, or stuffed?

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    Quote Originally Posted by Amonlym View Post
    Ouch really sorry to see this.

    Other possibility is it didn't like the over-fueling and popping, but wouldn't expect it to fail like that.
    Does one turbo broken explain the hesitation / surging felt initially? perhaps if it was blocking exhaust flow on one bank until pressure got high enough to spin what was left of the turbine wheel? what condition is the rear turbo in? is it repairable, or stuffed?
    I think the lack of power and hesitation would definatley have something to do with only one turbo working as it just wouldn't be pushing enough air for the fuel delivery under acceleration enrichment and then in deceleration conditions im guessing it was igniting the unburnt fuel in the exhaust track, that would explain the popping and banging.
    Front turbo is fine, rear turbo is the culprit but as for the extent of the damage to the compressor housing ive no idea yet. im hoping its salvageable and just fit a new core and balancing perfectly by someone reputable. Im not going through all this again.



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