Troubles once turning up boot

[GriffEdward]

Have a 1996 Manual converted Galant and am currently trying to turn up the boost , has been road tuned but cannot get it to go above 12 psi without misfiring/coughing amd farting above 4.5k rmp , if i lower boost to around 9-10psi it misfires/coughing and farting between 4.5k and 5.2kish rpm but sorts itself out after that, am utterly confused as to what it is , have checked plugs , replaced coils , hardwired the generic walbro upgrade mentioned alot on this page , FPR
Have searches forum but dont know exactly what to search , would greatly appreciate any help as its starting to piss me off 

[mitsiboyblue]

Have a 1996 Manual converted Galant and am currently trying to turn up the boost , has been road tuned but cannot get it to go above 12 psi without misfiring/coughing amd farting above 4.5k rmp , if i lower boost to around 9-10psi it misfires/coughing and farting between 4.5k and 5.2kish rpm but sorts itself out after that, am utterly confused as to what it is , have checked plugs , replaced coils , hardwired the generic walbro upgrade mentioned alot on this page , FPR
Have searches forum but dont know exactly what to search , would greatly appreciate any help as its starting to piss me off 

Hi there, just a shot in the dark here.....
when the vehicle was converted to a manual (presumably) was the ECU replaced with a manual ECU or did the original remain? As ive hear they will run but there slight differences which might affect running now your playing with boost.
Dave O

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[GriffEdward]

I am not quite sure due to previous owner getting conversion done but he claims the ecu was replaced with a 98 manual metal case ecu , i received all the spare parts the previous owner had when i bought it off him and a plastic case ecu was one of the spare parts and there is a metal case is mine so i think previous owners claim is accurate, the current ecu had been retuned so i don't think the problem is ecu based i think it's more hardware based but am entirely baffled as to what it could be
Appreciate the idea though ! ��

[mitsiboyblue]

I am not quite sure due to previous owner getting conversion done but he claims the ecu was replaced with a 98 manual metal case ecu , i received all the spare parts the previous owner had when i bought it off him and a plastic case ecu was one of the spare parts and there is a metal case is mine so i think previous owners claim is accurate, the current ecu had been retuned so i don't think the problem is ecu based i think it's more hardware based but am entirely baffled as to what it could be
Appreciate the idea though !

I think if my memory serves me right my Legnum 1998 Vr4 manual transmission has a black plastic ECU case. What i can do for you tomorrow is check mine and give you the part No.
If this will give you a starting point on yours so you can rule it out ?
Dave O

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[GriffEdward]

That would be helpful man ! Try sort this out by process of elimination

[Confused]

Is it a hard cut for about a second, or uneven hesitation?

Might be difficult to do, but can you get a video of it doing what it's doing, and upload it to YouTube.

It could be good old fuel cut, or it could be spark/fuel delivery issues (more unlikely given what you said you've tried changing)

[mitsiboyblue]

That would be helpful man ! Try sort this out by process of elimination

Here's my ECU Part No. MD340288, black plastic ECU case. 1998 2.5 v6 TT Manual transmission. I've also attached a picture. Hope it helps rule out things.
Also check your fuel pressure as with more boost you need good delivery at the injectors.
Dave O

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[GriffEdward]

The code on my ecu is MR409118, unsure whether that means anything , Have an aftermarket fuel pressure reg, with the boost at about 10-11 psi it misfires harrrd at 4.5k-5 but then sorts itself out after 5k but at anything above 12psi it misfires very hard after 4.5k

[mitsiboyblue]

The code on my ecu is MR409118, unsure whether that means anything , Have an aftermarket fuel pressure reg, with the boost at about 10-11 psi it misfires harrrd at 4.5k-5 but then sorts itself out after 5k but at anything above 12psi it misfires very hard after 4.5k

I think that part No. is AYC ECU not the engine ECU.
a quick check on Google images shows a smaller metal cased ecu labelled AYC, same location in the center console area.


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[mitsiboyblue]

I think that part No. is AYC ECU not the engine ECU.
a quick check on Google images shows a smaller metal cased ecu labelled AYC, same location in the center console area.


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Correction...... i can see people advertising as engine ECU also..... CONFUSED NOW !!!!

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[peter thomson]

Have to agree that is not and engine ecu number

[TAR]

MR409118 is the ASC control unit and is located under the dash on the passengers side inner wing (in cabin).

The engine ECU is located behind the centre console below the radio.

[mitsiboyblue]

MR409118 is the ASC control unit and is located under the dash on the passengers side inner wing (in cabin).

The engine ECU is located behind the centre console below the radio.

Going back to your original post, im just wondering, and for anyone else reading this..... could this be MAF issue?

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[mitsiboyblue]

Going back to your original post, im just wondering, and for anyone else reading this..... could this be MAF issue?

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At first i thought it could be: plug /coil / lead related issue ' blowing out the spark' but if rights itself past 5k im not sure? unless boost rate is starting to level out or drop off.
Have you checked or replaced spark plugs?

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[Nick Mann]

Sounds like it could be fuel cut to me. Is it worse in higher gears?

[GriffEdward]

Ive check the front plugs and they seem to be fine but havent got around to the back , it does seem to be slightly worse in higher gears

[Confused]

Is it a hard cut for about a second, or uneven hesitation?

Might be difficult to do, but can you get a video of it doing what it's doing, and upload it to YouTube.

Rather than wasting time messing around trying to remove ECUs, can you spend your time answering these questions and recording a short video?

[mitsiboyblue]

Ive check the front plugs and they seem to be fine but havent got around to the back , it does seem to be slightly worse in higher gears

It does also seem to point to fuel cut (over boost) and your driving through it as the boost levels out over 5k.
So.... fuel cut occures, boost drops as expected, RPM 's at that point are still relatively quite high but by the time you've got the turbos spooled up again you've gone past peak so fuel cut doesn't re-occure.
Its a theory that could explain your issue.


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[GriffEdward]

Rather than wasting time messing around trying to remove ECUs, can you spend your time answering these questions and recording a short video?

Sorry mate have been abit busy, is quite difficult to hear over the exhaust but it misfires all the way from 4.5 to redline https://youtu.be/lU7hhsXsg58

[mitsiboyblue]

Sorry mate have been abit busy, is quite difficult to hear over the exhaust but it misfires all the way from 4.5 to redline https://youtu.be/lU7hhsXsg58

Misfiring right through from 4.500 rpm to redline... that was not explained before, that could be something else but definitely not fuel cut. not right through to redline.
I'm gunna take a guess and say fuel pressure / filter should be a good reference point.
Diagnostics and to the best of your knowledge an accurate discription of the fault and symptoms is critical otherwise we are all taking a shot in the dark here to try and help you.

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