CD5A 4G93T GSR (WOT problem)

[hamsap]

Hi guys,

Have gotten into some problems with the car jerking when WOT.

Engine - CD5A 4G93T
Stock form
ECU: 5663
Manual (if that helps..)

When WOT, I noticed that the boost comes in much earlier but the car is not pulling/ moving. We've gotten the spark plugs changed and gapped correctly (factory recommendation of 0.7mm - 0.8mm), gotten a wideband dynojet A/F meter strapped on and the A/F ratio seems fine (WOT reads around 11 - 12.5)

The next thing we did was rewire the fuel pump to get its electric supply directly, hence making it work more efficiently. Worked ok for a day, and the next day the same problem persist: Gradual acceleration on the accelerator= fine. WOT=bogs down the car, not accelerating as it used to be but I noticed boost comes in much earlier.

Ok, we have come to a few possibilities on why is this happening:

1.)Fouled spark plugs
Couldn't be cause the plugs are only 2 weeks old. Rating is 7, used 6 previously and it lasted me for only 2 weeks before it started misfiring

. Properly gapped at 0.8mm proportionately on all four plugs

2.)Faulty internal wastegate/ boost actuator
Boost reading stayed constant at 0.6 - 0.7 all the time. Now if it is jammed, then I would be reading a higher boost. If the wastegate actually opens up to earlier, wouldn't I see a lower boost reading or a boost reading something like 0.6 then 0.4 and then 0.6 again?

What I'm trying to say here is that if the actuator opens up the wastegate much earlier then it's suppose to be, I shouldn't be seeing a constant 0.6 bar of boost right?

3.) Faulty fuel pump
This might be the problem, I dunno. Just need to see if any one of you have faced such problems before. Now if it's a faulty fuel pump (or for that matter, injectors, FPR, fuel rail) which is not delivering enough fuel to the engine, I would be seeing a A/F ratio reading of 11 - 12.5 right?) Or is this because the ECU is somehow smart enough to detect there isn't enough supply of fuel and hence retard the timing?

My car is the second car that is facing such problems. Mech is still cracking up his head trying to figure out what's wrong, so hopefully there is someone who had faced such similar problems would be able to shed some light

P/S; Fuel filter has been changed 3-4 weeks ago

Thanks!

 

[Cheong Mou Kei 4G9XT]

brader, got check da sparkplugs cable o not...? since u mention change new plugs olidyo faulty powerunit...not veli sure wat dey call it da square thing connected to da sparkplugs cable 1

 

[hamsap]

brader, got check da sparkplugs cable o not...? since u mention change new plugs olidyo faulty powerunit...not veli sure wat dey call it da square thing connected to da sparkplugs cable 1

Oh you mean the coil pack or something? Nope not yet. I mean if its screwed up, it should screw up all the way right? the problem with it is the problem arises once in a while..

Anyways, thanks for your recommendation. Will go check it out.

Thanks bro!

 

[Cheong Mou Kei 4G9XT]

yeah....try check da sparkplug cable first loe...let us keep update on yo situation 10q

 

[levin818]

Hi hs,
what is your engine mileage?
If it is above 120,000km then u should check your ECU.

 

[Cheong Mou Kei 4G9XT]

huh...i never heard ecu got miliage lifespan 1 b4

 

[rorytate]

Hi Hamsap,

Well, personally me and Cheong Mou Kei had a test on my car, I tried with 1.1 bar and my car jerks like crazy and at low rpm it doesnt seems to work properly, like flooded the combustion chamber. Slow response in short

So I changed to CMK's plug cable and boost at 1.1 bar, it went all the way smooth, no such problem. You might wanna check your cable and your fuel filter.

Regarding on the ECU, the capacitor could have leaked out. Just need to replace the 4 capacitor in the ecu(for mitsu car's only - unsure about other cars)

When your car bog down means that your combustion chamber is flooded with fuel. You might wanna drop a little on your fuel pressure.

 

[hamsap]

Hi guys,

thanks for all your prompt and helpful reply.

Opps, left out a little more info.

mileage: 96,000km
Stock standard boost


Rorytate,

Ermm, your previous experience is very interesting. When fuel overfloods in your combustion chamber, it would theoritically means that your running rich right. So when that happens, the wideband A/F meter should be able to pick that up, no?

I mean, unless if the ECU is really smart and reacts fast enough to retard the timing then maybelar..but im just curious why the A/F reading still reads at 11.5-12 at WOT, full-boost...

Had a little spare time the other night and i took out the MAF sensor and cleaned up the 'honeycomb' and the funny looking little transistor with alcohol. Surprisingly, the car doesn't act weird anymore but i seriously doubt that that is the main culprit.

And i thought women are unpredictable..bah! was i bloody wrong :)

 

[Cheong Mou Kei 4G9XT]

hamsap : after u clean da airflow sensor got any effect ark..?

 

[rorytate]

hamsap bro,

ermm..put it this way...when you are running rich

at low rpm and suddenly you floor down, it will feel bog, coz the ecu will retard the timing a little(automatically) but with the loads of fuel being shot in the combustion chamber. As the spark firing will be normal , so the amount of fuel are not able to combust with the spark firing that is being provided, thus sometimes when you shift, it give a misfiring due to richness(at low rpm)

CMK, yes by cleaning the MAF iit helps a little, but let's see what's Hamsap's response after this

 

[hamsap]

Hi CMK & Rorytate,

The car seems to run fine after getting it cleaned and have been driving it for 2 days and it seems ok.

Rorytate: Yeap, understood. What I would like clarify is, if it is running rich the A/F meter will show a lower reading right? At low RPM, it hovers around 12-12.5-13. WOT at full boost is 11-12.5. So theoritically, it should be running at optimum A/F at it's respective RPMs and throttle positions, A/F loads, etc..

Well if the ECU does retard the timing, then aiyah, A/F meter oso seems meaningless. Well, as far as the base of discussion is based on it retarding the timings and all :)

 

[hamsap]

Hi Hamsap,

Well, personally me and Cheong Mou Kei had a test on my car, I tried with 1.1 bar and my car jerks like crazy and at low rpm it doesnt seems to work properly, like flooded the combustion chamber. Slow response in short

So I changed to CMK's plug cable and boost at 1.1 bar, it went all the way smooth, no such problem. You might wanna check your cable and your fuel filter.

Regarding on the ECU, the capacitor could have leaked out. Just need to replace the 4 capacitor in the ecu(for mitsu car's only - unsure about other cars)

When your car bog down means that your combustion chamber is flooded with fuel. You might wanna drop a little on your fuel pressure.

Bro rorytate;

Any where more I can find out about replacing the capacitors? Is there a particular ECU (ie, 5663, 7377, etc) that is pronse to capacitor leakage? Lastly, how much would it roughly cost to get the 4 of them replaced by professional's hands?

Thanks in advance.

 

[hamsap]

UPDATE:

- Tried a set of working NGK plug cables - no use..

- Tried another MAF sensor - Same thing...


Got fed-up and tried the decarbonizing thingy.. Ermmm it's ok now! :)

I noticed that JUN9970 has posted such problems he had with his car before at teammatrix, but the thread went dent. Thread link below:
http://sg.msnusers.com/TeamMatrixMotorsports/enginetalk.msnw?action=get_message&mview=0&ID_Message=23072&LastModified=4675499723848992984

Is JUN around? I would like to know what was the main culprit and how'd he rectify it..

 

[dolly]

bro hamsap,

the ecu will pull timing if it is sensing knock. According to what you said, after you did that decarbonizing thing, everything was ok, it might be you were experiencing knock (very possible also at low rpm high load). you might also be getting knock due to high IAT (inlet air temp).

Might want to check your knock sensor/ put your car on a dyno and listen to the engine with a stethoscope

btw are you running high boost + stock gsr intercooler? does this jerking only occur during hot days, but fine during nights?

how are you reading the afr? bear in mind, narrowband o2 is really only good for reading 14.7:1

 

[hamsap]

bro hamsap,

the ecu will pull timing if it is sensing knock. According to what you said, after you did that decarbonizing thing, everything was ok, it might be you were experiencing knock (very possible also at low rpm high load). you might also be getting knock due to high IAT (inlet air temp).

Might want to check your knock sensor/ put your car on a dyno and listen to the engine with a stethoscope

btw are you running high boost + stock gsr intercooler? does this jerking only occur during hot days, but fine during nights?

how are you reading the afr? bear in mind, narrowband o2 is really only good for reading 14.7:1

Hi Dolly,

Yeah, low RPM at high load. At high RPM, it's not as smooth as it used to be.

Knock sensor, okay, will get that checked out.

Am at stock boost with a VR4 intercooler. It happens both hot days as well as at night :)

It's from a dynojet wideband 02 afr meter which the sensor was strapped to the tip of the exhaust during the reading of the AFR readings