17 replies to this topic

[tmh983]

My TT converted outback has a fairly noticeable shudder coming from the engine at about 2000rpm, just as boost starts to come on. It get worse by 2500rpm and then improves and is gone by 3500rpm.
I originally thought it was a symptom of the failing auto gearbox, but now i've replaced the entire driveline from the gearbox back and it still does it.

Could it be a failing coil pack breaking down under load? Is there any easy way to test the coil packs?
Is there any aftermarket upgraded coil packs for the gen 3 tt?

[tmh983]

btw, the plugs are brand new, the fuel filter is brand new, the fuel pump is a newish walbro.
It still goes hard in the upper rev ranges, although seems a bit sluggish coming onto boost compared to other tt's i've been in, but i still get 0.7bar at 2200rpm so its not that bad.

[Alex]

Convert to single. Cure the AIDS.


Coil packs tend to break up higher in the revs, and get progressively worse the higher you rev. Not break up in the lower revs and improve with revs.

Speculating here, but that's what happened to me when a coil pack started to die. Same with most people I know too. Try borrowing a set of known good ones, and then at least you can rule that out.


Where did you source Walbro from? Could be fake?

Plugs - what are they? What are they gapped to?

[Jimbo]

Get yourself some GD coils, i put 04's on my GTB and it worked a charm.

[tmh983]

Coil packs tend to break up higher in the revs, and get progressively worse the higher you rev. Not break up in the lower revs and improve with revs.

I don't think this is correct, I think in general terms, ignition problems will show up worst at high load, low rpm.

The Walbro is definately genuine, I can't remember exactly what the plugs are, but they are the correct iridium plugs for the lib b4.

Jimbo - did you have problems with your coils before you put the GD coils on?

[Alex]

Iridium plugs. There's your problem.


They're rubbish.


Replace with either copper or platinums.

[tmh983]

hmm, but the b4 comes with iridiums from the factory, so i can't see this being the cause of my problem.

my plugs are pfr6g's which are actually platinum not iridium. so i can rule out plugs as the problem.

[RX25SE]

Could the fault be occuring on change over?

[tmh983]

No it's way before changeover. I tried unplugging the lines to the ecv to rule it out and it didn't make any difference

[RX25SE]

True that missfires occur under load but I can't help thinking ignition.

As Alex suggested, I would try another set of coils and go from there.

[Cam.]

Fixed a mates WRX with this exact same problem the other day. After testing injector pulses and coilpacks, I found that one of his fresh spark plugs had a tiny tiny crack in it. Causing it to miss slightly.

Hopefully it's an easy fix

P.s +1 for platinum plugs.

[Alex]

Just curious as to how you know your Walbro is genuine?

My first one I ever bought was a fake. Bought in online from a "reputable" seller on a forum group buy.

I ended up buying another one from a reputable, licensed shop (Just Jap Kirrawee). Differences were significant.

Plain white box vs printed Walbro branded box.
Flimsy thin gauge wiring vs broad, thick gauge wiring
Flimsy plug vs robust plug
Diffences in engraving on pump unit itself
Photocopied instructions vs clearly printed instructions.

Etc.

Curve ball:
What up pipes are you running? They're notorious for cracking and leaking. Have you still got the factory heat shielding? Remove and inspect for leaks. The factory flexi joins are total rubbish. If you plan on persisting with the troublesome TT, have a set of custom up pipes made up. One of the better things I did when I was delusional about TTs, as changing up pipes was woeful and made me borderlne homicidal.

[tmh983]

I just put a brand new set of ordinary copper plugs into it, and also managed to find a spare set of coils to put in.
It feels slightly more responsive, but still feels like its has a miss under load.

I'll have a look at the exhaust to see if I can find any leaks.
I've got a spare set of injectors here that i'm going to have cleaned and flow tested and then i will install them.

[Alex]

Just curious as to how you know your Walbro is genuine?

My first one I ever bought was a fake. Bought in online from a "reputable" seller on a forum group buy.

I ended up buying another one from a reputable, licensed shop (Just Jap Kirrawee). Differences were significant.

Plain white box vs printed Walbro branded box.
Flimsy thin gauge wiring vs broad, thick gauge wiring
Flimsy plug vs robust plug
Diffences in engraving on pump unit itself
Photocopied instructions vs clearly printed instructions.

Etc.

Curve ball:
What up pipes are you running? They're notorious for cracking and leaking. Have you still got the factory heat shielding? Remove and inspect for leaks. The factory flexi joins are total rubbish. If you plan on persisting with the troublesome TT, have a set of custom up pipes made up. One of the better things I did when I was delusional about TTs, as changing up pipes was woeful and made me borderlne homicidal.

Just wondering if you have read any of that?

[tmh983]

Yeah I read it. Regardless of whether the fuel pump is genuine or not, it's not a fuel pressure problem, I've checked it's holding pressure all the way to redline at full boost.

I'm going to check the exhaust for leaks when I get time to get under it and pull the shielding off.

[Alex]

Have you got a fuel pressure gauge in your fuel system?

Have you monitored fuel pressures all the way to redline?

[tmh983]

Yeah I borrowed a mates gauge for a few weeks to make sure the fuel pressure was ok under all conditions.

[tmh983]

I can now also rule out a faulty ecu causing it.
I had already ordered a manual ecu off import monster to replace my old auto ecu.
Ecu arrived today, chucked it straight in, no difference to the shuddering.

I noticed I can actually see the boost gauge flickering in time with the shuddering.
I also noticed that I can feel a really strong pulsing in the rubber fuel supply pipe to the engine. Its too slow to be the injector pulsing, maybe just one of the injectors is cactus, or maybe the regulator is stuffed?
Can someone else who has an ej20t start it up and put your hand on the fuel pipe while its idleing and tell me what you feel.