Major boost cut at higher revs

[Lee H]

More problems with the car this week.

Rev 3 turbo running 1.1 bar on a standard ecu, been running ok at this for a few months until this week.

When I go full throttle and hit full boost the car will pull cleanly until higher in the rev range and then just has a huge misfire and nearly throws me through the windscreen. It varies at what revs it does this but it does it every time now. Ecu light doesn't come on and no fault codes.

Tonight I changed the dizzy and plugs and went out for a run and it did 7 full boost clean runs to about 7k rpm, holding 1.1 bar steady. Thought I had cured it and then on the way back decided to have one more try and the fault is back.

Seems to be ignition related as I believe fuel cut would flash the ecu light and need a reset? Car has no vsv connected and has an electronic boost controller but unsure how this would effect the ecu safety features.

Help please.

[Lefty1991]

Have you tried lowering the boost and seeing if it still does it.
A hard speed change that feels like your going through the windscreen does sound like fuel cut, but not at 1.1 bar

[Nic]

Does your gauge/EBC show the max boost level? it could be spiking above 1.1bar and hitting the fuel cut limit.

[Lee H]

Yes. Apexi AVCR. Peak boost is about 1.08 bar each time.

Would the ECU light not come on with fuel cut?

[Tedtiler]

I take it the ecu light is working? Tried a diagnostic?

[Lee H]

I take it the ecu light is working? Tried a diagnostic?

.

Yes all working fine. Showing no fault codes.

[Tedtiler]

No fault codes leads you to simple stuff I reckon. Ht leads, Electrical connectors to dizzy, ignitor etc, check those wires for continuity too.

[Gullzter]

Sorry to hijack thread but how do i check my fault codes? Ive got no guages, boost controllers etc all running standard atm

[Lee H]

Bridge TE1 and E1 in the diagnostic port and count the flashes on the ecu light. There will be a list of codes on here somewhere. If it just flashes constantly there are no codes.

[Gullzter]

Yeah i read somwhere that it flashes the amount of first digit then pause then flashes the amount of next digit etc.
Was just wondering about the testing procedure, the car is away just now so ill try when it gets back.
Is the diagnostics the plastic capped thing next to oil filler?
Where is the ecu light?
Thanks

[Lee H]

Changed the leads for a spare set I had lying around on Sunday and now it has a smaller misfire constantly on boost. Seems like it's some sort of ignition problem then!

[jon]

Check the state of the ignition coil, they tend to crack with age.

Also try cleaning up the back of the coil and the bracket it bolts to, as it earths through the bracket.

[Gullzter]

Check the state of the ignition coil, they tend to crack with age.

Also try cleaning up the back of the coil and the bracket it bolts to, as it earths through the bracket.

That will probably be my next move

[Nic]

When I go full throttle and hit full boost the car will pull cleanly until higher in the rev range and then just has a huge misfire and nearly throws me through the windscreen. It varies at what revs it does this but it does it every time now. Ecu light doesn't come on and no fault codes.

Your description sounds exactly like fuel cut. Do you have a gauge or boost controller that shows the peak boost level? It could be the boost pressure is spiking above the 1.1bar, I'd start by checking all the vacuum lines.

[jon]

When I go full throttle and hit full boost the car will pull cleanly until higher in the rev range and then just has a huge misfire and nearly throws me through the windscreen. It varies at what revs it does this but it does it every time now. Ecu light doesn't come on and no fault codes.

Your description sounds exactly like fuel cut. Do you have a gauge or boost controller that shows the peak boost level? It could be the boost pressure is spiking above the 1.1bar, I'd start by checking all the vacuum lines.

Fuel cut will turn on the ECU light though and record an error code. It will also prevent positive boost pressure until the engine is switched off.

The OP is reporting that neither of these 2 things happen, so it can't be fuel cut.

[Lee H]

Check the state of the ignition coil, they tend to crack with age.

Also try cleaning up the back of the coil and the bracket it bolts to, as it earths through the bracket.

I have recently replaced this with a good used one as mine was rusty and cracked but I will remove it and double check it.

What's puzzling me is why it was fine for 15 mins or so after a change of plugs, makes me think it is something I disturbed in the process of changing them ie leads!

[Moo]

Sounds like boost spikes. Do you have any boost cut limits set on the EBC? I'd try turning down the gain on your EBC a tad or turning it off entirely and test again. That's a quick, easy and free of charge thing to try before you start swapping out bits.

[b4ss]

More problems with the car this week.

Rev 3 turbo running 1.1 bar on a standard ecu, been running ok at this for a few months until this week.

When I go full throttle and hit full boost the car will pull cleanly until higher in the rev range and then just has a huge misfire and nearly throws me through the windscreen. It varies at what revs it does this but it does it every time now. Ecu light doesn't come on and no fault codes.

Tonight I changed the dizzy and plugs and went out for a run and it did 7 full boost clean runs to about 7k rpm, holding 1.1 bar steady. Thought I had cured it and then on the way back decided to have one more try and the fault is back.



Seems to be ignition related as I believe fuel cut would flash the ecu light and need a reset? Car has no vsv connected and has an electronic boost controller but unsure how this would effect the ecu safety features.

Help please.

Hi did you ever get to the bottom of this, i am have the same issue with no ECU light or error code. Just wondering which ignition part resolved it in the end?
Thanks,
Tony

[DangerJim]

I had this problem and it was HT leads. The end of the lead had broken up and some of it got clamped between the spark plug and the head when I changed the plugs. Took ages to carefully remove it all.

[Matsumoto]

What was the cure for this? My Rev 2 is doing the exact same....before abd after turbo swap (straight swap CT26)