Macen

In third and fourth gear, when full throttling, the engine hesitates (the power generated is "jumpy") between 3000 and 4500rpm. If I only open the throttle half, and boost 0.4bar, I get no hesitation.
The engine also shakes a bit more at idle.
All this after a day at the track.
The spark plugs were changed two months ago.
The engine is mild street ported. Stock turbos. Mapped Apexi PFC. Blitz SMIC.

cewrx7r1

iTrader: (2)

Have you checkd your AFRs? Too rich or bad ignition are common causes.

Dudemaaanownsanrx7

iTrader: (23)

How much boost are you running? Is it spiking at those rpms at all? And do you have an upgraded fuel pump? Old fuel filter? Could be running out of fuel

GOB

is it happening at cold?

windom

iTrader: (1)

Do you want to WOT when it's cold?

1QWIK7

iTrader: (33)

Check TPS adjustments.

Or grounds?

Macen

Yes, the fuel filer is old. Could be that.
Fuel pump is stock. Injectors are open 83% at max.
I boost 0.85bar at full throttle. No boost spikes.

Macen

Changed the plugs, but still the same. The power generated is a bit jumpy. Not very smooth.
What do you think about my old spark plugs? Changed them three months ago after the engine was mapped.

http://macen.nullnet.com/images/IMG_0146.jpg

The engine runs fine when full throttling above 4500 rpm.

alexdimen

iTrader: (13)

Do PFC's have fuel cut?

NewbernD

iTrader: (1)

They do. If you overshoot your target boost by .25 bar they will fuel cut.

alexdimen

iTrader: (13)

Ok, so it's not like the stock ECU. I just looked at the boost/fuel cut table I have and .85 bar is perfect for fuel cut between 3k and 4k rpms.... but that's for the stock ECU.

Macen

Did a compression test and got 100psi on both front and rear. Bounces for front were all even. Rear one of three was a bit lower.

Vacuum is 400mHg at 900rpm idle. It was 500mHg a few weeks ago.

Macen

Did a new compression test with a modified piston compression tester. Engine was cold during the test.
Got 50-50-25 at the rear rotor.
Stuck side seal, or broken?

Link to the test in slowmo.

Macen

Can a steam clean, or Marvel Mystery Oil/ATF help the, if stuck, seal to come loose?

Macen

Today I found that the hose from the turbo y-pipe to the pressure chamber check valve was loose. Searched the forum and found out that this will cause a drop in vacuum at idle, which happend to me.

Now let's hope the seal will unstuck and even out my compression readings.

TRWeiss1

iTrader: (20)

Good luck man...After reading your first couple of posts, I was going to ask if you'd filled up recently. I got a bad tank of gas, and it took me about 350 miles to burn off. It caused a bad idle, and hesitation/sputtering at WOT at the rpm range you described. Of course just cruising and under light throttle it was fine.

Also could have been fuel injectors starting to leak...

Anyway, sounds like you've identified your problem. Best of luck!

Macen

I'm not sure if the loose hose causes the <4000 missfire. But I'm sure it causes the low vacuum at idle.

I see that you've got a KLZE engine. Cool! I had a KLDE in my MX-3.

Macen

A stuck side seal caused the problem.

TRWeiss1

iTrader: (20)

Glad to hear that you got it figured out!

puma

iTrader: (2)

and what did you do to fix it?

Macen

Teared the engine apart.

TimeMachine

iTrader: (10)

Lol, naturally

puma

iTrader: (2)

well i thought he tried the water in the engine trick, it could have worked out for him, hence why i asked.

Macen

I tried the water trick, but it didn't help.