Hello,

Since a few weeks my 4AGE 20V Blacktop hestitates a bit when cold. The first, let's say about 5 minutes, it struggle to climb in rpm like all torque is gone. After that it runs just awesome. Any ideas about a possible cuase?

This is what i've done thus far:
1) New rotor, distributor cap, plugs and cables (only 9000 km old)
2) Checked the timing with a timing light and it's about 8-9 BTDC
3) Measured the resistance of the primary and secondary coil and it's perfect
4) measured the o2 sensor and that's also perfect
5) measured the distributor and it's good also (didn't measure the gap between the rotor and the contacts yet)
6) Installed a new battery while i had the idea the old one was a bit bad
7) Changed from my Ramair filter to a NEW genuine Apexi filter, seems to make it a bit worse
8) Balanced the itb's past year
9) Engine was completey rebuild about 10k km ago with new pistons, bearings, valve grinding, valve adjustment, new oil pump, water pump all new gaskets etc etc

I'm out of clues. Only thing i could think about is either (one of) the injectors, fuelp pump or fuel pressure regulator. Any idea how to test those?

This is how the spark plugs look (after 10k). I took them out after a short ride. I don't think they look too bad, maybe a bit too much carbon, which might be a sign of running a bit lean. On the dyno (about 7k km ago my A/F was just perfect (between 0.85 and 0.9) at full throttle.

Bump

Water temp sensor fault ?
Inlet air temp sensor fault ?

Error codes ??

water temp sensor is okay, measured it. Didn't measure the IAT, that's a good tip.

There are no error codes in the engine.

onnaj wrote:2) Checked the timing with a timing light and it's about 8-9 BTDC

I am sure that you checked the timing with TE1 and E1 shorted, so you could
try increasing the ignition advance by 2 or 3 degrees, and see if it improves.

Cheers... jondee86

Verify that your spark plugs are gapped correctly. If they arent, your engine will sputter and skip etc while it warms up.

onnaj wrote:water temp sensor is okay, measured it. Didn't measure the IAT, that's a good tip.

There are no error codes in the engine.

TBH I can't imagine the inlet air temp. will change enough to affect the running of the engine from cold to hot.
If your engine has done this since the rebuild then you might want to try bleeding the coolant system and remember to put the heater, if fitted, onto its "hot" setting when doing so.

The plugs are gapped correctly, checked the iat and changed it but no difference at all Timing is set with te1 and t1 shorted and was 10BTDC, now it's about 8BTDC. With both settings i have the same problem.
I don't want to advance the timing too much while i'm on ron98 fuel while 100ron is the stock fuel.

The problems started about 1000 km ago before that i didn't have problems at all. Installing the new apexi intake partially worsened the problem. That's why i might suspect the fuel system.

The lack of torque and a more efficient intake making the problem worse suggest the engine is running lean. Maybe you could try temporarily restricting the fuel return pipe from the fpr to see if there is a change ?

I might try that yes, that's a good idea.

Also you can try blocking off a part of the throttle bodies

This is to try and increase intake port velocity

Do you have the stock intake trumpets in place?

Davegt27 wrote:Also you can try blocking off a part of the throttle bodies

This is to try and increase intake port velocity

Do you have the stock intake trumpets in place?

Yes i have the stock trumpets in place with an AE111 Apexi open air intake system.