lean cyLinder

[MinamiKotaro]

#2 cylinder is very lean. The header pipe is solid white, other three are black. Most likely culprit? My injectors are F.A.S.T., almost new, and supposedly flow matched.

[panel]

Can you swap injectors around at all to see if it's the same scenario ? Can you pop them out and crank them into 4 jars and check the flow ?

[mads b (dk)]

I had lean 2 and 4 because off header design..... solved by adding 6% extra to injectors in 2 and 4

Tapatalk

[MinamiKotaro]

Can you swap injectors around at all to see if it's the same scenario ? Can you pop them out and crank them into 4 jars and check the flow ?

I can but it's a pain in the butt. Lol. Guess I'll just knuckle down and do it.

[MinamiKotaro]

I had lean 2 and 4 because off header design..... solved by adding 6% extra to injectors in 2 and 4

Tapatalk

Hmm. I believe that pipe had been leaking at the slip joint.

[mads b (dk)]

There are no slip joint... it's a homemade header....

Tapatalk

[MinamiKotaro]

There are no slip joint... it's a homemade header....

Tapatalk

I meant on mine.

[Piledriver]

Batch or sequential?

[MinamiKotaro]

Batch or sequential?

Batch.

[Piledriver]

IIRC you can still use fuel trim if set for semi-sequential, but it effects 2 holes.

Semi-sequential doesn't need the extra sensor or a cam speed wheel, it just provides guaranteed injection timing, and should be IMHO default. Regular batch squirts when it gets to it.

Just enabling it and playing with the injection timing might have some positive effect by itself.

[mads b (dk)]

IIRC you can still use fuel trim if set for semi-sequential, but it effects 2 holes.

Semi-sequential doesn't need the extra sensor or a cam speed wheel, it just provides guaranteed injection timing, and should be IMHO default. Regular batch squirts when it gets to it.

Just enabling it and playing with the injection timing might have some positive effect by itself.

On vems you can trim fuel on every cylinder if its connected to its own driver, you don't have to run fully sequential

Tapatalk

[MinamiKotaro]

IIRC you can still use fuel trim if set for semi-sequential, but it effects 2 holes.

Semi-sequential doesn't need the extra sensor or a cam speed wheel, it just provides guaranteed injection timing, and should be IMHO default. Regular batch squirts when it gets to it.

Just enabling it and playing with the injection timing might have some positive effect by itself.

I'd have to upgrade to MS2, wouldn't I?

[Piledriver]

I'd have to upgrade to MS2, wouldn't I?

My bad, I forget MS1 still works.
You are stuck with fixing the root cause, which is actually probably better anyway.

[MinamiKotaro]

Ok, I took #2 plug out and it was covered with white ash. I swapped #2 and #4 injector. We'll see if the lean condition migrates with it.

Also, two of my injectors measured 12.9 ohms resistance, the other two measured 13.5 ohm. Any cause for concern? Should I make sure to pair the two 12.9s and the two 13.5s on the same circuit?

[MinamiKotaro]

Update:

Cylinder #2 was still lean even though I swapped the injector. Cylinder #3 was also lean -- not as lean, but notably leaner than #1 and #4. #2 and #3 are on the same circuit. I got to thinking: a long time ago, one of the injector wires pulled out of the relay board and grounded against the case. Perhaps that injector circuit was damaged, somehow. I got a new relay board and this seems to have fixed the problem. Plugs #2 and #4 look exactly the same as #1 and #3. Also, my AFR has changed dramatically (richer) so I guess those injectors are firing better. Had to retune.

Edit: Did a compression test on #2 and #4 (easy to get to) and they were both with a couple psi. The valve clearance was also good.