Series 5 Non turbo still missing at higher RPMs.

Ok so I have been through the engine and bay twice now and still haven't found the problem.
When I start to get into the higher RPMs it starts missing, however I don't see it leaning out according to the wideband. Around 11.5:1 at full throttle.
The issue starts at about 3500 sometimes and others at 4 or 5k. depending on throttle position.
Now, that being said I have tested everything according to the FSM and all has checked out ok, if not repaired or replaced.
I have added several grounds, checked for leaks, tested any and everything a couple of times now. Even swapped out the ECU and no change at all.

What could it be?!!

The engine has a large streetport, stock ecu, no emmisions and a few other things..

 

Heres are a pic FWIW.

 

every time i have a misfire its from bad plug wires, yours look new though.

 

400 miles on rebuilt engine. New NGK plugs and wires during rebuild.

Just re routed the crank vent to the stock charcoal canister and took it for a test drive Seems to be fine up to 5000 RPMS In first but still missing and backfiring when I shift to second and give it full throttle. Voltage is good. Timing is dead on.

 

Fuel injectors recently cleaned? Maybe it just hasn't broken in enough yet? [400mi is pretty early for WOT to Red line, ne?] Aftermarket leading coil?

Sounds very weird.. >_<

 

Cleaned injectors at rebuild. Even had some turbo secondaries in for a while. Problem was worse then.

Compression was tested at 300 and was fine.

Used bearings. New compression seals I'm not to worried about.

Stock leading coil. What you see in the picture is an air pump for the VDI.

 

No ECU codes coming up.
Is 11.5:1 AFR to rich? Would that be causing these problems?

 

11.5:1 is actually a little lean for an S5 nA! although i've discovered if the ignition isn't 100% it'll misfire...

does it help to be like 50% throttle? or 75%?

 

11.5:1 AFR for an N/A too lean? Im thinking is way too rich. Im running my TII at 11.7:1 Idle and 11.5:1 full boost. Anything lower will make my car buck and miss pretty hard.



A buddy of mine made 155rwhp on his stock ported N/A and I can see him going rich after 6k rpms. AFR drops to from 13.5 to 12.5 during that point. It isnt street ported though..


Say you drive pass the staging point while bien at 50% throttle position, then after 6k will it miss? Also 400miles on rebuild is way too early to be WOT...

 

I will do some throttle position tests this weekend.

Guys, the rebuild was not of new parts needing a super careful break-in.
It was built of good in spec used parts I swept off the floor of my shop. ;D

 

nice car man i had the same problem but mines is crappy motor anyways mine was a timming like the lil screw on top of the throttle body or maybe the distributar i know its not a distributar but i cant think of the name at the moment lol

 

That was also your first post.

 

put a wideband on a stock car, the S5's run in the 11's stock. i think they are trying to keep EGT's low (they are, 730C), to keep the cats happy.

but you're also right, that running that rich needs an ignition system that is 100%.

 

Ok. I have Innovate wide band on stock ECU with a RB header and Bonez high-flow cat. Even after recalibration still looks like the same numbers.
Ignition system seems to be working just fine, however I do see a small problem.
Timing is not advancing with the revs. It only goes so far and stops. Is this correct. Looks like about 20 degrees or so.
Also when I rev it slightly with the timing light on it, it will sometimes drop back a little bit retard, and if I rev it again, it goes back to where it should. Some times I can do this one rev after the other and it goes back and forth every time.