1st + 2nd gear 5500 rpm break up. 3rd gear load pull 40 to redline (it will pull)

[supersilverspeed]

So I have read many threads and tried numerous things. No luck yet.

I have a fully built 2.0 motor. Manley rods, wiseco hd pistons, 280 cams ', titanium valve springs and retainers, valve guides , jmf intake manifold , dual Walbro 400 pumps, 2150 cc injectors , jmf fmic, 2.5 ic piping, tial 50mm bov, aem tru boost, etc. Ngk 8mm plug wires ,(new) new transistor, new br7es plugs gapped at 0.22
I am running speed density, gm iat & 4 bar omni sensor.

The car was running good up until a few days ago. I went to the track and the car launched , boosted through 1st and second, when shifting into 3rd it would break up, clear up and then again break up going into 4th. Since leaving the track the car started breaking up 1st and 2nd gear at 5500 rpm wot. But If i put the car in 3rd gear at 35 mph and wot it, it will pull to 8500 no problem. Right after i can decel and try a 2nd gear pull and it will break up.

I have tried new plugs and wires , also checked timing, did a compression test, did a boost leak test, checked all wiring. Checked all connections !!!

Car drives normally not under boost. I just don't know what direction to go into if anyone has a suggestion it would be much appreciated. I also have data logs of the car doing the issue.

 

[rnitto]

That sounds like something in the map. Does the A/F get rich or lean during the break up point? My buddy's built car was breaking up and it was as simple as gapping down the plugs a bit more.

 

[spadepro22]

Im having a problem similar to this. I've tried new wires(ngk), plugs(ngk bpr7es gapped to .020), fuel filter, checked injectors and fuel pump(running e85). Im going to the junkyard today and pull a cas, coil pack, and transistor to see if any of those help. I'll replace with new if any of the parts fix the problem. I'd try fuel filter since you don't have that listed and check fuel pump and injectors also.

 

[rnitto]

spadepro22 - Good point on the coil pack, anything to do with ignition is definitely another thing to check.