Hi guys, I can't seem to figure out why my engine is cutting out at and above 5800rpm. Maybe you guys can help.

I'm wondering if my injectors are too small. On the dyno, as soon as I hit 5800rpm (330rwhp) my engine starts to hiccup. It does it everytime on the dyno and on the street (in every gear). My program is set to run to 6500rpm. It started after I ported my heads. The only modification I made at that time was to port the heads and intake.

I'm using a stock opti (which I believe is working great), stock coil, 8mm Taylor wires, and NGK TR-55 plugs gapped at the stock .050".

I've had the problem for a long time. I've tried two different computer programs, one LT1 Edit one I made, and I'm using one right now from Bryan @ PCMForLess. It doesn't make any difference, so I've ruled out it being the computer program.

Its not the rev-limiter being set too low, or me having a speed limiter.

I'm wondering if I should try closing my plug gap a little (to .045" or .040") or put in 30lb injectors. I've got a new fuel filter too by the way.

If anyone has any ideas, I'd love to hear them.

Thank you!
Steve

 

i'd look into fuel starvation or a bad coil.

replace the coil and check the coil wire, fairly inexpensive.

 

Do you have an LT4 knock module? Did the problem come after either the rockers or headers? If so and you dont have one get one, the added noise wil give you knock retard.

 

Guys thanks for the ideas!

I do have an LT4 knock module. I installed the LT4 knock module with the PCMForLess tuning, but that didn't noticeably change anything. I put the headers and rocker arms on a long time ago, and it ran to 6500rpm all day long before I ported the heads. After I ported them, it picked up a TON of power, especially with Bryan's tuning. Thats what makes me wonder if the injectors are too small.

My initial thought was it could be fuel starvation because stock 24lb injectors are supposed to be good to around 400hp, which is roughly where I'm at, but I've seen guys on this board making 350 and 360rwhp on stock injectors.

I'm going to pull my coil off and put an Ohm-meter on it, and see if its in good shape. I should have done this a while ago, but I just haven't had time.

By the way, I can rev it over 6000rpm without it cutting out if I'm not at WOT. When its at WOT, thats when it cuts out.

Thanks again for the ideas!

 

Does it sound like a popping or a backfire? Or does it sound like it's nosing off like a fuel or air shortage? If it's the latter, you may want to check your fuel pump and see if it's within spec. If it is popping, you may want to look into the coil, wires (expecially coil wire), and plugs (cracks, etc...).

 

Mine has been doing the same thing for a couple of months now, but mine is mostly stock so I'm pretty sure it's not the injectors. I put new Taylor wires on, an MSD coil, changed plugs, new fuel filter, lt4 KM, etc., etc., and I still haven't found the problem. I've searched through all the posts here, everything says pretty much the same thing. Good luck, let me know if you find out what's wrong.

 

hairbear21, there isn't any popping or backfiring, just like it cuts out like its missfiring. It isn't nosing off either, its an abrupt loss of power (like its cutting out on and off). Its like really bad detonation, but I know thats not what it is.

I just had the plugs out a couple thousand miles ago, and they look great (are all gapped appropriately, and not cracked).

I'm going to give the coil wire and coil a looksie when I get home (I'm out of town).

jgonzales, if I figure anything out, I'll let you know!

Thanks!