ENRKyle20

Car runs like a champ at low rpm, cursing speed, or under hard acceleration until it hits 4800-5200 then it loses a lot of power and backfires a lot. I assumed it was the stock fuel pump but I just installed a 255LPH pump and its the same. Next will be the fuel filter. I don't think that's going to fix the problem. what do you suggest looking at next?. ignition? Is there anything a scan will reveal? (need to wait a few days until i get a new battery for my laptop)

Hal Fisher

Does it do it when just reving? Then probably not the fuel pressure. Check for codes. If neither of those it could be opti, icm, coil. Not sure about other things.

Hal

ENRKyle20

I have not tried reving it that high with it in neutral. But i will give it a shot to see how it responds. I dont have any codes at this time. I guess I need to throw some iginiton parts at it soon.

ENRKyle20

ok. I did a rev with the clutch in, went right up to 6800 no problems, no misfire, nice and smooth. This is a decent indication that the ignition is up to the task (at least while not under a load, but I cant image that changes TO much for the ignition system). So no I am leaning a little close to fuel filter not being able to flow enough at that rpm under load.

But now i have other problems to chase, after that rev I lost all oil pressure. Started a thread in the LT1 section about that.

bw_hunter

I wouldn't say that revving in Neutral tells you the ignition can handle the under load condition....all you know is that it can rev in a no load situation.

I guess you can change the fuel filter and I hope that works but it seems odd that it''ll rev to a specific point and then die...wouldn't you expect it to vary a little. Anyway, a filter is cheap and easy.

userchemical

well i can tell you from experience its your ignition system. Time to do opti, plugs wires and maybe a coil.

First check your coil see if its missing. spray the coil with some water and look for sparks coming off the boot. If you don't see any sparks that means that the wire boot is still nice there. I would say spray your opti too, but it would be dead for sure after that and you can barely see it. But either way that's your problem, the opti. While you're there might as well do plugs and wires. if you know what you are doing its a 1.5 hour job.

ENRKyle20

plugs on this motor with the pacesetter midtubes is very close to imposable. I had a hard time with the motor on a stand. The plugs only have 700 miles on them anyway, so I would leave them alone. The opti and wires are MSD (I kno thats a downgrade from delco).

95M6Z

My car began doing this after about 2000kms on the new opti it had lots of ***** down low but sputtered up top. Look into converting to coil packs and be done with the opti! thats what I'm doing

ENRKyle20

whAT does that cost?

95M6Z

Under a grand, probably in the $700 range .But for me I've replace 2 optis' so the price becomes pretty reasonable if it means no more crossing fingers that the opti will live. I'm not an expert on what else you need for the conversion but I believe you need a good opti base. Your best bet is to search on here because I know I've seen people post about the conversion. Hope you can get it running good! I hate when mine runs crappy!

Injuneer

Bailey LTCC, uses the optical signals from the Opti:

http://www.bailey-eng.com/LTCC.html

EFI Connection, deletes Opti, uses an LS1 PCM:

http://www.eficonnection.com/eficonn..._cylinder.aspx

But you shouldn't need a multi-coil system to get that engine over 5,000rpm. Stock ignition should be able to handle it. Revving the engine under no load proves nothing, nada. There is very little load on the ignition system under that condition. Put the engine under load and WOT/max RPM and the ignition system has to work much harder.

userchemical

well i say you learn how to get them out, i can have my plugs out in 10 minutes.

ENRKyle20

not with pacesetter midtubes..

Hal Fisher

Trying to understand the difference on ignition under load - no load. I guess under load there is a lot more gas in the cylinder and it could be blowing out a weak spark?

Hal

ENRKyle20

yea when you got the throttle open it gets a lot more air in the cylinder and and more gas, then its compressed, that's more stuff making it hard for the spark to jump. more stuff resisting the transfer of electricity. I already have them gaped pretty small to try to save my opti and to prevent problems like this. its at .035"

if its harder to spark in the cylinder then it may find an easier path outside the combustion chamber.