Severe misfire at about 1/2+ throttle under 3k rpm. Help!

We may earn a small commission from affiliate links and paid advertisements. Terms

dtob

dtob

New Member
Hey guys,

Tried searching but couldn't really find too much help. Lots of bogging threads and misfire threads but not exactly my problem. I'm going to check and make sure the dizzy is firing tomorrow with my timing light but I have a new 255lph pump, tried different MAP sensor and TPS. Gonna get a new dizzy anyway because I'm rocking the LS dizzy on my LS/Vtec.

Any ideas?

I did read something about a main relay. What the hell is it and what does it do?
 
Blanco said:
Does it make a sound like marbles in a can?
Click to expand...

Hahaha.. no.

I just misfires. I think my dizzy might be the problem. I'm going to get a new one soon. Just thought you guys might have something else for me to look at while I'm at it.
 
Ya it runs really strong after 3k but from idle to 3k is misses but misses less the higher rpm I go. eg. at idle its really bad but at 2500 it only misses a little and after 3 not really at all.

PS its an ls/vtec with eagle rods, srp 12.2:1 compression slugs, type r oil pump, dohc vtec water pump, 255lph fuel pump, chipped P28 on crome, arp head studs, skunk2 IM, etc etc etc. Its built pretty good, all plastigauged. I'm sure its something electrical. Hopefully the distributor fixes it. I tried a different tps and map sensor so I know that's not it. Hoping its not a fuel problem but well see.
 
Blanco said:
The tune is what I was concerned with.
Click to expand...

I have an ostrich hooked up to my ecu with a wide band o2. I have a B16 base map with the GSR fuel and ignition super imposed on it. I have it tuned safe to run a mid to low 13:1 afr throughout the RPM at different throttle postitions.
 
Ok, so I found out what the problem was and if anyone else has the same problem or encounters it in the future this might work. The problem has been consistantly getting worse so I figured it was time to actually start replacing parts. Started with the plug wires and plugs. Cleared the problem right up.
 
I replaced the plugs and wires the first time I rebuilt it and only put about 700k on it before rebuilding it again but I must have nicked one of the wires when I was putting the engine back in. I just did the plugs again because it couldn't hurt to do it. I am still having a hard time starting it when its cold so I checked the resistance on the TDC sensor and it checked fine at 450ohms but the engine was already warm and the CEL goes away when the engine is warm. I'm going to look into it a little more tomorrow. Might check the wiring and re-solder my connections.
 
Check your plug gaps too. Sometimes when it bogs or detonates it can blow the plugs open a lil. Seen it happen before....
 
You must log in or register to reply here.
Back
Top