Misfire Very Similar To Forsfed's

[b00stingsx]

ok, im getting the very same symptoms that FORSFED was getting. my car is a 92 gsx 5sp, and is misfiring at about 4700+ rpms under wot, however under no load, it redliens just fine.

when i open up my valve cover, what exactly am i looking for? where are the "plungers of one of the intake lifters," and what do they look like. Does anyone have any pictures of this?

i want to know this so that when i go out to my un-heated garage, i can get the engine opened up, diagnnose the problem (if this is the problem), and get back inside.

thanks for the help guys!

[A//// Guy]

Might want to start simple and replace the plugs and wires. Those are the biggest culprit for misfires and stuttering under load only.

[b00stingsx]

sorry, i should have added taht... i have 8mm accels and bpr7es's gaped at .028. another thing i need to replace is my o2 sensor... but i kinda just have a feeling that its somthing different.

[FORSFED]

Like EclipseTurbo said, check the basic things first, any sensors or tune-up items that are not within spec can cause misfires, sparks, poor performance, you name it. As just about anyone can vouch for on this board, it is extremely rare for stock lifters on a virtually stock car to blow-out. Considering I don't know the history of the car it's hard to tell why it happened. I'm not saying it isn't your problem as well, just not too likely is all.

In any case it is an easy thing to check quick and all you need to do is look at the valvetrain. If a lifter is blown-out, the rocker arm that rides underneath the cam will no longer be in place because one end is supposed to be connected to the lifter that's wasted. It's pretty hard to miss once the vc is off. You could also check your plugs and if one shows lean and the other three a pretty good burn, that is also an indicator to the disfunctional valve problem.

[Shane@DBPerformance]

Just way too rich maybe?

[b00stingsx]

but if i was rich, wouldnt i be getting o2 values that are in the 90's? here is one of my loggs:


TIMA, COOL, FTRL, FTRM, FTRH,, O2-R ,RPM, KNCK
28.00º,85.63ºC,81.12%,99.84%,99.84%,,,0.92V,,,,290 6.25rpm,1.00
25.00º,85.63ºC,81.12%,99.84%,99.84%,,,0.94V,,,,296 8.75rpm,0.00
23.00º,85.63ºC,81.12%,99.84%,99.84%,,,0.94V,,,,303 1.25rpm,0.00
18.00º,85.63ºC,81.12%,99.84%,99.84%,,,0.94V,,,,306 2.50rpm,0.00
15.00º,85.63ºC,81.12%,99.84%,99.84%,,,0.96V,,,,309 3.75rpm,0.00
14.00º,85.63ºC,81.12%,99.84%,99.84%,,,0.96V,,,,312 5.00rpm,0.00
14.00º,85.63ºC,81.12%,99.84%,99.84%,,,0.96V,,,,318 7.50rpm,0.00
14.00º,85.63ºC,81.12%,99.84%,99.84%,,,0.96V,,,,331 2.50rpm,0.00
15.00º,85.63ºC,81.12%,99.84%,99.84%,,,0.96V,,,,337 5.00rpm,0.00
15.00º,85.63ºC,81.12%,99.84%,99.84%,,,0.96V,,,,343 7.50rpm,0.00
15.00º,85.63ºC,81.12%,99.84%,99.84%,,,0.96V,,,,350 0.00rpm,1.00
15.00º,85.63ºC,81.12%,99.84%,99.84%,,,0.96V,,,,353 1.25rpm,0.00
15.00º,85.63ºC,81.12%,99.84%,99.84%,,,0.96V,,,,359 3.75rpm,0.00
16.00º,85.63ºC,81.12%,99.84%,99.84%,,,0.96V,,,,365 6.25rpm,0.00
16.00º,85.63ºC,81.12%,99.84%,99.84%,,,0.96V,,,,365 6.25rpm,0.00
17.00º,85.63ºC,81.12%,99.84%,99.84%,,,0.96V,,,,378 1.25rpm,0.00
17.00º,85.63ºC,81.12%,99.84%,99.84%,,,0.96V,,,,381 2.50rpm,0.00
17.00º,85.63ºC,81.12%,99.84%,99.84%,,,0.96V,,,,396 8.75rpm,0.00
18.00º,85.63ºC,81.12%,99.84%,99.84%,,,0.94V,,,,406 2.50rpm,0.00
18.00º,85.63ºC,81.12%,99.84%,99.84%,,,0.94V,,,,400 0.00rpm,0.00
18.00º,85.63ºC,81.12%,99.84%,99.84%,,,0.94V,,,,412 5.00rpm,0.00
18.00º,83.75ºC,81.12%,99.84%,99.84%,,,0.94V,,,,412 5.00rpm,0.00
18.00º,85.63ºC,81.12%,99.84%,99.84%,,,0.96V,,,,425 0.00rpm,7.00
15.00º,85.63ºC,81.12%,99.84%,99.84%,,,0.94V,,,,418 7.50rpm,7.00
15.00º,85.63ºC,81.12%,99.84%,99.84%,,,0.94V,,,,434 3.75rpm,6.00
16.00º,85.63ºC,81.12%,99.84%,99.84%,,,0.96V,,,,440 6.25rpm,6.00
16.00º,85.63ºC,81.12%,99.84%,99.84%,,,0.94V,,,,443 7.50rpm,6.00
16.00º,83.75ºC,81.12%,99.84%,99.84%,,,0.94V,,,,443 7.50rpm,6.00
16.00º,85.63ºC,81.12%,99.84%,99.84%,,,0.94V,,,,462 5.00rpm,6.00
16.00º,83.75ºC,81.12%,99.84%,99.84%,,,0.94V,,,,459 3.75rpm,6.00
16.00º,83.75ºC,81.12%,99.84%,99.84%,,,0.94V,,,,471 8.75rpm,6.00
16.00º,83.75ºC,81.12%,99.84%,99.84%,,,0.94V,,,,478 1.25rpm,5.00
16.00º,85.63ºC,81.12%,99.84%,99.84%,,,0.94V,,,,478 1.25rpm,5.00
17.00º,85.63ºC,81.12%,99.84%,99.84%,,,0.94V,,,,481 2.50rpm,5.00
16.00º,85.63ºC,81.12%,99.84%,99.84%,,,0.94V,,,,484 3.75rpm,4.00
17.00º,85.63ºC,81.12%,99.84%,99.84%,,,0.94V,,,,478 1.25rpm,4.00
17.00º,83.75ºC,81.12%,99.84%,99.84%,,,0.92V,,,,487 5.00rpm,5.00
17.00º,85.63ºC,81.12%,99.84%,99.84%,,,0.94V,,,,506 2.50rpm,4.00
15.00º,85.63ºC,81.12%,99.84%,99.84%,,,0.90V,,,,500 0.00rpm,18.0
12.00º,85.63ºC,81.12%,99.84%,99.84%,,,0.90V,,,,515 6.25rpm,25.0
13.00º,85.63ºC,81.12%,99.84%,99.84%,,,0.84V,,,,509 3.75rpm,29.0
10.00º,85.63ºC,81.12%,99.84%,99.84%,,,0.92V,,,,531 2.50rpm,35.0
09.00º,85.63ºC,81.12%,99.84%,99.84%,,,0.70V,,,,509 3.75rpm,35.0
09.00º,85.63ºC,81.12%,99.84%,99.84%,,,0.86V,,,,543 7.50rpm,35.0

[FORSFED]

By the looks of it you've got lean issues at higher rpm, so for some reason you're not getting enough fuel. If you're feeling hesitation from 5k up it's because there is so much knock that your timing is being pulled back next to nothing and therefore the car has no power whatsoever. You've listed an safc, why don't you try richening things up on the upper band and see what happens. You have to remember that just because your afc settings worked well in the summer, they are more than likely going to be too lean for the winter due to the cold air.

[b00stingsx]

oh, yah the mods are in my sig (didnt they show up?!). here they are though:

big16g w/ 34mm flapper, k&n filter, home depot spec intake, 550 rc's, walbro 190 w/ rewire, safc, pocketlogger, custom 3" exhaust, 7es wires gapped at .028, acccell wires.

i have played with my safc quite a bit, added tons of fuel to it at 5k, doesnt change.

this issue is making me so uptight. it started after i installed my walbro 190 (last mod i did).

any other ideas of what is going on before i tear into things?



ps. i didnt have the settings in the summer, i had the safc installed this winter, way before this all started.

thanks again for helpin me out!

[TheBlizzard]

Have you checked your fuel pressure? Have you checked for boost leaks?

CRAIG

Oh yeah and check your alternator fuse (Right Nash)? :jammin:

[TheBlizzard]

I was also wondering, is there computers that don't have a shift key? What do you think AJ? I am beginning to wonder since a lot of people don't seem to have one.

CRAIG