asianspeed

Please help me. This is the only thing holding me back from boosting.

The car misfires about 3-5 seconds after I start it. Because the car is cold, it idle's at about 1200 rpms...doesn't seem to misfire, but it might be. And then it starts to shake and run rough, and the rpms jumps up to 1,600 rpms and stays there.

I've got a misfire in cylinder 4. I switched the plugs in cyl 3 to cyl 4....just to see if the misfire changed. It didn't....it's still in 4.

I also disconnected the plug wires, so the distributor is working.

I also checked the plugs...beside for being a little rich, they look good. They're brand new plugs, two steps colder, gapped to .032.

I also checked the fuel injectors with a screwdriver....it's clicking...so it's working.

I just can't figure this out. Would gapping the plugs differently help?
Would new plug wires help?
What could this be???

Please if you have any ideas please post. Thanks in advance.

PM-Performance

what fpr do you have? i ahd the same prob with my aem fpr , when i stinalled my walbro 255 it maxed out the sotck orfice and had to change it to the middle one.

its a long shot, but worth a try

asianspeed

I've got the stock fpr. I'm using the map limiter, which doesn't need an aftermarket fpr.

Smashback

You're thinking FMU, not adjustable FPR.

Sounds funky though, I have no clue.

PM-Performance

i dunno then man , i think its fuel related, but try to gap thme to 30 and see what happens , youd be suprised, i had some dumb *** probs and the gap fixed it

Speed PHreak

Are you plug wires good? You could have one thats arcing and causing a misfire on that cylinder. Sounds like one thing you didn't check from your initial discription. I know it's off the wall, but happened to me once.

asianspeed

Can I run a 30 gap on cyl 4 and then 32 on the others? Or do they all need to be gapped the same? I read on another post to start at 32 and keep going lower until there is no misfire...so I'm going to go and try that.

asianspeed

Speed Phreak, I was thinking that too. I'm going to switch wires with another cylinder and see if the misfire changes as well. However, I did pull the wire out of the distributor and there was current jumping...and then I pulled it from the spark plug side and I could hear the current jumping as well. So I think that the wires good, but I'll check anyway.

After that, I'll regap the plug.

Whooopasss

You see a miss fire as a cel code right? last time we had a misfire on 3 and 4 on the gsr that we were working on, it had a bent valve on 3 qand 4.

asianspeed

Speed Phreak, I was thinking that too. I'm going to switch wires with another cylinder and see if the misfire changes as well. However, I did pull the wire out of the distributor and there was current jumping...and then I pulled it from the spark plug side and I could hear the current jumping as well. So I think that the wires good, but I'll check anyway.

After that, I'll regap the plug.

asianspeed

Ok, I think I've found the problem. I did a compression test and I got 175 across the board. So that was good. Then, after I put all the plugs back in and started it up...nothing was wrong. Then it went into misfire mode again...and I rechecked the injector with a screwdriver. And it's no longer clicking like it used to. So I think that I'm going to have to take it out and get it checked. Is there anyway to test it myself?

Thanks for all your help everyone. I'm glad it wasn't a bent valve.