bad miss

[Crazyx4]

engine has a bad miss around 3000 rpm's. i have changed plugs,wires,cam sensor,crank sensor,coil pack,ignition module,checked crank thrust. I need help. thanks

 

[deathraider6996]

Coil pack/ignition known working unit? Just curious because I had the same problem.

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[Crazyx4]

I'm going to try another one this weekend. It's off my brother's car. thanks

 

[Crazyx4]

Tried the other ignition module and had the same miss. Can the O2 sensor cause this issue. I turned it 1/2 turn and it acted if it may have helped the problem. Still has a miss. Maybe the XFI going out?

 

[TurboBuRick]

Start it cold and let it run for only a few seconds and shut it down. Carefully feel each header pipe coming off the head. Look for the cold one. That's your dead cylinder. From there pull the plug and try to narrow down if it's fuel or spark that's not there.

Rick

 

[cesarpena]

Mine did the same thing after 2 new coil packs. One from autozone & one from O'reileys. Had to return both new. Check coil pack.

 

[1fastcobra]

Bad injector
Have u replaced your timing chain?

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[dank GN]

How's your MAF? ?

 

[TexasT]

So the brother coil not doing the miss on his car?
Plug wires ohm good. Sure they are snapped onto plug? Inspect plug ceraminc. Maybe swap some plugs to different cylinders and see if it changes.
Fuel filter new? Pressure dropping at this rpm?
Tap on the maf at idle or swap it w/brothers to rule it out.
Cam sensor in good condition? Lots of miles?
Crank sensor clearances correctly? Turn the engine may be one of the hall effect fins is bent.

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[Crazyx4]

started the car and let run a few seconds. checked the headers and they all seemed warm. checked the ground wires on the block and the body.so I thought I would try let the car run to warm up and check to headers with my temp. gun. I did find the the #3 to be alot hotter than the other one's. the injector must have something wrong. the #3 temp. was around 550 deg. and the rest was around 320 deg.,is that scray or what? I have never checked this before, so I don't know what the temp's should be. I have 96lb injectors but I'm thinking about going with 120lb one's. any suggestions? I haven't pulled the injector's out yet. I would love to have one to try. so I guess I will save up to buy the new one's. thanks for the help. I don't have a MAF. everything else checks out ok.

 

[TurboBuRick]

Your running xfi? Check map signal?

Can you get a log key on engine off? And another one idling?

 

[Crazyx4]

yes, xfi. haven't tried to map it with the engine off.

 

[Crazyx4]

I think that I have found the miss. Changed the plugs again. Had NGK 4554 in it and put NGK 5820 in. The thing runs now. While doing a few logs in the driveway, the TPS sensor went out. Changed TPS and I hope it's all good. THANKS FOR THE HELP. Going to the track ASAP. Before it catches another BUG.

 

[Crazyx4]

What spark plug is anyone else running that has close to the same setup as I do?

 

[Nero328]

I am having this exact issue right now and have also noticed #3 running much hotter than any other cyl. I have also changed everything you have with the exception of the plugs at this point. It's very weird because it doesn't seem as bad at higher Rams but is a dead miss at idle. Any thoughts.

 

[bison]

Tried the other ignition module and had the same miss. Can the O2 sensor cause this issue. I turned it 1/2 turn and it acted if it may have helped the problem. Still has a miss. Maybe the XFI going out?

You need to figure out if its a random miss or the same cylinder. If it's that prominent you should see a charge in surface temp on the header tube. Check tube temps and see if you can see an obvious problem there. If you do move the injector over to another cylinder and see if the problem moves. This is assuming you already verified the cylinder isn't leaking excessively or any harness or pin issues and all grounds are good


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[bison]

I am having this exact issue right now and have also noticed #3 running much hotter than any other cyl. I have also changed everything you have with the exception of the plugs at this point. It's very weird because it doesn't seem as bad at higher Rams but is a dead miss at idle. Any thoughts.

A dead miss should be easy to figure out. The cylinder will be cold.. Does the cylinder have good compression yes/no. Is there spark yes/no, is there fuel yes/no. I usually test for spark first because it's easiest for me. I would hear a compression issue typically while cranking. If it sounded like a low hole Id do a compression test. If I came up with nothing Id look for a fueling issue. If no voltage issue and harness was not shorted then I'd move the injector and see if the next hole dead missed. At this point if have found something. If a fueled cylinder dead misses for a couple minutes the plug will be soaked if the intake valve is opening at all. Dry plug after running yes/no. Dry move injector. Wet look for ignition short to ground (not via spark plug). Wet with low cranking compression but still misfires and holds air when you apply shop air Id look for broken rocker arm or flat cam lobe


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[Nero328]

You need to figure out if its a random miss or the same cylinder. If it's that prominent you should see a charge in surface temp on the header tube. Check tube temps and see if you can see an obvious problem there. If you do move the injector over to another cylinder and see if the problem moves. This is assuming you already verified the cylinder isn't leaking excessively or any harness or pin issues and all grounds are good.


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I should have explained that...I tested and all Cyl were 148-149 PSI. All of my grounds are solid and I double checked the pins in the ECU and they are all good. I haven't been able to pin down which Cyl yet and the temps are pretty consistent with the acception of #3 which is almost 200 degrees higher for some reason! This is a brand new motor, all internals are new. See build in my signature. I have also replaced, crank sensor, cam sensor, coil pack and ignition module, plug wires and now plugs.

 

[pacecarta]

What spark plug is anyone else running that has close to the same setup as I do?

track ...autolite racing AR3933
http://www.summitracing.com/parts/atl-ar3933

little warmer for streer would be ar3934

 

[bison]

I should have explained that...I tested and all Cyl were 148-149 PSI. All of my grounds are solid and I double checked the pins in the ECU and they are all good. I haven't been able to pin down which Cyl yet and the temps are pretty consistent with the acception of #3 which is almost 200 degrees higher for some reason! This is a brand new motor, all internals are new. See build in my signature. I have also replaced, crank sensor, cam sensor, coil pack and ignition module, plug wires and now plugs.

You don't have a dead miss then. How did you test for fuel and good spark. There's a lot more pins beside the ecu


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