Misfiring issue

[1998Suburban]

Weak coil perhaps? I've seen them do weird things as they get hot. Your comment on cold vs. hot misfires makes me wonder

 

[DallasTahoe]

Weak coil perhaps? I've seen them do weird things as they get hot. Your comment on cold vs. hot misfires makes me wonder

It's a brand new coil, changed when I changed the cap rotor and wires

 

[ccapehartusarmyINF.(ret)]

well i know my plugs have to be gapped at .040

 

[ccapehartusarmyINF.(ret)]

Weak coil perhaps? I've seen them do weird things as they get hot. Your comment on cold vs. hot misfires makes me wonder

thats got me scratchin my head to usually things get better when the engines warm like with myh suburban i get rough shaky idle and lean codes when its idling cold
and when it warms up it idles perfect

anyone think it mite be a bad manifold gasket? can a manifold gasket cuase the fuel mix to get that lean to were its causing misfires ?
just a stab in the dark

 

[DallasTahoe]

Yea I don't get it either, for about the first 30 minutes it runs good, no bouncy idle, just nice and smooth then, the idle gets really rough I don't get it at all


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[1998Suburban]

New coil doesn't necessarily = good coil. Do you have the old one or can you swap it for another? I've had so many crappy new parts it isn't even funny. I had a bad Wells coil out of the box on a Grand Am and it took me forever to figure that out. Would run perfect for 20 min or so then die.

Have you checked fuel pressure when it starts running rough?

 

[DallasTahoe]

New coil doesn't necessarily = good coil. Do you have the old one or can you swap it for another? I've had so many crappy new parts it isn't even funny. I had a bad Wells coil out of the box on a Grand Am and it took me forever to figure that out. Would run perfect for 20 min or so then die.

Have you checked fuel pressure when it starts running rough?

Yea I've got the old coil, I just bought a new one just because, it wasn't needed. I'll swap it back out tomorrow. I just put in a new Delphi fuel pump a month ago while it was having this problem and it made no change....

 

[1998Suburban]

Any change by putting the old coil back in?

 

[DallasTahoe]

Any change by putting the old coil back in?

I haven't changed it yet, I will in the morning, I wanted to run my scanner on it today while I drove all day to see where and when my misfires were happening the most. It's definitely only in low rpms (below 1000) and only when cold. On the freeway I get no misfires at all whether hot or cold. I'm thinkin you may be right about the coil, one of my dad's old trucks had coil issues when it would get hot but it was the old oil filled coils, but it makes perfect sense even though it's a different style, I'll find out in the mornin I guess

 

[ty707]

Keep getting this code, when I had a tech come and check it out before I put in a new fuel pump I had no problems but he said that normally when the regulator goes bad you'll get that p0306 or p0304 or p0308 or all of them at the same time depending on how bad it is, any truth to this? Anyone had experience with this?


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are your rpms dropping while your driving?