bad misfire on 5.7 vortec

[westman995]

97 yukon 4wd. Seems like I'm getting a miss on 3 cylinders. No codes show up other than the p1345 which Its had since I put the engine in a few years ago. I can tell the exhaust manifolds don't get hot on some of the cylinders.

Just replaced the intake gaskets since I bought them a while ago but never put them in. Didn't help at all. Old plastic gaskets looked pretty bad tho.

Truck doesn't have cats on it so its not plugged cats..

Any ideas?

Oh ya and if I rev it up, once it gets past like 2300rpm it stops shaking. But it shakes so bad and has no power I can't even drive it

 

[westman995]

Anyone? I'm lost. I'm hoping to get this thing running right before winter comes around

 

[BirchyBoy]

Are you somehow tricking the system into thinking the cats are working?

 

[westman995]

I have some non foulers on the rear o2 sensors so they're spaced out from the pipe. This was done sometime ago and never had a problem so I don't believe it to be any part of my problem. Plus the rear 02 sensors don't change much as far as I know.

 

[westman995]

Anyone?

I want to put a new cap and plugs in it but I don't have money to throw parts at it that may or may not work.

I notice that when its running I can hear almost like a clicking noise. I turned the distributor a bit and it stops if its turned far enough. That's why I want to put a cap on it

 

[westman995]

Judging by the infrared thermometer, I'm getting a no fire on 3 cylinders. I changed the plugs, nothin different.. no misfire codes come up.. I have no idea what to Do next.. anyone seen anything like this before?

 

[ezdaar]

pop cap, check tabs inside for heavy corrosion. clean them and the rotor.

Pull fuel pump fuse.

Pull wire from dead cylinders, shove nail into spark plug boot or old known working sparkplug.Touch plug to exhaust manifold/
have friend turn engine over.
DO they Spark?

Pull plugs from dead cylinders. after vehicle idles for a min, are they coated in fuel?

Do some testing and narrow down your problem..

Obviously your timing is WAY! off now that you have dorked it around a few times..

 

[westman995]

Have the cap off right now, ill clean it up n put it back in. Last time I checked it had spark, ill check it again. The timing isn't adjustable. I understand If its too far off it'll run ****** but its always ran fine, for years and I never had the distributor set

---------- Post added at 03:42 PM ---------- Previous post was at 03:40 PM ----------

And no I don't think the plugs are coated in fuel, as far as I could tell.. which brings a good point to maybe being the injectors

 

[ezdaar]

Dude, you turn that distributor, your adjusting timing. ECu will try to comp, but it can only go so far..

AKA, it IS adjustable.

 

[westman995]

I've always been told you can't adjust it. But I guess to an extent it can be. I cleaned the cap and rotor and now I'm getting a random misfire code. Its never done that before even when I moved the distributor all over.

It is running SLIGHTLY better. Has a little more power but still runs like total shit.

I'm almost thinking I need to just buy a cap and rotor for it either way.