3800 NA bad miss

[alliedmike]

Hey guys.. I have a 98 bonneville with the 3800 non supercharged engine. i have been having an issue for a while now. the engine misses quite bad when its first started up (cold or hot) for anyware from 30 sec to up to 2 min, and some times but not allways it will do this when under a load even after it is driven a while. the codes i get are Random mutipule cylinder miss fire. or cyl 3 miss fire or cyl 2 miss fire. . i have replaced ignition module, coil packs, plugs and wires,, fuel filter, and had fuel pressure checked by my mechanic, he says its with in factory spec (even while missing). i have also checked all the wires and connections i can get to, made sure plug wires are not grounding out, i am at a loss for what it could be. all i have left to replace is injectors and the ecm any thoughts on this? thanks alot guys!!
Mike

 

[chopped39]

Swap injectors 2and 3 with 4&5 and see if misfire moves to those cylinders. 4 nuts and fuel rail comes right off.Dont let it dump gas down injector holes when injectors are pulled out of rail. before you do anything when car is first started and missing tap on injector and see if misfire stops.if it does stop find someone around you that cleans injectors.Not in the car.take them out and have them cleaned.they will back flush and ultra sonic clean them replace filter screens in top of injectors and flow them. Common problem with gm injectors

 

[alliedmike]

sounds like we are thinking on the same page.. now i have a set of pretty new known working 30# injectors from my grand national i was going to swap them all out..unless the factory injectors are much smaller than 30# do you happen to know what # injectors are stock in the series 2 3800?

 

[murphinator]

sounds like we are thinking on the same page.. now i have a set of pretty new known working 30# injectors from my grand national i was going to swap them all out..unless the factory injectors are much smaller than 30# do you happen to know what # injectors are stock in the series 2 3800?

I think they are 22#

the sc'ed cars are 33#

dont swap sizes if you dont have a tuner to swap the ifr tables

I have some N/A injectors for $15 ea. if you need a couple

 

[KL Mallender]

Check intake manifold for internal coolant leak(plastic cracks from EGR heat) but you would normally notice the loss from resevoir but no leaks to ground.
Happens a lot.

Kevin.

 

[chris mccord]

Broken valve springs are common as well.