Vortec 4.3 misfire

[96Astro]

I have a 96'Astro with less then 140k. After damp weather it would misfire a bit. Then after a long period of sitting, it would start at all. Cap and rotor where replaced and it ran sometimes good sometimes misfiring with a check engine code. It seem to improve after driving the vehicle 20 miles or so, but would always act up the worst after sitting overnight or more than a day.
New wires and plugs were finaly introduced, and the problem is worse. Im at my ropes end with this issue, and dont know if I should start in on the nightmare that is the CSFI SYSTEM. Ive done my research on these 4.3 motors and dont have the money to go through every little thing from cheapest fix to most costly.
PLEASE HELP

 

[guyonearth]

This is most likely not a CSFI problem, and they're not really a "nightmare", matter of fact, they're pretty easy to service. If you're having a problem on cold starts/damp days, the first thing you need to replace is the ignition module AND coil, one or both may have a crack that is letting your signal ground out. Also, obviously, make sure your wiring is in good condition. I would see this problem occasionally on the old Astros I had, and when I popped the hood on a damp morning, the engine would be covered in condensation sometimes.

 

[Warstud]

Probably your Rotor.

 

[A_Harman]

If the Check Engine light is on, go to your local AutoZone and get them to read the codes for you. This they do for free. Knowing what the code is would be a great help in deciding what needs to be fixed.

 

[Bgallagher]

Originally Posted By: Warstud
Probably your Rotor.


That's what I was thinking too. Those engines are easy to work on and depending on what your budget looks like it might be worth replacing the rotor, plugs and cap in that order. At the very least replace the rotor and pull the plugs. Check for anything abnormal and regap them (replace them preferably.)

 

[SteveSRT8]

Never seemed to be any sense in replacing a rotor without a cap IMO. But sometimes a good cleaning of the contacts will help, too.

The wires are highly suspect if moisture is involved...

 

[The_Eric]

Originally Posted By: SteveSRT8


The wires are highly suspect if moisture is involved...


Yep.

You said plug wires have been replaced, but what about the coil wire. I don't know why, but on these CSFI engines (6 and 8cyl alike), they're really hard on coil wires. Seen many burn through and arc to various points. Also check on the coil.

 

[Trav]

Originally Posted By: The_Eric
Originally Posted By: SteveSRT8


The wires are highly suspect if moisture is involved...


Yep.

You said plug wires have been replaced, but what about the coil wire. I don't know why, but on these CSFI engines (6 and 8cyl alike), they're really hard on coil wires. Seen many burn through and arc to various points. Also check on the coil.


I remember years ago Bosch said the coil wire was higher resistance than the plug wires to prevent EMI/RFI. I always thought it was because it did 4, 6, 8 etc times the work and maybe got hotter internally and broke down.

 

[Warstud]

Originally Posted By: Bgallagher
Originally Posted By: Warstud
Probably your Rotor.


That's what I was thinking too. Those engines are easy to work on and depending on what your budget looks like it might be worth replacing the rotor, plugs and cap in that order. At the very least replace the rotor and pull the plugs. Check for anything abnormal and regap them (replace them preferably.)


Actually meant distributor cap.

 

[JetStar]

Be careful with your choice in parts. An autozone dist. cap took my 96 GMC down, It wouldn't run 6 months after installation. Good thing I kept the OEM 100K mile cap. Put it back on, fired right up. Still on the truck today AFIK.

 

[2004tdigls]

check the distributor, they wear badly at the tail where the gear is located, my friend had the same problem in his 4.3.

its a huge problem in these motors as they age

https://www.youtube.com/watch?v=se63j2q_5GA

http://www.astrosafari.com/viewtopic.php?f=43&t=6569

http://www.s10forum.com/forum/f107/check-your-distributor-gears-502203/

 

[The_Eric]

Originally Posted By: Trav
Originally Posted By: The_Eric
Originally Posted By: SteveSRT8


The wires are highly suspect if moisture is involved...


Yep.

You said plug wires have been replaced, but what about the coil wire. I don't know why, but on these CSFI engines (6 and 8cyl alike), they're really hard on coil wires. Seen many burn through and arc to various points. Also check on the coil.


I remember years ago Bosch said the coil wire was higher resistance than the plug wires to prevent EMI/RFI. I always thought it was because it did 4, 6, 8 etc times the work and maybe got hotter internally and broke down.



Interesting. Thanks for sharing that tid bit.

 

[Warstud]

The Distributor Caps on these have issues with the vents on them plugging up and moisture being trapped inside... causing hard starts. Try taking off the DC and cleaning the terminals on the inside and coat them with dielectric grease. See if that helps.