missfire

[kb3jhp]

I have a 98 GMC Sonoma with the 4.3vin w it runs good except it has alight miss when the rpms are held at a constant speed like cruising on the highway I had it hooked up to my scanner and could watch all the reported miss fires and they are all random I also no that cam retard being off from dist gear wear can do this. my? Is will -12 degrees make it miss like this?

It has had 2 new caps and rotors acdelco
2 sets of plugs acdelco
New acdelco wires

it does not send any codes

I also had it hooked up to a pico ign scope and test fine but it only miss while driving i wish i could have it hooked up while driving

i want some other ideas before replacing the dist gear

[MT-2500]

Yes.
If it is off more than 2-3 degrees neg or positive.
Also a lean running condition can give a missfire.
Check fuel pressure and MAF sensor. also.

Reset the cam retrt setting as close to 0 degrees as you can get it.
Is your dist adjustable? Or one of the fixd ones?

Here is how to do the base setting on dist.
http://files.automotiveforums.com/ga...hp?photo=51302

After base setting some need fine tune by turning the dist.
MT
MT

[kb3jhp]

it is set the shaft is shaped so you cant turn it

[blazes9395]

Your not talking about just normal advance are you?

[MT-2500]

Originally Posted by kb3jhp

it is set the shaft is shaped so you cant turn it

As said make sure you are reading cam shaft retard.
Pull cap and move engine to tdc compression and check the dist setting as in picture I posted.
Also make sure you have a AC Delco cap and rotor.

The no adjustable dist clamps can slotted sideways with a drill or rat tail file to get some adjustment on dist.
But if it is around 12-15 degrees off I would pull dist and turn the dist gear a half turn.
A rebuilt dist and some times a gear replacement will have the gear a half turn off.
A half a turn on gear will usually bring the setting back in from 12 -15 degrees off.
Good luck
MT

[kb3jhp]

Originally Posted by blazes9395

Your not talking about just normal advance are you?

I put the new dist and it fixed the miss the truck also seems to have more power. The cam shaft position sensor is in the dist so when the dist gear wears it will read -cam position even if the cam is not out time with the crank. On the 4.3s the dist can not be turned to correct for wear I sometimes wonder about Gms engineers. So the only way to fix this is to replace the dist gear. I wonder if this would be a could check to see how good the engine was maintained my bravada with one hundred thousand miles the same as my truck was only out -1 but it was maintained by my dad and had Mobil 1 every 3000