I wanted to try and get some input from you all before digging around in the motor too far. I hope this is in the right section, apologies if not.


My Bravada started missing after sitting for a few days. At first,I thought it was the fuel filter. Changed it, which helped a bit. But it still misses at idle (P) up to about 1k to 1200 rpm in park, but stops missing at higher rpm. It also misses at WOT when in gear, but stops missing when I let off the gas.


It threw a P0303 (I know, cyl 3 misfire), which makes sense. I unplugged the #3 wire, which gave me a steady miss and the same P0303.
I'm hoping it's just a simple tune up in order. Starting to wonder when the guy put the plugs in it.


What do you guys think?

 

If you don't know the history of the vehicle, a tune up would be a great place to start. These things are very fussy when it comes to plugs, cap, rotor & wires.


AC Delco 41-993 plugs .060" gap.
AC Delco D328A distributor cap.
AC Delco D465 rotor.
Autolite 96871 plug wires (cheaper & better specs than AC Delco).


Stay away from aftermarket stuff on these parts.

 

Checked out prices on rockauto, about $70 for everything you listed, before shipping. That's pretty good for all ac Delco parts.


Is a fouled or worn plug the likely culprit? Either way,I wanted to do a tune up, so they'll be the first thing I get to.
At first, when I saw the steering shaft in the way, I thought "oh crap". I saw in another post, it's easy to just unbolt it and move it.

 

A ton of things can cause misfires, but best to start with a good basic tune up.


If you take the intermediate shaft apart for access to #3 plug, Lock the steering wheel so it can not turn while the shaft is disconnected from the gear box. Damage to the clock spring will occur if the wheel turns.

 

I know all about the clock spring and related issues. My uncle used to be an army motor pool mechanic. He drives a Subaru, and he had to do something that involved removing the shaft, and he forgot to lock the steering wheel, and it moved. When he went to turn, he heard a pop, and his lights stopped working til he got everything replaced.
Good thing the Bravada has a locking steering wheel.

 

Yes Rock auto is where I bought al my tune up AC Delco parts and your right that is a good price from them on these parts. This is the best place to start like the Capt. has said. Also look at the engine at night with no or low light to see if you see any arching on or around the plugs and wires and coil. This can tell you if your leaking any voltage to a plug which can cause a miss fire.

 

I was also thinking about running Marvel Mystery Oil through the PCV line to help clean the valves. Did it on the Alero, and it drove like a new car. The throttle response was much sharper, too.

 

Just changed the plugs, and the miss is almost completely gone. In drive, it only misses now at WOT. When I get the wires and put them on, that should clear it up the rest of the way.

 

Did you replace the distributor cap and rotor?

 

Not yet, those are next after the wires. Got ac Delco plugs from Autozone just so they'd be done, ordered the Autolite wires from RockAuto and next week, I'll get the cap and rotor from them.
I'm just glad the miss is almost completely gone, except for WOT in drive. Even then, I've heard the wires being worn out would cause it to miss at high rpm under load. The wires will probably fix it all the way. Still going to do the cap and rotor, so I'll at least know when it was done, and it'll be with the right parts.