This is my '85 BRAT, bone stock.

 

Put new NGK plugs and NGK wires on it last weekend, just 'cause it was due for that stuff. Cap/rotor looked good at the time and wasn't replaced, besides,, those parts aren't that old.

 

Anyways,,, now it has a rough idle, and misses until it gets into the upper RPMs. Has since doing plugs/wires.

Pulled the plugs today, they look to be even in color throughout the set. Ceramic is still fairly white looking, just a tint of discoloration on the side electrode.

 

Re-checked for the umpteenth time, that I do infact,,, have the plug wires routed correctly on the cap and plugs.

Rechecked disty timing, it's about 8.5* BTDC.

Checked for vacuum leaks, found a couple of possibles and repaired them.

Pulled plug wires individually as it sat idling. No matter which one I pulled, engine ran worse. So it isn't just one cylinder causing it.

Swapped in a different "used" cap/rotor, no change.

 

Been hearing a snappish sound out of it for the past few weeks while driving to/from work. Sound is coming from the headerpipe(s) from what I can tell while driving it.

It is not "spark knock".

Sounds more like a late firing cylinder. Comes and goes, and doesn't relate to engine load, IE: pulling a hill, lugging engine down, what have you. Just does it when it wants too.

 

Ran some Seafoam thru it in the tank prior to this tank full. While the Seafoam was in there, no "snap" noise. Get another tank of gas and it's back. Gas is from same station I always get it from. Down to about 1/4 tank on this last fillup.

 

Somebody, please,,, give some ideas to check on. I'm at wits end here....

Your way better at this than I could be and I know you have a lot more experience than I do. Could you have an advance or vacuum problem in one of your restricted lines? The ones with the little plugs. I know they get clogged. I just remember them being there and I'm not remembering where they go right now. I'm assuming no leaks and its not oil related and your o2 sensor is good. All sensors and thermo switches are normalish. Anti-freeze smells normal. Cat?

 

Anyways,,, now it has a rough idle, and misses until it gets into the upper RPMs. Has since doing plugs/wires.

 

Somebody, please,,, give some ideas to check on. I'm at wits end here....

 

Swap the old wires/plugs? back in.

Check resistance of the new wires.

Make sure coil top is clean.

Sounds like a classic vacuum leak - maybe something came loose while you were doing plugs and wires? Spray around with a can of carb cleaner and see if you find something?

 

GD

Yeah, I was thinking vacuum leak myself.

Spent time yesterday looking things over and didn't find anything obvious. (I did find a couple of the hoses that attach to the breather can that had split the day I did the plugs/wires.)

Need to round up all the empty cans around here and take them in, maybe I'll have enough from them to get a can of carb cleaner.

 

Now I get to hunt down the reason the headlights decided to not work last night. Ziltch, nada, nothing....

Thinking of naming this BRAT, Murphy...

Fix both issues today.

 

It was indeed a vac leak. Hose had come off a nipple on the manifold. Was laying right beside it and looked as if it was ok. Different view angle exposed it.

 

Headlight issue turned out to be burnt connection in the connector for the dimmer switch.

Tom

 

Thanks for posting your solutions.

 

I've got the same carb issues..I'll look into those possibilities when my "Subaru driving season" comes back this fall.

 

(And thanks to GD for your suggestions)

And here I thought it might be something more complicated.....

 

"I'm at my wits end......"

And here I thought it might be something more complicated.....

 

"I'm at my wits end......"

 

Honestly,, I was "there" at that time.

 

Swapped plugs and wires, lifted breather can just enough to allow ease of wire routing under it.

 

Hose that came off isn't routed to breather, and really isn't close to any that are. So I don't know why/how it came off.

 

Didn't actually "see" it until I leaned over the breather, putting my head where the spare tire goes. There it is....

Was having the same problem on my buddies brat. this helped. thanks guys!