93 mark stumbles light throttle when warmed up

[Moes8]

my dads 93 has been "bucking/stumbling" at light throttle after it is fully warmed up,sometime it will only do it once in an entire day,other times it will do it 3-5 times

he replaced the plugs and wires ,

checked for codes,there were none.

someone told him it might be his coil packs? what are the symptoms of those going bad?



when the engine is cold it never does it,

also medium throttle or harder and it never does it,the runs awesome other than this stumbling.

any ideas?

 

[98LSC32V]

Could very well be coil packs. On my old 95 LSC that had new wires and plugs, going uphill with load on the car it would stumble/hiccup. Replaced the coil packs and no problems after.

 

[The Rev]

I am having the same problem. I planned on replacing my coilpacks anyway, this might speed this along. Its almost as if when giving very light throttle nothing happens, the throttle is as responsive in low levels as I'd like.

 

[ladenblowfish]

My mark also has the exact same problem. I've changed the plugs, wires, both coils, all filters, seafoam, and both o2. Nothing has fixed it.

 

[PIMPLINC]

my 94 is the worse now... after putting on the LMS MAF kit it got way worse which leads me to think it is fuel related, looks like it is running really lean in the mid rpm's so i am going to throw on a gauge and see what it reads under all conditions.....it kinda sounds like back firing to me in the intake, I have to pull the drivers side valvecover off & have a look at the valve trane...

 

[Staffamerica74]

I had this condition. I started out thinking it was fuel related so I did a filter and the 255 walbro pump. No better, Went and did fuel injectors went to 30lbs. Still no better finally I went and got some screaming demon coils and viola fixed.

 

[unity]

See if you can check fuel pressure. I tell people its just like testing blood pressure, when you go to the doctor they check it your blood pressure almost always. Its a good thing to always check when the car has a problem too.

You may want to check out the MAF. A cleaning with non-filming electric parts cleaner can never hurt. Just don't touch the actual sensor with q-tips and such. Just spray liberally.

Coil packs could be the issue also as pointed out. The can go bad just from age alone, not milage. I have had issues with them too. In fact the ones I had problems with were just months old! Talking about chasing my tail trying to find a problem! I ruled them out, after all they were new!