Mysterious Misfires… Need HELP

[Shrek51]

These stupid misfires have been driving me absolutely nuts any input is appreciated (i’m NOT a mechanic)

for damn near close to a year now, i’ve had misfires on cylinders 3 and 4. I just took it into the mechanic about a month ago, they checked plugs, plug wires, coil pack, replaced MAF, New air filter, injectors (also ran 2 cans of seafoam injector cleaner through it with premium gas) and the shop did a vacuum seal check with their smoke detector.

Where do i go from here? what’s left to replace or look at?

 

[Shrek51]

95” V6 Convertible^

 

[shovel]

by "check" on the coil pack do you know what they mean by that? those are a pretty common cause of misfire BUT they can be conclusively ruled out so there's never a need to fire the parts cannon on them.

Have you inspected the EGR diaphragm and tube?

 

[ttocs]

yea by "check" they might have literally just looked at them and said they look ok to him. I would replace the plugs, plug wires and dist cap to say I checked them.

 

[Shrek51]

by "check" on the coil pack do you know what they mean by that? those are a pretty common cause of misfire BUT they can be conclusively ruled out so there's never a need to fire the parts cannon on them.

Have you inspected the EGR diaphragm and tu

yea by "check" they might have literally just looked at them and said they look ok to him. I would replace the plugs, plug wires and dist cap to say I checked them.

ive done plugs about 4 months ago, the old ones coming out looked the same as the new, and old owner did plug wires a couple weeks before he sold me the car (year ish ago) and as far as testing the coil pack i assume they would’ve just swapped them around to the ones that weren’t misfiring to see if it made changes, pretty sure that’s what they told me anyways. Haven’t looked into the dist cap, or EGR, what might i be looking for there? apologies haha i’m not a mechanic at all

 

[shovel]

There is no distributor on a 3.8. there is no value in swapping plug wires around on the coil pack because it's waste spark. A competent mechanic would know that. You measure across the three primary and three secondary coils for continuity and dc resistance. You inspect for cracks in the potting, and if it passes all that you do a dark room and pull the wires one at a time and check that all 6 behave exactly the same.

EGR is all visual inspection and leak testing and manual vacuum test on the diaphragm.

It would be wise to inspect the evap solenoid and hoses too. If they're original it's about a 100% chance those need replacement anyway but a stuck open solenoid and deteriorated hose to the canister would mean a wandering idle and misfire at part throttle.