alright i have a 96 3.8L A4 with 117,000 miles on it. my problem is i get a slight misfire or stumble under load. i also got to backfires last night as well. i just changed the plugs about 3 weeks ago due to same thing but without the backfire and not as bad of a misfire. i have taylor 8mm wires on there that where put on at about 60000 miles. Stock cat and EGR as well. i think it could be my cat is clogged, but to test this under low RPM i put the car in 2nd gear start last night and it missed again from a stop. any ideas, i am trying to avoid changing the plugs again(PIA!!), but if i have to i will. any help would be great. THANKS!!

 

I would say your plugs are healthy, its possible for a plug to fail that quick but rare. Especially if you put a good brand of plugs. Plug wires are supposed to last 80,000 to 100,000 miles. Maybe you got a faulty plug wire. I have a hard time thinking that a clogged Cat would cause a misfire.

 

i find a clogged cat hard to believe to, but some people on here have sworn that they have gotten misfires and the cause was the cat. the plugs by the way are AC Delco rapid fires, they cost me just under $30 at autozone.
oh and one more question for anybody that has done this, is it difficult to change a tranny mount bushing and torque arm bushing

 

I think you had a bad wire,and made it worse w/the plug replacment. Plug wires are pretty weak,as to cant stand up to pulling/tugging. Just from bending the boot sometimes is enough to cause a break. Sometimes breaks are bad enough to hear Snap,Snap. Or visible when dark,you can see the arching.
Get new wires and use the anti seize lube that comes w/them on the inside of boot that goes around plug
No backfire with clogged cat,Engine gulps and serious lack of power WOT, my cougar had that with clogged cat.

If you had hesitation only could be Fuel filter, Its the wires.

I dont want to advise you on the mounts(even though easy),I might omit something that may cause injury to you. Because safty issues in supporting a vehicle,and it components,combined with installation.General saftey practices. learned aptitude. But a bottle jack,peice of wood,car stands,floorjack,some tools,the right mount and a friend who knows to help perhaps is what you need.
T.

 

The situation with you cat is very easy to diagnose. Turn on your A/C and gently rev your car. If it's clogged you'll be able to hear a slight rattle coming from the cat. Sometimes when a cat shells out the "honeycomb" inside the cat gets lodged and doesn't rattle all the time, so it might be easier to put it on jackstands and carefully bang on it with hammer or mallot. That will dislodge the internals and you'll be able to hear the rattle. I'm not saying bang on it like you're beating down a door or anything.... As for your misfire, a clogged cat would give you numerous problems. Chances are you've got a broken wire or worse case cenerio, a shot coil pack. Be sure to check all your plug boots to ensure they're all installed correctly. When I changed my wires I didn't seat the boot on the wire all the way and it allowed a slight arch and misfire. My car hesitated under a load just like yours. When you reinstall the boots on the wires it's a good idea to put a little bit of Vaseline on the boot so that's easier to remove without damaging the wire taking the chance of pulling it out of the boot itself. Chances are it's something simple you're just overlooking so good luck.

 

thanks for the replys guys, i am going to check the plug boots tonight when i get off of work. as to the bushing question, i removed my old rear axle(3.08 gears and no LSD) and installed a new used one (97 z28 3.42 gears and LSD) pretty much by myself with a little muscle from my friend, without a lift, using jack stands and a floor jack. also installed eibach springs snd shocks, SLP CAI, B&M shift kit(internal), rims, stripes, panhard, and about 4 systems(damn theives) so any info on swapping tranny bushing and torque arm bushing would help. bascially looking for if it is a pain in the ***, how long, and any seat of the pants differences(ride, perfornmance). thanks again!!

 

revs fine in neutral? misses under load? coil pack HMMMMMMMMMMMMMM NOW theres an Idea!

 

It could very well be the cat but you would also have a big loss of power and maybe even some surging.

 

i think i'm having the same probs with my car, 3.4L, again with newish plugs and wires,

i checked the coil packs and they all read within the proper resistance levels for both the primary and secondary,

also my gear stick seems to shake more than i'd like it too, not much, but i can definately see a pattern, also wouldn't a slight misfire be hard to detect whilst idle-ing?

so any advise hear would be appreciateb by the both of us,

ps, my cat is stock, with 140K kms, but with no rattles when i hit it

cheers
ian

 

wow i did not think this post would get back to the front page. anyway the problem was a bad coil pack, so i change all three so i would not have to worry about it later on down the road. car runs fine now, cat is okay, though with 124,000 miles i wonder how clogged it is. my main concern now is how much longer my tranny is going to last. if it craps out this summer, i think i might change to a 5-speed. well thanks again for the help.