1994 century 3.1 misses bucks when accelerating

[therick2169]

hello, ok I have a 1994 buick century 3.1 bought 3 years ago with 29k miles now has 66k miles. Car has always run perfect like new, decided to change plugs and wires since manual said they should be changed at 30k. Went with the autolite double platinum plugs and wires. Old plugs looked worn but normal, everything went fine and car drove great. 5 days later i noticed a miss while driving on the highway and once at a red light. The next day it missed 3 times taking a hour long highway trip. On the way back however it was horrible, missing and bucking the whole time. Took it too mechanic they regap 2 of the plugs and did a fuel injector flush clean. Picked up car ran just as bad if not worse. Took car back in they cleaned the egr valve out and said drove around for a long time and no problems. Picked car up and still ran horribly. Am not taking it back to them. The car idles fine and will run smoothly as long as i baby the accelerator with the least amount possible to increase speed - i can get all the way to highway speed 65-70 no problems driving it that way but if I try to moderatley accelerate say to pass a car or just enought where the engine would supposed to do that kickdown before it takes off - thats when trouble occurs. The car misses and bucks and shutters - i can fell it all through the car from the engine to exhaust - I can also hear like a click spark pop sound in the back part of engine where rear plugs will be. Autoshop said they put it on machine tested all plugs and wires and no problems. The car just runs horribly now and was fine until I changed the plugs and wires! I cant keep driving it like this! Does anyone know what this could be? does the old 3.1 not like the new plugs - should i go get some cheap copper ones? And also when I first start it and drive it doesnt do this - its after a minute when its warm when the problem happens - even in neutral it seems like it loses half its power when you rev the engine - completely different sound from when it was first started. Please help someone!!!

 

[dcraig1000]

first off, buying platium,titanium, or double whatever really does nothing for a car. regular ac delco spark plugs is what you need. but thats not your problem. you either cracked a plug or damaged a wire during installation. i know you said the shop tested the plugs and wires. you can take that with a grain of salt though. did they run a diagnostics scan of the engine??? is your service engine soon or check engine light on? or does it come on intermittently? probably not because they would have found the problem. the other possibilities here are that one of the coil packs are bad, or the icm is going bad. when the car is under a load such as acceleration, if a coil pack is going bad, the car will jerk or fishbite. a good way to check the wires is to start the car in th dark and watch for spark jump from the wires.

 

[therick2169]

they said they ran a diagnostic and was fine, no engine light on ever, the thing that i dont get is that it started 5 days after I put on the new plugs and wires..

 

[therick2169]

its like itll idle fine and I can slowly and gradually accelerate to speeds but if I try to moderatley accelerate it feels like a backfire bucks and hesitates

 

[therick2169]

just drove it on lunch break, the first minute or so it runs perfect I was able to punch it twice and responded great with good throaty sound no miss, but third time after it warmed up it started missing again the rest of the drive. I can cruise at constant speed or light acceleration but any moderate or heavy it bucks and misses and even when the missing stops and it does go it feels like at half power no throaty sound like when its first started

 

[journeyforce]

Did you go over the plugs and make sure all were tight and not loose? Did you make sure to add a dab of dielectric grease to the inside of the spark plug wire boot? Are all the plug wires on the plugs and the coil tight?

How did you route the wires? did you put new wires in the wire looms(a black plastic piping) that were attached to the old wires? Those are to keep the plug wires from getting a misfire through induction due to rubbing against each other

It sounds like this misfire is related to the engine having warmed up. as it does not seem to miss when it is cold

 

[whitehead_troy@yahoo.com]

Can anyone help...I have the exact same problem with my 94 Century 3.1 It is exactly the same jerking and bucking when you try to accelerate gradually. Some one has to have an answer for this problem. Ive heard others try and describe this problem in different way.

 

[HotZ28]

Can anyone help...I have the exact same problem with my 94 Century 3.1 It is exactly the same jerking and bucking when you try to accelerate gradually. Some one has to have an answer for this problem. Ive heard others try and describe this problem in different way.

This is an 2-yr old thread, but the advice already given here is accurate. You apparently have secondary ignition misfire i.e, coils, wires, plugs.