Super rough Idle, with Bosch Plugs

[GaryFenza]

So heres the thing. About 10,000miles ago and i put in double platinum Bosch Plugs. The idle is so bad right now its unbelievable. I feel like someone is pushing the car up and down and side to side. The engine is throwing no codes at all, i put a new MAF on today(actually used, but new enough and clean) um...no vacume leak that i know of. Not overheating, and the exauhst puts out a bad puff(not consistent). Now i heard that the 3.1 v6(the one i have, model year 2001 Grand Prix SE) does not like Bosch plugs. So my question is......could these be the Bosch plugs that i used and do you more expierenced guys think this could be the problem, i know what im doing, but im only 17 and just dont have the expierence yet to know.

thanks,

[chevyguy93]

push hard on the wires at the plugs and make sure they clicked into place. it sounds as if its misfiring and one of the plugs isnt getting a spark. im not sure about bosch plugs. I put some in my cavalier and it was great, but i've heard they arent that great in the gp. I'd possibly stick with an oem plug if your experiencing problems. so if pushing on the wires doesnt help, unplug them one by one and see if the the idle gets any rougher. if u unplug one and it stays the same, you know you either got a problem with the plug or the wire. just be careful

[richtazz]

I've expressed my personal opinion about Bosch plugs (JUNK!!) many times. Since your car is an 01 model, you need to have the car checked for an exhaust blockage. Even though GM's extended warranty on W-body catalytic converters only covers the Grand Prix with the 3800 engine, it could still be your issue. If you temporarily remove the upstream o2 and the car stops missing (it'll be loud due to the open hole in the exhaust), then you have an exhaust restriction possibly caused by a blocked cat. If that doesn't help, deep six those Bosch plugs and put some real ones in, preferably AC-Delco or NGK iridiums.

[GaryFenza]

ok, well today at the body shop, by dad is ordering new spark plugs, the kind that the manuel to the car recomendes, the ac-delco ones. Im gonna put them in, the wires are new and dont seem to have a spark arch in the dark, so i think there all good, so it seems. I'll let ya's know what happenes once the plugs go in. If that dont help i'll do the o2 sensor check for exauhst blockage. Thanks for the suggestion, didnt think of that

[tblake]

chevyguy93, Although its a great diagnostic aid to unplug each spark plug with the car idling on a distributor ignition, its probably not such a good idea with a GM distributorless ignition. First reason because those coil backs can generate 10,000 volts and that voltage has to go somewhere, could be through you, and if not through you, it could arch through the coil pack itself and zorch the ignition module.

A better way to do a cylinder drop test on these type of cars is to crab yourself some vacuum tubing cut into six 1 inch lenghs. unplug each plug wire at the coil packs, and insert the vacuum tubing between the coil terminal and the plug wire. Start the car. It will run hopefully just fine. Then take a test light and clamp it to a good ground and short out each cylinder by touching the exposed vacuum line at each coil tower. If the RPM drops, the cylinder is doing its job, if not, your found the bad one and need to diagnose further to see if its ignition/fuel/compression related.

[GaryFenza]

i gots a rough idle with double platinum bosch spark plugs, put them in about 12,000 miles ago. i get a vibration in my seat a little with a 2001 Pontiac Grand Prix SE 3.1 V6 with 124,000 miles. Is this normal for this car(i heard the 3.1 was known for roughness) or do you guys think that these bosch spark plugs could cause this. Because sunday i am putting in the OEM plugs i just ordered from GM, the single platinum AC DELCO's. Do u think this might calm down my idle.

[GaryFenza]

well there was a small leak on the PCV hose which caused the popping from the exauhst which now went away. There is still a rough idle with engine vibration. I mean the car does have 124,000miles 3.1 v6 grand prix 2001. Im putting the OEM single platinum AC Delco plugs in on Sunday, do you think this might calm it down, and could the Bosch plugs actually cause a rough idle