Car runs terrible

[97WS6-Bird]

So I changed my spark plugs and it took me 6 hours because the headers were in the way. I replaced them with Bosch Platinum 2's. On this forum I was told to go with NGK, but I already bought the Bosch's and didn't listen. The new plugs are terrible. When I try to go fast it seems to misfire a little and is just rather weak all together. I checked the wires and they are good. Code scanner says all kinds of cylinders are misfiring. So now I've got to do it all over again with NGK iridiums. Is there anything else I can check to make sure the plugs aren't to blame.

[Joe 1320]

How many miles on the car? When was the last time the plug wires were changed? Do you still have the metal boot protectors on the plug wires?

[Injuneer]

Are you sure you got them in tight, without breaking the insulators? If you have a fat socket, it can mislead you into thinking the plugs are in tight, when they aren't. The tight quarters can cause some broken porcelain insulators. Also possible that the metal clips on the ends of the wires are not tight on the tips of the plugs. While the +2 plugs are probably not the best choice, they shouldn't cause that bad a problem. Do the Bosch plugs come pregapped (0.050")? Did you check the gap(s)?

[97WS6-Bird]

The car has 99K miles and I bought the car about two months ago and just wanted to replace them because of bad cold starts. There was only one metal boot protector on plug 7. A few of the boots I can't tell if the boot is completely seated in there because of tight quarters on plug 2 and 5. but I had plenty of sockets to choose from and even had to use an open end wrench on some of them ( 2, 7, and 8 ). The Bosch Platinum+2's are not gapped because they come with two insulators.

[97Bandit]

I know another one that caused my car to have a bad misfire. if the spark plug wire going to the number 7 cyl (one at the back on driver side) is old or installed incorrect the wire burns easily because of how it runs behind the exhaust manifold. If you give it a slight tug and hear a crunch theres ur prob, just an idea.

[Joe 1320]

The factory ignition componants were engineered for a 100K mile lifespan. The distributer, coil, module, plug wires and plugs will all degrade over time. Judging by your mileage, you're right at where things would become suspect. If it were me, I would systematically go through the entire ignition system. Check the ohms of each plug wire, verify that the distributer (optispark unit) is functioning, not to mention a check of the fuel pressure and volume.

Without knowing the history of the car, it complicates things. If I had to do the plugs, I would change the plug wires at the same time.

[97WS6-Bird]

I re-checked the plugs and wires and 1 of the plugs I could tighten about 2 whole turns Would that be enough to make it ride bad?

[Injuneer]

With one cylinder losing compression and probably misfiring, you coud be losing 30-35HP on that cylinder alone. Then there's the effect of the unused air leaving the cylinder in the exhaust and throwing the O2 senor off on that bank of the engine, PCM adds excess fuel the other three cylinders don't need, and you lose some more HP.

I thought the Bosch plugs had multiple ground straps, not multiple insulators????

[99Firebird3800]

^^ Not to mention the fact that, unless the vehicle came with Bosch plugs from the factory, I would never put them in a vehicle. They are the single largest gimmick product I've ever seen.

[97WS6-Bird]

Yeah you're right I meant ground straps. I'm going to replace them when I get plugs. I tightened the plug more and got one more boot to click and it's running the way it used to.Thanks for all your help.

[Trash man]

Yeah you're right I meant ground straps. I'm going to replace them when I get plugs. I tightened the plug more and got one more boot to click and it's running the way it used to.Thanks for all your help.

even tho u cant gap em, just check to make sure they arent pushed onto the insulators, i've gotten plugs from parts stores where they were crushed down, needless to say those went back

[97WS6-Bird]

I'm going to buy wires in a few weeks and will throw the Bosch plugs in the trash and get NGK iridium plugs. Hopefully that will make a difference in horses and gas mileage. Is it true you have to remove the power steering pump to install new wires? If so I'll wait till I can afford to buy a new pump because I need one of those anyway.

[Injuneer]

Its not easy, but you can thread the plug wires through the PS pump bracket without removing the pump. One of the first mods I did to the car in 1994 was to install a set of Taylor 8mm wires. My neighbors thought I was nuts... brand new car and every weekend it was up on blocks getting some new part....

[97WS6-Bird]

Thanks Fred . That's what I'll do.

[RAF7789]

+1 on the Taylor 8mm and NGKs
Scrap the Bosches .