rough idle after spark plug change

Have you figured out the problem? I had te same thing happen after getting a tune-up at Pep Boys and they used bosch plaitnum plugs and I am learning from this site those are cheap plugs. I took it back to Pep Boys the day after they did the tune-up and they saw nothing, 2 weeks later they did a diagnostic and there is something they say happening with the injectors but a code is not coming up and they aren't capable of checking each injector. Any help would be greatly appreciated.

Get someone to install the correct NGK plus and you're problem will be solved. Bosch platinums aren't "cheap" (except compared to NGK platinums..), they are just junk and don't work right in any car that I know of.

Perhaps these guys did something silly and TQ the plugs down way too much. I install mine myself and the TQ spec is 16-22 ft-lbs for the

95-99 Max, a lighter pressure than you would think is needed to secure the plugs into the head. Ask 'em how much they TQed the plugs to. If they don't know, then it was probably too much.

CD

Thanks for the advice, I'll ask them and if they don't know or if it's too far down, do I have them put it at 16-22ft?

Yup. remove (hopefully without problems) the plug and re-install at

16-22 ft-lbs of torque.

CD

How is changing the torque going to change how it runs? the few thousands difference in depth are not going to change anything. They will be easier to change next time though.

You could be right, but then I have Platinum +2s running in my wifes 96 Altima. Torqued perfectly by me and they've been running fine for the past 20K miles. He may need to just dump the Bosch plugs and switch back to NGK Platinums (Torqued 16-22 ft=lbs!:))anyhow because the Maxima's ignition system is more sophisticated, and possibly more sensitive.

CD

It's -imposible- for that to make any difference in the way a car runs, unless they broke them installing them. The problem IS the bosch plugs!!!!!

Hey Steve

Do you th>

Well, I bought some NGK plugs and my husband and I are going to put them in this evening. So I will let you all know how it turns out.

Can't say, given the plats look like new at 90K when they are pulled, I can't imagine these others lasting any better!

I did a readup on DENSO and NGKs iridium website. ironically, iridiums only last half as long as plats. Apparently the technology of iridiums can only be fully exploited if the engine was designed for it in the 1st place. NGK plats are still best for longevity in the Maxima . .by design:) NGK Coppers are best for cheapeness.

CD

What is the advantage?

They are harder than platinum, so you can make a smaller tip that will last a reasonably long time. The smaller tip would make for better combustion and cleaner emissions. On cars designed for iridium, they can last around 120K miles, so its biggest advantage is durability . . .when a car is designed for it.

CD

O.K., we put NGK spark plugs on and it runs the same. What should we do next?

Thanks

Now I'm confused, you said they last half as long as plats but last 120K?

If you put iridiums in the Maxima, which was designed for plats, the iridiums will only last half as long as the NGK plats that the Maxima was designed for. There's a Toyota, I believe, that comes OEM with iridiums. On that car the plugs can last up to 120K miles. In other words Toyota designed that engine with the iridiums in mind. Perhaps the way heat is extracted from the cylinder head is changed, threading on the plug is longer or shorter, etc.

CD

I have been following this and related threads for a while....

Finally cured my rough idle problem today... broke down and replaced all coils and the plugs with new NGK's. Problem gone... and so is about $400. Most expensive sparkplug change I ever did....

Thanx..