Is is OK to unscrew the metal tip of an NGK spark plug?

I recently purchased new "Hi-Performace" plug wires from a local auto store, and NGK BPR6ES spark plugs, gapped 0.032-inch. The plug wires would not fit over a "normal" spark plug. I had to unscrew the metal TIP of the plug, then it would fit perfectly. Is this OK??? Are they the right type of wires for a used 1991 Volvo 240? Now, my car seems to be running much rougher, seems to have a slight miss at idle speed, and has lower gas mileage. Is the plug/wire causing is to run this way?

Also, what is the correct gap? My Haynes shop manual says 0.028 - 0.032-inch for Bosch or NGK-equivalent plug. But the auto store says 0.040-inch. Which is correct?

Is it the combination of wrong wire and/or wrong spark plug gap? Or something else?

I have also the changed air filter, distributor cap, rotor, timing belt, and fuel filter, all in the past 6 months.

-- 1991 Volvo 240, 102k miles --

Hello .. Definately remove the screw on tip if the wires require it. Be sure their good quality wires and not a "cheapie set". My 82 Turbo came with wires that require removing the screw on tip from the factory. My header pipe cracked at the same place and I welded it w/mig and thats been over 50,000 miles ago and its still holding fine. Its a very common place for cracking and welding is a good repair option and shouldn't be more than $40. dollars. All muffler shops can and do weld these cracks on a daily basis. Later-Gary.

Recheck all your installation for a loose connection and/or the wrong firing order.

Also, my local independent Volvo shop owner af long experience claims these engine should not have BOTH resistor plugs and resistor wires. Use one or the other.

Too much resistance can couse performance problems, he claims.

BTW, I haven't uses those tips on a spark plug since I change one in my lawn mower.

Sure thing. That is why the tips screw off. Sometimes you do and sometimes you don't, what ever works is fine. I do recomend checking the plug gaps before you install them, and every ten or fifteen thousand miles afterwards. I have had no problem running plugs sixty thousand miles or so...

Thanks for the info, that rules out one more possible cause of my recent problems.

A local muffler shop just told me that I have a crack in my "exhaust header", apparently in the bend underenath the heat shield. To weld/repair this section costs $75-$100 (not recommended??), or $195 to replace it with a new header.

Can this part be repaired? Is it better to buy an entirely new section? Will a cracked pipe in this section cause rough idle, lower gas mileage, etc.? I have checked for anything/everything on the INTAKE side of the engine, but could not find any vacuum leaks, clogged or missing hoses. Now the plugs seem to be OK. The only thing left seems to be the EXHAUST side. Am I missing anything?

-- 1995 volvo 240, 102k mi --

You should make this a new query.

Anyhow the downpipe between the manifold and CAT is insulated and doubel skinned. Thats why you can only buy them at Volvo and why they are so expensive. Welding I think is not possible.

Yes the pipe should not have a leak couse it will give false readings at the oxygen sensor.

Reg,

Jorn

PS really rare a 1995 240....

Gap as per Haynes.

In your struggle to install the wires correctly is it possible that you damaged a wire or connector???

Any wire sets I have put on Volvos required that the tips be removed. That is the design of the connector. Other connectors types may require the screw on tips. All plugs come with the tips just in case you need them.
--
David Hunter

Shade:

My Bentley manual shows .28 to .32 as the correct gap. Thats what I use on my 90 240DL wagon. You can't count on the plug coming with the correct gap so I always check each one and adjust if necessary.

The wires should attach to the plug with the tip screwed on. Sometimes the steel connector within the insulated rubber tip gets off center ( or the connector gets crushed in shipping) making it impossible to attach to the plug. That might be the problem. If you can't get the wires connected with the plug tip in place take them back.

The wrong gap and wires attached to the plug without the tip in place can certainly cause the rough idle/performance you describe.

While expensive the factory Volvo wires are really first rate.

Hope this helps.

Jerry Judge