spark plugs

[pacman67]

Guys, can't seem to find a definitive answer. My 2003 xc70 is very lumpy on lpg tickover. It has had a set of Bosch irridium plugs but still pretty rough. Seems to be ok at initial switch over from petrol but once up to full temp becomes rough and is noticeable sometimes at about 2k rpm as a minor misfire. No engine codes by the way.

[volvobaggen]

If you switch back to petrol, does the symptoms go away? What kind of Lpg-system is installed in your car?

Lpg is harder to ignite than petrol. Its important to use spark plugs with only one ground electrode to ensure a reliable spark. I use the cheap standard copper spark plugs from NGK and Denso and never experience misfires. Of course, the rest of the ingnition system must be in tip-top shape.

If the ignition system is working good, I would bring the car to a lpg specialist and to check mapping, injectors and filters.

[pacman67]

Yes if you switch back to petrol it's fine. Plugs were changed due to similar symptoms, when removed the existing NGk plugs had some cracking in the ceramic area. The bosch ones are single electrode and iridium etc. the only other issue I've had is water leaks from the "thingy" that heats the lpg, and a poorly fitting pipe that doesn't carry water and isn't a gas line, I think, the pipe diameter is a fair bit bigger than the flange it fits onto and is well compressed by the jubilee clip. I do have an lpg specialist nearby, so may run it in.
Ps, no idea what the system is, was on when bought, how can you tell ?

[classicswede]

Post up some photos of the LPG components there installed in the engine bay

[CNGBiFuel]

Sounds like more than plugs but Denso list my engine B5244SG as needing 0.9mm, but this caused stalling with CNG, suspect LPG would be no better.

Denso K20PR-U (usually cheaper I've coem to swear by them as others do on here)
NGK BKR6ES

Gap: 0.9 (Did not work stalling when cold)
Gap: 0.7 or 0.028 thou (works a treat)

Leave thsoe LPG plugs at £30.00 each well alone. Denso K20PR-U You should get all five for a tenner.

[pacman67]

Originally Posted by classicswede

Post up some photos of the LPG components there installed in the engine bay

Will do, just busy with work at the mo, and dark when I get home.

[pacman67]

Originally Posted by CNGBiFuel

Sounds like more than plugs but Denso list my engine B5244SG as needing 0.9mm, but this caused stalling with CNG, suspect LPG would be no better.

Denso K20PR-U (usually cheaper I've coem to swear by them as others do on here)
NGK BKR6ES

Gap: 0.9 (Did not work stalling when cold)
Gap: 0.7 or 0.028 thou (works a treat)

Leave thsoe LPG plugs at £30.00 each well alone. Denso K20PR-U You should get all five for a tenner.

Worth sending for a set at that price, and see what happens. Thanks.

[volvobaggen]

Originally Posted by CNGBiFuel

Sounds like more than plugs but Denso list my engine B5244SG as needing 0.9mm, but this caused stalling with CNG, suspect LPG would be no better.

Denso K20PR-U (usually cheaper I've coem to swear by them as others do on here)
NGK BKR6ES

Gap: 0.9 (Did not work stalling when cold)
Gap: 0.7 or 0.028 thou (works a treat)

Leave thsoe LPG plugs at £30.00 each well alone. Denso K20PR-U You should get all five for a tenner.

True, Denso is more bang for the buck than anything else. Cheaper, 100% japanese and Toyota OEM.

I read somehwere that Toyota V6 engines used to come from the factory with 3 cylinders fitted with NGK and 3 cylinders fitted with Denso, so they are probably not that different

What I don´t like is that NGK has a factory in France that makes spark plugs under the NGK logo now. French plugs are installed in the Volvo 240, but it will be Denso next time.

[pacman67]

Can we just confirm plug before I order. My engine is the 2.4lpt 200bhp, on denso site I looked on it lists a different plug type to your recommendations, or are they promoting the dearer stuff only.

[classicswede]

I think your age engine would have the long thread plugs