Yesterday I changed my spark plugs after old ones had been driving about 5000 miles. I've heard that the condition of spark plugs can say a lot about the engine, so it would be nice if somebody could give me some idea, what's wrong with mine (B230F, LH-Jet 2.4).

All the previous times (I change plugs every 5000-10000 miles) electrodes came ususally covered by gas, slightly gone black. But this time the electrodes have sand-yellow / orange / bright-rust color, are completely dry and look "corroded". Unfortunately no digicam to post the photos. BTW, plugs are NGK V-Line BPR-6-E(S)

In addition I can say, that temp gauge pointed normally at 8 o'clock in the days of "oily" plugs and now is pointing usually at 9 o'clock (engine runs hotter).

I've checked also the O2 sensor (Lambda Sond) voltage: 0V from sensor side, 25 mV average from ECU side (why?), ground OK, heating OK. Because of financial reasons I can not get a new one now, but generally I'm satisified with fuel consuption even without that sensor. Please don't take the catalytic converter damage and emissions into matter.

Thanks in advance.

A few tips for you:

1. I would encourage removing the accordian tube between the throttle body and the Air Mass Meter. Clean it out, and bend it around while inspecting for hairline cracks. -you're probably going to find a few where the accordian tube has been rubbing against the fender wall or the battery cable. Get the tube as clean as possible, and then wrap it in electrical tape (use a lot) until you can get a replacement tube.

2. It sounds like you may be overdue for an O2 sensor change. This will easily pay for itself in a few months with increased fuel mileage. Check out the following page for cheap 3-wire Bosch sensors that can be used in your Volvo: Bosch #13913 and #13953. Don't discount the importance of this sensor, it's 2nd in command of your fuel mixture (behind the AMM).

3. Check your engine for vaccum leaks. Verify that the two tubes from the charcoal canister to the throttle body are properly attached and not cracked, -and also the vacuum tubes at the intake manifold near the flame trap. Also check the Fuel Pressure Regulator vacuum line. A cracked or split vaccum line will allow extra air to enter the engine and lean out the mixture.

4. Get a good set of spark plugs. The best that you can get are the official Volvo ones from your local dealership or FCP Groton. They cost $11 for a blister pack of 4 plugs ($9 at FCP), and are superior quality than anything else you'll be able to find. If you can't get the OEM Volvo plugs, NGKs are a suitable backup, and the Bosch Super (copper) plugs would be 3rd in line. Do not use Platinum plugs in your Volvo since the ignition system is not designed for the higher impedance of a Platinum plug. (there are service buletins that cover this topic)

God bless,
Fitz Fitzgerald.
--
'87 Blue 240 Wagon, 246k miles.
'88 Black 780, PRV-6, 145k miles.

NGK has a very good web site, with a FAQ section. When following the thread "How do I read a spark plug", you eventually get to this page, complete with pictures and diagnoses:
http://www.ngksparkplugs.com/techinfo/spark_plugs/faq/faqread2.asp?nav=31200&country=US

Hope this is of some help.

Erling.
--
My 240 Page

Erling:

Regarding your website - What great stories!

Bravo!

Jim

Thank you for a good link. My plugs are something between "normal wear" and "abnormal erosion". But for just 5000 miles, can we call it a normal wear?

Forgot to mention "clicking" sound coming from veery heated exhaust manifold after switching off the engine. I can not get away from my idea that motor is actually overheating and temp sensor is lying. Together with the strange o2-sensor voltage fact, can it be something like too lean mixture or a wrong timing?

Maybe too lean..I always use the 'standard' plug . I tried Platinum and no sucess.
--
john,, 1985, 245:Ti, 251k mi..so.california,,,1974, 145, 230k mi. ..