Which spark plugs for my 325e '85

[Kalimsnor]

Hi,

My sparkpugs are ready to be replaced. I don't have a lot of time lately to be doing repairs, but this is minor enough to do at home. Can someone tell me which sparkplugs are ideal for my 325e from 1985, type 1?

I took them all out to do a compressiontest and took a quick video. 5 of them look rougly like this one, properly brown:

The 5th cyl was the only one that looked different, a lot less healthy: - can anyone tell me why one of the 6 spark plugs is different from the others?

Thanks!

[BristolE30]

I usually just pop my reg into Eurocarparts, Auto doc etc and use the standard Bosch ones that come up!

[Kalimsnor]

I read online that the Bosch sparkplugs are not good for E30s, because they often break on our models.

These seem to be compatible to my 325e, what do you guys think of DENSO? https://www.autodoc.nl/denso/1667065 Or maybe these NGKs? https://www.autodoc.nl/ngk/1042577

[BristolE30]

I read online that the Bosch sparkplugs are not good for E30s, because they often break on our models.

These seem to be compatible to my 325e, what do you guys think of DENSO? https://www.autodoc.nl/denso/1667065 Or maybe these NGKs? https://www.autodoc.nl/ngk/1042577

I’ve used only Bosch on both my E30’s (316 and 325) and never had an issue. They rolled off the factory floor with Bosch, so Bosch would be fine.

NGK are also a good alternative, but it’s much for muchness in my opinion.

[Kalimsnor]

I read online that the Bosch sparkplugs are not good for E30s, because they often break on our models.

These seem to be compatible to my 325e, what do you guys think of DENSO? https://www.autodoc.nl/denso/1667065 Or maybe these NGKs? https://www.autodoc.nl/ngk/1042577

I’ve used only Bosch on both my E30’s (316 and 325) and never had an issue. They rolled off the factory floor with Bosch, so Bosch would be fine.

NGK are also a good alternative, but it’s much for muchness in my opinion.

Thanks for the help, I'll go get those Bosch ones then!

[Brianmoooore]

You need to address why your engine is running rich! Unless you habitually make very short journeys that don't get the engine up to working temperature, there's something wrong.
The 'different' one might well be oil contamination.

[fixedwheelnut]

You need to address why your engine is running rich! Unless you habitually make very short journeys that don't get the engine up to working temperature, there's something wrong.
The 'different' one might well be oil contamination.

Popular cause is corrosion in the round wiring plug below the inlet manifold, it causes a variation in the reading from the engine temperature sensor.

[Kalimsnor]

Ended up having to get the DENSO, Bosch was out of stock. https://www.autodoc.nl/denso/1667065

Thanks for the tip Brian. I'll go look into that next week!

You need to address why your engine is running rich! Unless you habitually make very short journeys that don't get the engine up to working temperature, there's something wrong.
The 'different' one might well be oil contamination.

Popular cause is corrosion in the round wiring plug below the inlet manifold, it causes a variation in the reading from the engine temperature sensor.

Don't think it's related, but my temp sensor is broken - see viewtopic.php?f=2&t=279833&p=2967088

[Brianmoooore]

Don't think it's related, but my temp sensor is broken - see viewtopic.php?f=2&t=279833&p=2967088

Could be. Different sensor, but they lie alongside each other, and wiring for both goes through the C191.
You should unplug the engine ECU and identify pin 45 of the plug, which has a brown/red wire going to it. Measure the resistance from this pin to a good body earth, then reconnect the plug, start the engine and run it up to full temperature, then stop the engine, quickly disconnect the ECU plug
again, and re measure the resistance.