Wrong colour spark plugs?

Have been checking my spark plugs regularely lately... They are all white as snowr, indicating to me that my engine is running lean... btw. it is a RENIX with 130k miles on it... (compression test checked out just fine)

It's NOT oil deposits. I DO know the difference...

Any of you guys seen this colour on your RENIX spark plugs? Is it supposed to run this lean? (you never know what the car manufacturers think up to reduce emissions...)

I have changed almost everything on my engine (TPS,CPS,O2 sensor, fuel pressure regulator, fuel filter) except engine temp sensor and MAT. You think theese could be at fault? (haven't tested the engine temp sensor, as I'm expecting a new one to arrive any day now. The MAT seems to be a little bit off when tested, but the only reliable way I have to test it at different temperatures is to test it in water, and I fear this might affect results??)

I have searched for any vacuum leaks without any luck, and I have blocked my EGR system without this affecting anything (so it seems). (Except it cured my high idle problem once and for all... :laugh3: )

Anything I missed?

BTW: Going to try to order a MAT sensor from partsamerica again soon. They were temporarely out when I placed my last order.

Sorry for replying to myself just to get back to the top of the list... But I can't believe noone has noticed the colour of their spark plugs when replacing them????

have you checked fuel pressure? 31 lbs with vacuum, 39lbs without vacuum

no, but i have changed the regulator. Of course it could be the pump, delivering enough volume but not enough pressure... (does not stutter at high revs/high load)... will check tomorrow.

I had the white coating on my plugs when I tried running the platinum plugs by Bosch. I've read there are cooler and hotter plugs (depends on the length of the insulator). Your plug is getting too hot thus causing the white build-up. Since you have replaced everything else, maybe a cooler temp plug is the answer. What plug are you running?

try another type of gas as well-- the additives that some companies put in their gas will cause a tanish-white deposit too.

Renix engines tend to run lean in the first place so maybe just a cooler plug will help you out.

Thanks for the tip on RENIX usually running lean. I suspected as much, but didn't KNOW.

Don't know what kind of plugs i'm running..... came with the Crown tune up kit. It's not tan-white, it's white-white-white like snow-white like copy paper white-white.

By all my experience it DO look like a severe case of running lean....

Fuel additives- ruled out. (not like this on my other car)

Will check tonight:
Fuel pressure -> check for bad pump.
If ok -> Re-fit my old O2 sensor... Just becuse my new one is new doesn't mean it can't be faulty....
Vacuum leaks -> will block all unnessecary vacuum outtakes on manifold (egr/heater/cruise/pre-heated air valve etc)

Will do later this week:
replace coolant temp thermistor
replace brake booster valve/grommit

Are you getting any lean popping out of the exhaust?

I do get some popping when using the negine for braking downhill.

And, an experienced mechanic actually commented that my car smelled like it was running extremely lean, without me having mentioned the problem to him...


Checked fuel pressure tonight. Reads 32psi with vac connected and 40psi when disconnected.... pump and regulator -check.

Switched back to my old O2 sensor, will check spark plugs later this week.

re-torque the intake bolts as well when you're in there-- notoriously problematic on Renix 4.0l.

have re-tightened manifold bolts... got 1/3 round on 3 bolts... thinking of replacing gasket just to be shure...

PITA to replace, but worth it in the end!! double check the gasket at the throttle body base and the rubber grommet at the MAP sensor tube as well-- both can give you multiple cylinder lean condition. While you're in there, re-clean the ports and passages around the IAC motor and verify the pintle valve has an even tapered tip to seat in the throttle body.

OK. This is what I've got so far:

Hooked it up to a emission tester. Readings indicated it was running VERY RICH at idle...?..?... but my plugs were still white as snow, indicating that it would be running rich at idle and lean during regular operation....

Important discovery made: When I blocked the thin tube from manifold to valve cover the co and o2 values became spot on right!!!

This puzzled me, as the rubber grommet in the valve cover is brand new and positively air tight. I then discovered that the fat tube going from valve cover to air cleaner box vas leaking seriously where it connected to the valve cover....

My sollution:
- block thin pipe outtake at manifold.
- block thin pipe outtake at valve cover.
- block fat pipe outtake at air cleaner box.
- mount grommet with small vent hole in "fat pipe outtake" on valve cover.
- put thin and fat pipe in my BIG box of discarded parts.

Excited to see spark plug colour after a few days, as well as measuring fuel consumption.... (my last reading only gave me 11mpg!!!! and that with driving like an old lady... mixed driving, never above 50mph)

Can't really say I've put my mind into how the original system was supposed to be working.. only guess there would have to be som valve in the fat pipe preventing the engine from drawing in unlimited amount of air outside the tb?


HAVE I DONE SOMETHING WRONG THAT I WILL LIVE TO REGRET???


PS. Don't you da**ed eco-fanatics slap me over the head with "you are releasing oil vapours into the enviroment" ! Even if my engine was spraying oil all over the enviroment if still wouldn't be as bad as what my current (up till now) 11mpg consumption does to it!! btw. I have very little blow-by. do not have to top up oil between 4k mile oil change.

Sounds like you had a vacumn leak somewhere else, and plugging up the crankcase vent was enough to compensate.

There is a commonly overlooked sensor on the Renix. It is the manifold air temp sensor located rearward from the TB. You can check it with an ohm meter. It can and will directly effect how rich/lean you are running. Normally it fails in the too rich mode, but you never know.

Is there any eroding of the tip edges or is the plug insulator simply nice and white?

having trouble finding any other vacum leaks...

Every part of the plug exposed to the combustion is white... perhaps slightly less white just where the spark touches....

Will be back soon with details on how crank-vent-plugging affected engine... initial impression is - it's using less fuel.