Rusty white spark plugs

[Romb 0]

Hello all,

 

Pics below, the plug nearest the cam belt was quite rusty from the outside so some water could have entered there, no biggy imo. However, the 2nd plug is clean outside but rusty inside and not sure whether that's a problem. It was really really tight, almost couldn't get it out, probably deposits on the thread. Doesn't look like water from outside dripped in as outside is clean. Any idea what could make it rust inside ? Gasket / coolant leak ? No fumes from exhaust.

 

Also 3 are white, possibly because of too cold a heat range. They were NGK BCP6ES, but catalytic converter was removed so less heat and 7 heat rating would probably have been better. Swapped them for Bosch FR7DC+.

 

Whiteness could indicate an overly lean mixture. Bit awkard that the 2nd one seems fine. Could it be 3 injectors being clogged ? Do injectors need cleaning after 150k miles ?

 

Car drives fine, but some years ago it did consume half of a paper air filter, just disintegrated and got sucked in.

 

So 3 q's :

- rusty inside plug

- white plugs

- injector cleaning

 

Thanks, your feedback is much appreciated !

 

Learning moments each day for me over here :-)

 

Edited February 23, 2020 by Romb

[welshpug 1,661]

the one plug is likely to have had water sitting on it, which can cause a misfire by grounding the electrode, though this would typically lead to a blackened wet plug.

 

heat range from ngk to bosch are not the same, 6 in ngk are the same as 7 in bosch, an ngk 7 is a bosch 5 !!

[DamirGTI 342]

Rust on the spark plug tip , from my experience , has been mostly caused by some kind of internal coolant leak ... leaky HG , cracked head , cracked cylinder liner ...

 

Or could be moisture/water condensation reaction with sulfuric acid from fuel/oil within the cylinder that triggered rusting in that cylinder , but only if the engine was left standing for long periods unused this might've happened , or you live in the area with a lot of temperature inversions during the year .. i'd expect that liner will be rusted internally too in that case . 

 

D

[Romb 0]

4 hours ago, welshpug said:

the one plug is likely to have had water sitting on it, which can cause a misfire by grounding the electrode, though this would typically lead to a blackened wet plug.

 

heat range from ngk to bosch are not the same, 6 in ngk are the same as 7 in bosch, an ngk 7 is a bosch 5 !!

Wow, thanks ! Were it not for your feedback those plugs would have be in there for some years.

 

The shop didn't have NGK7 and gave me Bosch 6 as being equivalent. I was ok weird, went for a snack, changed my mind and went back to swap them for a 7, thinking the specifications would be universal across brands. Going by numbers above the Bosch 6 they gave me would be somewhere in between 6 and 7 NGK.

 

Very confusing those brand own specifications. I did do some prepping (obviously not enough) and saw some US brand conversion tables but those nr's were really different (like 20 = 7 or something) and I thought that was simply because of metric vs imperial or something, but the NGK and Bosch numbering was so similar I'd took them to be equivalent.

 

Also saw a sheet where higher nr's were colder instead of hotter and thought it was a typo or something, but now it seems it was correct, NGK higher is hotter, Bosch higher is colder.

 

Will search for a conversion table.

 

Do you think the Bosch 7's are fine for a de-catted Pug or better get some NKG7 or Bosch5 ?

Edited February 23, 2020 by Romb

[DamirGTI 342]

If you're engine is 1.9 DKZ or 1.9 DFZ cat. equipped , then NGK '6 grade plugs are correct for them by the OE ... 

 

1.9 DKZ and DFZ engines with cat. runs slightly hotter plugs as standard (one grade hotter than non cat. 1.9 engines) .

 

If you want to change them always go for one or two step colder plug , so either NGK 7 or 8 grade plugs instead of 6 .

(with NGK , higher number means colder plug heat range)

 

.. NGK and Eyquem plugs are preferred for XU engines .

 

 

D

 

 

 

 

Edited February 23, 2020 by DamirGTI

[Romb 0]

45 minutes ago, DamirGTI said:

Rust on the spark plug tip , from my experience , has been mostly caused by some kind of internal coolant leak ... leaky HG , cracked head , cracked cylinder liner ...

 

Or could be moisture/water condensation reaction with sulfuric acid from fuel/oil within the cylinder that triggered rusting in that cylinder , but only if the engine was left standing for long periods unused this might've happened , or you live in the area with a lot of temperature inversions during the year .. i'd expect that liner will be rusted internally too in that case . 

Thanks, doesn't sound too good :-)

 

Car was indeed parked outside for a long time rarely used, now in a somewhat climatized garage.

 

Will check for coolant consumption. It does lower somewhat but attributed that to sweating through the old lines.

 

Car runs pretty fine, no excessive smoke, decent idle and pulls ok, although timing 0 to 60 is not the best for my ego :-)

 

Job's like these really are like a Pandora's Box, along the way I notice more and more to be done. A bit off-putting at times but I like wrenching and realize it are luxury problems. Hope the cilinders are fine though, really don't want to do an engine swap, no room for crane and like to keep matching engine/chassis.

 

Plan is to do all the side stuff, oil and water lines (bakerbm), alternator, battery, cambelt, water pump, radiator, valve clearance, oils, plugs, plastic trim refurbishment, rust treatment etc. I could possibly remove the head and see what's going on and change the HG while at it. But if I go the route of checking fundamental wear I might as well do the crank bearings and piston rings. Is that possible with engine in car and on high jack stands ? Without turning the engine upside down it seems quite hard to keep the upper halfs of the crank bearings in place while installing the crank. Plus applying high torque to big end nuts etc. might be tricky (and dangerous ?) lying under the car.

 

Think it's doable ?

[jackherer 543]

48 minutes ago, Romb said:

Will search for a conversion table.

https://www.opieoils.co.uk/t-spark-plug-heat-range.aspx

 

 

NGK	DENSO	Pulstar	Champion	Bosch	Heat
2	9	-	18,19	10	Hotter
4	14	1	14,16	9	↑
5	16	1	11,12	8	↑
6	20	1	9,10	6,7	↑
7	22	1	7,8	5	↑
8	24	2	6,61,63	4	↑
9	27	2	4,59	3	-
9.5	29	-	57	-	↓
10	31	-	55	2	↓
10.5	32	-	53	-	↓
11	34	-	-	-	↓
11.5	35	-	-	-	↓
12	37	-	-	-	Colder

 

[Romb 0]

Thank you !

[Romb 0]

1 hour ago, DamirGTI said:

If you're engine is 1.9 DKZ or 1.9 DFZ cat. equipped , then NGK '6 grade plugs are correct for them by the OE ... 

 

1.9 DKZ and DFZ engines with cat. runs slightly hotter plugs as standard (one grade hotter than non cat. 1.9 engines) .

 

If you want to change them always go for one or two step colder plug , so either NGK 7 or 8 grade plugs instead of 6 .

(with NGK , higher number means colder plug heat range)

 

.. NGK and Eyquem plugs are preferred for XU engines .

 

Hi Damir,

 

Just to be sure; in the matrix above to the right it states 'Heat', does that refer to engine heat, so 'Hotter' means better heat resistant plug, or refer to the heat resistance of the plug itself, so 'Colder' is better for a hotter engine ?

 

Don't cat engines run hotter than non-cat engines (less exhaust free flow), so if you de-cat you need a slightly less heat resistent plug ? Is the NGK 7 less or more heat resistant than NGK 6 ?

 

Thanks !

[DamirGTI 342]

"Hot" and "Cold" on the chart above represents spark plug heat range , not the "engine heat" .

 

Its the rating of the spark plugs ability to dissipate combustion heat from the spark plug firing tip to the cylinder head water/coolant jackets .

 

Hot grade spark plugs dissipate combustion heat slowly , contrary to the cold grade plugs which dissipate combustion heat more rapidly .

 

Standard grade or one to maxi two step colder spark plug is recommended if you tune the engine , as the combustion temp. rises there's always risk of pre-ignition , combustion detonation , overall higher engine running temp. or even overheating ... one or two grades colder plugs can help in such conditions .

Thus , almost always you want colder if you "deviate" from standard spec. grade plugs .

 

D

 

 

 

Edited February 24, 2020 by DamirGTI

[Romb 0]

1 hour ago, DamirGTI said:

"Hot" and "Cold" on the chart above represents spark plug heat range , not the "engine heat" .

 

Its the rating of the spark plugs ability to dissipate combustion heat from the spark plug firing tip to the cylinder head water/coolant jackets .

 

Hot grade spark plugs dissipate combustion heat slowly , contrary to the cold grade plugs which dissipate combustion heat more rapidly .

 

Standard grade or one to maxi two step colder spark plug is recommended if you tune the engine , as the combustion temp. rises there's always risk of per-ignition , combustion detonation , overall higher engine running temp. or even overheating ... one or two grades colder plugs can help in such conditions .

Thus , almost always you want colder if you "deviate" from standard spec. grade plugs .

 

D

 

 

 

Super, fully clear

 

I'm not pushing the car, all stock and with the cat emptied out the engine is probably running cooler because of easier exhaust gas exit. Would you then take the standard NGK6, which is then a tad colder plug then necessary as the engine runs less hot without cat, or go with a step colder anyways, i.e. NGK7 ?

 

I really value your expertise (and Welshpug and others here :-)

[DamirGTI 342]

NGK '6 grade plugs are fine for DKZ engine as per the OEM spec. .. and , no you got that wrong way round ! - NGK in '6 grade are hotter plugs , not colder .

 

No major engine mods - no need to deviate from factory spec plugs , you'll be just wasting money on another set of plugs .

By "major" engine mods which will need an step or two colder plug i mean - turbocharging , supercharging , NA but with increased dynamic compression ratio etc.

 

D

 

[Romb 0]

20 hours ago, DamirGTI said:

NGK '6 grade plugs are fine for DKZ engine as per the OEM spec. .. and , no you got that wrong way round ! - NGK in '6 grade are hotter plugs , not colder .

 

No major engine mods - no need to deviate from factory spec plugs , you'll be just wasting money on another set of plugs .

By "major" engine mods which will need an step or two colder plug i mean - turbocharging , supercharging , NA but with increased dynamic compression ratio etc.

 

D

 

Thanks Damir

 

Above, with NGK colder I didn't mean compared to other plugs but compared to the engine. The empty cat allows easier exhaust emission which I assume drops engine temps. Compared to a catted engine (running hotter) which has prescribed the NGK6, I figured that for a de-catted engine the NGK6 is possibly a tad overly heat resistant and too cold for the application.

 

But probably marginal difference and will go with your feedback; no major mods except empty cat, so Bosch7 equaling NGK6 would be fine.

 

20,- euros saved to put elsewhere on the car :-)

[Romb 0]

On 2/23/2020 at 11:25 PM, DamirGTI said:

NGK '6 grade plugs are fine for DKZ engine as per the OEM spec. .. and , no you got that wrong way round ! - NGK in '6 grade are hotter plugs , not colder .

 

No major engine mods - no need to deviate from factory spec plugs , you'll be just wasting money on another set of plugs .

By "major" engine mods which will need an step or two colder plug i mean - turbocharging , supercharging , NA but with increased dynamic compression ratio etc.

 

D

 

Damir, on a sidenote, I was doing research about bearing replacement and ended up at below link, coincidentally where you 9 years ago were doing the same process, pretty funny ! And nice cat :-)

 

http://www.guy-croft.com/viewtopic.php?t=2440

[DamirGTI 342]

Indeed i was , miss those days must say ... fast forward 9 years and sadly that cat is long gone by now , the car is still here but looking a little bit different now , and no i haven't took the advice about the bearings being "sour" ! (bad/oxidized) .. they where fine .

 

Shame for the GC forum though as i really learned a lot there about engine work (there used to be much more technical stuff and projects , but most of it was erased by the owner/Guy during the years)  .. it all went bust forum wise around the globe ... i blame Facebook , Twitter , Instagram and other social network crap .

 

D

[Romb 0]

Nice !

 

I was also doubting that suggestion about oxidization.

 

Agree with social media, but this forum seems alive and kicking, many really know what they do here and share advice. Super helpful