Dry fouling on cyl 5 and 6 plugs; going nuts. Help?

[supernova_6969]

hi guys!

 

I have this L28 turbo, megarsquirt 2 car that i bought already built (engine rebuilt 1000kms before I bought it).  the guy told me all i had to do was tune the tables and it'd be great (last time I buy an already modified car).

 

It ran really rough, idled poorly, and did weird things under boost (boost, drop boost, reboost, etc).  the AFR was all over the place (both too rich and too lean).  I changed the plug wires (which leaked current everywhere), played a lot with the tune a lot with somewhat better AFRS overall (still very rich though, with intermittent issues)

 

Long story short, i decided to change the plugs (yeah yeah, should have right away, screw me, I'm on a tight budget) and I tested and cleaned the injectors, which function well.  

 

first run after that, I let it idle till it was warm, then took it out for a 5 minute spirited drive (with 3-4 times running full boost for 2-3 seconds), then back home.  

 

I checked the plugs right away and I found this:

 

 

the plugs are in the following order: 6-5-4-3.    essentially, the plug 6 is very dry-fouled, plug fire dry-fouled, and plug 1-2-3-4 are super clean, like new still. 

 

looking into the matter, I tested compression, and I have 170+ in all cylinders. neither 5 or 6 are the lowest of the bunch. 

 

I thought maybe the injectors (which are batch fired 1-2-3 and 4-5-6) had a problem even if I had tested them, so tonight I switched the plugs and the injectors around so the 5-6 got the clean plugs and the injectors from cyl 3-4.  I did the same run and got the exact same results: plug 6 is very dry-fouled, plug fire dry-fouled, and plug 1-2-3-4 are super clean, like new still. 

 

I'm thinking it could be one of the three following issues: 

-somehow cyl 5-6's inj. are not getting proper current and might be staying open for too long or something (which I think is unlikely, since it's batched with 4 as well and that guy's cool). 

-maybe something is wrong with the spark.  either the distr. is faulty, or the wires (even if the wires are are new) and 5 and 6 aren't getting good spark.   (i'm thinking the coil is fine, since 1-4 have no issues)

-maybe my valves are poorly adjusted and creating issues (they are a little noisy, although the high compression suggest they should be mostly fine.

 

I'm going to look into these issues, but does anyone have other suggestions? one thing to mention is the engine runs REALLY rich right now (betwen 9:1 under boost and 12:1) i know it's an issue and i plan on working on this, but that's not the problem for the fouling or else ALL my plugs would be similarly fouled (I guess). 

 

any suggestions is more than appreciated. I'll post as i test things..

 

 

 

 

 

[TimZ]

hi guys!

 

I have this L28 turbo, megarsquirt 2 car that i bought already built (engine rebuilt 1000kms before I bought it).  the guy told me all i had to do was tune the tables and it'd be great (last time I buy an already modified car).

 

It ran really rough, idled poorly, and did weird things under boost (boost, drop boost, reboost, etc).  the AFR was all over the place (both too rich and too lean).  I changed the plug wires (which leaked current everywhere), played a lot with the tune a lot with somewhat better AFRS overall (still very rich though, with intermittent issues)

 

Long story short, i decided to change the plugs (yeah yeah, should have right away, screw me, I'm on a tight budget) and I tested and cleaned the injectors, which function well.  

 

first run after that, I let it idle till it was warm, then took it out for a 5 minute spirited drive (with 3-4 times running full boost for 2-3 seconds), then back home.  

 

I checked the plugs right away and I found this:

 

plugs 6-5-4-3.jpg

 

the plugs are in the following order: 6-5-4-3.    essentially, the plug 6 is very dry-fouled, plug fire dry-fouled, and plug 1-2-3-4 are super clean, like new still. 

 

looking into the matter, I tested compression, and I have 170+ in all cylinders. neither 5 or 6 are the lowest of the bunch. 

 

I thought maybe the injectors (which are batch fired 1-2-3 and 4-5-6) had a problem even if I had tested them, so tonight I switched the plugs and the injectors around so the 5-6 got the clean plugs and the injectors from cyl 3-4.  I did the same run and got the exact same results: plug 6 is very dry-fouled, plug fire dry-fouled, and plug 1-2-3-4 are super clean, like new still. 

 

I'm thinking it could be one of the three following issues: 

-somehow cyl 5-6's inj. are not getting proper current and might be staying open for too long or something (which I think is unlikely, since it's batched with 4 as well and that guy's cool). 

-maybe something is wrong with the spark.  either the distr. is faulty, or the wires (even if the wires are are new) and 5 and 6 aren't getting good spark.   (i'm thinking the coil is fine, since 1-4 have no issues)

-maybe my valves are poorly adjusted and creating issues (they are a little noisy, although the high compression suggest they should be mostly fine.

 

I'm going to look into these issues, but does anyone have other suggestions? one thing to mention is the engine runs REALLY rich right now (betwen 9:1 under boost and 12:1) i know it's an issue and i plan on working on this, but that's not the problem for the fouling or else ALL my plugs would be similarly fouled (I guess). 

 

any suggestions is more than appreciated. I'll post as i test things..

So when you say the plugs are fouled, do the two plugs in 5 and 6 just have discoloration on the insulator, or do they literally not fire?  

 

In general, "fouled" means a specific thing - carbon deposits creating an electrical path to ground and effectively shorting out the center electrode, such that it cannot fire.

 

If you are seeing 9:1 AFRs with gasoline (this is not e85, right?), I'd expect some discoloration (probably more than that).  I'm actually a bit confused how the other plugs could look so clean with those mixtures.

 

I was also thinking maybe some oil leaking past the valve stem seals on 5 and 6, but I'd expect to see some nastiness on the ground strap in that case.

[Xnke]

Those plugs aren't fouled, and the 9.0:1 mixture readings are way off...what wideband sensor are you using again?

 

Airflow has a big part in mixture control too, if 5 and 6 aren't getting as much air as 1-2-3-4, then they'll read richer-because they are. Check your valve lash and your valve lift, make sure the cam isn't wiped out. Check both intake and exhaust! Either could be the issue.

 

When reading plug mixtures you MUST use new plugs, personally I prefer the NGK nickle-plated ones because that's the chart that NGK provides to read them with. Look at the plug end-on. You are not reading the insulator for mixture, it should be clean and white, maybe a little tan, 5 is "OK" but dark, 4 is normal.

 

First, read the ground strap. You want to see the plating burned off right to the middle of the bend, and no further. If the burn mark is closer to the ground ring, the plug is too hot. If the burn mark is closer to the tip of the ground strap, the plug is too cold.

 

Read the ground ring, you should see 50%-75% of the ring a light tan color, at a mixture of around 14.7-15:1. 75-100% light tan, that's 13.8-14.4:1, and is where you want it to be N/A. Sooty, jet-black, dry deposits are 11:1-12:1. They may flake off, they may be baked on hard. Don't count flaked off clean areas as "clean" in the 75-100% reading-you'll be able to tell where it's flaked.

 

Next, you look wayyyy down in the plug to the base of the insulator where it meets the shell-you should have the same light-tan coloring there. No silver speckles, no black speckles-that's detonation.

[supernova_6969]

hi!

 

thanks for the replies.  

when I mean fouled, I meant indeed that the porcelain insulator is no longer white.  I though that significant fouling led to the lack of insulation, not that fouling necessarily implied so much of it that it automatically shorted the plug.

 

these plugs are new;  I put them in about 3 kilometers ago and then drove 1.5 kms;  that's when i checked them for the first time and got clean 1-2-3-4 and dirty 5 and very dirty 6.    thinking the injectors might be the culprits, i switched the injectors from 3-4 (that had kept their plugs clean) to 5-6 and switched the plugs also so that 3-4-5-6 all have clean plugs, then drove the same 1.5 kms.  got the same result.  the then clean plugs in 5-6 were now dirty and very dirty.  

 

the original 5-6 plugs that I just threw away were completely covered with dry, sooty carbon, except there was a ton of it, like #5-7 in this photo (not my plugs, just an example)

https://encrypted-tbn3.gstatic.com/images?q=tbn:ANd9GcR7YkGUmE45SSo_WA3OnouMHPZVhMmUyYjwWZQGqvJqzEjuZeh2_A)

 

as for the o2 readings, I've been trying to tune it but was afraid to lean it out in case one of my cylinders wasn't getting any gas - I figured i'd keep everything mostly as is until I figured out why some the engine was misbehaving so much.  I know it's not great, but it's better than blowing a cylinder because of a lean detonation.  

the sensor is a standard innovate Lc1,  and the readings with the car turned off overnight (100% normal air) are right so i'm not too worried about it's readings.   the exhaust does smell rich, so it's consistent with a rich O2 reading (I get 9:1 when I'm flooring it, which is where the tables tell it to be much richer anyways, and 12:1 on iddle, where the tables are a little better tuned...).  I guess if I still get wacky readings after all my plugs are of the same happy colour, i'll look into the sensor..  

 

timz: re: oil past the valves, wouldn't I get a more wet fouling?  and yes, gasoline, 94 octane. 

 

Xnke: I'm with you, and checking the valve is on top of the list but I have a question..  how could gas get through the improperly adjusted valve, but not enough air (assuming the path to the valve is clear)?

as for the full read of the plugs, I think eventually I should do a more advanced read, but for now, I really want to figure out that whole 5-6 are on a different planet than 1-4.   

 

tonight, I might check the distributor to make certain everything is clean and allows for good currant flow. to be honest, I'm scared shitless of adjusting the valves, so i'll do it last.

 

one way or the other, thanks for the posts... and the ideas somewhat align with some of my hypotheses, so that's encouraging.  stay tuned. 

 

 

[supernova_6969]

Tonight (tuesday the 26th), I:

 

-checked my distributor and the cap is clean, the rotor is clean, and there appears to be no play in the shaft. (I also cleaned the slight white buildup inside the cap on the "posts"(?)).  there was no carbon tracking in there, which would have been real bad news.

-checked the plug wires and all the plugs get current (I saw and heard the current jump from the wire to the plug when I unplugged each of the plugs and the engine ran rough, although I think it's less marked (the roughness) when I remove number 6.  something is definitely going on there)

-I checked the injector wiring and it it all seems to work the way it's supposed to.  I also unplugged the injectors one at a time, and the idle got rough at every injector. 

 

so... yeah.  i'll check the valves.  soon.   unless someone suggests something else less daunting, which I will do soonER..    

Edited April 27, 2016 by supernova_6969

[Xnke]

Too much switching around at the same time. Only move one component at a time when you're trying to rule something out. By moving both injectors AND plugs, you've proven that it is neither the injectors, nor the plugs, but only the position in the engine.

 

Just because the valve opens, does not mean it opens fully. Also, the runner/port/intake/etc could have junk or clogs in it that prevents the same *mass* of air entering that cylinder...not that the cylinder is completely blocked.

[fraz]

i had a similar problem on an RB i own. Number 5 was always pig rich.

 

Turned out the fuel pressure reg was chinese shit and was leaking fuel into the vacumn reference line and running back into the plenum. The fitting was directly opposite number 5 port.

[Annunaki]

If you're scared of detonation because your running lean, you should also be scared of cylinder walls getting wash because your running rich. Keep your AFR around 12 at boost and 14-15 AFR at idle. Out of boost, highway, city, 14-16AFR. Innovative LC1 don't they need to be calibrated to read correclty? What ways of boosting/driving when you're checking your plugs? 

[supernova_6969]

ok, ok! *roll eyes and smiles*

 

I've actually started the process of find TDC for cyl 1 & 4 to be able to adjust the valves, but I don't have a 27mm socket to rotate the engine, and I need a helper to rotate said engine from under while I check for TDC through the spark plug holes.  I'm looking into both matters as we speak, so it should be done within days.  

 

While I am nervous, I know it's a straightforward process, so I actually can't wait to do it.  

[NewZed]

I've actually started the process of find TDC for cyl 1 & 4 to be able to adjust the valves, but I don't have a 27mm socket to rotate the engine, and I need a helper to rotate said engine from under while I check for TDC through the spark plug holes.

You don't need to know TDC to adjust the valves.  And you don't need to adjust the valves yet, just check lash.  All you need is a set of feeler gauges.  And you can turn the engine by putting the car in 5th gear and rotting a wheel.  Turn it until the valve you want to check is on the base circle, off the lobe.  Lobes pointing up.  Don't make it too complicated.  Make a chart, take the valve cover off, measure lash on all of the cam lobes that are properly oriented, and turn the engine over to do the others, until they're all done.  Do it cold so that you'll have the same conditions for all and take your time.  Then decide if they need adjusting.

 

The reason you can get rich in single cylinders is because the multiport EFI system squirts the same amount of fuel to each cylinder.  There's an assumption made that the same amount of air is entering.  Not like throttle body injection or carbs where the fuel and air are mixed first, then distributed.

[supernova_6969]

NewZed

thanks for the advice..

Since i'd never done it, I was going to stick to the shop manual procedure;  reading the manual, I thought it only gave hot values (clearances I 0.25mm(0.010) E 0.30mm(0.012)), so i thought that was the only way, but I just found that the manual also gives the values for a cold engine (I 0.17mm(0.007) E 0.024(0.009).  

 

In the end, I understand the process and will most likely follow your procedure.

 

the manual seems to suggest doing the valves when the engine is warm rather than cold: out of curiosity,   any reason to do it hot rather than cold? If I get them right cold, what are the chances of the differences getting the valve lash wrong once it's hot?

 

another thing is that everywhere I see, they give cold values for I 0.008 and E 0.009 instead of the ones i quote from the 1982 or 1983 manual.    i'm not certain which values I should use...  the hot values are the same though. 

[fraz]

when the engine heats up the alloy head and steel valves expand at different rates. Hence the different values for hot and cold.

 

You usually do it hot as that is where you want them to be when the engine is operating.

 

Since you have not done it before, it would be easier to do it cold first. Then you can take your time, learn to do it properley, and not worry about the engine cooling down while your doing it.

 

I usually do it with the car in top gear and i rock it back and forth and do them a couple at a time as the cam lobes are pointing up.

[supernova_6969]

ok, so I adjusted my valves.

I did it cold, with the help of my dad (thanks!).  ran the car and one valve was making noise, son I ran back home and checked them all and 3 needed a slight readjustment. don't know if we did it wrong in the first place, but it shows that doing it cold isn't all that bad, since most of them WERE ok and the others possibly wrong due to human error (my dad is much more confident than I am, and doesn't quadruple check everything..) 

I ran it for a minute, no more noise.  

for the record, I used what the manual said: 0.008/0.010 cold, and 0.010/0.012 hot.  seems the number for the cold ones translate well to hot....

Also, to rotate the engine, I used the big bolt that holds the timing chain sprocket.  no need to rotate a wheel or get under the car. 

 

I think there is a difference in performance, but it's still far from perfect.

I checked the plugs in between the two adjustments, and #5 seemed better, but #6 was still much more dirty than the others (I'd put in ones that were clean before setting out. 

 

I'll have to re-check the plugs in a few days to see if the last adjustment did anything. I'll post then.

 

thanks for everyone who chimed in so far. I really appreciate.  

Edited April 30, 2016 by supernova_6969