Hey guys just a quick question. Last night I was verifying my timing hadn't moved with a timing light and noticed that out of every 10 flashes or so only 8 or 9 would go off... read a noticeable miss on flash. I want to lean toward plug wires, even though they're like brand new as well as the cap and rotor and plugs. The only other thing I could think the plug is a bit fouled?

So I pulled number one out and the whole plug is sooty, not wet, just sooty. I can't really read it but the soot is even, the ceramic is lightly discolored and I can't really see the electrode strap break line. I'm half wondering if I should lean out the idle AFR and go from there. It is sitting around 14.0 at idle on the wide band and I'd imagine 14.7 would be a bit better. Just trying to figure out if I should start replacing components. Car drives fine, don't feel a miss and don't feel down on power but who knows.

Thanks in advance.

-Paul

 

Hey Paul I get this with my plugs as well. Sooty plugs mean that the plug is running too cold and can’t self clean. I run NGK 5s which are a pretty hot plugs so in my case I think my tune is too rich. I have been chasing this for a while through logging but I don’t have the answer yet. I know my engine will idle at around 14.7 AF. If I lean out at idle the engine will hunt and I wouldn’t want it any leaner anyway. When making power my engine seams to like about 12.5 AF. I think my VE tables are ok so the issue might be in closed loop. Could be the CTS enrichment, I’ve noticed that the CTS reads about 10deg C colder than the dash. So I could be getting too much enrichment if the CTS is wrong. It could be the INT or BLM targets but I just don’t have definitive data at this stage.
Anyway sorry I don’t have an answer for you apart from the fact that the plugs won’t self clean if they are too cold and that’s normally because the engine is running rich.

 

I'm running 7s so that could be an issue. At the same time these plugs have a bit of run time at idle on them figuring out the tune so maybe a new set first then retest. Thanks!

 

Most likely the inductive pickup on your timing light is occasionally not picking up a pulse.

 

NGK 7s are quite a cold plug and generally something you would see on the track were the engine is run hot and flat out. Factory equivalent NGK is a 5 so you could try that.
https://www.ngk.com.au/technical_info/heat-range/

 

I would think you need to pull a plug from another cylinder before determining the cause. Is it isolated to cylinder/plug on just #1 or are they all that way? You could have a leaking or failing injector? Could be the wrong heat range if they all are exhibiting the issue, or could be your AFR is a little rich, but I would want information from more than one plug before determining the corrective action.

 

He has a crossfire so it’s a wet intake manifold like a carby. I agree that it is wise to look at more than one plug but in this case I expect they will all be a bit sooty. I definitely think NGK7xxx are too cold. As a rule I would fix the issue before changing the plug heat range however in this case I think the heat range might be the issue.

 

So used to TPIs and LTX's lol

I would still be suspicious of how isolated the issue may be.

 

yep can’t really diagnose a fault via the Internet so it’s more about here is a list of potential causes.

 

For the heck of it I swapped the pickup to cylinder 6. Appears to be doing the same thing. I'll pull all the plugs thursday as that's the next time I'll have time. I'd expect them all to be about even though. But who knows with the changes. I've trimmed back the idle afr in the tune too.

 

I'm going to pull all the plugs today but last time I drove the car I took her up to about 5200 rpm and the thing just fell over on its face while also sounding like it was either breaking up or missing. All the ignition components are new so I'd suspect plugs first but I'm not sure at this point. More digging is required. It could also just be that it is running out of the ability to breathe through the stock intake but I wouldn't think it would sound like that... I'll keep you updated.

 

1 3 5 7


8 6 4 2

To me it seems the heat range is a little cold and the tune is a little fat. This was after a hard rip where I just dropped it in neutral and rolled into the garage. Appears to be even atleast.

 

Yep I’d agree with that. They are not too bad thought, so small adjustment only. I would try NGK5s and try that for a while.

 

Kind of what I was thinking. I'll lean the idle a little bit, being 15:1 won't hurt much at idle anyway and trim the whole curve some.

Try to see if I can find plugs locally and at a reasonable price. Those plugs otherwise have a lot of idle time on them still.

 

So the R5671 seems to only go as low as 7... looks like a 6130 may work but the projected tip is interesting. I would tend to think that a hotter plug would have to have some projection though.

 

As far as the timing light issue - I would not only try it on other cylinders - I'd try it on another car.

Remember - the better quality spark plug wires you use - the harder it is for an Inductive pick-up to get the leakage that allows it to function.


As for your plugs - it looks like you're a bit rich - but I tend to trust Wide Band Oxygen Sensors more than I trust how plugs look. You can probably lean out your hot idle a touch - but I wouldn't go nuts, I like to stay on the rich side of 14.7:1 . You might also want to do a leakdown test - just to get an idea how the rings are doing... While it looks like carbon - a little oil getting by the rings combined with a bit of a rich condition can be VERY difficult to accurately troubleshoot. To be clear - that's not what the plugs look like - but if nothing else - doing a leakdown test is good data to have.... As for going hotter on plug heat range - you need to be careful - it's winter (OK - it's not really that cold in North NJ, but the car is starting "cold" and the computer is adding fuel at startup because it's not 90 deg, and clearly you've been doing some idling.... A lot depends on how you use the car - if prolonged WOT is a part of your car's life - tread very lightly on plug heat range.... YMMV ...

.

 

I actually have the exact same plug wires on the 67 and never noticed a problem but I will definitely check again. But that being said, it would sound like (Doing some reading) that the type of plug I have in there right now is just not that good for a street vehicle with the shielded tip. The wide band idle is 14 now, it does jump around which is expected with a lumpy cam but the average is tracking around 14. My idea is to swap plugs, warm the car up take a rip up and down the street. (Long straight so I can tap out 1st and second a few times) and then roll it back into the garage and re-read them. So long as everything looks good I should be fine. The car does load up at idle though, starts bluish smoking. I would normally say that is oil... but between the burning in my eyes and the smell I can with 95% confidence say that it is just excess fuel. It correlates with how the car is running too, a few taps and it clears then takes a while to come back. I had done a leak down a while back and off the top of my head it wasn't anything horrible. The car does have 100k on it but did quite well.

Or alternatively the plug is too hot and melts a piston or something and the car tries to kill me.

 

Yep BCPR5ES or BKR5E (normally BKR5E) are what I run they are the equivalent of a Champion RC12YC which is what was recommended for my Edelbrock heads. I am thinking of going to the iridium BKR5EIX but I wouldn’t do that until you are happy with the look of your plugs.

 

So they didn't have the NGKs but they actually proce matched me a set of delcos that were a direct cross reference. More defined idle, power feels more on demand than it already was and get this... timing light works as it should now too. I did a hard 1-2 pull up and down the street and pulled #3 as it is the easiest to get:

Looks about right to me, light color on the ceramic, part line on the strap is in the middle of the bend, and light soot just about one turn on the base not heavy like before. Idle AFR is stable at 14.

Now I still have something going on at wide open but it would seem like this... watching the data log closely, as move above 5000 rpm my afr starts to decline from 12:1 to around 11:1. Now where it gets bad is right before the breakup happens the afr further drops to about 9.8:1.... which to me seems like my wide open isn't actually a break up so much as it is just too rich to burn right. Make sense?

 

There is a power enrichment table that you could look at. Also the timing should drop back a bit a WOT to about 36 Deg IIRC. I’m at work now but it can check when I get home. I can send you through my tune if you want, obviously the VE tables will be different but it still might be good to compare some of the other tables.