Need expert help, blowing through plugs, logs included

[Colinoscopy]

Hey all,

2010 135i 130k miles, new Turbos at 100k miles. Index 12 injectors, fully maintenanced and well maintained. Currently MHD stage 2 91 octane, downpipes, charge pipe and blow off valve.

I have a bit of a mystery going on here. I was getting a misfire on a couple different cylinders about 5k miles ago. I hadn't changed the plugs since owning the car (got it at 110k) so I threw in new NGK 95770 1 step colder gapped to 0.022. All my misfires went away.

Fast forward to the past couple of weeks, I'm getting misfires again, especially on cylinder 6. I pulled the plugs to find they had worn down significantly. Up to 0.032 on some cylinders. After only 5k miles?? I re-gapped the plugs and the car is running beautifully again (logs below). No major timing corrections, fuel trims are largely within normal limits, not running lean. Everything appears normal. Pulls really strong.

https://datazap.me/u/colinoscopy/dia...og=0&data=3-24

I was concerned the car might be going through plugs due to running hot/lean or blow by. I bought a cheap 30 dollar compression test kit at Harbor Freight, numbers are below.

Cylinder 1: 125
Cylinder 2: 125
Cylinder 3: 125
Cylinder 4: 125
Cylinder 5: 125
Cylinder 6: 125

I know these numbers are low, but at least they're consistent. I've also heard anecdotally and by testing that the harbor freight compression tool typically measures about 20 psi below actual. I added oil to the cylinders and numbers went up to 138-140 across all cylinders. (Hopefully "normal" wear for a car with 130k? I've heard +20 is when I need to worry.)

Anyways, why would I have gone through plugs so quickly on all cylinders? Some plugs had worn faster than others, but the gaps were all significantly larger than the 0.022 that I put them in at after only 5k miles.

Sorry for the novel, but I'm lost here and would love advice. Thanks!

Edit: The car has never been walnut blasted or carbon cleaned as far as I know. I'm having it done next week.

Second Edit: I did not have my foot on the gas (throttle open) when doing the compression test. Just now finding out this is necessary?

[iminhell1]

You had to have set the gap wrong.

The only other explanation is the center electrodes are junk and moving, which would crush the resistor above it. HIGHLY unlikely.

Also, throw that tester in the garbage (return it). Accuracy is far more important than consistently wrong.
I believe mine was around 180psi cold.
Could be you just didn't crank long enough. Face the gauge so you can sorta see it through the bottom of the windshield, crank until you don't see it rise anymore (needle will usually jump 3 times or so).

[Colinoscopy]

Originally Posted by iminhell1

You had to have set the gap wrong.

The only other explanation is the center electrodes are junk and moving, which would crush the resistor above it. HIGHLY unlikely.

Also, throw that tester in the garbage (return it). Accuracy is far more important than consistently wrong.
I believe mine was around 180psi cold.
Could be you just didn't crank long enough. Face the gauge so you can sorta see it through the bottom of the windshield, crank until you don't see it rise anymore (needle will usually jump 3 times or so).

That's the thing though, I specifically set them all to 0.022 with my gapping tool. I remember it clearly haha. I cranked about 6 times on each cylinder to where the needle wasn't moving anymore. As I said, I didn't have the throttle depressed so maybe that matters?

[bbnks2]

Originally Posted by Colinoscopy

That's the thing though, I specifically set them all to 0.022 with my gapping tool. I remember it clearly haha. I cranked about 6 times on each cylinder to where the needle wasn't moving anymore. As I said, I didn't have the throttle depressed so maybe that matters?

what do the plugs look like when pulled? black and fouled out?

[iminhell1]

Originally Posted by Colinoscopy

That's the thing though, I specifically set them all to 0.022 with my gapping tool. I remember it clearly haha. I cranked about 6 times on each cylinder to where the needle wasn't moving anymore. As I said, I didn't have the throttle depressed so maybe that matters?

I did mine both ways, closed and open, and got results within 5psi or so.


Just gooooglin, seems my numbers are right about where others are. Found a post (https://bmw.***********.com/threads/...t-vs-otc.3727/) where he notes the disparity in the gauges. And you're sill below the shitty gauge by a fair amount.
There is something going on.


Might be the gauge wasn't screwed in tight enough, maybe the o-ring is too bulky and it's rolling? maybe on the first crank the gauge turns just a bit and leaks some (I've done this).




And I do have one more idea at how a gap could open, bent valves.
If the plug is protruding (which I believe ours should be doing) and a valve is bent, there might be a possibility where the face could contact the ground strap.
I think I'm just making this one up though. I don't know how close anything in there is and I've never seen anything like it in practice. But strange shit happens sometimes.
You'd think if that did happen the valves would keep hitting it and it'd open more and more.
But it could explain the low compression a bit too.


Measure the reach of the plugs just to verify they are correct.
https://www.ngk.com/learning-center/...ach-calculated

[Colinoscopy]

Originally Posted by bbnks2

what do the plugs look like when pulled? black and fouled out?

The diode and ground electrode weren't black at all. Maybe some parts near the threads were a little black but overall they looked fine.

[Colinoscopy]

Originally Posted by iminhell1

I did mine both ways, closed and open, and got results within 5psi or so.


Just gooooglin, seems my numbers are right about where others are. Found a post (https://bmw.***********.com/threads/...t-vs-otc.3727/) where he notes the disparity in the gauges. And you're sill below the shitty gauge by a fair amount.
There is something going on.


Might be the gauge wasn't screwed in tight enough, maybe the o-ring is too bulky and it's rolling? maybe on the first crank the gauge turns just a bit and leaks some (I've done this).




And I do have one more idea at how a gap could open, bent valves.
If the plug is protruding (which I believe ours should be doing) and a valve is bent, there might be a possibility where the face could contact the ground strap.
I think I'm just making this one up though. I don't know how close anything in there is and I've never seen anything like it in practice. But strange shit happens sometimes.
You'd think if that did happen the valves would keep hitting it and it'd open more and more.
But it could explain the low compression a bit too.


Measure the reach of the plugs just to verify they are correct.
https://www.ngk.com/learning-center/...ach-calculated

My friend just did a retest with the same gauge, different car, throttle open versus closed and saw a 20 psi difference. I'll try that again and see. Maybe bent valves but what are the odds that the compression is the exact same across all cylinders with bent valves?

Thanks for your in depth answer by the way, I appreciate it. Did you happen to look at my logs? Do they look ok?

I did notice that under light load and low throttle pedal depression i was running kinda lean between 4-13? Might be weird but isn't 20 where I start to need to worry? I also saw throttle closures over the pull which doesn't make sense.

[iminhell1]

I didn't look at the log.
Right now it seems more mechanical than tune. Sort the mechanical first and don't adjust the tune at all, one thing at a time.

[bbnks2]

Originally Posted by Colinoscopy

The diode and ground electrode weren't black at all. Maybe some parts near the threads were a little black but overall they looked fine.

So how are you "blowing through" spark plugs? 5k miles out of a set of spark plugs is your basis for that statement? You've only had to change them twice 110k and again at 115k? I'm just confused at what the actual issue is here... Could your ignition coils just be old? If you have not replace the coils do it. Gaping plugs down will just mask the underlying weak coil issue and wear the plugs out faster.

Also, maybe you didn't gap them down to .022" as well as you thought to begin with? Compare new electrode to old and see if they are really that worn down. I doubt the plugs electrode really wore down that much.

[Colinoscopy]

Originally Posted by bbnks2

So how are you "blowing through" spark plugs? 5k miles out of a set of spark plugs is your basis for that statement? You've only had to change them twice 110k and again at 115k? I'm just confused at what the actual issue is here... Could your ignition coils just be old? If you have not replace the coils do it. Gaping plugs down will just mask the underlying weak coil issue and wear the plugs out faster.

Also, maybe you didn't gap them down to .022" as well as you thought to begin with? Compare new electrode to old and see if they are really that worn down. I doubt the plugs electrode really wore down that much.

My issue is that I replaced the plugs at 125k then at 130k the gaps were gigantic causing the car to misfire. I compared the old plugs with a spare new one I had of the same brand and model and the diode had in fact worn down significantly. They were gapped appropriately when I put them in at 125k miles.

I didn't realize old coils could burn through plugs, interesting. However, I do have 1 new Eldor coil on cylinder 3, the diode was also worn down on the plug.

I realize re-gapping is a temporary fix, I just needed the car to not misfire and run smoothly while I figure out the actual issue.

[bbnks2]

Originally Posted by Colinoscopy

My issue is that I replaced the plugs at 125k then at 130k the gaps were gigantic causing the car to misfire. I compared the old plugs with a spare new one I had of the same brand and model and the diode had in fact worn down significantly. They were gapped appropriately when I put them in at 125k miles.

I didn't realize old coils could burn through plugs, interesting. However, I do have 1 new Eldor coil on cylinder 3, the diode was also worn down on the plug.

I realize re-gapping is a temporary fix, I just needed the car to not misfire and run smoothly while I figure out the actual issue.

ok so sounds like you're chasing your tail with the compression testing. I assumed you meant you were blowing through spark plugs because they were fouling out with fuel and/or oil and that is what was leading you to believe you had low compression.

Physically wearing down the electrode though? That doesn't sound like low compression. Unless the car is misfiring like crazy constantly because of the low compression or something? Tune looks fine. Everything looks to be in check in the log anyway. Plug running really hot? take a look at your old plugs and google around for how to "read" a plug. Maybe try 1 step colder (n55 plugs) next time?

[Gizmo135i]

I would buy bmw plugs, they’re expensive but I’ve seen a lot of misfires from aftermarket plugs, even brand new or not too old. I’m not sure what is different about them but these cars can be sensitive. Also like others said weak coils or failing injectors could be causing issues as well.

[Colinoscopy]

Originally Posted by bbnks2

ok so sounds like you're chasing your tail with the compression testing. I assumed you meant you were blowing through spark plugs because they were fouling out with fuel and/or oil and that is what was leading you to believe you had low compression.

Physically wearing down the electrode though? That doesn't sound like low compression. Unless the car is misfiring like crazy constantly because of the low compression or something? Tune looks fine. Everything looks to be in check in the log anyway. Plug running really hot? take a look at your old plugs and google around for how to "read" a plug. Maybe try 1 step colder (n55 plugs) next time?

Ahh my apologies, yes I meant the diode is physically wearing down. Not really contaminated with anything. I was under the impression that running too hot can wear away the diode, and running too hot I thought meant running lean, and running lean had me worried that I might have low compression, that's why I did the test. Logs don't really suggest running lean though.

The plugs that ran out in 5k miles were 1 step colder NGK plugs. There were OEM stock plugs in there previously. Thanks for your tips

[Colinoscopy]

Originally Posted by Gizmo135i

I would buy bmw plugs, they’re expensive but I’ve seen a lot of misfires from aftermarket plugs, even brand new or not too old. I’m not sure what is different about them but these cars can be sensitive. Also like others said weak coils or failing injectors could be causing issues as well.

OK cool, yeah I plan on switching back to OEM to see what happens.