HEI coil screws caused me to fail emissions

[Shawn]

Never seen this before so thought I'd post it up for anyone having a misfire. Recently my 78 K5 failed emissions due to high HC. It had fairly new plugs, wires and cap/rotor in it. I could feel the misfire at idle and in drive. Threw another set of plugs, new cap and rotor on. Misfire still there and even worse now. You can see how bad my HC (unburned fuel) was here:


Found what was causing it. The 4 screws holding the coil inside were too long and breaking through the cap causing the rotor to sometimes spark up one of the screws causing the misfire. I felt kind of stupid for not catching that when I replaced the cap but I have never seen this before.


Confirmed its now cleaner on the HC side and should pass now.

 

[Fastereddie]

Never seen this before so thought I'd post it up for anyone having a misfire. Recently my 78 K5 failed emissions due to high HC. It had fairly new plugs, wires and cap/rotor in it. I could feel the misfire at idle and in drive. Threw another set of plugs, new cap and rotor on. Misfire still there and even worse now. You can see how bad my HC (unburned fuel) was here:
View attachment 513663

Found what was causing it. The 4 screws holding the coil inside were too long and breaking through the cap causing the rotor to sometimes spark up one of the screws causing the misfire. I felt kind of stupid for not catching that when I replaced the cap but I have never seen this before.
View attachment 513664

Confirmed its now cleaner on the HC side and should pass now.
View attachment 513665

Wow, thats a good find!

 

[K85 Octane]

A tough find

 

[Wes Harden]

Chinesium crap and a MBA saving pennies. Good catch

 

[Shawn]

Chinesium crap and a MBA saving pennies. Good catch

Agree. I can only assume the incorrect longer screws were the main problem on two caps. I even purchased the Carquest premium cap with brass terminals.

 

[imiceman44]

Agree. I can only assume the incorrect longer screws were the main problem on two caps. I even purchased the Carquest premium cap with brass terminals.
View attachment 513676

What I want to know is how did you catch it?
Did you see the sparks in the dark?

 

[Wes Harden]

guessing the ole Mk1 eye ball

 

[Shawn]

What I want to know is how did you catch it?
Did you see the sparks in the dark?

You could feel the misfire. I can't take credit for the find. Jay at the Carburetor Shop found something I totally missed on both caps. He has the expensive HC/CO analyzer too so we verified it was good to go for emissions. Not bad for no cat and no air pump. Final numbers here:

 

[Wes Harden]

Would have seen that right way on any 70s or 80s oscilloscope, which any shopbworth going to would have had. Not so much any more. I do miss not having an oscilloscope. Probably forgot sime of the more unusual patterns, still have enough retained. Not so easy to use on multi coil systems

 

[Shawn]

Would have seen that right way on any 70s or 80s oscilloscope, which any shopbworth going to would have had. Not so much any more. I do miss not having an oscilloscope. Probably forgot sime of the more unusual patterns, still have enough retained. Not so easy to use on multi coil systems

Yeah those are nice to have for older cars but like you said not usable on all the new stuff. You can find them cheap these days but the problem I have is floor space in the garage to keep something large. You need a full fledge expensive OBD2 scanner these days to read all the computers on board. I have something decent but still doesn't do everything. On my old 13 Audi S6, I had to buy VCDS Vag-Com which was like $500 to do certain tasks such as clutch adaption after tuning it that my fancy scanner could not perform. BMW has its own specialized scanners as well as the other manufactures. Its crazy all the crap you have to buy these days just to work on certain cars.

I wouldn't mind having something that can read HC and CO before I go to emissions but those things are like $5k! I found this old used Snap-On for $300 that needs some switches replaced but not sure if its worth the effort and would need a spot in my garage somewhere....

 

[Wes Harden]

yeah those old 2 and 4 gas machines also need calibration gas to keep them accurate, not sure they'd be worth the hassle.