Ignition coil soft failure (Page 1/4)
Yellow-88 AUG 13, 12:43 PM
Hello

Yellow is recovering nicely from a 6 year long coma, from being outside on jack stands. He did get regular WD40 baths and did fire up occasionally but ....

He has new Delco Platinum plugs, Standard 7mm silicon wires, Delco cap, rotor and pickup coil and a GM dealer recommended Delphi ICM. Heat transfer compound is correctly applied and a prototype heat shield now protects it from the heat. All grounds and contacts are clean and bright. His MAP, IAC, temp sensors and coil are as existed before he became comatose. Of course he got new coolant, oil, fuel and hydraulic fluid and he's almost show level clean.

He was running nicely until he recently developed a slight misfire, almost like a rich roll that's almost unnoticeable at idol, about 1100 and rock steady. The obvious symptom is an unsteady tack. Not bouncy or jumpy, just unsteady, especial around 3,000 and above. Tach sees only primary so I unplugged the filter because that's a possible source of a short to ground in the PI. No change to the running. No codes set and I don't have a "Scan Tool" to look deeper. Cylinder compression and fuel pressure at the rail are good. Base timing is 9 deg BTDC. Throttle response is good.

I think I'm seeing 2 different issues. Scratchy, irregular primary ignition with consistent regular misfire. The misfire does not align with the occurrence of the unsteady tach. I don't have access to a "Known Good" ignition coil or Map sensor. ( Sweetie says "No, you can't try mine!". I love her.)

So my question is; can a coil "soft fail"? Is one of the parts I didn't renew causing issues? Coincidence can happen but .....

Yes A/T, Yellow is on a short course of SeaFoam.

I will buy both coil and MAP but before I do, what do you think? Any better than others?
82-T/A [At Work] AUG 13, 12:59 PM

quote
Originally posted by Yellow-88:

Hello

Yellow is recovering nicely from a 6 year long coma, from being outside on jack stands. He did get regular WD40 baths and did fire up occasionally but ....

He has new Delco Platinum plugs, Standard 7mm silicon wires, Delco cap, rotor and pickup coil and a GM dealer recommended Delphi ICM. Heat transfer compound is correctly applied and a prototype heat shield now protects it from the heat. All grounds and contacts are clean and bright. His MAP, IAC, temp sensors and coil are as existed before he became comatose. Of course he got new coolant, oil, fuel and hydraulic fluid and he's almost show level clean.

He was running nicely until he recently developed a slight misfire, almost like a rich roll that's almost unnoticeable at idol, about 1100 and rock steady. The obvious symptom is an unsteady tack. Not bouncy or jumpy, just unsteady, especial around 3,000 and above. Tach sees only primary so I unplugged the filter because that's a possible source of a short to ground in the PI. No change to the running. No codes set and I don't have a "Scan Tool" to look deeper. Cylinder compression and fuel pressure at the rail are good. Base timing is 9 deg BTDC. Throttle response is good.

I think I'm seeing 2 different issues. Scratchy, irregular primary ignition with consistent regular misfire. The misfire does not align with the occurrence of the unsteady tach. I don't have access to a "Known Good" ignition coil or Map sensor. ( Sweetie says "No, you can't try mine!". I love her.)

So my question is; can a coil "soft fail"? Is one of the parts I didn't renew causing issues? Coincidence can happen but .....

Yes A/T, Yellow is on a short course of SeaFoam.

I will buy both coil and MAP but before I do, what do you think? Any better than others?




I wasn't going to mention the Seafoam, but I highly recommend it since you bring it up. Make sure you add it to your tank JUST BEFORE you fill up, while you're stopped at the gas station, getting ready to fill up. You want your tank to be completely full when you leave the gas station with Seafoam in it. I expect a PM from you telling me how amazing the Seafoam treatment was (after driving around for a week).

As for tach filter, if your tach filter is going bad, you can get new ones from Rodney Dickman: https://rodneydickman.com/p....php?products_id=265
NOTE: he's technically out of them for the Fiero, but all that means is he doesn't have them pre-assembled with the connector. But you can buy the non-assembled one, which is the link above, and then re-use the factory connector (prongs just easily remove). For an example of a failing tach filter, you can go to my daughter's video here: https://www.youtube.com/watch?v=J2603jsREaQ ... and zoom ahead to the 30 second mark.


For ignition coils, yes... coils can slowly degrade over time. Effectively, they'll not be able to produce the power they once could at increasingly higher RPMs. There are dozens of aftermarket ignition coils available. Some people scoff at them and say a stock coil is all you need. There is proven evidence that a higher voltage coil does in fact improve the engine performance at the higher RPMs. That is because the coil, at higher RPMs, is unable to produce a strong a spark as it can in the lower RPMs... so your engine will feel as though it's "running out of breath" in the higher rpms, likely because combustion is not occurring as rapidly as it should with a much hotter spark. Again, this gets poo-poo'ed on all the time, but it's understood in the automotive industry. It's the primary reason why each iteration of engine generation has gone to ignition improvements. For example, the Iron Duke has two ignition coils. It could have just used one, but they saw a benefit to using two, even on that wheezy engine. And in everything decent post 2000, they've introduced what is called "Coil On Plug" which provides a separate ignition coil for each individual spark plug. I purchased the Accel SuperCoil, which is a bright yellow ignition coil. I painted it with black engine enamel to look stock, and never looked back. I've not had any issues with it, but that was 15 years ago... it may be made in China now.

Dennis LaGrua AUG 13, 05:21 PM
We've seen intermittent coil failures and failures caused by faulty grounds. We have also encountered bad " performance coils ", Accel and Chinese brands in particular.
Test with an ignition test light while the engine is running ( careful high voltage is there) or better yet as in the manual ( with the engine OFF) measure the primary and secondary resistances of the coil on the bench with a voltohmeter.

------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

hunter29 AUG 13, 08:16 PM
Seafoam ? Really, it's safe for the 2.8 ?
82-T/A [At Work] AUG 13, 08:59 PM

quote
Originally posted by hunter29:

Seafoam ? Really, it's safe for the 2.8 ?




Yes, it's safe for any car, you just have to use it on a full tank. It doesn't make much of a difference on newer cars because there's really no such thing as exhaust gas recirculation in modern engines, but on cars like the Fiero... it makes a huge difference. You should run it every 30k miles, in my opinion. Again though, you just have to make sure you pour it in just before you fill up so you have a full tank of gas with it. You don't want to add it to a car that only has like a quarter tank or it can damage the catalytic converter.
Vintage-Nut AUG 13, 09:35 PM
GM dealer recommended Delphi ICM over the genuine GM 10482829 Ignition Control Module?

------------------
Original Owner of a Silver '88 GT
Under 'Production Refurbishment' @ 136k Miles

Yellow-88 AUG 13, 11:31 PM

quote
Originally posted by Dennis LaGrua:

We've seen intermittent coil failures and failures caused by faulty grounds. We have also encountered bad " performance coils ", Accel and Chinese brands in particular.
Test with an ignition test light while the engine is running ( careful high voltage is there) or better yet as in the manual ( with the engine OFF) measure the primary and secondary resistances of the coil on the bench with a voltohmeter.





That's comforting to hear.
Yes. I'm sure the numbers are in the book. That would show if all the winding are in the loop. Simple test. Thanks.

Thinking about what a coil is; a very long copper wire with a thin layer of insulation, wound tightly around it self, that gets hot and cold, again and again .... could have cracks or thin spots in the insulation. I don't know its CLTE/CTE off the top of my head but copper expands. A coil of wire can possibly rub against itself when it's wrapped in a tight coil. I think I'm answering my question.

I hear similar stories "off brand" and "performance" coils from the local GM dealer. They list a Delco at $130.
Yellow-88 AUG 13, 11:45 PM

quote
Originally posted by Vintage-Nut:

GM dealer recommended Delphi ICM over the genuine GM 10482829 Ignition Control Module?




For the price difference. The GM cross references to the Delphi in the parts guy's book. Since I could buy 2.5 Delphi's for 1 GM, I took a chance. ??
Yellow-88 AUG 14, 12:07 AM

quote
Originally posted by 82-T/A [At Work]:
Yes, it's safe for any car, you just have to use it on a full tank. It doesn't make much of a difference on newer cars because there's really no such thing as exhaust gas recirculation in modern engines, but on cars like the Fiero... it makes a huge difference. You should run it every 30k miles, in my opinion. Again though, you just have to make sure you pour it in just before you fill up so you have a full tank of gas with it. You don't want to add it to a car that only has like a quarter tank or it can damage the catalytic converter.



I did 5 gals to half can of SeaFoam. No Cat. When I burn that up I'll probably use straight 89 octane gas with some Marvel Mistry Oil. I did add a quart of MMO at the oil change. That goes back before my Father. Maybe just tradition but we always had shiny clean valves and piston tops. I know for sure that it will silence a clacky lifer.
cartercarbaficionado AUG 14, 03:36 PM
I would swap the old Map sensor in to see if it changes but you are describing what I was experiencing with the Delphi icm for months before it suddenly ran fine and then started stalling randomly.
try the very very cheap parts store ones. they won't last but generally rule out the icm as the cause and are worth the 20 bucks