Running rough/ choppy idle

[ZWILD1]

Went for a drive today and noticed car is running a bit rough with a choppy idle. Kind of feels like my first Z did when it lost coil 2&3 . I will start by pulling the plugs. Not sure if the coils were replaced or they are newer. It has just st over 50 k now. It's a secondary delete car by Marc Haibeck. Owner was suppose to give me all the records but never did. Who has decent coils . If I have to pull the plenum I will replace all the coils.

[viper107]

the coils are good for rusting at the contact tower(where plug wire plugs to)

[dredgeguy]

Jerry sells the coils

[secondchance]

David,

I suggest you call and verify where the coils were manufactured.
I bought a few coils from another vendor and, although in AC Delco packaging, were all manufactured in China.

[ZWILD1]

Thanks for the replies. I will have to check with Marc as he did all the work on the car. It got the engine package at 39 K. So it's possible it still has the factory units. My first Z didn't drop a coil until about 70 K miles. Back then I just replaced with AC Delco from the dealer. I still have the ones I removed. I replaced them all as a precaution. I could check the ohms on them.

I know many parts are now made in China. I have a factory GM throw out bearing and it's made in China sitting on the shelf. We were driving as it was a nice day and it was not feeling right. It was sputtering a bit pulling away from a light and running a bit rough. Filled up with gas and on the return trip it was starting to feel better. We were down to about a quarter tank.

[Paul Workman]

When it comes to troubleshooting, and troubleshooting electrical stuff especially, it is always much, much better to test the operation of the particular component rather than assume and just swap the part out.

The two periods in a part's service life where failures occur is when it is first put into service, and (of course) at the end of its service life. However...the worst failure period begins immediately when the device is first installed! The period is referred to as the region of "infant mortality"; initially higher than at any other time in the device's life. The 'saving grace' is this infant mortality period is quite short, relative to the entire expected life span of the a device.

I had a bad coil when I took delivery in '07. I measured the resistance across the primary and secondary terminals, and sure enough, one of the coils read OPEN between (I forget now - primary or secondary) posts.

I got lucky x 2. 1) it is possible to have a bad coil and NOT detect it with a normal VOM. To test the insulation integrity a MEGGER is required - and I wouldn't expect anyone but a decent repair shop would have one.
2) My "miss" was narrowed down to a particular coil by which cylinders were misfiring.

As with light bulbs, once one fails - the first to indicate it has reached its life expectancy - I replaced them all with OEM (Delco) coils - keeping a couple "good" ones for reference and as spares. But, MSD makes replacements, and Jerry's Gaskets carries replacements too.

[ZWILD1]

I got lucky on my first car. When I pulled the plugs I found plug #2 and #3 where not firing. I tested all the coils when I pulled the plenum and even though they passed I just replaced them all.