Our 95 SE, has developed a miss this last week, steadily growing worse. Originally it was only when the engine was cold, but it progressed to missing at all temperatures. Last year I had put in Bosch Platinum 2 plugs, before reading all the discussions about others bad experiences. I decided to install NGK plugs today. The Bosch plugs were showing some uneven wear. so I felt better about the project. What I noticed is that the front set of three plug wires (1,3,5) did not have the metal shield around the plug wire boot, while the rear three boots had the metal shields. It appears from the service manual that not all plugs may have these metal heat shields.
Is this the case? Only the rear cylinders have the heat shield around the spark plug boot?

The car is now sluggish with the new plugs, but the miss is gone. Something is the matter, need to keep checking. Maybe coils?

Only the rear stock. More heat back there.

Most of us don't run them at all with newer wires.

The rear 3 have the covers because of the intense heat buildup i imagine, and yes it is correct.

and as long as the NGKs were gapped correctly, those aren't an issue...

how new are the wires? they need replacing too, every 60k.

coils are fine. believe me, you'd know if they weren't.

sluggish could be many things. definitely going to have to give us more to go on.

Wires have about 8K on them, as does the O2 sensor, air filter, LIM gasket and UIM (APN)
Oil is Castrol Hi Mileage changed about 2K ago along with filter.
170K miles, 1995 Bonneville SE. It'* been warm to hot lately and I 've noticed some coolant loss, First since changing the LIM gasket and the UIM last year.
AS part of sluggish, there is no step down in the AT during hard acceleration.

-sp4149

Saturday the car ran fine no missing, no sluggishness. Sunday night it was missing again, at idle and at steady throttle, but not under acceleration. I checked the coils, all were very close on the secondary side readings.
Coil Primary Secondary
3/6 .9 ohm 5.9K ohm
2/5 .4 ohm 5.8K ohm
1/4 .3 ohm 5.9K ohm

No corrosion on the coils or posts. No codes set, I have Acton scanner with 95 adapter cable.

What would cause idles and steady throttle missing without setting a code? If it was a fuel issue it should be worse during acceleration or climbing a hill, but it'* the opposite.

-sp4149

Pull all 6 plug wires and post the resistance of each one in this order (shortest to longest):

1, 3, 5, 2, 4, 6. 'Wiggle' the wires around while the meter leads are inserted into each end looking for dropouts.

After you reinstall the wires, wait for dark and spray a light-medium mist of water (not filtered drinking water, you want minerals and crud) over the wires and coils with no underhood light on. Look for arcs. Carefully inspect each wire everywhere they contact anything metal. Dipstick tube (#3 and 5), hoist bracket/alternator support on the rear, blower motor housing, fans, or anything else. Make sure the #4 and #6 are not contacting the O2 sensor harness.

I started to check the plug wires tonight. I removed the engine cover that makes the engine compartment look uncluttered; and this is what I saw:



Seems like some wildland critter decided that this was a good spot to make a home. when I removed the nest, I found:



All the insulation on the orange wire was gone and the wire strands were actually severed in various spots. I replaced the damaged section, only to find gnaw marks on the black wire, which i also patched.



I test drove the car after the wire fixes and accelleration was improved and the engine quieter. i'm not sure that the missing is completely gone, but compared to what the car was like on the drive home before finding the nest, it'* an order of magnitude improvement.

Priceless! I guess there is not a Code for "Varmint Infestation on #5 Injector"
Maybe add "Refill Decon Containers" to the routine maintenace.

that'* why i run with mine off

Well tonight I checked the plug wires (AC Delco about 15K miles)

#1 - 2100 ohms

#3 - 3600 ohms

#5 - OPEN

I stopped, took the #5 wire off the car, tested again, different multi-tester, still open. This wire is routed in a plastic shroud alongside the valve cover. Despite the protected location it was covered with black grime. Could it have been carbon tracing on the outside of the wire? Because if it'* hidden location, the misting and nightime observation didn't show a problem. I'm buying the Belden premium wires tomorrow at Napa. Maybe I'll test the other wires when I take them off, but this was reason enough for me to replace the lot.

-sp4149