I am new to the forum even though this is my 3rd fiero. I just purchased a 1985 2.5. It has about 55,000 miles on the odo. I am undertaking a major tune-up on the car. Through research, I determined that AC Delco Rapid-Fire platinum plugs is probably the best, now the problem. These plugs are gapped at .45 in which it states not to adjust the gap. The factory states to gap the 4cyl. to .60. Has anyone encountered this? Should I set the gap at .60 per fact. or .45 per the plug. Also, I have seen that people have had some trouble running platinum plugs in Fiero, this seems to be centered around the BOSCH plugs. Any info would be great.

The reason they say not to adjust the gap is becuase they don't want you to scrape off any of the platinum coating on the electrode. If you bend the electrode arm back near the edge of it, so you arent touching it where the spark is going to be, you should be alright. Carefully use a feeler gauge to measure the gap.

The bosch platinum +4 plugs seem to cause a lot of troubles in Fiero 2.5 engines, especially the 87-88 DIS ignition ones. Rapidfire's are pretty much what everybody uses.

I used Bosch Platinium in mine, and didn't have any problem with it, though I have switched to a "V-Groove" type of plugs (no real difference in the firing).

If you bought plug for your specific car, it should already be set approximately around .60 (which is the right gap). The Bosch I bought and the "V-Groove" were both around the .60 gap.

Verify if they make plug of your type for your specific car with the right gap. You should really stay with the .60 gap (which means a spark being .60 long)

Anyway, if you don't change anything else in the ignition system, you won't feel any difference In doubt, just try it and give us a report of good and bad news

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BlackARROW >>-->
Gadgeteered Fiero 2M4 '85
"Get your groove on"