98 Neon misfire question

helping to troubleshoot a co-worker's car:

98 Neon (auto and A/C) that has the "service engine soon" light lit.

Hooked up my autotap, it showed a P0300 and P0301 misfire/cylinder 1.

tried to clear them, my autotap thinks the MIL is off, but it won't turn off, and my autotap thinks there are no more DTC's.

He's going to do the plugs - no one knows the vintage of them, so it's a good idea anyway... Plug wires all look good. Engine runs fine, if it's a misfire it's just enough to light the MIL.

One other thing of note - the belt for the AC squeals on startup and shakes the car pretty good at the same time, I'm wondering if that's being interpreted as a misfire?

or maybe if anyone has info on this TSB:

18-47-98 DEC 98 PCM - Symptomless Misfire DTC's/MIL ON
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does he need to flash the PCM? Will a dealer likely do this on an 8 year old car for free?
Reply to
ray
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Fixed. Plugs... worn out and huge gap as a result.

In his own words:

It was the plugs. I changed them last night.

The recommended gap is .89 mm, and what I found was: Plug# 1- 1.7 mm Plug# 2- 1.2 mm Plug# 3- 1.1 mm Plug# 4- 1.4 mm

After installing the new plugs I took the car around for a spin and immediately noticed the improved performance. Its especially noticeable when accelerating from a dead stop. I didn't clear the check engine light - I want to see if it will vanish after running for a few days.

Reply to
ray

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