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Old 06-25-2019, 04:21 PM   #1
TomM96
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Default slight misfire after starting, then better, but SES

A week ago i checked/cleaned the plugs (sounded a little rough after startup).
After my 1-1/2 hour service touch, there was no improvement, and soon a SES appeared (and no codereader at hand... there's an autozone literally within 1600 feet of my residence).

I spent 7 hours yesterday doing some basic checks. At the outset my preconception was that the IgControlModule ICM, plug wires were where the issue lurked.

I DID see a piece of carbon on a plug that Might have been causal, and i did discover some matted dirt on a couple of coilpack Towers, else , yet no smoking gun.
[If not resolved, I've resolved to try a new aftermarket TPS, because thrice last winter, each when ambient temps were below 17*F, the car exhibited behavior which several forum threads suggest is due to TPS deterioration: When stopping, the idle tended to remain elevated, about 2000rpm, and did not respond to manual retraction of the throttle to the stop screw.]

Here's what i saw... I'll review any comments:
.
Belden 7mm plug wires dated 2010- all ohmed out between 5.7 & 6.8 kOhm.
.
Plugs (NGK, <6000kMi) all ohmed out range OPEN
.
Fuel Injectors three 12.9-13.1 ohms, fourth 13.0-13.2ohms; all connector fingers seemed fully closed when at rest.
.
Spark coils /secondary 8.3-8.5 kOhm across Towers.
.
The ICM did not look filthy or guilty... so i declined to replace it with spares on hand (though that's a possibility going forward).
.
Since the ignition seemed possibly Innocent (confounding initial expectations), i tried to replace the TPS with aftermarket items on hand...
only to discover that MY 2000 design changes obsoleted my '97 stock!
.
Sooooo the overbearing Fear was stingy fuel injector burning exhaust valve, which has begun to Stick when engine Cold.
I steadfastly applied my (1970s Craftsman issue) gasser Compression tester,
30 hours after last driven; last 1-1/2 fuel tanks received a container of Techron additive: Test done dry at ambient temp 76*F--
All cylinders, after four crank-strokes read 210 psi...
rising to 215 at 5th stroke !!! Gasp/cough RELIEF
(maybe it was worth $2000)
.................................................. ........

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Old 06-25-2019, 04:30 PM   #2
OldNuc
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1998 SC2
Default Re: slight misfire after starting, then better, but SES

Most likely cause is plugs and wires followed by a failing ICM. The 00-02 ICM is not a long lived device so replace with a 96-99 vintage. Slight misfire and roughness are the first signs of a failing ICM and 9 year old common plug wires is long enough.

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Old 06-25-2019, 05:00 PM   #3
TomM96
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Default Re: slight misfire after starting, then better, but SES

Thank you, OldNuc !

Valuable advice-and convenient:
Two items i scavenged from my 97-
(1) tensioner
(2) ICM, with Magnecor 8mm wireset

Recovered both from storage last weekend, and put into car with plan to install in engine compartment...

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Old 06-25-2019, 05:41 PM   #4
OldNuc
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1998 SC2
Default Re: slight misfire after starting, then better, but SES

That would be my first approach.

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