99 Seville #3 cyl misfire

KEVINLAVANWAY

MEMBER
1999 CADILLAC SEVILLE
V8
FWD
AUTOMATIC
145,000 MILES

I have a 99 cadillac seville sts with northstar 4.6L v8 giving me a #3 cyl misfire code. Engine idles rough and is doggy under acceleration. Any ideas?

Monday, May 16th, 2011 AT 3:03 AM

6 Replies

CADIEMAN

MECHANIC
3,544 POSTS

Youll need to check the plug wire and plug. U really should scope the engine. Gl

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Monday, May 16th, 2011 AT 4:26 AM

KEVINLAVANWAY

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5 POSTS

I replaced all of the sparkplugs. All looked similar. I'll ck wires tomorrow. Are the coils or injectors notorious for going bad in these cars?

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Monday, May 16th, 2011 AT 4:59 AM

CADIEMAN

MECHANIC
3,544 POSTS

THEY CAN GO OUT FINISH THE TUNE UP LIKE I SAIDS U CANT FIND A BAD WIRE. YOULL NEED TO REPLACE THEM. THEY GET DAMAGED WHEN REPLACING THE PLUGS SOMETIMES. GL

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Monday, May 16th, 2011 AT 6:17 AM

KEVINLAVANWAY

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5 POSTS

Thanks for the help. I checked the injector pulse wires. They were ok. When I pulled the wires off the top of the coils to ck them, # 7 was covered with rust. Cleaned it up and regapped all plugs and now its good. Thanks again.

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Wednesday, May 18th, 2011 AT 1:22 PM

ALFRED022

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1 POST

I've have this same problem I hucked up my scanner to it and found the cylinder 3 has a miss fire, I've done a compression test which was 146 psi, I checked the injectors which are good, change the spark plugs, moved around the coil pack around to see if they were bad and there not. Also check the fuel line with a gauge and was at 45. And changed the value cover gasket. I'm stuck