Changed Spark Plugs - Service Engine Soon!?

edman · September 5, 2009

So I've got a 1996 5.7 GMC 1500... She's my baby. Only has 150k on her and still looks great. I figured after 150k on the original plugs it was more than past time to change so I started changing the plugs at my apartment complex when my landlord lady came storming out informing me that I wasn't allowed to do maintenance on my vehicle on the premises... So, only halfway done with the project (got the drivers side 4 done, new plugs and wires) I cranked her up to go somewhere else to do it and I noticed I had the service engine soon light on all of a sudden. No misfires at idle, and I gave her a bit of the leadfoot to see if she'd misfire under load and nada... In fact, she had quite a bit of pep to her step.

Is this just because I was running 4 new and 4 old? Or is this GMs way of trying to scare amateur DIYers from doing it?

Just wanted to get your guys opinion before I drive all the way across town and fork out for a code reader.

-Ed

JaymzSS · September 6, 2009

I wouldn't run it long like that. Change the other 4 out as soon as possible, and yes thats why your light is on.

it will come off after 3 cold starts OR you can disconnect your battery, and reconnect it to clear the code.

Also, Common mistake is not securly fastening your spark plug wires after new plugs. Make sure to go back over them when your finished up to make sure they're snug.

Good luck

Derek

edman · September 6, 2009

Got up with the sun this morning so I could finish the job before anyone was awake to complain. The passenger side was a bit of a son-of-a! until I took off the air filter housing and moved the duct outta my way! I was really quite amazed at the noticeable difference in reaction to pedal input after the changeout... Granted the original plugs/wires were 13 years old, but I figured I was at best just avoiding a future breakdown. Feels like I've got my old truck back almost.

Thanks for the advice on the code!

-Ed

pennzoil29 · September 6, 2009

Did you change the distributor cap and rotor while you were at it? You might also want to clean the throttle body. You will notice a big difference in throttle response.

2COR517 · September 6, 2009

Did you change the distributor cap and rotor while you were at it? You might also want to clean the throttle body. You will notice a big difference in throttle response.

x a bazillion. TB cleanup is huge. And get a nice AC Delco cap and rotor.

What's burning all that JP8?

edman · September 6, 2009

Didn't change out the distributor cap&rotor although now that you mention it I find myself smacking my forehead and making the telltale Homer Simpson "doh!" noise. As for the TB cleanup... I've never seen it done so I'd need a good set of instructions before I go messing around in there.

So what's burning all the JP8? Check the new sig... it's the only thing I know that gets worse gas mileage than my truck.