98 k1500 p0303 code

[BoxMN]

I drove to North Dakota this past weekend pulling a fairly big trailer load of timbers and tools and such (basement wall caved in, had to do emergency fix on the duck hunting camp...) Truck is 98 k1500 with 5.7 and 200k miles. Drove great up there, going about 70 with trailer.

On the way back, the trailer was lighter, only had a few spare timbers and a potato cultivator, and truck was lighter too. But we were driving about 80+. I noticed it seemed a bit sluggish at times, and felt a shudder now and then. The service engine soon light came on about Fargo. Checked the code today it was

p0303 misfire in cylinder 3.

Can't recall when I did plugs last, but I bet about 60-70k miles. Used ac delco plugs and wires, the good ones. Could it be just as simple as time to change plugs and wires again? Truck runs and starts great. I cleared the code but havent driven it since. Goiing to be using it for a week in late july so I want to try to fix it if I can.

Thanks for any advice!

-Box

[Jeremy airjer W]

If the correct plugs where installed than they should be good for about 100k. You are not far from needing to replace them again.

Another thing you can do is swap the coil with the 2,4,6, or 8 coil and see if the misfire follows the coil. If it does you know the coil will also need to be replaced.

[Scott K]

I have been running into some issues with Ac Delco spark plugs lately, and melting down on this era GM trucks. I would start with a new plug in the #3 cylinder before throwing other parts at it.

[Macgyver55]

 

Another thing you can do is swap the coil with the 2,4,6, or 8 coil and see if the misfire follows the coil. If it does you know the coil will also need to be replaced.

 Only one coil on the 98.  Not uncommon for cap or rotor to be bad though.  I would also start with the plug and/or wire, otherwise you may be looking at an injector.

[Jeremy airjer W]

 

 Only one coil on the 98.  Not uncommon for cap or rotor to be bad though.  I would also start with the plug and/or wire, otherwise you may be looking at an injector.

​5.7 liter........... my bad!

[BoxMN]

Thanks guys. Off to my parts guy, start easy and go from there!

[BoxMN]

Just a quick follow up... I put in new plugs and wires, and it ran fine. no codes. Then first trip about about 150 miles, it stuttered and died, then started right back up but running rough. Next morning ran good until it sat for awhile then didn't want to start, had to push pedal to floor like it was flooded. Checked plugs and bad #3 again, it was dark crud on plug, same as older set. Put in new dist. cap and rotor, and cleaned the plug (it cleaned easy). Ran good. But then another code and rough running.

Checked code and it was p0118 (i think) which was a error in engine coolant temp. I never saw a hiccup on my temp gauge and have plenty of coolant. The Google  told me normal fix was replacing the ECT sensor. so I did, $20 at napa. It is like a new truck again. so now have new plugs, new wires, new cap and rotor. running good.

My guess is the sensor was telling it run rich?.... which fouled the plug(s) and make it run like carp. I was thinking way more serious... glad it was easy and cheap fix.

Now to fix that darned trailblazer axle seal...