2008 Silverado, 4.3L Engine, PO300 Random Misfire Code

A black 2008 Silverado rolled into the shop yesterday afternoon. A bearded man in his mid thirties, medium height and weight slid out of the driver’s seat with what seemed great reluctance. He smiled at me as I greeted him, waving an invoice in his hand for my attention. He’ll be Steve Silver for the purposes of anonymity on the blog.

“I don’t even know if I should be here.”

That made two of us. I was kind of snarky yesterday, but I had enough sense to keep my mouth shut. Yes, folks, sometimes we in the service business get up on the wrong side of the bed, or smack their knee on the underside frame of a 99 Ford F150 getting off the creeper.  :)

“I’ll help if I can,” I reply with what I hope is a helpful expression. Mr. Knee hadn’t stopped throbbing yet, so I wasn’t sure. It might have been more of a grimace.

“I had my truck tuned up at Acme Auto (changed for anonymity). Do you know ‘em?”

I didn’t. The only time I usually hear about a shop is as a recommendation for something I don’t do here such as transmission rebuilding, or body work. Once in a while a shop has become infamous for screw ups, but that hadn’t happened in quite a while.

“Sorry. I’m not familiar with them.”

Mr. Silver hands me the invoice. It’s a nicely done computer generated sheet with a diagnostic check for a PO300 random misfire code, noting customer requested spark plugs be changed. The shop also recommended changing the ignition wires because the vehicle had over 90,000 miles on it, which had a notation of refused. They also changed an air filter.

“The truck still misses and sometimes backfires,” Steve told me.

“Looking at your invoice, my advice would be to go back and let Acme put on the ignition wires they recommended to you.”

Steve’s brows knitted and a frown formed. “That adds over two hundred dollars onto the bill. The wires shouldn’t go out this quickly. I told them they probably broke one while changing the plugs.”

“I don’t think so. You had a PO300 misfire code before they did anything,” I explained, pointing out that section of the invoice. “They went ahead with what you asked, hoping the same as you probably, that it was just a plug causing a misfire. I never give the customer a choice. I always change the ignition wires when I do the spark plugs on vehicles. They gave you the choice and it didn’t work out. The only thing to do now is get the wire set changed before you ruin the catalytic converters.”

“Can you guarantee it’s the ignition wires?”

“Unfortunately no. All I have to go on is their diagnostic check. Maintenance and common sense would dictate changing the ignition wires before getting caught up in parts changing anything else.”

“Fine. Go ahead and do it,” Steve said with a sigh. “Can you do it today? I only live a few blocks away.”

“Why not have Acme do it? They may even give you a slight break on the price.”

Mr. Silver is silent for a moment, looking away to the side of the shop at something… or nothing. He reengages a moment later. “I may have said a few things I shouldn’t have when I went back over to their shop.”

Uh oh. “I’ll make up the invoice.”

Steve picked up his truck this morning. Yes, I spent twenty minutes before I proceeded with the wires yesterday doing a diagnostic to make sure I felt comfortable doing the wires to fix the code. Sometimes you have to do things for your own peace of mind. That was one of them. With the new Delco wire set in place, all was right with the truck and it was ‘Hi Ho, Silver and away’. You didn’t think I was going to leave off without that postscript did you?   :)