Weird thing happened today

Clean the throttle body

 

When was the last spark plug change?

 

Re: vapor lock. It’s any time fuel vaporizes in the fuel line the heat source can be anything including parking in the sun on a 110*+ day.

 

I'll do that today

New plugs at 300,000 miles. So 47,000 on them.

 

You think that's not enough? There's no telling how hot it was under the hood so anything's possible. Especially down here in the Devils AssCrack. It's resetting the computer and it running fine thats weird to me. Well know soon though. I'm headed to work so well see what the mechanic says.

 

Vapor lock is pretty rare with fuel injection

 

Have you ever cleaned your MAF sensor? Rough idle issues can be a dirty MAF sensor.

 

If you believe vapor lock is the problem, maybe you should try some clothes pins on the fuel line.

 

The fact that the idle bumps up when you turn the air conditioning on tells me that the base idle is too low. You said it was idling down around 300 RPMs. I'd start by cleaning the throttle body

 

This. These two plus throttle position sensor (TPS) would be my first suspects with this issue. My 1st gen had rough idle issues for a month without throwing codes. Wound up being the TPS.

 

No tps on 2nd gens. Everything has an electronic throttle body assembly on it now.

It cracks the throttle plate slightly open, just enough to sustain an idle. If it's gummed up with carbon it can't flow enough air. Turning the AC on will make it respond and open a little bit more

 

I’m gonna clean the throttle body today at work. As far as the MAF sensor it’s a special cleaner correct? And what’s the way to clean it. I know they’re sensitive.

thanks guys.

oh and it ran perfect over to work today. Crazy.

 

Just get a can of MAF sensor cleaner. You can put a little on a rag and use it to clean the throttle body as well

 

This is my guess also.

 

All of these are great ideas but don’t address the suddenness of the malfunction. Dirty MAFs and throttle bodies would be a gradual increase thing not something that sitting in the sun would cause.

 

What? It tells me that he turned the AC on... My truck's idle has increased when the AC turns on since new. It does that because there's added load on the motor.

 

That what has me bothered. It ran great yesterday all day. No rough idle or anything. I'm off today so I'm going to clean the maf and throttle body and take a look around while I have things apart. Our mechanic didn't have a chance to put the computer on the truck so ill run to the parts house and see what their reader says.

I'm thinking of investing in the Bluetooth obd reader so I can look at it on my phone anytime. Do y'all suggest any one in particular?

 

he said the idle was very low down around 300-500 rpms. Thats way too low. Turning on the ac bumps the idle up to around 800 where it should be and things smooth out..

sounds like an airflow issue through the throttle body at idle to me. Easy first step is to clean it.

If he had a fuel supply issue like vapor lock or a bad maf the truck would lack power everywhere (up hills, down the highway, etc) and he'd likely see a check engine light.

 

Agreed that the idle is too low, at 300-500. My point was that the AC bumping up the idle is irrelevant; that just means there’s added load on the motor with the compressor running.

 

I understand what you're saying. My point is turning on the AC is just a quick way to get a little more air flow through the throttle body ( at idle, without touching the gas pedal) and see if things smooth out. It's not irrelevant, it's a clue that he might just be dealing with an air flow issue.

My thinking is, if he had any issue other than an air flow restriction, opening the throttle plate slightly more wouldn't help and it would still run poorly