Help diagnosing two issues 1) misfiring/stumbling 2) coolant loss

[andzac]

I had a similar problem with my 04 yukon cutting out on acceleration,I cleaned throttle body which helped a bit. I then changed sensor on gas peddle and it hasn't cut out in 4 months...knock on wood!

 

[Old Goat]

Low coolant problem.

Run your fingers around the heater core connections on the firewall. That's where my 05 Tahoe was slowly leaking.
Replacements for those are readily available ay O'rielly's.

 

[John03Z71]

Thanks for all the replies. I haven’t had much time to focus on this since the holidays, but the misfiring / hesitation issue reared its ugly head last night by finally throwing a P0301 code, and it got realllllly bad during one acceleration period that caused the check engine light to start flashing. I shut the engine down and gave it a minute then limped back home (not in limp mode, but basically went super easy on the pedal). Also P0442 is showing up twice. Im not sure they’re related though.
Any suggestions on where to start with P0301?
i put in new plugs and wires a few years ago, the slight misfiring / stumbling issue has been consistent for several years so I’m not sure a new plug or wire will fix it... it might just foul up the new plug and wire. They all probably need to be replaced again due to being fouled up from the misfires but I’m still n out getting to the root cause. Any suggestions besides plug and/or wire would be much appreciated, from a budget friendly DIY perspective vs throwing parts and money to see what sticks. Thanks again for all the helpful input.

 

[OR VietVet]

The P0301 code is a misfire in cylinder #1. I would pull that plug and the one next to it, #3 plug, and compare and get pics of both here.

The P0442 code is "P0442 indicates that you have a small leak in the evaporative emission system. Many times this is caused by a loose or faulty fuel cap. ... The P0442 error code is an evaporative emission control code and is an indication of a small leak being detected in the evaporative emission system."

Check this link out: https://www.engine-codes.com/p0442_chevrolet.html

The coolant loss could be related to the misfire in #1 cylinder because of a head gasket problem. Again, could be.

 

[Grebbler]

The P0442 could be the vent solenoid by the gas tank. I took mine apart and rinsed it out about 10 years ago. Still working.

 

[BentleyArnage]

Thanks! I was going to pick up a can of cleaner from the parts store and try that. If that doesn't work, I'll swap the part out and see if that makes any difference. How much would you want for yours that you say is still in working order? Feel free to PM me.

Coil packs are a huge issue on these. I'm replacing all of mine. I get the occasional random misfire, but once in a while I get the flashing check engine light which is for misfires. Back out of the throttle and baby it if you get one of those or you'll melt the cats. It's called a thermal event. Never remove the cats. The computer will failsafe the motor and it will never run right. When I get the flash, it's cylinder 2. That will be a coil, so they all go.

The coolant issue is probably the water pump. The leak isn't bad enough to drip but the coolant will evap or trail rearwards under way. You'll see the trail from underneath.

 

[afpj]

With all this stuff about the MAF, without swapping parts, is there a way to tell if it's going bad? What's the flow reading you're supposed to get at idle for instance? Anyone have a spec for that? The torque app can see that, have no idea what's considered a normal value.

 

[smcnair]

Biggest issue on ours with coolant loss has been the gaskets. Just replaced with Fel-Pro's and they seem to be holding fine.

 

[OR VietVet]

With all this stuff about the MAF, without swapping parts, is there a way to tell if it's going bad? What's the flow reading you're supposed to get at idle for instance? Anyone have a spec for that? The torque app can see that, have no idea what's considered a normal value.

You can get MAF cleaner at the parts store. Follow the directions.

Biggest issue on ours with coolant loss has been the gaskets. Just replaced with Fel-Pro's and they seem to be holding fine.

Fel Pro gaskets are excellent quality.