Vapor Lock!

[Hodgeee]

My neighbor has a 2009 tahoe and we started talking about our trucks. He has had a vapor lock issue for three years since moving to vegas.

His trucks on 80 plus degree days drives perfectly, until he stops somewhere for a while. When he then gets back in to drive, his rpms go all over the place, and he has a similar lunging problem at slow speeds, or when coming to a stop. After about half a mile of driving it goes away, unless of course he stops and lets the vehicle sit for a while. We in Vegas had about 4 days where the weather was low 70s, and he said it went away, and never comes back until the hot weather returns. He was told by the dealership that it was Vapor Lock and was common on 07 to 14 GM trucks and SUVs out here. Mine does this a little, but only when it gets into the 90s, but its not bad.

Ive been told by others in forums that they never hear about this. Ive also read that since they got rid of the return fuel lines on the fuel rail, that this problems started. I have been researching to see if there is a fix, to no avail. Very few posts, and next to nothing on this forum when searched.

Does anyone have an idea what could help? I have thought that maybe wrapping the fuel rails, and removing the bueaty cover could help, for mine does it exactly under the same condition, of sitting after the motor has warmed up. I drove his truck and its pretty bad, does it constantly if you stop for just a couple of minutes like to get a pop to drink or something at a convenience store. He said on 100 degree days, it just does it all the time.

I have noticed that when working on mine under the truck, that the radiator emanates a ton of heat, and also that they fuel rail goes right bye the catalytic converter and transmission. Was thinking of strapping an aluminum heat shield on the driver side cat, to see if this would help.

Appreciate any ideas.

 

[Dustin Jackson]

@Hodgeee I think I was the one that said that I've never heard about vapor lock being an issues with these vehicles.

I live in Redding, CA and when I compare the weather of my city to yours we have hotter days over here. I've had my Tahoe about 4 years and have driven it all around the western US at the peak of summer and haven't experienced what you are describing. Nor have I ever heard of a 2nd hand account of another person having a similar problem.

Curious if you have E85 where you are at and if you are up to testing with that to see if it changes anything.

 

[Hodgeee]

Interesting, ive driven a couple of these trucks, and some do it, most dont, its odd. Ive only read of a couple other people on forums with the same problem, but no solutions. Mine is very minor, hardly noticable. My neighbors is real bad. Im gonna try the wrap and report on it. I have now had two GM techs that say its common out here. I just dont know why some have the issue. I dont care about mine, but the nieghbor, if mine was like that, i would probably trade it. This is my third Tahoe, first time with probs. Ive read also that others had this with first and second gens too. So uncommon with any vehicle today.

 

[OR VietVet]

So, an answer to the E85 question, @Hodgeee?

 

[Hodgeee]

Found e85 station, gonna have him fill up
Today. Should be hot enough today.

 

[petethepug]

That’s also the behavior of an LS motor needing a tune up. The tech will clean the throttle body and run a fuel injector cleaner, add new plugs & leads.

Running a tank of e85 will also act as a tb cleaner and scrub any carbon deposits from the system.

 

[Dustin Jackson]

@Hodgeee I don’t think E85 is a cure all but it’s just a bit different than gasoline and I’m curious if your Tahoe behaves differently with it. I believe E85 has a higher evaporation temp than regular gas so in theory if vapor lock is occurring then E85 should react differently.

When I search the internet for “Chevy 5.3 vapor lock” I don’t get many results and the posts I have come across just mention possible fuel pump or tank venting issues so I’ll be curious what this ends up being.

 

[strutaeng]

It's probably something else going on. I've never heard of "vapor lock" before, and I would consider myself an intermediate, or maybe even advanced DIY-er (courtesy of YT diagnostics channels, LoL).

The way the ECU monitors fuel trims, O2 sensor data, spark advance, pwm fuel pump duty, etc, I would think it will throw the money light on if it detects something really out of wack. Maybe something intermittent?

Google says vapor lock was a larger issue with carburators and low pressure fuel systems. Carburators was before my time, so I don't know...

 

[Geotrash]

Can't be vapor lock at 43-45 psi on the fuel rail. The RVP of gasoline at 100ºF is no more than 9 psi in the US, and in places like Phoenix they formulate it for 7 psi in the summer. Gotta be throttle body, vacuum issue or something else.

 

[OR VietVet]

Having been in shops for 35+ years, I saw my share of vapor lock concerns with carbs. When the high pressure fuel injection systems came along, the concern with vapor lock, went away. So many components monitoring and making bunches of adjustments, per second. Correct fuel octane and clean fuel are important. There is always a reason that a manufacturer dictates a certain fuel in the owners manual and it is not because they are getting a kick back from the major oil companies. In this case, a tank full or two, of E85 is worth the effort and see what happens.