Intermittent Start And Poor Fuel Economy

[Jdavenport0622]

I recently purchased an 05 with 145k miles on it. Discovered after the purchase that it has an intermittent starting issue. Sometimes on the first try it will start up with no issues and other times it will crank and crank but not start, if it does start it runs awful and I kill it, but it always starts on the second try. I am also getting about 12 mpg city and 15 highway. I assumed it was fuel pump so replaced that and no luck. My list of things to check are coil packs, fuel pressure on the system and fuel injectors. I’m replacing plugs and wires as part of a tune up. Has anyone had similar issue and what was the fix? Anything else I need to test or look for?

 

[OR VietVet]

Welcome to the forum from Oregon.

2005 what? Vehicle info is appreciated. When it does crank and crank with no start, is when to check to see if has spark at plugs. What brand of fuel pump did you install? I hope it is not a cheap/iffy one. Eighth digit of VIN, a "T" or a "Z"? What parts brand are you using for the plugs and wires?

 

[TollKeeper]

For a 2005, 15 MPG is about on par with what I am getting with E15 gasoline.

When it does start, open the hood, and with the back end of a screw driver, tap on the MAF. If the engine dies, or stumbles, that might lead you in the right direction.

 

[Jdavenport0622]

Welcome to the forum from Oregon.

2005 what? Vehicle info is appreciated. When it does crank and crank with no start, is when to check to see if has spark at plugs. What brand of fuel pump did you install? I hope it is not a cheap/iffy one. Eighth digit of VIN, a "T" or a "Z"? What parts brand are you using for the plugs and wires?

2005 Tahoe. It was a Delphi pump. 8th digit is a T. Regulator and filter are built into the pump on my truck. NGK Iridium plugs and AC Delco Professional wires.

 

[OR VietVet]

Gas engine instead of flex. Still interested in the spark when crank and no start. Age and/or cleanliness of the MAF and MAP?

 

[Jdavenport0622]

For a 2005, 15 MPG is about on par with what I am getting with E15 gasoline.

When it does start, open the hood, and with the back end of a screw driver, tap on the MAF. If the engine dies, or stumbles, that might lead you in the right direction.

Maybe I’m just crazy but I owned an 05 Sierra back in 09 with the same exact power train as this Tahoe and I got around 15-16 city and 19-20 highway. A friend of mine has and 04 Yukon that is getting about 15-16 city and 19-20 highway.

 

[ks03]

any codes stored?
My next thought is to watch the security light when you’re starting it. Or key it on, and wait to see if it goes out after a couple seconds before cranking. Iirc the system enables/disables injectors, but not ignition so sometimes if the security system is trying to disable you it doesn’t start, other times (usually warm engine) it will start and run really rough, and low rpm. It does that because it’s literally running on fumes.

 

[Fless]

For the gas mileage issue (which I don't think is all that bad and agree with @TollKeeper), what axle ratio? 4x4? RWD?

 

[OR VietVet]

Driving patterns also figure in. Mostly short trips? Hard accel from stops? Octane and brand of fuel?

 

[Jdavenport0622]

For the gas mileage issue (which I don't think is all that bad and agree with @TollKeeper), what axle ratio? 4x4? RWD?

3.42 gears 4x4 and I drive like an old man. 10 miles one way avg speed of 50. Same set up as my 05 Sierra but worse gas mileage. I guess I expect too much.

 

[OR VietVet]

Mileage comparison? Miles on the 05 Tahoe compared to 05 Sierra at the time? Answer for octane and brand question?

 

[afpj]

Looked at fuel trims? Your at the mileage where MAF could be failing, or as someone already alluded to, really dirty.

 

[Jdavenport0622]

Gathered more info on my truck. MAF cleaned and giving good voltage and resistance numbers, map sensor cleaned and giving good voltage and resistance numbers, fuel pressure with key in on position is reading 52 psi and same during and after start. Pressure bleeds down to 13 psi an hour after shutdown. Unable to gather fuel trim info on my own. I took it to a shop a couple of weeks ago and the 2 days it sat there they said they couldn’t replicate the issue so they didn’t check anything. Even though I even showed them a video of the issue. Security light does not stay illuminated when I crank so I wouldn’t think that would be an issue