George's 2003 Sub "lucky7"

[Georgeb]

I don't suspect the evap system to be the cause. About the worst an evap failure can do is cause a minor vacuum leak and the driveability issues associated with that (would still start fine).

I suspect a faulty MAF, CTS, dirty throttle body or something like that. Maybe a leaking injector, but normally that would just cause a misfire on startup.

I don’t really suspect the EVAP either. And I agree about the injector leak. Seems it would only affect the cylinder it was related to and trow a misfire for that cylinder. I was starting to suspectthe CTS because the issue seems to be related to the engine temperature. And happens when its luke warm. I am not sure how the MAF is involved in things at startup. I thought about just grabbing a new CTS and throwing it at it but I don’t much feel like chucking more parts at it. I lost access to a decent scan tool and am waiting for my new scan tool to arrive in the next day or so.
I need a good resource for how to interpret the data I will get from watching the MAF and CTS.

 

[bucket]

I've seen those MAFs fail and actually keep the engine from starting unless you held the throttle pedal to the floor while cranking. In my experience, they hardly ever fail, but when they do, they can cause startup issues.

The CTS is easy to check with just a basic pocket scanner. Normally they have the most trouble on a cold start and that's a great time to check it against the ambient air temp. If it's off by 20 degrees or more, it's a dud for sure.

 

[Georgeb]

I've seen those MAFs fail and actually keep the engine from starting unless you held the throttle pedal to the floor while cranking. In my experience, they hardly ever fail, but when they do, they can cause startup issues.

The CTS is easy to check with just a basic pocket scanner. Normally they have the most trouble on a cold start and that's a great time to check it against the ambient air temp. If it's off by 20 degrees or more, it's a dud for sure.

Thanks! holding the pedal at full throttle tonight had no positive effect. Partial throttle seemed better but when it geeks out it takes a few tries no matter what I do.

 

[Rusty Nail]

did you try whackin on that Vortex box?

 

[Georgeb]

did you try whackin on that Vortex box?

Not sure what you mean...

 

[Georgeb]

Still Struggling
Typically acts up when luke warm ~120F
No start for 3-5 attempts. It actually starts and immediately dies.

Here is the sequence of events:
- Turn key to start
- Engine turns over (count of one)
- Engine fires for count of one and dies kicking starter back.
- Sometimes starter continues to try cranking and grinds the flywheel.
- Repeat until started.

Parts to date:
Fuel pump
Fuel pressure regulator.
ECT sensor

Service attempts and checks:
Clean MAF
IAT is correct.
Check MAP KOEO 14.5 PSI

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[bucket]

Know anyone else with one of these trucks? It's the same MAF for V6 and V8. I suggest trading MAFs and see what happens. If your problem goes away and they gain a new problem, then you know what to do.

 

[Georgeb]

Know anyone else with one of these trucks? It's the same MAF for V6 and V8. I suggest trading MAFs and see what happens. If your problem goes away and they gain a new problem, then you know what to do.

My buddies at the auto parts store let me borrow a new MAF..... No change..... I don’t know...

 

[bucket]

Maybe you already tried it, I don't remember. But, when it's acting up, have you tried giving it a little throttle while cranking? Have you cleaned the throttle body?

 

[Georgeb]

Maybe you already tried it, I don't remember. But, when it's acting up, have you tried giving it a little throttle while cranking? Have you cleaned the throttle body?

Yes to both. scrubbed the crap out of that throttle body with SeaFoam deep-creep and an old tooth brush. then rinsed it with carb clean and wiped it out with a rag.

Giving throttle makes no difference.. tried part throttle and also going in to clear flood mode.

I tried giving the manifold bolts a snugging and got about a 1/4 turn on each. Gonna try adding carb clean around the manifold when it acts up. Spraying it Carb clean once it starts has no effect on how it runs.

 

[bucket]

Well this is a tough one for sure.

I don't think it would be failed intake gaskets. That's normally just a cold start issue. And it still starts up, it's just the driveability that's poor. But ya never know.

 

[Georgeb]

So, with the slightly warmer weather it’s worse and smells rich when it does start. I wish it would give me a code or something.

 

[bucket]

Double check that the new fuel pressure regulator isn't a dud? Just check for fuel in the vacuum line after you have been driving it. If fuel is present, the diaphragm is bad.

 

[Georgeb]

Double check that the new fuel pressure regulator isn't a dud? Just check for fuel in the vacuum line after you have been driving it. If fuel is present, the diaphragm is bad.

Thanks but man I have checked that thing so many times! I even unplugged the line when I shut it down just to be sure. No luck there.

 

[Georgeb]

Solved! 2013 with 64,000 mi on it.

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