2003 trailblazer ext help

[rochockey83]

Hey everyone. I have a 2003 chevy trailblazer ext. Im having a problem with starting the vehicle. When the vehicle has been sitting and its cold you turn the key and it starts right up no problem. Now if i drive the vehicle for a duration of 20 min or more and then come back home and let it sit for about an hr it will crank for a good 4 or 5 seconds then finally start. I had a tune up done on this truck last week. As well had the throttle body cleaned at the same time. Filled up with a better brand of gas and used a bottle of lucas injector cleaner as well. Still the same problem. I have no check engine light as well. Anyone know where to start looking oh this. Appreciate it kindly, Thanks

 

[The_Roadie]

It might help if your vehicle profile was filled out. Welcome! But do you have the I6 or the V8? What did the "tune-up" consist of exactly? New plugs? What else? Did the shop disconnect the battery while cleaning the throttle body to reset the computer?

 

[rochockey83]

Sorry bout that. I have the v8 in this truck. New ac delco plugs and wires. They did not disconnect the battery when they cleaned the throttle body.

 

[RayVoy]

If you had a carburetor, I would say the engine is being flooded with fuel after the key is turned off. A problem with the carburetor.

If you had an injector for each cylinder, I would say one, or more, injectors were leaking and flooding the engine with fuel.

I don't know about throttle body injection, I don't know if it is close enough to the valves to flood the engine if it leaks; but, that would be where I would look first.

 

[IllogicTC]

If you had a carburetor, I would say the engine is being flooded with fuel after the key is turned off. A problem with the carburetor.

If you had an injector for each cylinder, I would say one, or more, injectors were leaking and flooding the engine with fuel.

I don't know about throttle body injection, I don't know if it is close enough to the valves to flood the engine if it leaks; but, that would be where I would look first.

We've got a throttle body, and injection, but it's not a TBI system I used to have a Dodge with TBI, it's the first stage beyond a carburetor where pretty much the injectors replaced the carb fuel setup.

My first guess is to either disconnect the battery, or pull fuses #10 and #28 (PCM I and PCM B) in the under-hood fuse block, for at least 15 minutes. Go ahead and plug everything back in and start it up - if it initially idles high (like up to 1500 RPM) for a moment, before slowly dropping back to the "norm", in a manner distinct from the initial startup rev you're used to, they didn't reset the system.

It's important for the PCM to be reset after the throttle body cleaning because the computer has grown accustomed to the dirty throttle plate. A clean plate must be relearned.

 

[rochockey83]

Should i disconnect both terminals or.just one side of the battery. Im honestly thinking it might be an injector. Any way to tell if its an injector ?

 

[IllogicTC]

Just the negative (black) cable, you don't have to go all-out, just break the circuit continuity.

If the reset doesn't help, I also would start thinking injector. I'm not sure if there's a way to test them, someone else probably knows how to test or at least visually inspect them.

 

[rochockey83]

I did notice if i push the gas down some it starts up easier just now so im thinking injector issue

 

[IllogicTC]

You may also look into the fuel filter. Earlier model years had an external fuel filter (newer just have the "sock" over the fuel pump intake I believe). If the filter's bad it could have allowed excess detritus to reach and foul an injector.

 

[rochockey83]

I will look there as well. The truck runs great. A ton of power just hard start up.

 

[RayVoy]

We've got a throttle body, and injection, but it's not a TBI system .

You are correct, the I6 engines use SFI (Sequential Fuel Injection), an injector for each cylinder. My second description. The OP, however, has the V8. I do not know if that V8 has a wet throttle body (TBI), or uses a dry throttle body and injectors mounted in the intake manifold.

 

[IllogicTC]

You are correct, the I6 engines use SFI (Sequential Fuel Injection), an injector for each cylinder. My second description. The OP, however, has the V8. I do not know if that V8 has a wet throttle body (TBI), or uses a dry throttle body and injectors mounted in the intake manifold.

Uses sequential, one injector per cylinder. Wouldn't make a whole lot of sense to do TBI on an engine with DoD TBI hasn't really been prevalent since about 1995, a few more applications here and there from that time but with pressure increasing now and again for greater efficiency and lower emissions, switching away from TBI was a no-brainer at the time.

 

[RayVoy]

Uses sequential, one injector per cylinder. .

Sorry, you are wrong. The 2014 5.3 uses SFI, the OP's 5.3 uses injectors in the intake manifold.

 

[IllogicTC]

Sorry, you are wrong. The 2014 5.3 uses SFI, the OP's 5.3 uses injectors in the intake manifold.

In the manifold is still not TBI. TBI is BEFORE the manifold.

TBI - Mounted like the fuel feed on a carburetor would be, except injectors.

CPI - A central injector was used to feed all cylinders by a system of tubes and poppet valves to spray fuel at each intake port. There were CPFI (batched) and CPSI (sequential) versions. Discontinued in the mid 90's.

Simultaneous MPFI - Mounted in the intake manifold, typically close to the intake valve. Fires every injector at once, regardless of which cylinder was currently performing an intake stroke.

Batched MPFI - Mounted in the intake manifold, typically close to the intake valve. Divides the injectors up into two or more "zones" usually, where one "zone" will fire each time one of those cylinders needs an injection. For example, a 1991 351 Windsor had MPFI, two zones, one for each bank. That means it'd fire all four injectors on one side each time.

Sequential MPFI - An advancement of MPFI. Granularity has been brought down to the per-injector level, complicating wiring but improving efficiency. Been used for years. The 5.3 has this, again it would make no sense to have batch or simultaneous when there's an option to turn off 4 cylinders (and thus just make a bunch of fuel accumulate in the system where the valves remain closed). That's also why pins 4 through 10, and 13, on connector C2 to the ECM are dedicated to fuel injectors, one for each injector. It'd be pointless to run all the extra copper if they didn't work sequentially.

All MPFI systems run slightly wet.

Direct Injection - Just like it says. The injector is mounted so that it sprays directly into the cylinder, rather than any chamber outside of it. Becoming the newest trend in injection technology.

 

[RayVoy]

In the manifold is still not TBI. TBI is BEFORE the manifold.

I don't think anyone is arguing with you. I think the problem is terminology.

TDI has the injector in the venturi of the throttle body. I think we all agree.

Multi-port injection uses injectors inside the intake manifold. The pre 2014 5.3

Direct injection uses injectors in the combustion chamber. The 2014 5.3

I think the confusion is with the term sequential. Multi-port requires timed injection and Direct requires timed injection. Both of these can be referred to as sequential injection. I choose to reference Direct as SFI

 

[TimRXUV777]

Fuel Pressure Regulator?