Fighting a number of issues on my build right now but mainly cannot get the truck to idle. LQ4 with a fresh tune from GP tuning. The engine will run at about 1600 rpms but will die below that. It has no codes at all.

After trouble shooting, I noticed the drivers VC gasket blew out and leaked some oil. I believe this was caused by improper PCV and catch can routing, so for now, I've bypassed the catch can and currently am running stock pcv setup. Drivers VC to the top of the intake manifold. Pass VC to the throttle body port.

I also went ahead and changed the oil and found there was a significant amount of fuel in it. I'm not sure if this is due to it being overfueled, running rich, etc? I do not believe it is an injector. I am running 50lb genuine new delphi injectors.

After all this, I went to start the truck and it fired up and idled great on its own for about 1-2 minutes, then died. Now it is doing the exact same thing - will not run unless i give it thorttle and hold it around 1600 rpms.

Does anyone have any suggestions on what else I can look for? Any advice is greatly appreciated. Thanks

 

Black gas out of the exhaust@1600 RPM ?
What size/brand of uel injectors.
PW at low spaaed ?

 

Appreciate the response! Yes definitely some black smoke on initial startup, especially after trying to crank it for a few times. Seems like it’s getting way too much fuel. However, I do not think it’s tune related. I have Matt at GP tuning all my injector, intake, cam specs, etc.

the injectors are 50 lb Delphi out of a 2010+ (I believe) 6.0 truck. Bought them brand new from Glenn performance

 

Make sure you coolant temp sensor is working correctly and you map sensor. If the coolant temp sensor is bad it will read -30 degrees and will add fuel that's not needed. If the map sensor is bad it won't fuel right either.

 

All sensors are brand new. Wouldn’t a bad one throw a code usually? I can swap them out, just trying to make sure that’s a possible cause

 

New sensors can be bad, especially if they're not real-deal GM. But even they can be defective. Trust but verify....

 

Without seeing the tune, all anybody can do is guess if it is right. Of course a datalog would be helpful as well.

 

I’d spend some time looking for vacuum leaks. Make sure all vacuum line connectors are in good shape and sound. If you’ve removed an air pump, make sure the associated piping/port to the intake is plugged. Unmetered air will make you run rich and give you idle problems. What cam are you using?

 

A little more info to add -

Before the tune, I had a baseline tune on it and it seemed to run/idle decently. However, I never really ran it long enough to see any issues pop up. After the tune, I went to fire it up and it won't idle. Seems to be way too rich, will eventually crank and fire if I hold the throttle around 1600 rpm. After trouble shooting for awhile and cranking it, this led to the VC seal blowing out. I then realized I might have a PCV problem where perhaps the engine is not being vented properly.

For the time being, I removed my catch can PCV setup and reverted back to stock - Driver's VC to the top intake manifold port, Pass VC to the port at the throttle body. Any other evap related ports blocked off. I also changed the oil (lots of fuel in the old oil). Went to start it up and it cranked and fired great. Ran and idled decently (a little high, around 800/900 rpm), but at least it was running on its own. Ran for about a minute or two, then died - now I am having the same issues all over again.

I swapped the IAC and confirmed it was not the issue, as well as the MAF. I did not change the coolant sensor yet, but when I had my scan tool plugged in, I believe it was reading an actual reading (not -30).

Let me know what you guys think. Thanks

 

About the only sensors you haven't replaced are the cam sensor and the crank sensor? Cam sensor is easy to replace. The crank sensor is a pain.
I've never had a cam or crank sensor fail on my LS swaps.
Crank sensor or cam sensor losing signal?

 

I don't think it can be crank sensor, as it does technically run, just doesn't idle on its own. From my understanding, a bad crank sensor just keep cranking and won't fire? Not sure about the effects of a bad cam sensor, but again, everything is brand new genuine GM/Delco

 

This is probably a reach, but could the location of the coolant sensor be giving me issues with idle? Perhaps not getting the right reading. Mine is relocated to the back of the drivers head rather than the front oem location

 

No that won't affect it.

Sounds like your tune is off

You said it idled before and didn't have this problem?

 

it’s kind of hard to say. I never ran it long enough on the baseline tune to really tell if it had any issues. But yet, it could idle on its own. However, right before I sent out the pcm for the new tune, I did notice it was dying at idle. I didn’t think much of it since I was getting a new tune anyway

 

Im not totally sure it’s the tune because I drained the oil yesterday (which has fuel mixed in it), threw in new oil and filter. Started it up and it idled for a minute or two at around 800 rpm. Then died again

 

I had similar with my car, fixed it on the third crank sensor

 

If you put in something besides factory injectors, I'm guessing you made other modifications to the engine. This fact alone means that your "tune" can't be right, as sending a pcm to someone for a tune on a modified engine is a hopeless endeavor. Then we have no idea what any of your sensors are showing, or if there are mechanical issues or wiring problems. This really needs to be diagnosed by someone with the equipment to read your tune and datalog what is happening, as well as the ability to check over everything electrically and mechanically. So far you have not even said if you checked fuel pressure.

 

the tube was done by Matt at GP tuning - he definitely knows his stuff and is a big tuner here on the forum. This is a temporary tune to get me up and running safely and it will be dynoed again by him upon completion of the vehicle. This tune definitely should be enough for it to idle.

as for fuel pressure, I have not checked yet but do plan to. Would low fuel pressure be causing these issues though?

 

I am going to check my fuel pressure tomorrow and go from there. I was looking at my setup and realized I do not have a Schroeder port on the fuel rails to put in a FP gauge. The rails are the return less metal fuel rails from a 2010+ NNBS truck I believe. Where can I hook up a gauge? Do I need to buy a T adapter and plug it in at the fuel line connection?

I am also running a corvette FP filter regulator. I used this to adapt my return style fuel tank to the return less rails. It is a genuine GM part but I’ve heard these could cause issues…

 

What pump?