5.3 C10 Swap Idle Issue

[skyphix]

Originally Posted by shortboxin

As for wanting to stall, if it's at 550RPM, it's okay except it will drop lower to the 350-400RPM range and then stall from there. If driving, then coming to a stop or slowing for a turn, it may just stall under the additional load. When you say cold, I will assume you mean engine cold. To that, I don't believe it ever high idles at all.

I should probably also mention that I assume it is a stock cam. I bought the engine used with 125K and just put new gaskets, seals, and externals like sensors and water pump on it.


I have not checked fuel pressure. I have a hard time believing that the pressure could be low enough to cause an idle problem, yet accelerate with no issues. I stomp on it and it responds very well. Am I wrong in that assumption?

Running a stock pickup and tank from an 87 R10 and using a 96-97 Chevy P/U pump.

Will do.

This is what he was supposed to do. I'm not 100% sure that's what was done... he asked a number of things, all answers below. He's been doing these for years, so I anticipate that he's just got files he downloads quickly and that's it. Maybe he did the wrong one?

PCM Part #12200411
Drive by cable TB
5.3 from 2004 Silverado (based on dished piston)
2532_ _ _ _ fuel injectors (VIN Z)
2002 return style fuel rail
Case grounded O2s

I can get better video maybe Sunday from outside the truck so it'll be easier to hear. I'm running S10 swap shorty headers with true dual exhaust, no crossover pipe, with side exit. I'm not running cats and I have Flowmaster "glass packs". In my opinion, I don't think I have any exhaust leaks, but I had to drill out 5 of the header bolts and one of them had some minor thread damage, so I didn't want to torque it a lot for fear of stripping it out.

Intake and throttle body is stock 2002 Tahoe. As far as I know, the engine was stock. I bought it used from a friend of the guy that owned the truck (he went to prison). As for cam, I can't be 100% sure.

In my opinion, I don't believe I'm having any issues with how the engine runs under acceleration or even at a steady speed. As for ports on the intake, the only ones I'm aware of are the port for the fuel pressure regulator, the port in back for the power brake booster and then the evap canister purge valve, which I'm still running.

So, the PCM is from the same Z code vehicle right? Z code means flex fuel injectors which I assume you probably already know, and are different than the normal 24lb injectors in the non flex vehicles. If the injector parameters are off, it would cause this issue.

I agree though on checking fuel pressure. I’m running the same tank/pickup/EP381 pump, with a corvette fuel regulator/filter and -6an lines.

I do mean cold engine temp - you can hear the difference in my two videos between cold idle and hot idle. Cold idle is the revving video, hot idle is the driving video. My exhaust IS leaky (I need to reweld a couple of spots) but all leaks are after the o2s and it runs great.) Open and closed circuit fueling within the PCM is what I’m really referencing at a technical level.


EVAP purge at the front of the intake is what I was most concerned about. I blocked mine off. And the big brake booster 3/8 barbed fitting was the one that got me - totally forgot to plug that and it did what you describe.

Me saying it sounds leaky or like it’s running rough, could just be your video. It’s hard to tell without standing right in front of it. The exhaust manifolds only call for 13-15 lbs so should be ok there.

My suggestion would be fuel pressure (could even be too high if you’re not running a return system and don’t have any regulator online,) clean the throttle body thoroughly. If neither of those address it, a conversation with the tuner to verify your injector settings are correct.