It's running, how do I get to the exhaust shop?

[hounddogs!]

Finally got the engine to run tonight. Hellzyeah! Unfortunately, 'running' means idling at obnoxiously high RPMs. I'm guessing 4000+.

I shut things down quickly, but need to get the PCM trained enough to get to the exhaust shop. (right now, I have open manifolds and the O2 sensors are dangling loose.)

1. To get things running, I put the wires that were in factory fuse block C1, pins A9, F8 and F9 onto an ignition hot post. Am I putting 12V somewhere it shouldn't be? I see diagrams that say they're all ignition hot, but haven't found the destinations.
2. Do I need to test the APP voltages, or should I assume they'll throw a code if something's amiss?

I see a GM procedure to learn a new throttle body that involves idling for three minutes then shutting things down for a minute. I'm not at all comfortable letting a brand new motor run like this for three minutes. Is there another procedure to get the PCM to relearn its neighbors?

**2003 5.3 - TB and PCM supposedly from the same vehicle
**Accel pedal, TAC module and harness between them supposedly from the same vehicle, but not the motor donor.
**Brendan at LTswap had the PCM to clean up VATS, emissions etc
**MAP, knock, cam and crank sensors are new. MAF is not.
**Stock rebuild except for BTR Stage I cam
**No codes
**With engine off, the throttle blade is closed.




Thanks for the direction guys.

[franken]

Needing a real high idle typically indicates a vacuum leak. I make no claims about ls stuff though.

[ls1nova71]

You are going to need a good tune since the cam isnt stock. I would suggest finding a way to trailer it to the exhaust shop, get the exhaust done, then let it run a bit. Although 4k rpm sounds awful high, so like the other guy said, sounds like a vacuum leak, and a big one such as the fitting for the brake booster not being hooked up. Have you checked everything over real good to make sure you didnt miss anything?

[hounddogs!]

Originally Posted by ls1nova71

You are going to need a good tune since the cam isnt stock. I would suggest finding a way to trailer it to the exhaust shop, get the exhaust done, then let it run a bit. Although 4k rpm sounds awful high, so like the other guy said, sounds like a vacuum leak, and a big one such as the fitting for the brake booster not being hooked up. Have you checked everything over real good to make sure you didnt miss anything?

I don't see any open ports on the intake so here's a dumb question - where is the brake booster vacuum *supposed* to come from? I clipped the end of a fitting on the pass side /rear to find vacuum.

Another thought I had is that the O2 sensors are seeing clean air. Would the PCM just keep adding fuel to try and get A/F down from an infinite number? This afternoon, I'll remove the sensors, throw the O2 codes and see if the computer will find a limp home baseline that I can work with.

[ls1nova71]

Yes, if you dont have exhaust, then the oxygen sensors wont work, but then they shouldn't be doing anything until they warm up anyway, and I didnt think you let it run that long? They wouldn't make the idle that high though. The port for the brake booster is at the back of the intake on the left side (drivers side).

[Clyde65]

I used a mobile exhaust guy after my swap. I couldn’t watch him put the truck on the trailer to get it in the air, you have to see it! Think of driving your truck on a log, truck on two wheels and log is over a large crevasse....

[hounddogs!]

OK, not liking the looks of this. Pics are from the DS rear of the intake - the 'plug' is about 3/4" diameter. I tried to run a wire into the end; it's a solid cap. Everything can slide maybe 3/16", but I don't feel any threads/ears/keys to hold it in one position or another.

[72MARIO]

Thats where the power brakes are supposed to be connected. Its a quick release fitting and you need that part from a vaccume brake truck

[truckdude239]

you need the quick disconnect for there with a hose fitting do not throw away that cap they are not advible anymore it took me like 3 months to find one since im not running a brake booster i still need to remove mine and install the plug, i jus thave brake hose with a lugnut stud blocking the hole, you cna push the red ring ina nd pull he plug out

[hounddogs!]

Belated update - the racing idle was from a vac leak. When the OEM fuel purge line is gone altogether, it leaves a big hole in the manifold.

The plug on the rear DS was swapped out and the brakes are happy.

Thanks to everyone for checking in.

Loren