Fresh rebuild and cam, rough start and idle...is this normal?

[gulleyman]

I just had my engine rebuilt and this cam installed

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I had the ECM tuned at Nelson Performance but they said they didn't have the software to do a "livetune" on an OBS so it was just a mail order type tune.

At first it was hard to start and idled really rough like it hadn't even been tuned, they tapped out the little hole in the Throttle Body to allow more air through and that helped it idle a little better.
It still sounds like it might stall out when if first starts but then smooths out pretty good once it gets going, sometimes it won't start with the remote start anymore on the first try, the second time it will have to crank several times before firing off. They said it might take a while for the computer to adjust itself, it's been a couple weeks, 15-20 short trips and at least 200 miles.
Is this how it's supposed to run with the cam or should I take it back to Nelson or the mechanic? The motor has less than 400 miles on a fresh rebuild with the new cam. What do you guys think?

 

[Aloicious]

what truck/engine is this all in? I'm guessing its a vortec since you're having nelson do a tune on it. if so, what hole are you referring to in the throttle body? I know the fbodies had a hole in the blade for idling, but our trucks use a IAC motor, the blade shouldn't have a hole in it at all. that may be your problem, if you've put a hole in it the IAC motor is likely fighting that extra air intake. I'd look into that first. otherwise it may be something in your tune, cams change alot and rarely would a mail order tune get it right on the first get-go, alot of what a mail order tune is, is educated guessing.

 

[gulleyman]

It's a '97 Yukon with the 5.7 Vortec, it does have the hole in the blade and Nelson made the hole a little bigger so it could breath better and that helped a little but it still doesn't seem right. Thanks for the head's up on the mail-order tune trial and error. I wish I knew someone who did a live tune here locally, I emailed BBTune and they said they couldn't do it either, crap!
The guy that rebuilt the engine said I could bring it by and he'd have his guy look at it but it's gonna cost me, maybe they can do a live tune. I think I'm gonna make Nelson take another crack at it first since they warranty the tune.

 

[Swims350]

so they made a vacuum leak? sounds like a real good shop to me, get the thing tuned right and be done with it.

 

[Aloicious]

i'd say get a new TB blade, there shouldn't have been a hole in it to begin with, and even if for some reason there was, it certainly shouldnt have been reemed out larger. I've had 2 stock L31 TB's and neither had a hole in the blade, though I have seen some LS engines that have one. but I'd fix that first and see if it corrects your issue before worrying about the tune. on our throttle bodies, if they wanted to alter the airlfow at idle the needed to adjust the idle set screw while logging the IAC steps, not making holes in the blade. you can try fixing it in the tune, but with a mutilated TB blade it will be REALLY hard to get the idle conditions correct through the mail. they may have screwed you over by doing that. you can get a new blade without the restrictor on it from CFM tech, I think they're like $40 or something.

no tuner will be able to do a logging mail order tune on a '97. unfortunately.

 

[Swims350]

I was gonna say the hole or holes were probably from the restrictor that cowlboy was talking about removing and plugging the holes. I would get a new blade or plug the hole w/ epoxy and rivets or something.

I don't know about a vortec setup but tbi setup that's a big cam, it's almost the same as the comp 268h which has 218 duration on both sides.

 

[Aloicious]

oh yeah, that could be the case. if you do plug the holes, make sure you do it with something that will be 100% solid, you don't want whatever you use to come loose (immediately, or over time) and get sucked into the combustion chamber. it astounds me how people do irreversable things like drilling/reaming holes in the TB blade. I mean there is a screw right in front of the blade spring on the TB that adjusts the blade angle to let more or less air in. if our TB's weren't adjustable thats one thing, but the screw is right there in front of their face.

thats not overly huge for a vortec, my zz4 is .474"/.510", 208/221, LSA 112 and its pretty mild, his paper is kinda hard to see on my screen but I think its .467/.495, 212/218, LSA 110.....if thats correct, the 110LSA will be a bit harder to tune, and could be contributing to your idle issues. it sounds like it'll be a decent cam once you get it running right though.

 

[Swims350]

yea and it should have a bit of a lump idle anyways. The comp 268 h has 218 and is 454 lift and 110 lsa, and it has a lumpy idle in a carb'd setup.

The tbi can be adjusted too, but I don't know if its to let more air in or not, it's a screw behind a cap that moves the throttle shaft, so it's more idle speed, and not supposed to be adjusted but it can be.


I think in this case it's just like the above said, the thing needs to be at a shop that knows what the heck they are doing when it comes to computer mods and chips and what stuff has been done to the engine.

 

[FastOrange]

that cam should be easy to tune. i was recommended the XE268H when i was going TBI.

 

[Swims350]

what's the h on yours stand for? never knew they had a xe268h.

Mines a 268h but because the h is for high energy series, where you xe is xtreme energy series.

maybe hydrualic?