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First time actually asking a question here so take it easy on me. :confused: I've searched and searched, but I can't find someone talking about exactly the same symptoms as I have, and whatnot. I finished up installing a tfs 30602002(220/224 .575 112lsa) cam in my lq4 today. My problem begun when I crunk it up for the first time, it's runs real rough(shaky) :urgent: and the ses light will blink for a while and then goes off for a while, and comes back again, continously. Also, after warming up, it doesn't want to start or idle on its own. What I want to know is; is this normal or does it indicate another problem? For instance, I know it needs a tune for this bigger cam, but I wanna know if its normal for a untuned lq4 to act this way.

 

 

 

 

 

Thanks in advance. :)

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Well I've got a story for those of you who wanna hear. Today I took my truck out on its initial voyage and after driving about only a mile it started this VERY LOUD tapping. It sounded like a spun bearing, but I knew that couldn't be, I was still breaking in the springs and not reving it over 2 grand. I thought for sure though, one of my ls6 springs had failed me and I had dropped a valve on the piston. I started to call up the junk yards around here about a used lq4 for my pickup, but before that I decided to pull the valve covers. Low and behold, what did I see, about half of the rocker arms were loose and the bolts could be turned by hand. I just about started crying tears of joy, when I realized my tap could potentially be fixed by tightening down a couple bolts. So, when I get done writing this I will go out and tighten those bolts and hope it runs like a champ. The moral of the story is to always tighten your rocker arm bolts more than just snug and use a bigger ratchet than a qurter inch drive like my stupid self did.

 

 

Sorry for my lame story, I'm just shocked at these chain of events. :)

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Well I was two footing it, but now that I found that rocker arm problem it'll run on its own. But still idles up and down a couple times every time I stop or shift to a different gear(i.e. Drive to reverse). I'm gonna get a tune asap, and until then I'll be easy on it.

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Well, what I meant was 1 was finger loose and the rest were not to spec(22ft/lbs). All I've got to do is reset the tps after I adjust the idle screw about a half turn now. I talked to a guy about tuning my truck and he said he can't make it idle with tuning, something about the iac won't open far enough. He said he could tune idle on 03+ trucks with electronic TBs, something about how there butterflys are elctronic and idle can be set through the computer, pretty much to any speed you want.

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During your engine build, if you have a cable driven throttle body, do yourself a favor and unbolt your throttle body from your intake and use a Torx T15 bit to flip your set screw upside down. From the factory it's only accessible from underneath and it sucks to try to adjust the set screw once the engine is in the vehicle and you've got everything hooked up. By flipping the set screw upside down, you've made it possible to make adjustments to the throttle blade easier.

 

Once you have the engine idling somewhat ok, use the scanner to verify a few parameters. Look at IAC (idle air control) counts to see if they're in check. Why? The idle air control valve in the throttle body has a max range between 0 and 310 (usually) to attempt at holding your idle right where you command. The idle air control valve (IAC valve from now on) is designed to let by-pass air flow into the engine simply to hold idle steady and it opens/closes depending on if the computer detects the idle falling or getting too high. Most well tuned engines regardless of cam size can make use of the 0-310 range which the IAC valve has but sometimes you have to help it by opening or closing the throttle blade a little.

 

This is where the idea behind drilling throttle blades comes in. Don't do that yet! Thankfully you read this thread before shoe-horning your LS1 into some tight engine compartment and you flipped your throttle blade set screw over so you can open or close your throttle blade by little increments at a time. Most of us need to open it.

 

If the IAC counts in the scan are basically stuck at zero no matter what, that means the IAC valve is closed because it's trying to limit how much airflow is being sucked at idle. This either means your throttle body is open too much, or you could potentially have a vacuum leak somewhere and this should be addressed before continuing. Did someone previously drill a hole in your throttle body and now it's getting too much airflow this way? Assuming your seals are in working order and your TB isn't holy (pray.gif) you simply need to close the throttle blade a little bit as long as it doesn't stick shut. You'll know what this feels like when you hit that "stuck" point when the blade is closed all the way - hopefully you don't hit that.

 

On the flip side, if your IAC counts are maxed at 310 it means your IAC valve is sucking as much air as it's allowed to and that's really the only thing holding your idle somewhat steady. banghead.gif This is where you need to open your throttle blade by adjusting the set screw with the T15 bit. How much? Well...read on. There are a few parameters or "rules" for opening the set screw you should keep in mind, and you'll use the VCM scanner to tell you most of it.

 

Start the engine and wait until its fully warmed up. Add tps voltage to the scanner and start opening the throttle blade up with the set screw a small turn at a time as the IAC position will change slowly, hopefully dropping from 310 to below 100 counts. Adjust it so that it is 70-80 at hot idle. Keep an eye on tps voltage, as you want to keep it under .76v and this is just a rule. If it climbs over .76v before you get your IAC counts below 100, try loosening the set screw and rotating it back. You may have to drill a hole in throttle blade if this does not work, but that is the last resort.

 

After you have all this adjusted, turn the engine off, unplug the IAC harness and TPS, turn key forward to on (with the engine off) for 10 seconds, then shut off and reconnect everything. What this process does is it performs a TPS relearn so when you're idling without touching the gas, the PCM sees where the "new" 0% throttle position is instead of being at 1-3%.

 

Once this is done, let the engine cool down to as cold as possible and re-perform the idle-airflow.cfg config I attached above because now your base running airflow needs are different.

 

 

Hope that helps.

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  • 9 years later...

How do you adjust with an electronic tb instead of the cable style.  Having a hard time eliminating the rev hang in my 08 Silverado 5.3 after a Howards Rattler cam install. It acts luke it is in cruise control still. On third round of tune bow and still won't snap back like it should.

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