having a little trouble with the lt1. cruzing down the road, say at 2000rpm, and let of the gas it will stay at 2000rpm for a few seconds. the throttle is not getting stuck. if you rap the gas real fast the rpm's will come back down to idle.

the car has a
cc306 cam
lt4 cnc'd top end
and tuning done by pcmforless.com

any suggestions? could it be the tune?

there is no engine lights or anything, the engine runs great other then that.


also, how loud are guide plates normally on a lt1?

 

does your VSS work?

 

yep

im at a lost, i've looked at everything i can think of

 

hmm...not sure what to tell you then.

 

Did it just start doing it after the tuning??? for the cam swap??

My 01 z28 did this on the first tune and the reason they did it on ours was because of the size of the cam trying to get it to idle properly at idle so the idle is set way up when coming to a stop but in turn it seems to stick at 2000 rpms when letting of the gas. Because if it drops below that too rapidly our cam would make the whole car surge. But with our second tune the guy fixed that. I am not sure what exactly he did, but he said that it was a trick some tuners use to keep it idling, but he knew how to tune it properly without it doing that. Also have you messed with anything on the TB for idle quality?? Drilling blades?? adjusting throttle stop??? Possible causes as well.

 

I can almost guarantee it something with the TB. See if you can swap another TB on and see if it goes away.

 

well ****, i did adjust the throttle stop out so it would idle

i take it, it has to be put back to stock location then? the car doesnt want to idle below 1000rpm. does this mean i need to have the pcm reflashed to raise the idle back up? i had p0300 taken out so we wouldnt get a rough idle code all the time. will the computer eventually learn to idle the engine right? also the car doesnt want to idle when first started before the throttle stop was adjusted out. can the tuner add more fuel on startup?

thanks

 

yes, move the stop back out and get the ECM reprogrammed to lower the idle. Do you have to cable to adjust it yourself?

Also, you can have them bump up the idle at low coolant temps to take into account the rough idle at startup.

 

is it the stock tb, i know with my ported tb it wouldnt stick but the rpm would stay consistent with 2k.... i later seen my throttle bodys needed to be sanded dont a lil bit to be completely flush.... so i would check to see if your blades are completely flush. as for the tune did alvin or brian do it??? they usually nail the cc306 right on the first tune.... if not there pretty decent about a retune if its quick enough.

 

I had the same problem about a month ago with my TPI 305. I would be driving and the rpms would seem get to be stuck even when I took my foot off the pedal. So I popped the hood and lubed up the slider on the throttle body cable and I haven't had the problem since.