04 tahoe will not idle after cam swap

[cervan]

Im sure there have been a billion and a half threads on this exact issue, but ive gone over just about every single one and have not found a solution. Truck is an 04 tahoe with a stock 5.3 and electronic throttle body. Owner did a ls1 "hot cam" swap which includes springs. he installed the springs and cam and asked for me to lend him a hand tuning it.

Here is what ive done so far, the engine will not idle whatsoever below 2k rpms, in fact i have not been able to successfully get the engine to idle without assistance from my foot on the accelerator whatsoever. Adjusting the baseline airflow from 6g/s all the way up to 64 in 2g/s increments has not shown any benefits other than better top end response. Engine will not start without pressing the throttle about halfway and will fall on its face below 1500 and will only attempt to stabilize at around 300 rpm. This tune is all over the place because i was trying multiple things to see what would help it, i havent found anything yet that would solve the idle issue. Adjusting the VE from 80-100 kpa below 1200 rpm helps slightly, but doesnt solve the issue. im also getting maf errors, but adjusting the delta seemed to fix that. is it possible this cam is simply too large for the 5.3 to idle at 800 rpm?

Any help is greatly appreciated. jeffs log file.hpl5.3 modified tune 2.hptIMG_E0310.jpg

[5FDP]

Log more stuff. Like RPM, fuel trims, o2 sensors, command afr etc etc.

Are you positive the cam was installed dot to dot, no vacuum leaks??

That cam isn't huge, it should start up and run okay. It shouldn't need 2,000rpm just to stay alive.

[cervan]

I didnt even realize i didnt log rpm, i apologize. I will take a log tomorrow including more channels. Im not positive that its on correct timing and i didnt see any vacuum leaks. however wouldnt the cam offset show if its correctly timed?

[1364838952]

We put the GM Hot Cam into my sons '02 silverado with a 5.3L engine and tuned it quite effortlessly. It required very little to get it to start up and idle. Very few changes from the factory tune. You have something else wrong. Either the cam was not installed correctly, or you have a serious vacuum leak, or some other issue that we can't figure out/guess over the internet.

I'd recommend you GO BACK to the factory tune and put all parameters back to stock. Once you go back to a completely STOCK tune, you can increase the RAF #'s across the board by +2.5 as a baseline to start it and get it running. Also increase the idle RPM's to 850RPM across the board, just to get it to run & idle, and then address your timing. Your 400/800/1200 timing columns need to match in all tables such as your IN PARK, IN GEAR and HIGH OCTANE & LOW OCTANE. You can then interpolate those tables that have a "O" and "600" column. After you get it up and running, you can then do your VE & MAF tables FIRST, then BASE IDLE AIRFLOW, and then timing tables.

If you want a copy of my sons current tune, I will post it up for you at your request. He does have L/T headers, and NO CATS so his VE tables probably won't be a perfect match for you.

I forgot to mention my sons truck is DBC and we did have to open up the set screw on his TB to get the Idle Air Counts down to the 60-70 range. I assume your DBW TB will handle that for you by way of RAF tables.