Chev133

Hi, I've had 3 tuners, and 1 mail order tune (Patrick g) & no one can tune it. The latest tuner said maybe the cam was ground wrong. It's a comp 224r & has been install as per the installation card (within 1degree). Has anyone heard of this ? It doesn't idle propley, if you coast along & back off it will almost stall, then all of a sudden it will launch forward. I'm on the verge of putting the 5.3 back in or selling it.

jimmyblue

iTrader: (11)

Idle can take a lot of fiddling and scanning, over and
over, to get right. This isn't the forte of mail order or
some guy who wants to get you on and off the rollers
as quick as he can. It took me some weeks of off and
on tweaking, for a 224 on 116 cam - a closer LSA is
even more challenging to get the low end right.

If you're hiring it done that could chew up a lot of
shop rates money, unless they have something in
pocket - but even that depends on your car being
like the others, no mystery impairments or whatever.

rennat_2006

iTrader: (10)

Take the throttle body off and clean it out really well. You may have a sticky iac that would definetely make it harder to get it dialed in and do exactly what you describe.

Chev133

I have a new n/w 102mm t/b. I tried the ome one & it did the same thing. where is the iac on a 08 Silverado 1500 ? I removed & refitted the engine, & im thinking that maybe I pulled a wiring terminal out somewhere.

LSX Power Tuning

iTrader: (4)

Email me all your information about what you have changed from stock and your tune and a data log and I will look at it. I doubt Patrick missed anything but another set of eyes wont hurt. My info is my signature below.

jimmyblue

iTrader: (11)

There's a lot of negative talk about the bigger
aftermarket TBs being different in how the IAC
channel behaves. If the cross-section is much
different than stock, the stock airflow vs IAC "map"
will be wrong. Saw this on my TB when I filled the
IAC port and drilled it too small.

You might want to eyeball this, your new piece vs
the stocker casting, and relieve any place where
the 102 seems too skinny. There isn't really a
downside to oversizing the channel (just makes
the IAC more in control of the flow, higher up in
counts, but the stock channel size is enough to
make that so already).

If you need more air, and opening the IAC more
doesn't give it, then you'll get unstable as the idle
RPM loop "winds up".

Chev133

this t/b hasn't got a separate IAC valve. its got 1 6 pin plug that goes into the t/b & that's it. here are all the mods to the engine.
6lt block
4 inch stroker crank (403ci)
je pistons (10.8 comp)
224r comp cam 112 lsa
ls7 lifters
tsp 2.5 heads
lsxrt inlet
nick Williams 102mm DBW throttle body
100mm ls7 maf
100mm tube
volant CAI
try y full length headers
hi flow cats
double row timing chain

jimmyblue

iTrader: (11)

OK, well, you asked for IAC but seems there should
be none. So what kind of PCM are you using to run
this DBW TB? Sounds now like it had trouble with
(whatever) stock TB there was (DBW or cable?).

Let's roll this back some. Was there ever a time when
this motor ran right?

redtan

iTrader: (5)

You're surprised that noone can tune a 403 stroker motor through an email?

Mail order tunes are good for stock or mild bolt-on engines. Might be ok for small cammed cars but would not be running perfect.

You have a 403 with cam, heads, bigger MAF, bigger TB, FAST and you think some guy 1000 miles away is going to magically think of what your engine wants?

I would take it to an actual tuner in person and let them drive the car on the street and the dyno so they can be there to actually see what it's doing and what it needs. Without that I don't think you're going to get a perfect tune over email.

Chev133

I've had 3 tuners look at it on their dynos. its still running the OME pce. it was perfect with the 5.3lt motor. its always had a DBW t/b. I even tried the t/b from the 5.3 & it did the same thing. the truck is a 2008 Silverado 5.3 1500 4x4.

ctd

iTrader: (1)

How does it start & idle from cold to warm? No driving. What about throttle blips?

Did you forward the tune files to LSX?

Chev133

I've had so many tunes in it, at the moment it starts & idels ok. Sometimes the starter will keep cranking when you let the key go. It's just very rough around the edges, the service air bag light comes on now. I contacted TSP to ask about the cam & when I told them about the issues, they asked me if I got a specs sheet with the 100mm maf to give to the tuner. I didn't get it, I've got it now so ill give it to him & see what happens now.

Old Geezer

iTrader: (3)

" Sometimes the starter will keep cranking when you let the key go."

Suggest you correct the wiring/switch issues, before you start on a tune....

Chev133

the starter issue has something to do with the tune. after looking at other forums about the 100mm maf & how hard they are to tune.... I've decided to go back to the OEM maf.

wild1100

iTrader: (3)

Switch to speed density and see what happens. Do you have hptuners?

LSX Power Tuning

iTrader: (4)

He sent me one tune and there were several items that were not right that could cause it to have idle problems IMO.

locrzn

iTrader: (9)

I have a simular situation, mine idles great in and out of gear. My 6.0 is stock bore and stroke, runs perfectly on the street, starts great the first time but when I'm letting off coming to a stop sign or in traffic its wants to die, when I finally stop it idles as it should. My cam is on a 112 lsa, duration is 224-233 and lift is 604-617.

Chev133

I put the OEM maf & stock tune & it's better already. Now ill bring it back to the tuner.

Slowhawk

iTrader: (12)

Your setup is very basic. Just make sure all the grounds are tight, expecially the one on the driver side front.

Mike454SS

iTrader: (4)

It sounds like it's an 08 vehicle, so probably an E38 PCM...that being the case, the PCM cranks the starter, not the key...a lot of people don't realize this, and still hold the key like with older cars and let it go when they hear the engine fire...if the engine isn't firing, the PCM will continue to crank for a certain amount of time.