TUFF LT1

Well the new cam is in and now comes the tuning. I'm having trouble with the car idling once it is in open loop. I bumped up the idle in park to 900. Here is the problem once in open loop the car won't idle by itself. My IAC counts never go below 90 or so. Also my left side BLM's are running at 103 and the right is at 180 ish. As the car got up to temperature I started to get small popping noises out of the exhaust. What is going on here???

TUFF LT1

Oh yea, I also installed new rockers and 30# sov injectors. I already changed the injector constant to 31.7.

TriPinTaZ

You need MORE TIMING in CLOSED THROTTLE tables at idle. Try bumping it up by 5 degrees. But also those slight popping sounds also seems like a lean condition.


you said the car has a hardtime idling ONCE ITS IN OPEN LOOP. OPEN LOOP isused when you first start the car and the 02's are not warmed up yet. CLOSED LOOP is enabled once the car warms up to the specified temperature (40 C i think) then stays in CLOSED LOOP.

In open loop mode the 02 sensors are ignored and fueling is provided by the MAF sensor, OPEN LOOP AFR tables and VE tables.

in closed loop mode the 02's are actvie and the PCM uses the MAF and VE tables for fueling but then the 02's give hte PCM feedback and PCM changes the fueling based on the 02's

It is not always neccessary to even touch your VE tables, most mild to moderate heads and cammed cars are not radical enough for the PCM not to be able to correct with the MAF and 02's. The VE tables are only used as a base fueling # for the PCM's fueling algorythm and changing them in a mild to moderate car will not provide any advantage.

If the car is poping in open loop ( cold ) then the easiest thing to try is to use the OPEN LOOP AFR table to add a little fuel at cold start up idle. see if this with the increased closed throttle timing helps.

but Im unsure if you are mistaking open loop and closed loop for one another.

TUFF LT1

Yes I'm sorry I made that mistake about open and closed loop. The car will idle when it is started up and is cold but once it warms up i get a slight popping ( almost a thump ) every once in a while. My MAP readings were 50 ish at 1400 rpms. And like I said my IAC counts never went below 90. Would any of this be causing my BLM's to be split like I mentioned earlier? Thanks for the info and the correction TriPinTaZ.

TriPinTaZ

AFter Seeing your SIG.....YOur PORTED MAF is causing most of your problems.

Porting the MAF ends destroys the calibration. If you remember when it was stock it was divided in half. Each HALF had its own sensors on the MAF. once you took the divider out its ruined. Trust me i fell into the P&P MAF craze...and it worked fine when i was stock. But once I built my 383 it was the cause of 90% of my problems. Especailly SPLIT BLMs...

Good luck.... Get new unported MAF ends or you will never get it right. Descreening it is fine. And the MAF translator.....I would throw that in the garbage too. Get the PCM tuned professionally or do it yurself if you ahve hte software.

Its not a restriction, I put down over 400 HP at the wheels thru a stock MAF ( descreened tho )

TUFF LT1

Yea, that was the first thing that I did when I started putting the car back to gether. I sold the translator and bought MAF ends that were untouched. I still think that maybe something is wrong with my IAC counts being above 90 all the time. Thanks for the tips tough

TriPinTaZ

With my CAM my IAC counts were always pegged at 160. The way I fixed this was by slotting the screws on the TPS sensor so I could adjsut it. the TPS needs to read between .5 and .9 volts at closed throttle.

So what I did was , start the car and monitored the IAC and TPS sensors. I started screwing the Throttle plate stop to open the throttle blades and when the TPS voltage would go below .5 volts i would rotate it a little the tighten the screws back down on the TPS sensor. I did this until my IAC counts were at 30 with the A/C off and the TPS voltage was between .5 and .9 volts.

TUFF LT1

Thanks for the info! I got my IAC counts down to 52 or so today by drilling out the breather hole in the TB. The car seemed to hold a better idle but still had a slight miss ( or burp if you want to call it that ) once in a while after it had been idleing for a few minutes. Also when I removed my throttle body I had a small film of raw fuel covering the backside of the TB??? I think that since I'm running so rich on one side, maybe that is causing the "burp" and is actually pushing raw fuel back up into the intake. I still need to find a way to get my IAC's down to 20-40 or so. Would that cause the car to have the split BLM's that I'm seeing?? Thanks for all your help so far!

TriPinTaZ

Bad 02 Sensor ?

bunker

acctually what you want to ultimately do is not have a hole in your TB blade but acctually close the blades even further by turning the adjusting screw on the TB (ussually covered by tb gasket when stock), what this does is make the IAC counts go up, with a big cam you want to forse as much of the air through the idle passages as possible instead of the TB blades because of CAM REVERSION, the IAC passages are located right at the ports, when you close your blades even more then stock this makes the IAC open up, causing more of the air to be directed through the idle passages at the ports, this will fix the split blm issues that results from install of big cams (assuming all is well).

If you log it, as you close the blades you'll see the BLM's stabilizing, ussually the right side goes to 160 & left side goes down to as low as 108 after cam install, thats why you have to close the blades, what you did by drilling the blades is not helping & now you prolly will end up having to seal up that hole to fix things up.

Matt.

TUFF LT1

Thanks for the good info Matt! You hit the nail on the head I'm telling you what! I drilled out the hole and am in the process of fixing it right now. I'm going to try and do what you said about closing the throttle body blades. Wish I'd have read this before drilling. Hopfully this will fix my problem so that I can get the car back on the road with the new cam

TUFF LT1

I forgot to mention that I have two dadamaster logs if anyone would like to take a look.

bunker

sure send it my way: bunker@telus.net