WS6snake-eater

Any ideas why my MAP is reading at 3.0V and 70kpa at ilde? I just installed a g5x3 on 112 lsa and PP stage II ls6 heads. TB has been ported also, and TB hole was opened to allow for a better idle. IAC's are 25 at idle with a/c off and 50 with a/c on. IAC's are showing 70 in drive while cruising. I keep setting code P0121 wich is a TPS poor performance code, and I believe it is related to the MAP reading. I assume that the the pcm thinks that the TPS should be showing more voltage since the MAP is showing 3.0v at idle according to the freeze frame records, and thus causing the P0121 code. I'm not throwing any MAP codes however. Also MAF readings are at 11.3 g/s at idle with a/c off, and 12.1 q/s at idle with a/c on. Timing is holding pretty steady at 20 degrees while at idle. I need an idea of where to start. Do I have a vacum leak? I did some searching and found that maybe timing should be raised slightly to create more vacum. Did I drill my TB too big, are my IAC's in line? I fugured the big *** cam would create more vacum not less. I'm really lost here guys. For the most part the car seems to run pretty good. I think I am still missing some power though. The car has a slight "auto cruise control" effect to it when letting off the gas. And reverse doesn't idle for **** unless the car is really warmed up. It dies almost evertime I try to back out the driveway, but is fine once I put it in Drive. Sometimes it won't downshift and just holds at about 3,000 RPM, this is a rarity however. While searching I found that a lot of people with P0121 have had the same drivabiliy problems. I feel pretty confident that the P0121 is somehow related to the MAP reading, does anyone have some input on this? Do any of my readings look out of wack? BTW before some smart *** chimes in with the usual "use the search button, that's what it's there for" response; I just spent 3 solid hours digging through old post, and while I found a lot of great info, nothing has been able to answer my specific questions. But it did help me narrow it down. Any help would be greatly appreciated guys.
Thanks

Brains

iTrader: (7)

tis the nature of the beast My cam idles around 65-70 kPa as well (238/240 on a 112). You can tweak the test range in LS1edit for the TPS code though

ChrisB

That's the problem . Big *** cam = less vacuum at idle.

Brett SS

I went through this same thing a while ago and once we worked it out we got Ken Kelly to add the Min and Max MAP parameters for the P0121 code into LS1Edit. You can find it under the Engine Diagnostics section, just increase the Max value to 75 and the code will not be thrown anymore.

gomer

iTrader: (13)

I had the same problem when I installed my TSP231/237.. Jason at TSP fixed it in LS1edit, email him if you can't get it figured out.

WS6snake-eater

Man thanks a lot guys. Was the code causing your cars to hang up and not shift right? Gomer I remeber reading something about you having the same problems as me. Also it seems that when the light is on, that the car goes into a low octane mode, would that make since?

NoGo

iTrader: (2)

MAP factors into the MAF 'gut check'. If the PCM thinks that the MAP is junk it can't do the MAF 'gut check'. All timing reference is done via the airflow into the engine (ie the MAF). If the PCM can't verify that the MAF is reading properly (using the speed density check, which requires the MAP) then it should switch to the more conservative table.

Bad30th

iTrader: (13)

Thanks for this info - good post !

Rob (Bad30th)

WicketMike

iTrader: (13)

the stock P0121 parameters are 55/65 , change them to 75/85

Brains

iTrader: (7)

Nah, mine shifted like crap before too. Something wrong with the primary shift control device aka ME... (I got a six speed)

WS6snake-eater

HAHAHA Funny...that's because you were "granny shifting, not double clutching, like you should"!!!!!

Brett SS

Yes it was also affecting my 1-2 shift as it would shift too early no matter what I tried. After changing the values in edit and making the code not get thrown the shifting was perfect again.

WS6snake-eater

How about reverse, has anyone had problems with major surging and dying only in reverse?

WicketMike

iTrader: (13)

i had the problem. i put it in reverse and let it settle before backing it up.