need help on a new transmission not shifting right
09-21-2010, 12:10 PM
#1
On The Tree
Thread Starter
iTrader: (3)
Join Date: Sep 2010
Posts: 146
Likes: 0
Received 0 Likes
on
0 Posts
need help on a new transmission not shifting right i just bought a 98 ls1 trans am and i am getting a new tranny put in it. the trans is all stock and he got it all put together and went out to test drive it and it stack shifts 1-4 in about 45 feet and cant get it to stop doing it and the torque converter wont lock up. the car has H/c/i and i was told that the car might need to have the battery and the fuse to the computer removed to take away any program left in the computer could this be the problem??? need help im trying to take it to a show on wednesday and he cant get the problem figured out any help would be greatly appreciated
09-21-2010, 12:38 PM
#2
TECH Regular
iTrader: (8)
Join Date: Mar 2008
Location: Plain Dealing, LA
Posts: 445
Likes: 0
Received 0 Likes
on
0 Posts
You cant "take away" the tune from the computer unless you have it reflashed. What happened to the previous trans? Did it shift right? I would say if you have h/c/i you probably need the car tuned.
09-21-2010, 12:52 PM
#3
On The Tree
Thread Starter
iTrader: (3)
Join Date: Sep 2010
Posts: 146
Likes: 0
Received 0 Likes
on
0 Posts
the car has been tuned already so thats why im wondering what the heck is going on it doesnt make any sense any ideas now knowing that the car has been tuned for the same trans already??? the car was shifting alright then it started cooking 3-4 on the highway so im not sure whats going on any help would be great
09-21-2010, 01:05 PM
#4
TECH Regular
iTrader: (8)
Join Date: Mar 2008
Location: Plain Dealing, LA
Posts: 445
Likes: 0
Received 0 Likes
on
0 Posts
Who tuned the car? Is it mail order, dyno'd, or a friend? I would start by making sure the tune is correct. If you find that the tune is for sure good and the old trans shifted ok until the 3-4 burned up then I would say the new trans is the culprit. What converter are you running?
09-21-2010, 01:22 PM
#5
On The Tree
Thread Starter
iTrader: (3)
Join Date: Sep 2010
Posts: 146
Likes: 0
Received 0 Likes
on
0 Posts
the guy i bought the car from said if i remember right it was tuned mail order by a company that is pretty reliable i cant remember the name off the top of my head though.. the car shifted good before so im not sure what the hell my old dodge pickup did this same type of thing and i had to take the battery terminals off and take out source voltage and it was fine but im sure this is nothing like that idk what to do im lost as of right now and its hard to try and figure things out at work
09-21-2010, 02:14 PM
#6
PO121 or QUICK SHIFT 1-2-3-4 AT WOT after cam or throttle body install FIX Found this on another forum posted as a single thread but wanted to have in this thread for easy reference also
PO121 CODE OR QUICK SHIFT 1-2-3-4 at WOT by 40 MPH FIX
Found this info on another forum and I know many people have popped up with this issue and wanted a fix. This would appear to be it. Hope it helps someone.
The curse of the P0121 Code... This code is infamous for giving people with larger cams fits...everything from traction control troubles, to shift point issues to just the good ole' P0121 code showing up for seemingly no reason making people scramble to purchase new Throttle Position sensors, adjust their set screws, etc, etc.
Before I go any further have a gander at the DTC information provided by LS2.com
http://www.ls2.com/boggs/dtcs/DTC%20P0121.htm
To outline a few key points
Quote:
The MAP is greater than 65 kPa
Quote:
The predicted throttle angle does not match the actual throttle angle
Quote:
All conditions present for 20 seconds
Now, that 65kpa map figure comes into play in nearly every LS1 Car/Truck because its the max map setting in most of the calibrations for the sanity test as shown here
Under normal circumbstances a stock cammed A4 will probably idle at around 35-40 map. When switching to a larger cam with more overlap your map readings could go up to as high as 70 or more kpa map which is way outside of the normal boundries. On a stock cammed car you'd probably need to be at around 30% tps to hit that same map number which is where that predicted throttle angle quote comes into play.
Now onto the last quote the 20 second timeframe. This will Usually come into play more often than not at idle with large cammed vehicles because many times your steady state map will be within the map sanity guidelines so there is a good possibity you might not see this code pop up immediatly.
There are a few ways you can cure this issue
a. Do as suggested in the help file which is to just set the min to 0 & max to 100
b. Adjust them to YOUR liking so you'll be within a reasonable limit. This will help determine if there IS a real issue with your TPS sensor later down the line.
So there you have it, as good an explanation I can come up with for that bastard code. So the next time you go WOT in your auto LS1 with a large cam & you go from 1st to 4th by 40mph or just a nagging p0121 code for no obvious reason you now have the info needed to fend it off.
__________________
__________________
09-21-2010, 02:29 PM
#7
On The Tree
Thread Starter
iTrader: (3)
Join Date: Sep 2010
Posts: 146
Likes: 0
Received 0 Likes
on
0 Posts
stupid question but can that be fixed with a snap on scan tool or does that need to be sent off and tuned.. im going to assume it needs to be tuned
Last edited by khoward8509; 09-21-2010 at 04:57 PM.
Trending Topics
09-21-2010, 05:16 PM
#9
On The Tree
Thread Starter
iTrader: (3)
Join Date: Sep 2010
Posts: 146
Likes: 0
Received 0 Likes
on
0 Posts
with the car already tuned would you say i could do it with a hand held tuner?? will my trans guys diagnostic tool tell what the map is reading so i know for sure that is what is going on with it i would hate to tell him i am gonna take it home and do that and then it not work. so if that is what it is i just need to send it to a tuner and tell them to widen out the kpa on the map
09-21-2010, 06:14 PM
#10
Your trans guy should have a device to plug into the trans that bypasses the stock computer. This way it would take one test drive to determine if the problem was in the transmission or the tuning.
