lterm reading high in open loop mode

ok we're trying to get my friends gm847 formula tuned and i noticed the first time i hooked it up that his lterm value was in the 150-range instead of just reading 128 until it gets into closed loop. i dont remember having this problem in my car, but why would it be reading those high values until it gets into closed loop mode? changing the maf tables wouldnt do anything (for open loop) would it? should i start thinking about changing the ve tables?

Nothing unusual... the long terms are saved in the PCM, and used for both open and closed loop. They just can't change when the PCM is in open loop, and the PCM will only used the numbers stored in Cells 16, 17 and 18.

If you clear the PCM, all Cells will reset to 128 and it will start and run at 128 in open loop the first time.

a alright. changed the plugs, wires, o2's. car started fine/ran fine in opeloop, then got into closed loop and ran like crap/died. threw code 33 (high map) and the abs inop light came on a couple of times. reset the codes and retuned the maf tables a couple times. ran ok in open loop then did the same thing. after doing this a few times it started running like crap even right when we started it (in open loop). next thing we're gonna try is changing the map sensor, checking the harness. any other ideas? btw, thanx for the posts (on both boards)

Intake leak? Do you have a log of the car?

i got a couple logs when we were trying to get it running. what would the best way to check for a manifold leak be? (cant really hear anything). i'll have to wait till i get home to get the logs though.

What's you MAP value at idle? Part throttle?

map value was around 75 at idle and between 60-100 for part throttle but it wasnt a very smooth/good log to determine part throttle values.

map value was around 75 at idle and between 60-100 for part throttle but it wasnt a very smooth/good log to determine part throttle values.
That MAP value is too high. You're not pulling enough vacuum. At idle, it should read about 45-50 kPa and at part throttle, around 30-40 kPa. WOT, it should be 95-100 kPa. It should never be close to 100 kPa for part throttle operation. It sounds like you have a vacuum leak somewhere.

He's also got the O2 sensors in open collectors.

More info from the same post on another forum.....

http://www.fbody.com/cgi-bin/lt1/read.cgi?msgid=276799

He's also got the O2 sensors in open collectors.

More info from the same post on another forum.....

http://www.fbody.com/cgi-bin/lt1/read.cgi?msgid=276799
I appreciate it Injuneer. That would definitely explain the "lean" condition seen in closed loop.

thanx for all the info. we extended the exhaust back 1-2 ft. just to see and sure enough ran a lot better in closed loop. still needs to get the rest of the exhaust hooked up, then we can start tuning. i didnt even think about the car not running good open headers cause when i started mine open headers it was fine but now i realize that it was only on for a minute or so (open loop). alright. thanx again for the info