Spellbound

I have a 2000 SS that has a built tranny and 4000 stall converter in it and recently, I've noticed as I was drivng down the freeway the converter starts unlocking for a bit, then locking. This all happens on flat roads and no load on the engine. The engine has has the usual intake mods and an underdrive pulley and has been dyno tuned. The only change I've made recently has been the additon of 3.73 gears via a 12 bolt swap. I've had the issue one time before and I took it back to the tuner and it was fixed for a while. I don't recall if it happened before or after the rear end swap though.

When I get time, I will take it back and have the tuner look at it, but until then, anyone have any ideas?

01ssreda4

iTrader: (96)

I had this happen years back on a 700r4. It was due to a broken temp sensor. Programming did not allow converter lock-up until coolant reaches a certain temp. By the sensor being faulty, it was throwing the computer for a loop and was causing random locks and unlocks around 45 mph. BTW, the temp gauge in the vehicle was still working at the time, so perhaps there were 2 different ones. On the SS, I have noticed light throttle lock-up happen precisely at 113 degrees as i'm leaving the house. This is on an aftermarket temp gauge in the coolant bypass line. It apparently restricts lock-up below that temp just like the old 80s model 700R4 did. Funny how in 15 years things dont change much.

Spellbound

Funny you mention the sensor issue. I am having overheating issues as well but only in stop and go traffic. Going down the highway it seems to be fine.
I have an aftermarket water temp gage to go along with the dash one and I have noticed that the dash gage can be freaking out sometimes while the pillar gage is reading normal. Come to think of it, I think the unlock/lock issue started after my overheating issues started. I may not have noticed it because I don't drive it to work anymore except for the other day when I noticed the problem.

Anything else?

01ssreda4

iTrader: (96)

IMO, overheating in traffic but not on the highway indicates airflow issue. Motors need airflow whether by wind on the hwy or artificially by the fans. Stop and go overheating points to fan issues to me. Could be a relay or a fan motor. Both are cheap and relatively easy fixes.

Joshiedoom

iTrader: (4)

had this happen as well, broke TPS sensor not throwing a code. Subscribed

Spellbound

Hmm, I can hear the fans come on when the car is at idle....I wonder if it's my 166,000 mile radiator, it could have clogged arteries, lol. I also have two tranny coolers w/ fans mounted in front of the radiator, I'm sure that is a contributing factor. The overheating problem started last summer when my EWP went out and I put a stock water pump back on.

matt72489

could this cause the car to be sluggish and not accelerate as it should?? bc i threw the code for PO121 and it was the TPS.... didnt mean to hijack the thread sorry

Joshiedoom

iTrader: (4)

Yes it takes 10 minutes to change one out. They are really cheap as well.

jimmyblue

iTrader: (11)

A flaky ECT connector could also do this and I've seen
those - also bugging idle & mixture as you pop in and
out of closed loop.

HuggerOrangeZ

I've also heard about this happening when the engine detects misfire.

Since aftermarket converters are smaller than stock converters, the engine detects misfire and unlocks the converter.

Don't know if this is the problem in your case though.