TBI Off Idle Transition Problem

[440sixpack]

Engine seems to run up smooth in park. so now I'm wondering if it isn't a transmission issue.

Transmission cable is tight. from what little I've read this is not correct ?

 

[Bextreme04]

Engine seems to run up smooth in park. so now I'm wondering if it isn't a transmission issue.

Transmission cable is tight. from what little I've read this is not correct ?

I would take it to a well respected local transmission shop and have them check and adjust the TV cable. The best way(I have heard) is to have someone adjust it based on the actual line pressure using a gauge. A good trans shop should be very familiar with this and be able to do this correctly. This MUST be done correctly because incorrect TV cable adjustment is the number 1 most common way to blow up a 700R4. I'm assuming this is a 1992 4L60? The 4L60e came out on trucks starting in 1993, but a 92 would have had a 4L60(not "e") which is basically a 700R4. I'm just wondering since this was a transplant, if you transferred the whole engine/trans/harness over together or if it was cut and spliced into the original '77 harness? What was the donor? How was the TCC apply wiring run?

 

[440sixpack]

looking at the pan it's a 700r4.

It has a new complete Painless wiring harness going to the computer in the dash.

 

[Bextreme04]

looking at the pan it's a 700r4.

It has a new complete Painless wiring harness going to the computer in the dash.

There is no difference between the pan on a 700R4, 4L60, or 4L60E. A 4L60 is a 700R4 produced after 1990, its just a nomenclature change. A 4L60E will have an electrical connector on the passenger side top of the valve body rather than a TV cable opening. This is so the computer can electronically control the shift and line pressure solenoids rather than manually like the TV cable does. https://www.novak-adapt.com/knowledge/transmissions/automatic/th700r4

There will be an electronic connector on the drivers side of your case that has the pins for TCC lockup, a governor cover, and most likely a VSS sensor if it is a 4L60. A 700R4 would most likely have a mechanical speedo provision. If your painless harness is going to that electrical connector on the trans and also to the VSS, I would suggest you disconnect the TCC lockup connector and see if the situation goes away. If it does, that means the computer is locking your torque converter on initial throttle tip-in, which shouldn't be happening. A 1992 should be locking the torque converter in 3rd at very light throttle and in 4th most of the time.

 

[AuroraGirl]

I think i read a TSB somewhere where GM produced revised PROM chips to correct harsh apply, that seemed to be too sudden for some people, but i could be meshing memories. Does this TBI use a Prom CHIP, and does the TPS have a consistent swing, and is the tbi injection spray nice and not a trickle, it could be a dumps fuel and then jumps into action rather than smooth consistent, maybe check pressure if that is big at all for tbi

 

[440sixpack]

It has a cable on the RH side and a square electrical plug in on the LH side. so you're saying disconnect that and see if it helps ?

 

[Bextreme04]

It has a cable on the RH side and a square electrical plug in on the LH side. so you're saying disconnect that and see if it helps ?

Yes, the square electrical plug on the LH side is the torque converter lockup control. If you disconnect that and the problem goes away, then you know the lockup was being applied at the wrong time.

 

[440sixpack]

Tried that and it didn't change anything. I'm going to look things over again and if nothing seems off I guess I'll just live with it.

I wonder if my '77 pedal assembly has a different fulcrum or something than the TBI models ? maybe it builds up too much force when you push on it and then just jumps off idle.