Overhauled engine and now tranny acting up why??

[AbramF_496]

All right so I got my engine rebuilt and now my tranny will not go into passing gear normally
Feels like fuel pump is not giving my engine enough gas.

I really would like to know if replacing fuel pump would help since NOW
after all these years THE FUEL PUMPS FOR GMT400's
HAVE GONE TO LIFETIME WARRANTY!!!!
Awesome right I know lol
Bought a Delphi pump since my 3rd airtex finally went out

The things that happen that make me feel like the fuel pump is the culprit are below
When I hold the brake and press the gas at the same time it revs up try's to move and then after letting off gas it shuts off completely
Next when I'm on the expressway I was going 60+ and all of a sudden it started to shift back n forth out of overdrive it was something I've never witnessed before :[

Throws no codes out and no lights come out on dash as something wrong with engine so it must be fuel delivery or trans

Please help for the sake of my GMT400

 

[poncho62]

No computer codes?

I am thinking it has something to do with how the rebuilt engine is set up. Maybe the tech that installed it left a plug undone or something. The trans on them are shifted and controlled by the ECM

 

[someotherguy]

...which is why fuel delivery problems can confuse the transmission. Too much TPS input from mashing pedal farther to make it "go."

Time to put the fuel pressure gauge on. When was last time filter was changed? Which engine, 454 or 350?

Richard

 

[AbramF_496]

No computer codes?

I am thinking it has something to do with how the rebuilt engine is set up. Maybe the tech that installed it left a plug undone or something. The trans on them are shifted and controlled by the ECM

Alright so I further inspected it and there's a ground wire that is on the frame but not on the engine
There are 2 steel ground cables right where the air-condition drips out

If u could tell me where both grounds go

Second I drove it around for a while in third gear
And it finally threw a code and went to Oreilly
Says one code and it's the MAP SENSOR
So according to that the ECM like the other guy said makes perfect sense
I bought the lifetime warranty one so i am going to change it out

Thanks guys will follow up immediately when changed
Should swap out in about 5 minutes real simple Install

 

[AbramF_496]

...which is why fuel delivery problems can confuse the transmission. Too much TPS input from mashing pedal farther to make it "go."

Time to put the fuel pressure gauge on. When was last time filter was changed? Which engine, 454 or 350?

Richard

It is a 350 and I changed out the fuel pump about two months ago and the filter was changed at same time
Maybe just got a faulty map sensor or not pushed in correctly I'll fidel with it ASAP

 

[someotherguy]

Alright so I further inspected it and there's a ground wire that is on the frame but not on the engine
There are 2 steel ground cables right where the air-condition drips out

If u could tell me where both grounds go

Those dual braided straps go like this - one goes from the frame up to the firewall, and another goes from that same spot on the firewall to the rear of the passenger side head. I also believe Vortec-era trucks like yours may have a medium gauge (14, maybe 12) black wire with a ring terminal on it that attaches to the head at that spot too. Will be hard to see and very easy to overlook for reattaching while heads or engine are out.

Richard

 

[AbramF_496]

Those dual braided straps go like this - one goes from the frame up to the firewall, and another goes from that same spot on the firewall to the rear of the passenger side head. I also believe Vortec-era trucks like yours may have a medium gauge (14, maybe 12) black wire with a ring terminal on it that attaches to the head at that spot too. Will be hard to see and very easy to overlook for reattaching while heads or engine are out.

Richard

Awe well dang I have no idea but would that ground effect the performance of my engine?
Changed the map sensor and still have the code of course but truck still won't go into overdrive is what it feels like for sure.
Where is the ECM ??

 

[someotherguy]

The PCM is the black finned box above the driver's side fenderwell. It's very likely NOT the issue. And yes, lack of proper grounds can cause all kinds of problems.

Richard

 

[AbramF_496]

The PCM is the black finned box above the driver's side fenderwell. It's very likely NOT the issue. And yes, lack of proper grounds can cause all kinds of problems.

Richard

Well crap I wish my dad's suburban was here so I could see exactly where that random ground goes :[
Gonna look for some pics or something.
Scanner only gave the map sensor code so I have no idea what's making it not get into overdrive since I can manually shift with my column shifter
Driving me nuts about this problem
Just rebuilt and now I can't enjoy the power sheesh
Takin it on Monday to my mechanic.

Will follow up ASAP

 

[AbramF_496]

Oh!! Would the computer need to be flashed or anything of the sort since I have a shift kit and what not when installing new engine? Hmmm