97 3.1 poor low rpm accel, good high

[redroan351]

I have checked history and couldn't quite find what I was looking for.
-From a stop, as I push down the gas pedal, there is no power. I can push it down a little more, yet there is no change, like the computer isn't adding fuel to the air that is going through the intake. So at this point it's anywhere from quarter throttle to half, I can actually move it up and down with no change. Then at about 20, it gives it the fuel it would have at that throttle position and just takes off. Then makes a normal shift and then immediately falls on it's face again, same thing, I can move the throttle up and down between part and half and no change, then at about 40 it blasts off again. At full throttle it is fine, though while in full throttle it wont go to overdrive.
-So it seems that the computer is confused at low throttle and is ok at high.
I think throttle position, torque converter solonoid, or other trans solonoids maybe.
Sorry for the length, thanks for any help, I'm at a loss. Roan.

[richtazz]

Check engine light on? if so, did you pull the codes? A TPS (which sounds like your issue) will usually trip a CEL, but not always.

[redroan351]

No light. though this has been happening for a little while now, in all conditions, but I've had the battery disconnected many times in between and thought at first it could some how be related to the idle relearn process, but then for the first time just this morning it acted perfectly normal at take off and through all throttle positions. I went a few miles, stopped, turned off key and took key out to gas up. Restarted and it drove fine again, stopped and parked and left it running about 20 minutes and got back in and it was back to starving in low rpms then blasting off at about 20.
Thanks for the help. I have replaced the engine though it did this same thing right before that while I was diagnosing the old engine. Also I just put a fuel pump in and a multifunction switch (made the special tool out of aluminum that I bent in three right angles and drilled a hole in the middle) and replaced the vacuum line under the battery that was causing incorrect A/C flow and probably other problems. Thanks all, Roan.

[richtazz]

With everything else you've done, I'd check the rest of the vacuum lines for cracks, fuel pressure regulator (and the vacuum line to it for fuel residue) and the wiring harness to the ECM for corrosion.

[redroan351]

Ok, so checked the fuel pressure regulator and no leakage and fuel pressure does go up slighty as the vacuum line is removed while running. All vacuum lines appear to be in good working condition and the idle acts accordingly when they are remove.

Harness looks ok. So this this happens exactly the same every time. I can move the gas pedal down to an inch, inch and a half and nothing changes, just slow accel. I keep it there and dont move it, and all of a sudden at about 20 mph it just blasts off like it should have been the hole time, with the gas pedal in exactly the same place, I never moved it. After the shift it does the same thing on till at 40 mph it blasts off, pedal in same place.

Thanks for help..

[redroan351]

Anyone got any crazy ideas? I feel dumb.

How are the coils opperated on these, is there some kind of backup power given to them when it feels it's falling on its face?

At what voltage is the throttle position sensor, and what rpm's is the transmition supposed to shift at part throttle?

Could the torque converter work this way, just kicking in all of a sudden at a certain pressure, which is the same every time?

Could a MAP act this way if the ECM didn't realize it was there? Could a CKP be bad and still run well at higher throttle?

Thanks for listening, Roan.

[maxwedge]

You need a full scan and look at the tps response, fuel trims and so on, anything less is guess work, sounds like a dead spot in the tps, tough from here to tell without a test drive, also look for loose or corroded engine grounds. Part throttle shift is co-dependent on engine vacuum as well as throttle opening and load. Check the baro reading, key on engine off when scanning also.