92 Lumina 3.1 missing at part throttle

[92beater]

New to this forum, and I'm sure I'll be back from time to time to keep this car running lol.

here's the story, a couple weeks ago the crankshaft position sensor went out and in the process of diagnosing it, I took out the ignition module to have it tested, later discovering the crankshaft position sensor was bad. Anyway, during removal of the module, I unhooked the battery to avoid shorting anything out. My experience with this car is that when you disconnect the battery it resets the ECU and the car will take a couple days of driving to "relearn" all of its settings. So the car doesn't want to idle at lights, etc... Well it has not "learned" in 2 weeks now, and yesterday whil on the highway, it would keep missing. At normal cruising speed of around 2K rpm, it would be fine but if you would give it some throttle, it would sputter and jerk rather violently, then if you gave it considerably more throttle, it would smooth back out and accelerate, but it seemed to be lacking alot of power. I can't get it scanned at the dealership today because they are closed, so I was seeing if anyone on here had any idea.

My initial thought is a throttle position sensor, but that is based on past experience with other vehicles.

[j cAT]

Originally Posted by 92beater

New to this forum, and I'm sure I'll be back from time to time to keep this car running lol.

here's the story, a couple weeks ago the crankshaft position sensor went out and in the process of diagnosing it, I took out the ignition module to have it tested, later discovering the crankshaft position sensor was bad. Anyway, during removal of the module, I unhooked the battery to avoid shorting anything out. My experience with this car is that when you disconnect the battery it resets the ECU and the car will take a couple days of driving to "relearn" all of its settings. So the car doesn't want to idle at lights, etc... Well it has not "learned" in 2 weeks now, and yesterday whil on the highway, it would keep missing. At normal cruising speed of around 2K rpm, it would be fine but if you would give it some throttle, it would sputter and jerk rather violently, then if you gave it considerably more throttle, it would smooth back out and accelerate, but it seemed to be lacking alot of power. I can't get it scanned at the dealership today because they are closed, so I was seeing if anyone on here had any idea.

My initial thought is a throttle position sensor, but that is based on past experience with other vehicles.

check tps with ohm meter with battery removed connect meter to tps slowly rotate throttle and it should vary resistance smoothly. if its jumping in value its bad.....look at maf check connections and interior sensor wires

[92beater]

Originally Posted by j cAT

check tps with ohm meter with battery removed connect meter to tps slowly rotate throttle and it should vary resistance smoothly. if its jumping in value its bad.....look at maf check connections and interior sensor wires

Thanks, I'll try that. Hopefully that is the problem, it's an easy/somewhat cheap fix.

[92beater]

Well it is not the TPS sensor, I ended up just picking up one on the way home, then put it on and it runs the same. I read that if the replacement TPS has slotted (or oval type) mounting holes then it needs to be adjusted, but it does not. I can return it, but now I am wondering what else it could be. I am going to try the fuel filter next.


I also just realized that since the engine is not throwing a CEL, then having the car scanned at a dealership will tell me nothing. The car has new plug wires and the ignition module and coil packs were checked when I replaced the crankshaft position sensor and they were all good.

[Bearwulf]

Have qualified shop scan and clear all ECM error codes on primary and secondary diagnostics, you may have a bad circuit.
It may be injector driver prob. in which case there are no codes to check as any codes created are cleared when ign. is turned off.

[cadgear]

Diagnostic codes can be stored even if no MIL is present. Certain specifications of the OBD standard indicate that the MIL will illuminate if the problem can affect vehicle emissions. Some other codes may not directly affect those, and so will not light the MIL.

As far as the problem, check to make sure you didn't knock any vacuum lines off. Make sure all the wires you disconnected are snug. Check your wires, too. Might've opened up or cracked some insulation or the wires themselves going to the plugs, depending on the last time they were replaced you might have that ahead of you.

Vehicle re-learn is usually complete within 2 - 3 driving cycles. Most major parameters are restored within the first 20 minutes of normal driving. But OBD I systems aren't as strict nor as informative as the newer OBD II specifications.

[92beater]

Thanks for the advice, I will try having a shop scan it this week. In the meantime I am going to pick up a fuel pressure gauge and check fuel pressure at the schrader valve on the fuel rail. If I'm not seeing the correct fuel pressure I might have a kinked fuel line or possibly the fuel pump might be bad.

[j cAT]

Originally Posted by 92beater

Thanks for the advice, I will try having a shop scan it this week. In the meantime I am going to pick up a fuel pressure gauge and check fuel pressure at the schrader valve on the fuel rail. If I'm not seeing the correct fuel pressure I might have a kinked fuel line or possibly the fuel pump might be bad.

because the cps was defective and engine was miss firing with no codes I would guess that the cat is restricted so have them check for this.....