My 3.1 has more tq under pt-thrtle, than full??

[85_305]

Why does my '91 3.1 have more tq and "pull" under part-throttle than full throttle? It's VERY annoying!

Thanks,
Matt

[1988GTU]

You notice if it is bogging out from too much fuel at wot?

[SappySE107]

What vehicle? You can put that info in your profile and it shows up in the drop down under your name.

Ive had that on my 91 3.1 grand prix. Fuel pump died later on but I dunno if it was related. I was always messing with my engine back then so god knows what helped or hurt.

[IsaacHayes]

Clogged cat too maybe? At full throttle it can choke the engine too much, but part throttle it's able to keep flowing enough to not notice...

Up until my friends car had cat problems I never really thought much about them, but this sounds like it could be clogged cat related..

[86euro]

My vote goes to clogged fuel filter or weak fuel pump.

[85_305]

You notice if it is bogging out from too much fuel at wot?

I wonder this. I really dont know though. But say you give it quarter throttle to get moving in traffic (BTW i only run 91+. I can TELL a difference in gas mileage and performance), the car hauls balls. It doesn't redline, but it moves quick. Now, if I were to floor it, I can honestly tell it going SLOWER than when I was under part throttle. I don't think it's a bog though..

What vehicle? You can put that info in your profile and it shows up in the drop down under your name.

Ive had that on my 91 3.1 grand prix. Fuel pump died later on but I dunno if it was related. I was always messing with my engine back then so god knows what helped or hurt.

Sorry Chief, I will add my vehicle when I'm done replying But my fuel system is brand new. And I just had a mechanic check the fp thinking it was going out, but it ended up being the CPS. Now, the car idles funny when warm (you have to shut it down and restart it to idle right), and even when idling "right" it sometimes stalls or idles ultra low.

Clogged cat too maybe? At full throttle it can choke the engine too much, but part throttle it's able to keep flowing enough to not notice...

Up until my friends car had cat problems I never really thought much about them, but this sounds like it could be clogged cat related..

It has a custom Flowmaster exhaust on it, but as far as I know the stock cat was kept on. Now, the car DOES smell sweeter.. my buddy asked if I ran premium to which I replied yes.. and i SOMETIMES smell the eggy sulfer smell from the cat, but I dont know if it's shot or not. How can I tell for sure?

My vote goes to clogged fuel filter or weak fuel pump.

The fuel pump is brand new, and I just had it checked (problem ended up being the CPS.), but a fuel FILTER I suppose could be a potential problem. Are they hard to get to on these 3.1's?

[PCGUY112887]

My 3100 does the same, I just thought that's the weird way they worked.

Difference between 50% throttle and 100% throttle, well I can feel/tell no difference.

[85_305]

My 3100 does the same, I just thought that's the weird way they worked.

Difference between 50% throttle and 100% throttle, well I can feel/tell no difference.

Yeppers. Shouldn't be like that. I have NEVER had a car pull that sh*t on me. And I dont like it. There HAS to be something wrong or at least something I can do to fix that.

[PCGUY112887]

Humm, well my fuel pump is new, everything else seems to be in tip-top condition.

Maybe clogged cat? I have 117k miles.

[85_305]

Humm, well my fuel pump is new, everything else seems to be in tip-top condition.

Maybe clogged cat? I have 117k miles.

I have 151k miles. COULD be a cat I suppose.. and even if it's not it's probably a good idea to get a hi-flow one for the heck of it. So I will give it a try sometime. Anything else you could think of?

[Carlspike]

I noticed you have many different issues with this car in different posts. It's possible that they are all related. That makes me wonder if your computer is messed up, when they fry they can do wierd things. As for bogging at WOT I'd agree with everybody and say check the cat and fuel filter. the 3.1/3100 is a torquey (sp?) engine and you may not notice a huge jump between 75% throttle and 100% throttle especially if the engine is already wound up. The only other thing I can think of is bad blow-by. My friend had a 4.6 ford that ran better at half throttle than full because at full throttle he got really bad blow-by. The engine would rev but the car wouldn't go. That's a longshot but it does happen.

[85_305]

I noticed you have many different issues with this car in different posts. It's possible that they are all related. That makes me wonder if your computer is messed up, when they fry they can do wierd things. As for bogging at WOT I'd agree with everybody and say check the cat and fuel filter. the 3.1/3100 is a torquey (sp?) engine and you may not notice a huge jump between 75% throttle and 100% throttle especially if the engine is already wound up. The only other thing I can think of is bad blow-by. My friend had a 4.6 ford that ran better at half throttle than full because at full throttle he got really bad blow-by. The engine would rev but the car wouldn't go. That's a longshot but it does happen.

Yep sure are a few different problems. All very annoying ones lol. But I dont believe there is any blowby in this 3.1. It runs strong, has INCREDIBLE throttle response still, has never lost in a race (though, racing DOES suck because the damn tranny shifts so high but that's another thread). I had an old 3.1 w/ 240k on it and that thing ran top as well. But the vehicle consumes very little if any oil between changes. And I mean I could give maybe 50% throttle sometimes and the car takes off and you can feel the torque rush, whereas if I floor it it doesn't seem to have that "rush". How difficult is it to get to the fuel filters on these cars?
How could I tell if the ECU is shot?

[Carlspike]

This car is OBD1 right? If it is then take a paper clip and bend it in a U shape. Stick the paper clip into the top right 2 slots on the data link connector. Turn your key to the on position and this should inform you of any codes you have. You should get a code 12 also, that means the compuer is communicating. If you don't get a 12 then you could have a problem. but just having code 12 doesn't mean your computer is good though either. ECU's can be tricky to diagnose. As for the fuel filter it should be on a fuel line near the tank. It shouldn't be too hard to get to but it's probably rusty if it hasn't been changed in a while. If it hasn't been changed in a while it wouldn't be a bad idea to change it anyway - it's a regular maintenance item.

[85_305]

Ya it SHOULD be OBD1, I am not positive though. Now that I think of it, I had the fuel lines replaced, along with the pump and injectors I think. I am pretty sure it's not the filter :/

[mfewtrail]

Bumping this old post...

My '93 3.1 MPFI behaves the same way as you guys described(noticed it recently when playing around). The fuel pump(7,000 miles on an OEM AC Delco replacement), nor filter(7K miles on it also), nor catalytic converter are to blame(no cat on the car to get clogged, I have an aftermarket exhaust). 60-70% throttle seems to be the optimal point for acceleration in its current sate. At this throttle level, I can slightly modulate the gas pedal and initiate shifts right around 4800-4900 indicated rpms and the car accelerates great like this(for what it is). 100% throttle = a lot of noise and much slower acceleration..shiftpoints at WOT occur at an indicated 5500rpms or so. The engine is north of 200,000 miles and runs perfectly otherwise(30-32mpg on the highway, doesn't use a drop of oil, etc.). I'm leaning towards valve float due to tired valvesprings being the culprit here.