no power at full throttle?

[jesse0880]

in my 91t, I'll put the petal to the floor and it seems like it has no power. All the way up to about 70% throttle and the motor responds like normal. My ignition components new and timing is dead on. any ideas?

[CJMR2T]

First thing, is the MIL (check engine light) on and or have you checked for any codes???

Have you checked of for boost leaks? Does it seem to be stickly throttle percentage based or could it be RPM or Manifold pressure (boost) based?

[Medusa]

At what RPM does this occur? If it feels like it has no power at 1500 RPM at full throttle, well that's because it doesn't. You're drowning the engine if you're at WOT at low RPMs. Its better to ease your way up to full throttle.

[jesse0880]

The more throttle I give it, the slower the acceleration and at full throttle its like no power with hesitation. If I drive across town at half throttle I couldnt tell the difference. Its when I wanna get to 12 psi is when the motor says no! I checked the plugs and all are normal except #4 is black. wtf?

[MR2BOY23]

Change the plugs

Check your air/fuel filter

[warhawk]

change out the plugs, sounds like you probably have a vacuum leak as well.

[PinkTaco]

check for vacuum leaks and adequate fuel pressure

[mr2181]

check #4 wire, under load,which in your case is at 3/4 to full, it could be arcing or grounding out..rotor cap, button???

[MR-3sgte]

Originally Posted by mr2181

check #4 wire, under load,which in your case is at 3/4 to full, it could be arcing or grounding out..rotor cap, button???

If it was grounding it would do it constantly no matter if hes at 20% throttle or 70% throttle id check your cat to see if its clogged mr2's are known to burn and consum oil and if your burn it all that oil cakes up on the cat.

[CJMR2T]

Originally Posted by MR-3sgte

If it was grounding it would do it constantly no matter if hes at 20% throttle or 70% throttle id check your cat to see if its clogged mr2's are known to burn and consum oil and if your burn it all that oil cakes up on the cat.

Not necessarily true... I've seen tons of cars that would have misses and start breaking up under higher loads and was due to plugs and or wires...

The voltage output from a coil varies with load. Under light loads, BMEP (Break Mean Effective Pressure) (cylinder pressure basically) are low thus it doesn't take much voltage to jump the gap. Under high loads the BMEP is much higher thus requiering muvh higher voltage to jump the gap.. It is very possible to have a small crack that with low voltage will not arc though it to the Head or where ever, but as load increases and thus voltage requierments increase, the voltage could easily be high enough to arc though the crack..

Remember, Voltage finds the easiest path to ground. So under low loads it could very well be easier for this path to be though the plug but under high loads though the faulty spot in the wire.

Seeing as how he originally said that the ignition components were all new then in a later post said he checked the plugs and found #4 to be black, the first place to look is ignition components. If it were clogged cat, yes this would hurt power but it wouldn't cause 1 cylinder to faul a plug (really fast from my assumption) sound more like a missfiring cylinder which gets worse as load increases which most of the time is an ignition problem.

[MR-3sgte]

all the black suit you find on the 4th plug could be from un burned fuel the spark plug could be cracked or not getting any spark at all also causing more fuel to enter your cat destroying the cat. IMO who cares about the cat were obd1 where i live for any obd1 vehicle i inspect it visualy and a gas cap test as long as theres a "big bulky looking thing" along the downpipe or your exhaust it counts as a cat.

[dualsportdave]

It isn't an MR2, but my 88 Celica All-Trac (also used the 3SGTE motor) - It was throwing a code 53 for a knock sensor. I believe the timing was always retarded too much, it had decent power, but if I floored it, it would hit fuel cut too easily (which then feels like someone turned the car OFF - very disconcerting when passing..) - Check base timing with the jumper in the check plug. Also read the codes on the dash - series of flashing lights on pre-96 vehicles. My car had a JDM motor in it from a previous owner, don't think it was ever right completely.

[jesse0880]

There is not a cat on the car, and I put new plugs in and let the car idle for about 5 minutes and the pulled the plugs again. #4 had wet fluid on it. hard to tell if it was oil or fuel. could I use a timing light to see if there is any spark going through the plug wire? I ohm'd it out and its with in specs but I want to test if spark is flowing all the way through the wire.

[MR-3sgte]

Originally Posted by jesse0880

There is not a cat on the car, and I put new plugs in and let the car idle for about 5 minutes and the pulled the plugs again. #4 had wet fluid on it. hard to tell if it was oil or fuel. could I use a timing light to see if there is any spark going through the plug wire? I ohm'd it out and its with in specs but I want to test if spark is flowing all the way through the wire.

Ok jesse lets take it back to basics. Gasoline evaporates oil and coolant dont thats what your finding on the 4th plug. Try a compression test on that 4th cylinder sounds like a bad head gasket to me. If you want to test the spark take out that 4th spark plug connect it to the 4th plug wire and ground the electrode of the spark plug on anything that is metal (preferably the valve cover) while having someone cranking the motor over if a spark jumps youve got spark to that cylinder. Any other questions pm me.