Boost problems

I have a profec b greddy boost controller and a greddy boost cut controller. I can still push the stock boost which is 10 max i think, but when i try to go for 15psi the engine light comes on at 10psi and then wont let me boost past 0 untill i turn the car off and on again. I am almost sure that the problem is the boost cut controller because i have already checked the turbo pressure sensor and ecu. Is there any sort of test i can run to see if the boost cut controller has gone bad? Oh, and directions on how the boost cut controller is hooked up would also be most helpful!

there is a fuel cut on a deuce at 12psi, if ur using the stock bost gauge...its slow so ur prob hitting 12 and dying before the guage can read 12, SEARCH to find out how to get rid of the fuel cut off to boost to 15psi

i have an aftermarket gauge and it only reads 10 when the cut happens. Another MR2 owner i know is having this same problem and we both cant run our boost controllers!

If you simply cork the vac line to the OEM Map sensor, you will eliminate fuel cut for free and for sure. You will also lose the functioning of the OEM boost gauge which is worthless anyway :)

:2cents: You may hit the cut a 10psi because of the weather and location of your area. :2cents:

How would i go about corking the vac lines? i have not been working on cars long and i am pretty new to mr2/imports. Is there anyway that it could be told how to do on this forum, or a web site that i have not found on this mod? I will welcome your replies and help, thanks!

It is very simple.

If you know where the vac line is that leads to the map sensor, pull it off the sensor and stick a screw in it. It's now corked :) ... I would put a hose clamp around it to make sure the screw doesn't go anywhere.

Let me know if you need help locating the sensor.

i looked through out the whole MR2 mannual and i could not find anything to do with the map sensor! Does it have a different name in the mannual? I thought it might be also called a boost pressure sensor. I plugged this up and got the stock boost gauge not to work, but my boost is still cut off at 10 psi, and is a little more sluggish! Im lost!

MAP sensor is the boost pressure sensor.
Corking it will not affect your drivbility.
Did you leave it electrically connected? ... it should only be plugged on the vac line.

Have you cleared your codes since hitting fuel cut?

What i did was pull the hose from the bottom of the map sensor and screwed a screw into the top of the line. It may have seemed sluggish because it was about 101 degrees outside today, and the last time i ran it the temp was about 80. (forgot to take that factor in) Did i place the screw at the right end of the hose?
To answer your question about clearing the codes, I disconnected the battery. I am not sure if this will clear all of the codes, or if i have to do more.
Is there a chance that i might have a vacuum leak, making it unable to push high boost?
sorry for being such a newbie, but i really want to understand whats going on with my car! thank you for your help!

You have the screw in the correct location.

When it is very hot outside, you are very likely to get knock response and the ECU will retard timing and limit boost which will make you feel extremely sluggish. Really hot weather is not fun for turbos.

Do you have a real boost gauge?
If so, what boost are you making?

yes i do. The gauge pushes 5 psi. when my boost controller is on low, and on high it sometimes will push 8, but when it hits 10psi. that is when the engine light comes on and it wont let me push it past 0psi.

I have also noticed that my MR2 seems to be misfireing. I am going to change out the ignition system and see if this will help. The boost seems to be responding well by shooting straight up to ten as soon as I floor it. The only problem is that the engine light comes on and boost is cut! Maybe from the old ignition system?

I have replaced the ignition system and I am still having the same problem! There is also a light that comes on becides the engine light. It is a sort of engine light except the light is red and appears at the bottom right of my cluster. I have no idea what this light means and cannot find it in the mannual. Could there be a relation between the two?

What all did you replace?

Is the red light a picture of the engine with a fan in front of it? If so, that is a problem with your intercooler fan.

I replaced plugs, and wires. So not really the whole system.

Yes, that is the light I am talking about. What happens is that I will get a boost cut and then that light will come on soon after, or the light will come on and then I will get boost cut. Do these two (boost cut and the intercooler fan light) go hand and hand?

You should get a new Toyota Cap & Rotor as well.
What plugs did you use and what gap?

Fuel cut triggers the yellow check engine light.

The red fan light comes on when the circuit is trying to start the fan and it can't.
Have you done anything to your fan?
Does it come on?

Test: Start your car up and unplug the sensor on your engine lid. It's just a little plug. Undo it. The fan on the IC should come on if everything is healthy.

I got the NGK copper tipped plugs, the gap is .028

Yes, the fan is controlled from a switch inside the cab. I did not make this mod the owner did before me.

Good on the plugs.

Does the fan come on?

Yes, its the loudest thing on my car (becides the exhaust)

This would not be the cause of boost cut would it?

what are the most common reasons for fuel to be cut?

could the motor switch over to fuel cut because the fan is not comming on... to prevent detonation ya know?

does fuel cut and boost cut have the same effect, in that the egine light comes on and you cant boost anymore?