10 Pounds boost 4500 rpm cuts out

[Jer1471]

Hello everyone,

I live in Juneau Alaska and have the only mr2 turbo second gen in town... I've been havin probs with the mechanics ever since i picked it up... It is mech stock except for down pipe and headers. I have spent more than I care to admit on trying to fix the prob of it cutting out at 4500 rpm and full boost. Just as it starts to get fun I have to let of the thortle. Its drivin me nuts!!! Juneau is a town of 29,000 and we do not posses a dino machine to test it while the turbo is kickin on... Mech told me to change the fuel pump and that did not help any... Then the brain box... no good... I am able to push it over 4500 rpm if i go into it with lower boost but as soon as it hits ten it cuts out and jerks back and forth like some one learning to drive a stick. I love the car and want to upgrade it and keep it for the long haul but cant seem to fix this prob... Its been a year now and I wanna have some fun this summer... It does have high miles 165,000mi but 121,000mi of the those were from the old man that bought it new in California.... He moved it to Juneau and stuck it in his garage... Unfortunatly another kid got there before I did and drove it with out keeping up the mantinace very well.. He also did a really crapy job of installing a boost gauge on the dash.... Could his shoddy work have anything to do with it? Well any help would be greatly appreciated... The boost works fine at the lower RPM's it reads 10 all the way to about 4500 rpm...
Thanks all,
The Alaskan

[todd0305]

I think that you are experiencing fuel cut. Normally the stock CATs (catylitic converters) and your actuator limit the boost to 8psi. But since you have a down pipe, the engine is breathing better so you are getting a little boost out of that. The ECU is sensing that you are boosting high and shuts off fuel to the engine to prevent damage. Stock turbo can go up to about 14.5 if you get a boost controller and a fuel cut defenser to prevent the fuel cut. You can buy an eletronic boost controller for about $250, but you can also make one out of stuff from a local hardware store for about $20, and an FCD for about $100. I would recommend upgrading your fuel pump and injectors. Stock ones are 450cc but you can buy used supra ones. They're 550cc I believe. The boost gauge measures boost from the turbo, so it does not contribute to your prob. Hope this helps

[MR2Jedi]

Yep, sounds like fuel cut to me too.
here are some options. I would go fot the free one.
In order to prtect the engine from over boosting,
the factory ECU cuts fuel at 12 psi of boost.
It's a sudden, violent break in acceleration called "fuel cut."

In order to boost higher than 12 psi, you need to address fuel cut.
These are your options:

$99 - HKS FCD - if used properly, raises fuel cut to 17 psi. Most people have it set up wrong and it eliminates fuel cut completely.

$99 - GReddy Boost Cut Controller - completely eliminates fuel cut.

$7 - Build your own FCD with Radio Shack parts

FREE - plug the vac line going to the OEM MAP sensor. This completely eliminates fuel cut and it also stops the stock boost gauge from working (it's a worthless gauge anyway).

Now you have to decide. Is the HKS FCD something you want?

[Jer1471]

Thanks for the comments. You dont know how excited I am to try out your suggestions. I've been trying to get it running right for to long.... I will post again after I give the Fee option a shot... Thanks again guys!

The Alaskan

[Jer1471]

Well it turns out that wasnt the prob... I took it back to the shop and we are going to see if a new distrubuter helps it any... They are also going to test the blow off valve and coils... Well its back to the drawing board... Thanks for you insight though.

[Gairloch]

How did you test it?

You might want to research this a little further and see if you can't get a more solid lead. Throwing parts at a problem until it goes away is a very expensive method of diagnosis.

If your car has a BOV that's not stock. It should have an internal wastegate if I'm not mistaken. (I'm more of an NA guy.)

Has anyone ever seen faulty ignition components lead to behavior like he is describing?

[MR2Jedi]

nope....

[Mike@Fidanza]

are you sure you plugged the right hose?

did you try unplugging the sensor?

here is a pic and some info on the sensor.
http://www.mr2-tech.com/bgb/mechanic..._0488_0001.jpg

i'm sure you probably allready know about this site but i'm going to to post it just in case!
http://www.mr2-tech.com/bgb.htm

Hopefully one of these links will help!