bogs/falls on it's face when under hard Acc./boost

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bogs/falls on it's face when under hard Acc./boost

Postby Schneidy95 » Tue Sep 03, 2013 6:06 pm

Well Everyone I did weeks of research on this problem and still wont go away. I recently got a 91 all trac turbo( i'm a newb).
From the day I brought it home it has been not accelerating right when throttle around 50% When I acc. slowly through the rpm's it looses a lot of power around 5,500rmps and higher, but is smooth till then. When acc. more than 50% throttle it will hit a point were it just stops acc. quickly, and feels like its not getting enough fuel/air/getting rid of burnt fuel(exhaust) or the timing is retarded. :shrug:

It has a 3' down pipe and stock exhaust but the cat is gutted.( I am missing a header bolt) I changed fuel filter, checked for vacuum leak with carb cleaner. I disconnected TPS, but weirdly the running of the car never changed, even idle with it disconnected. Like it was never working in the first place.. I did install a MBC, Disconnected T-VSV. I checked the TVIS flap/door and seems to open and close fine. I also checked plug wires. The car boosts just fineI run premium fuel.

All in all Idles fine, but when acclerating quickly or when making boost, lets say more than 2-4 psi or 50% throttle car jumps/looses some power/bogs. sometimes in lowers gears 1-3 it will lurch like it has lots of power, then stop, then lurches again shaking the car and almost giving me whip lash. I'm at wits end here..

I thank you for any help in advance and appreciate you for taking time to read this long post. -Jacob
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Re: bogs/falls on it's face when under hard Acc./boost

Postby underscore » Tue Sep 03, 2013 6:51 pm

Schneidy95 wrote:( I am missing a header bolt)


Fix this first, if it's leaking it will cause issues.
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Re: bogs/falls on it's face when under hard Acc./boost

Postby Schneidy95 » Tue Sep 03, 2013 7:33 pm

It does seem like its leaking because of the black exhaust residue on the block. Ill start with that tonight. thanks
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Re: bogs/falls on it's face when under hard Acc./boost

Postby Schneidy95 » Tue Sep 03, 2013 8:52 pm

Its the stud all the way right. (The last one) the turbo is in the way of getting a drill on it.. The whole thing must have to come off? as in everything from the header down. So take off the 4 bolts from the headers.. The the five or six connected to the down pipe? Or is there an easier way. Thanks
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Re: bogs/falls on it's face when under hard Acc./boost

Postby underscore » Tue Sep 03, 2013 9:11 pm

The way I did it (I had the opposite stud broken, far left) was drain the coolant, pull the rad (2 bolts, 2 clamps, 1 plug), unbolt the downpipe from the midpipe (3 bolts), unplug the O2, unhook the oil/water lines at the turbo (4 nuts, 2 bolts IIRC), unbolt the manifold from the block and pull it all as one unit. Order new gaskets for where the oil and water lines meet the turbo, for the small cost it's worth not having to redo the whole procedure again should they leak alter on. Then drill the stud out, tap and helicoil the head, put it back together with a new stud. You might want to replace the exhaust manifold gasket as well, the leak might've ruined it a bit.
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Re: bogs/falls on it's face when under hard Acc./boost

Postby polm » Tue Sep 03, 2013 10:39 pm

I had a problem extremely similar to yours when I bought my car. Make sure you have proper boost control (either the stock tvsv or an aftermarket boost controller) and unplug the map sensor which is located on the firewall next to the ac idle up valve (it says: "sensor assy map" on the sensor). Plug the vacuum line that goes from the intake manifold to the sensor with a screw. Unplug the battery or pull the efi fuse for a couple of minutes to reset the ecu and go for a run. If the problem is gone then your map sensor is bad. Replace it with a stock one or leave it this way if you want to completely remove fuel cut (not recommended if you don't know what you're doing). It is important not to unplug the electrical connector from the sensor as the ecu needs a reading from this sensor to work properly or else you will go into limp mode. By setting it up this way the ecu will always see the atmospheric pressure as a signal and it won't affect your acceleration. Since the map sensor is solely used for fuel cut in the car's stock form, the only downside to this will be no extra security for overboosting. This is exactly what a fuel cut defender does though the fcd lets you keep a fuel cut since it only alters the voltage the ecu sees without completely removing it like the test suggest. It worked for me. Try at your own risk.
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Re: bogs/falls on it's face when under hard Acc./boost

Postby Schneidy95 » Tue Sep 03, 2013 11:45 pm

The only sensor i can see from what your explaining says (sensor ass. Turbo) and has a vacc. Line coming from the bottom but doesnt go to the intake. Like in the picture. But the ac idle up valve (the one with the screw) has a vacc line going to the intake man.If im looking at the wrong one let me know please.
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Re: bogs/falls on it's face when under hard Acc./boost

Postby polm » Wed Sep 04, 2013 12:27 am

Schneidy95 wrote:The only sensor i can see from what your explaining says (sensor ass. Turbo) and has a vacc. Line coming from the bottom but doesnt go to the intake. Like in the picture. But the ac idle up valve (the one with the screw) has a vacc line going to the intake man.If im looking at the wrong one let me know please.

Yes that's the one and yes it goes to the intake manifold check behind follow the line and you'll see.
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Re: bogs/falls on it's face when under hard Acc./boost

Postby Schneidy95 » Wed Sep 04, 2013 1:35 am

Well that didnt work. I didconnected it by the little filter or plastic jet. And just plugged both ends with screws and zip ties.
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Re: bogs/falls on it's face when under hard Acc./boost

Postby Rpz123isme » Wed Sep 04, 2013 2:10 am

Dont unplug the electrical portion of the pressure unit. Only the hose side. And it sounds like you unhooked the wrong one. The pressure uniy only has one vac line going to it
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Re: bogs/falls on it's face when under hard Acc./boost

Postby Schneidy95 » Wed Sep 04, 2013 2:33 am

Yes, there is a single vaccuum line going out the bottom of the sensor. It runs along the fire wall and is one of 3vac. lines that go to the left side of the intake man. I did not unlug the sensor. I ony spliced the vaccuum line and plugged both ends. The stock boost gauge does not work now. I belive that is supposed to happen.
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Re: bogs/falls on it's face when under hard Acc./boost

Postby polm » Wed Sep 04, 2013 3:20 am

Well its not supposed to work if you disabled the tvsv like you're supposed to when you install a boost controller...go read the write up about installing a boost controller, you need to cap the line that goes from the wastegate to the tvsv. If you did that correctly then the boost gauge wont work anymore and therefore your boost controller will be the one controlling your turbo pressure. To me it seems like that wasnt done correctly therefore the boost controller and tvsv are interferring hence the bogging. Oh and btw its important that you dont disconnect the electrical connector on the tvsv, the ecu needs to think that its still controlling boost or else it'll act strangely. Only cap the vacuum line or else it wont work. You have to cap the line on the wastegate too.
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Re: bogs/falls on it's face when under hard Acc./boost

Postby underscore » Wed Sep 04, 2013 4:40 am

If you're having issues take out the MBC and put it back to stock, if that fixes it your MBC install was wrong, if it doesn't then your problem is something else.
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Build thread http://www.alltrac.net/phpBB2/viewtopic.php?f=44&t=44216
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Re: bogs/falls on it's face when under hard Acc./boost

Postby Schneidy95 » Wed Sep 04, 2013 2:45 pm

underscore wrote:If you're having issues take out the MBC and put it back to stock, if that fixes it your MBC install was wrong, if it doesn't then your problem is something else.

Its done it since i got it. It was stock then.
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Re: bogs/falls on it's face when under hard Acc./boost

Postby Schneidy95 » Wed Sep 04, 2013 3:10 pm

My temperture guage doesnt work inside the car. Could that be putting it into cold mode?
Here are some pictures. Second is the map assy that i did last night. I spliced and caped both ends of the hose. I didnt unplug anything. Next is the tvsv . Also didnt unplug anything, just spliced and pluged both ends. The fist one is MBC. But like i said this problem was right away when i got it. All it had was a 3'dp and the temp guage in the car doesnt work. And diff. Air filter.
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