Finally got my car running a few weeks ago. It's a '91 with a turbo engine swap. But it's still not quite done, as in coming right off the down pipe and a few minor things. If I accelerate lightly it'll boost enough to blow off through my Apexi BOV and doesn't stumble.

However, according to the boost gauge, at idle, it pulls about 15 inches of vacuum and when I'm cruising it's at about 10, and when i try to accelerate, I can get it to about 0-2 ish psi but if I try to accelerate any more it stumbles and looses power and pops as if it's running rich. Idk.

I front mounted the top mount and I have an Apexi BOV and relocated the battery. I have an Rtek 1.5 chip and a walbro 255. And a downpipe and exhaust. However, at the moment, it's just runing through the DP because I haven't been able to make a pipe to join it to the rest of the exhaust.
Could the lack of backpressure cause it not to boost?

There are a few lines that went to the stock TID which I don't know if the air has to be accounted for by the AFM. And also, there is a check engine light, but when I ground the connector, it doesn't flash to Indicate a code.

And btw, bought the engine from Japan2LA and it runs good and has good compression. It's just being a PITA.

Anyways, Sorry for the long explanation/question. Just could use help figuring out what's wrong.

Thanks a lot, Ben

 

Was the emissions harness used a turbo or NA harness?

 

I used the NA harness and spliced in the necessary connectors from the turbo harness

 

Good deal because if you mated a turbo emissions harness to an NA front harness then it would need to be altered or it would cause problems similar to yours. At least you know this is not contributing to your problem.

 

True. I've been driving it like this and it's getting me back and forth to class. So I guess I can't complain too much. Thanks man.

 

Anyone else? I'm really confused. Going to try to get a wideband as soon as I can afford it so I can get an idea of what's going on. All help is appreciated.

 

check yer ground to the engine. ive had one do that because of a bad ground. also try unplugging yer tps sensor and driving it to see if if boosts normal. if it does, replace tps.

 

Check for codes?

 

I experienced the exact same problem you are having after completing my swap.

Is your chipped ECU an N374(J-Spec) or N370(USDM)?

Are you using the OEM boost controller?

Have you ever wondered why you can floor it while in neutral and you won't hit boost?

It's your neutral safety switch. Get a multimeter and make sure you have it hooked up to the right wires and that it's functioning correctly. If you need help figuring it out let me know and I'll take some pictures of mine to confirm wire colors, etc.

If you do not have emissions testing where you live I would recommend removing the rats nest, air pump, etc. Mainly for simplification of the system.

If you are 100% sure that your neutral switch (on the transmission) is hooked up correctly then I would recommend trying a different N370 ecu in there.

 

More info on the Neutral switch. Black wire is the ground wire while Green/Black goes to pin 1R at the ECU. In neutral, pin 1R should be below 2 volts w/ignition key to on and while in gear, pin 1R should read approximately 12 volts w/key to on.

 

when i try to ground the test connector to check for codes the light won't flash. But I have a check engine light when driving. And I don't believe it's the neutral saftey switch. I may go for a drive and try to take a video of the problem

 

And it's a N370 ecu. And I don't have an aftermarket boost controller. What is the OEM boost controller?

 

OEM boost controller = blue solenoid valve (2 vaccum lines attached to it and a small harness) is with the other solenoids (passenger side behind power steering pump), but it's blue not grey and shaped differently.

I still suggest you check the neutral switch wiring, if you have some ramps it takes about 10 minutes to do.

 

Checking the reading at the ECU should be good enough and it doesn't require ramps.

 

Seems easier to drive up on some ramps then to pull the kick panel, carpet back, ecu cover, etc.

Just sayin.......

 

Ok, yeah I have the blue solenoid/boost controller hooked up. However, it is one of the things I had to splice in and therefore, although I am 90"ish" % sure I hooked it up correctly, I could have made a mistake.
And as far as the neutral saftey switch, I have ramps, however I'm also lazy and therefore neglected to put the kickplate and carpet back down till I knew everything was working so I could check either place. I guess I'l look in the haynes or FSM and check it.
Also I have an aftermarket FPR that was on the car with the NA engine. I tapped a s4 fuel rail and put barb fittings in it and modified the brackets on the s4 rail and then, although not ideal, I JB welded them on in the right spot. But now, having the turbo engine, I would like to be able to run my FPR but need a fuel rail. Anyone got any ideas? I just figure running the walbro 255 and stock injectors and everything that it might be getting to much fuel. But thats a lot better than lean.

 

Also check the fuel pump resistor relay according to spec and see if it falls within the stated ranges found in the FSM.