KA-T Once warm will not boost
 

Hello, I need some insight on what may be going on with my KA-T.

When you first start the car and drive it the car will run and boost fine through all gears. Once the car gets warm the car will no longer boost, you can slowly accel to redline and the car drives perfect, just won't go into boost. Car does run rich.

I have done almost all basic checks, no vacuum leaks, no boost leaks, maf reads ok, distance from maf to turbo is ok all other sensors check out, fuel pressure is good, timing is good, swapped distributors.

Has anyone come across this issue?

Its a 97, stock motor, isis turbo kit, Z32 maf, 255 pump, enthalpy tune, HKS555 injectors.

I have had 3-4 different people look at this, one of them has worked in a shop that has done full build on cars, one owns a body shop/ repair shop, and I work in the service department at a dealership, we are not kids and not dumb, just getting owned by a little 4 cylinder Nissan. Please toss up some ideas, I miss driving this damn car.

Thanks for any ideas

Bryan

Have you checked for CEL codes? start there and post results.

My scanner wont read, it has a obd1 computer in a odb2 car. has the conversion harness.

Dont need the scanner. Just turn the reset dial clockwise on the S13 ECU for a few sec and turn it back again while they key is on positon not started.

U might have your vacuum for the waste gate wrong

That wouldn't cause your car not to boost. If anything you will be overboosting.

Ill try the code check.

Internal wastegate.

Making a turbo not boost is pretty hard
A broken shaft
stuck wheels or binding
and stuck open flapper
Big boost leak
etc.
If you haven't check the turbo yet? I would start there.
There's usually some sort of sound associated with those scenarios.

Its feels more like an ignition issue as opposed to the turbo malfunctioning. Its a brand new turbo.

Cracked manifold?

This is a Mechanical issue.....No electrical issue can keep your engine from producing exhaust gas. That is unless it does not run. You metioned only when it gets warm, I would check to see if the turbo is binding. I have seen brand new turbo's that are out of tolerance. Thermal expansion would be a explanation for this. Good luck problem solving!

Definitely start there...

That's true most mechanical issue you have some sort of audible noise.

Often in your scenario. Check for codes, Verify connectivity to the critical sensor specially since your using a conversion harness. Even that I'd double check.

Most cracks are hairline cracks and dont usually stop anything from boosting. Crack manifold early signs are exhaust leak noise but still boost with no issue.

You'll be surprised most of this are actually electrical problems where the ECU is running on safe mode. This is why it's critical to check for CEL and verify what it's complaining about. Possible sensors that can do this is your MAF, CTS, KNOCK, GROUND, BAD Connection on ECU, BAD ECU and etc..

Ill check it out the turbo. If it is the turbo this will be the second bad new turbo. If it is that add a +1 to the tally of people getting burned by cheap knockoff turbos.

Just found coil voltage is dropping upon accel.

Didn't you say timing is good? If you are dropping voltage the ecu should throw a code, and probably retard timing. This should not stop you from building boost. maybe a brick wall feeling but zero boost no!

How is your dash light at night? Is it a lil dimmer than usual? It might be a charging issue? Voltage drops only through accel? Idle issues? Could be alternator on its wAy out?

Found voltage into the coil was 10.7v, removed an alarm that was installed on the voltage was now 13+v car ran awesome for about 5-10 min then started falling on its face again. Now the output voltage of the coil is 10.5v. This is no fun.

Alternator? Low voltage equals high latency of injectors and low coil output.

Alternator voltage stays constant.

Hmmmmmmm. Only when warm....... One of those I would have to see.

The car is driving longer before messing up, but the ignition check wire pin #1 loses voltage as rpm increases. It goes down to 10.4 volts above 4k rpm. All grounds have been checked and alternator has good output. A new wire has been run, starting to think the ECU may be bad. It is a s13 ECU with a conversion harness to a S14.