So i have a 87 T2 with s5 manifold and turbo
block off plates
blitz bov (does not seem to want to work...)
intake
Exhaust 2 1/2 no cats 1 resonator
a new Bac ( turning the screw does nothing)

not sure what else i just got the car a little while ago

So i start the car it will idle around 2k and pull 16 on the boost gauge
then after about 20 sec it drops to 1500 and jumps burrrmbrrum to 1800
so just back and forth 1500-1800

When i start to move (step on the gas) its smooth no stutter no drop all the way through and accelerates beautiful its just at idle it has problems boost is at 5 no spikes no drop just solid 5 (which i thought was low for that turbo?)
I have been trying to figure out what this is and no luck.

like i said above new BAC timing is done tps right not sure what else to do i got the car this way, guy before me had no idea what to do with anything on this car.


Ben

 

This is almost always a vacuum leak or TPS issue. If you still have the stock TID (turbo inlet duct), it's notorious for cracking and causing a rough idle.

The wastegate spring in both S4 and S5 turbos is rated for ~6 psi. You need a boost controller to raise the level, and then you need a new fuel pump, injectors and ECU.

 

Okay ill check the TID and maybe replace all the hoses to see if its a leak.
I was thinking that since before i had it the car sat for a while.

Also i forgot it has a walbro 255.

If i can fix this idle soon my next plan is rtek 2.1 injectors (720s) and intercooler

thank you for the fast input

 

Use propane or Carb Cleaner or something similar to find a vacuum leak. Also set the TPS to 1 volt on the Green/Red wire after the car is "completely" warmed up.

 

After fixing/ruling out any vaccum leaks.

I would suggest setting your timing with a light, adjust the idle via the idle screw, adjust the throttle cable tension, let it warm up and then set the tps with the test light method.

That searching idle is most likely timing and/or your TPS being out. <-- if not a vacuum leak

 

Okay this weekend i will be replacing all the hoses and checking timing and tps as well. since im throwing the front mount on it should be easier to get to everything.

Thank you again.
oh and i can spray carb cleaner all over and nothing bad will happen?

 

You may also need to adjust the variable resistor to smooth out the idle. The walbro pump will raise fuel pressure, and make the car idle extra rich at 10-11 AFR (with the stock FPR that is). In the short time I had one, I had to adjust the resistor all the way lean.

 

Hmm okay i never thought about that but i was thinking it ran a little rich too
ill do that as well would that change my idle tho