Please diagnose this problem

[blitz]

I just got a new turbo and 3 inch turbo back exhaust. then I run into this problem. car is 1985 S12 200sx CA18ET.


OK, when I 1st start the car, it didn't go to the warm up mode at all. then the vacuum on the boost gauge is not at the very left but at the left edge or middle of the 1st bar on the vacuum side. I have autometer boost gauge, and before I got this new turbo and exhaust it always goes to the warm up mode and vacuum reads at below 20 (20-22) in-Hg on the boost gauge. now it's between 15-12 in-Hg when the engine is cold. when the engine is warm it's fine. Today was a cold and rainy day, so it should go to the warm up mode.

then there is the drive/cruise problem. it feels like the car getting too much fuel randomly. It'll buck/miss now and then . it feels like when you just learn manual transmission and you buck the car. not that drastic; it is very subtle but you can feel it (another benefit of blown shocks). it happens at random around 2.5k-3.5k rpm at partial throttle (1/8th maybe) or when speeding up very slowly and the turbo is just start spooling. to me it feels like the car is getting too much fuel.

what can be the problems and what are the solutions?

what does the vacuum pump do? when is it working?

This is what I did monday:

I tighten up the clamps on the charge pipe. I wanted to change that stock charge to TB hose w/ silicone, but it's 2.25 instead of 2.5. so I just tighten the stock one to the max. I haven't got a chance to look at the engine as it rains all day yesterday, and I don't have covered parking space.

[PukkaSilvia]

what turbo is it? new or new to you?

I would say you have an air leak somewhere.

I would also say that it is normal to have a slight difference in vac with different turbos but You may also get issues with cold idle if you have an exhaust blow so have you seated everything well?


but on the other hand you could of knocked something electrical while you were working on the car, check everything,electrical connectors on the air flow meter,ht leads,dizzy cap wires etc

[323ian]

You have an air leak.

[blitz]

thanks for all reply.

turbo is new to me. it's a T25, comes from CA-DET S13. it spools fine though, with no unusual noises. I will check timing because we didn't check it. will also re-tighten all the bolts on the exhaust. will recheck all the electric connectors.

- exhaust blow? what's that?

[PukkaSilvia]

tractor syndrome