Car is an 87 NA with 89 JDM TII engine, harness, ECU, transmission, full exhaust, suspension, lots of goodies.

Last year I had the swap done by a Rotary shop, along with a 20B cosmo fuel pump. After a couple months the engine blew going 130mph on the freeway on a hot day at WOT. Big surprise right? I never actually diagnosed why it blew, I figured because it was stock fuel on a hot day with full exhaust going 130 at WOT.

So another JDM engine got slapped in that they had lying around, this time with 750cc RC secondaries, and an Rtek 1.7.

The car starts up fine, super fast, no problem at all. Goes down idle, and has a poor unstable idle with misfires. When you tap the gas it stumbles before it revs up. It revs up poorly, again with misfires. Just overall through the RPMs it runs rather poor, various little rich misfires here and there. From about 3000-3500 rpm it actually runs quite well and builds up boost but after about 4k it just falls on its face. The car also has terrible gas mileage and the tailpipe smells horribly like gas.

The swap was done by a Rotary shop, everything is very clean and professionally done well. The shop was aware of the problem, but before attempting to fix the problem they put my car aside because they got super busy and I told them it was ok if they put it on the back burner. Well last week they called me and said they are shutting down due to failure to renegotiate the lease of the property because the landlord is being a dick so I had to pick up my car because they had to let all the employees go and close down.

So here I am with this car that runs like snot and wondering what I do next. I have visually and physically checked the integrity of all the wiring and also checked for vacuum leaks. The battery is brand new, the alternator works fine. The timing is in spec. It has fresh 91 gas.

I started probing the ECU and checking voltages pin by pin. The TPS was a tiny bit off but was in adjustment. The MAF (N370) was half a volt off with KOEO, (2V compared to 2.5V+ spec) so I got a used one on the way. But the most peculiar thing was that the pressure sensor (N370) was way off with no vacuum or with vacuum applied. I was getting .6V at the ECU, and it calls for 2.8V-3.6V (depending on test conditions).

Would a faulty MAF or Pressure sensor cause the symptoms I have described? I am also wondering if the pressure sensor is bad and the computer thinks it is under load at all times would it fire the secondaries or would it have to see certain load AND a set RPM in order to fire the secondaries?

Anyways, any thoughts?

Thanks for any help

 

If either the AFM or MAP sensor have incorrect voltage outputs, it will absolutely affect fuel delivery. The secondaries are triggered by RPM and manifold pressure (atmospheric or greater), so you could run into issues where they would not come online if the MAP signal were off by a lot.

 

this reminds me of the "restrictor pill" thing on the Rtek Forum.
It may not be related but just read it and see if it hits a nerve.Ok?

 

Thanks for the replies. So I got a pressure sensor and a MAF sensor on the way. Next week I'll see if they change anything.