I have a 86 n/a Rx-7. I did a turbo swap with a freshly rebuilt s4 engine. I change all vacuum lines and hoses, spark plugs and wires, fuel filter, adjusted tps and replaced it, water thermo sensor, intake temp sensor, n318 afm, n318 map sensor, s4 turbo ecu, injectors, fuel pump relay, changed all gaskets, oxygen sensor, checked all 1 way valves, oil metering pump, checked manifold linkage, cleaned all grounds and checked the timing. The car has trouble starting and has a rough idle. When cold it has a really hard time starting and I have to pump the accelerator pedal for it to start. When accelerating it has a little bucking but otherwise runs good. I have been messing with it for a while now and cant figure it out. If you know what would be causing this any advice would be greatly appreciated.

 

Seems like a vacuum leak, but everything always does.

What RPM does it buck at?

 

It bucks at all rpms and when im going up hill or accelerating it get a lot worse probably very noticeable to other drivers. I changed all the vacuum lines on the car still made no difference.

 

Check timing. Sounds like ur off a tooth. Highlight your leading timing mark, make sure you're looking at the correct mark. Make dbl sure it's the correct mark.

 

Also do a fuel pressure check.

 

Im using the n/a fuel pump will that make any difference? I checked the timing and its good. I don't have the knock box on installed either. Does the turbo model have an atmospheric pressure sensor like the n/a model?

 

check your spark plug wires for correct sequence?..Shhh..it happens..

 

are which harness are you using for the engine?.
the N/A harness that the car came with or a S4 TII harness?

 

since a compression test does not really require much time or effort you should just start there before possibly running around in circles.

we all want to think we can build a perfect engine, truth is that doesn't always happen no matter how much attention you pay to the process.

 

Im using the s4 turbo harness... I had to move a couple wires to make it work.

 

I did a compression check to make sure all was good it had 3 even bumps on front and back rotors and plenty of compression. Im pretty sure its something electrical or fuel related causing it to do this just not sure what.

 

If I hold the accelerator peddle to about 1/4 throttle it will start fairly easy then when I let off it will it will die or have a week bumpy idle at 700 rpm.

 

grab a can of carb cleaner and start hosing down the intake systems to try and track down any leaks. it sounds like you have a rather large leak somewhere.

 

Ok ill give that a try. I got part of the problem figured out today. I had a bad water thermo sensor on the water pump housing. Still doesn't start the best, but its a little better