My Rx7 runs quite odd I start it it runs i have gotten it to idle perfectly at 750rpms I rev the engine it gets upto 2500rpms and it spits and sputters and won't go past 2500rpms idles fine won't go past 2500rpms and back fires

 

Ok here's some more details i have 2 rx7's one was newer but bad body shape and the radiator was ready to go but wasn't sure when so decided to drive it anyways as we all know the rx7 runs hot to begin with and when the radiator blew up on the highway there wasn't anything i could do to save it except start all over so that engine is in the garage waiting rebuild the problem i have is the new engine does the described stuff above i was looking around in the engine compartments of the two and relized that the resistor that hooks directly to the fuel injectors had been some how bipassed so i figured well peice of cake take the wiring harness of the car that ran flawlessly and stick it on the new engine and it should clean up the problems maybe..............not the case now i have a completely dead engine is there something i could have hooked up incorectly or are there difference's in the harness's on the 2nd gen's i'm not sure where to go from here if i put the old one back on i doubt the fuel starvation problem is going to go away please help

 

What year are your RX7s? S4 and S5 harnesses are different.

 

the one that has the unchopped harness is a 87 and the one that has a chopped harness is a 86

 

You should download the FSM and make sure that you hooked everything up properly...

 

Both of those are S4, so they are interchangable.

 

where in the FSM would that be?

 

OK i feel like an idiot now i went ahead and looked over the harness and realized i missed the most important thing the ground wire the only major problem i'm having now is with it idling it doesn't die it just idles really funny and from high rpms it drops to almost 500 and the ecu thinks its dead but then it jumps back up there (this is with the clutch pushed in the whole time) but once it trys to idle its up and down all over the chart 1500 750 sometimes 500 and its hard to get control of it with the mixture so i don't believe thats it.......