1987 rx7 n/a

This is a brand new rebuilt engine, and when i fire it up it runs as long as i give it gas and keep the rpms up slightly, but it will not hold an idle.

Besides issues with timing and a vacuum leak, what else could be the cause of this kind of behavior?

note: Installed a brand new wiring harness from mazda (don't think that really affects anything but throwing it out there just incase).

 

Is it a factory reman, or did you have someone rebuild it?
Is it hard to start after it cuts off?

 

i vote vacuum leak, there is so much stuff you have to install on the engine, that its rare that everything is happy right away. its probably something dumb, like an unplugged AFM or loose clamp or something.

the TPS and timing are probably off too, which doesn't help, but hard to set on a cold engine

 

I rebuilt it, with a compression ratio of 7:1 in the front housing because its used and 8:1 in the rear. Fires up easily enough as long as the engine doesn't flood after i turn it off.

Could it perhaps be something on the intake that i need to adjust?

 

Yeah i figured the tps might have something to do with it. Ill try to adjust that.

Anyways, thanks for the feedback.

 

Fresh used housing rotary builds do not run 100% normally right off the bat. It is common to have to bump up the idle to the 1200-1500 range to keep them running stable for a few days or weeks until compression comes up some. If yours does not want to idle at 800, then don't try to get it to, raise the idle to 1500 and put some miles on it, then revisit the idle adjustments in a month or 2.

 

Noted, thats really helpful thanks.

 

Fix the vacuum leak and half of your troubles go away.
Case and point: I missed a vac line on my N/A and it would sit at 1200 with a lopey idle..
I found it,fixed it.BOOM! 800 Rpm,rock solid.