Basically the situation is this. My Rx-8 was equipped with the Zex wet shot system. Most of you are probably familiar with how it works. Its solenoid operated during full throttle situations.

One day after using nitrous, the solenoid stayed stuck in the open position, continually spraying nitrous without my control. I tried to pull the car over as fast as I could to shut it down, but my upper intake manifold exploded and the only thing I could do was call a tow truck.

I replaced the UIM and all the other broken plastic bits. I even had to replace the throttle body because the butterfly valve had been bent during the explosion.

The car starts right up, but holds idle very very poorly. The car is AT, and will even stall when putting into drive. Once you get driving, it seems to behave normally... there is not a noticeable loss of power but the motor begins to make a "growling" noise around 5krpm+

I am going to replace the plugs today and check the oil for shavings. I understand there is a good chance the engine is screwed... but nevertheless I want to weed out all the simple things first.

Does anybody have any suggestions to what the poor idle, and growling noise could be? I know that loss of compression symptoms include hard starts and marbles in a coffee can, but my rx8's issues seem to be different.

 

HOLY Crap!

Damn dude.

I throw a couple of things out there (just spit balling here)
Check the maf screens
Maybe Jet air hoses in the LIM blew off

Sorry it's not very helpful and you likely already have checked

Man, jeeze wow .. I dunno but it doesn't seem good.

Please keep us posted.

 

Can you moniter engine info? If not get an obd dongle and the torque app. That way you can check a few things like your maf g/sec and fuel trims.

Beyond that I don't have a clue. Hopefully it's not major.

 

I highly doubt the solenoid got stuck, you probably just sprayed under 4000RPM. The UIM exploding with nitrous on automatic RX-8's is known to happen when you spray at too low of an RPM because the fuel pools.

Ask EasyE1, back in the day I think he went thru 3 upper intake manifolds. The best way to set it up is with and RPM activated switch. When I had nitrous I just didn't arm it (switches conveniently located) until I was swinging past 4000RPM or so.

 

got any "done blowed up" pics???

 

Nope, I totally just got screwed with a faulty solenoid. I had to shut the bottle off to get it to stop spraying. It was still spraying with the car off on the side of the road. I did my research and was always cautious about the 4k rule.

Still trouble shooting btw, plugs didn't help, no shavings in the oil.

 

have you disconnected the battery during all this? Make sure the gaskets are in good order? Vacuum actuators on the UIM good to go? Poor idle typically is a vacuum leak. But with an issue like this you have to eliminate things one by one. Also make sure the lines on the lower intake manifold are still in place.

 

cracked/broken apex seals are a possibility, a compression test is what you need to determine internal seal damage or not ...