Running on one rotor...maybe?
 

Ok, this isn't about my car, but it is bothering me that I couldnt' figure out what was going on.

Mods:
Single Turbo
Big fuel system (850/1600)
PFC
..and everything that goes with that.

Symptoms:
-Rough idle, sometimes dies just for fun
-Slow to rev
-Horrible Sound (like it's on one rotor)
-Undrivably low power

Tests:
-Thinking it was a fuel problem, injectors were tested. They're getting gas (and upon unflooding, gas would shoot out the spark plug holes)
-Spark issue? Got spark. Thinking it was running on one rotor, we wanted to figure out which one. Removed leading plug wire from front rotor, started and sounded the same as if we had left it on. Removed leading plug wire from rear rotor, started and sounded the same as if we had left it on. WHAT?! So each rotor sounds like it's running on one rotor, but they are both able to run, but it sounds like one isn't.
-Compression? Sounds strong, very strong. It's a recently rebuilt motor with proper break-in and tuning. But what the hell, we dumped some ATF in there. Started and ran the same, with the requisite white smoke-field.

Thoughts? I'm at a loss for this one.

So you haven't done a real compression test yet?

Map Sensor?

No, but we both know what bad compression sounds like, and it doesn't.

No :gay:

I would do a real compression test, sound is hardly something concrete to go by.

I would too, but thinking outside that box, whatcha got?

I'd say this would be a good place to look, if you haven't already reviewed this thread:

https://www.rx7club.com/showthread.p...ighlight=rotor

Hyperite, I'm not one to hold a grudge or be sore about something for long, but in this case, I just couldn't resist :D

(of course, substitute w/ the appropriate link: http://www.fd3s.net/compression_test.html) :p:

But seriously, #s don't lie. It can't hurt to run the test real quick. At least you can rule in or rule out something real quick. Hope it turns out to be somethin small :)

EDIT: That quote's from here, in case you're wondering: https://www.rx7club.com/3rd-generation-specific-1993-2002-16/check-engine-light-w-severe-power-loss-when-gas-advice-needed-424868/, post #16

GTFO. I don't want your opinion, I don't want your advice, I wouldn't care even if you knew the solution 100%.... I just don't like you.

Not my car, and I'm not going to pay for someone else's car to get tested. But I'm sure you were just waiting for the opportunity to jump down my throat, so congrats.
:bigthumb:

Fouled plugs can cause this, change them.

Brand new plugs, and I don't know that they would. Each rotor runs independently, and should be at the same time too, but i have my doubts.

Awww...you hurt me feelings :rolleyes: PMSing a bit, are we? :p: Sorry...you post on a public forum, you're gonna get replies from the public. That includes me. ;)

Pay? You can do it yourself! For free! What's the gauge cost at Advance Auto/Autozone? $2?

No, actually I saw this by accident and just found it incredibly ironic that you were doing exactly what you were chastizing someone else for doing. Pure coincidence. But then again, everything tends to come full circle, now doesn't it? ;)

Oh, and the whole waiting to jump down your throat...hmm...sounds like you have me confused w/ Jim :)

i got a good little check for you to do,,,pull spark plug leads off the front rotor,,,and try start the engine up,,, then unplug the back rotor and replug the front,,,, if one rotor isnt working then you will find out which one it is this way,,
If what you saying is right it will only run with the plug leads on 1 rotor,,, to be honest though mate if you have spark theres only a couple of options it can be,,,,and im willing to bet its got low compression,,,,has the engine just been rebuilt?

https://www.rx7club.com/attachment.p...d=117011&stc=1
Long time coming.

Yeah, that's the check we did. Rear rotor runs with the front leading wire off. Front rotor runs with the rear leading wire off. But then plugging them both in sounds EXACTLY THE SAME as it did when just one was connected.

The engine was rebuilt a few months ago, and I'm very confident that the compression is fine. Been around enough good and bad motors to know the feel and sound of a motor that should be running.

Glad to see you got thick skin :rlaugh: You shouldn't dish out what you can't take. Typical internet super-egos. Why am I not surprised... :rolleyes:

sorry forget to mention,,,id unplug both plug leads on front and back,, not one like you mentioned you had tried. if it runs on both rotors,,,then it cant be compression

can i ask has the engine just suddenly gone like this over night or is it because of something that has been installed recently

No chance in hell it'll turn over with just the trailing plugs hooked up, so no need to yank 'em both. Again, yes, compression does not feel to be an issue.

Suddenly...while driving, I'm told (no boost)

have a check of timing sensors ,,,make sure clearance is ok and all plugs clean and everything , all wires ok (hows vacume off engine)....... the only other thing i can think of other than timing sensors ,,,is a massive overfueling problem .. but i cant see why that would suddenly just happen, have you checked fuel pressure at the fuel rail?
maybe its like one of the guys said-> the MAP sensor,,,maybe unpluged broken wire or broken unit,, ( i read that when this thing fails it causes really bad over fuelling and poor engine running) have you tried pulling engine check light codes?