jonezey00

So I'm new to world of the wankle. I've been working on cars all my life, but never on these crazy spinning engines. I've had my 94 7 for about 3 weeks now. It is moderately modded and the dyno showed 406hp on 17psi.

here's the problem... Last thursday night an STI wanted to play, so I rolled on in 5th gear and put a quick end to his happiness. Everything looked fine... boost held right at 17 up to about 4500rpm when I let off. I then slowed for an off ramp, and when I got back to accelerating again, it was missing. It was a challenging rest of the ride home being that it wouldnt idle and produced almost no power below 2k. I suspected fouled plugs, but then I looked at the boost guage, and noticed it pulsating. doesnt matter if I am in vaccum or boost, it's constantly dancing in 2lb increments.

I found this in one other post, but when I went to the next page, the page was no longer there. Sorry if this has been asked before, but any help would be much appreciated.

windom

iTrader: (1)

Compression check ASAP. Check for equal 80-100psi ticks on all faces when turning over. I would do the check while changing your plugs.

GoodfellaFD3S

iTrader: (213)

Doesn't sound good.

What rpm are you idling at, and how much vacuum are you pulling?

You were running 17 psi on pump gas?

dgeesaman

iTrader: (7)

I'm very sorry to say that this HAS been discussed before. Look it up under 'blown engine'.

Seriously, when you come down off of a very hard run and get lumpy high idle, super shaky engine, it's usually because the engine spit an apex seal.

Any idea why it happened? More boost than it was tuned for, cruddy gasoline?

Dave

rotaryinspired

iTrader: (3)

Sounds like every blown motor I have ever seen. Good luck and keep us updated.

who tuned it for the 17psi? How old are the injectors, fuel filter, and so forth?

You need to figure out why it blew, so it doesn't happen again.

jonezey00

I will look through my paperwork to see who tuned it. DAMNIT this is not what I wanted to hear. and yea 17 on pump fuel, but it only held 17 until about 4500 where it dropped to about 12-13. Someone asked about where it was idling at and what idle vaccum... always idled around 1000 on the big tach (850 or so on the PFC) and it was pulling about 17 vac on idle.

again knowing nothing about a rotory... if an apex seal is broke, does that mean it's exchanging air/fuel between the 2 chambers that are side by side? and at this point would it be best to pull the engine and send it away??? if the compression test comes back bad of course

GoodfellaFD3S

iTrader: (213)

Find out what it is idling at and what vacuum it is pulling now, that'll help us determine if you blew the motor or not.

That boost pattern you described makes no sense. You aren't running stock sequential twins are you?

tt7hvn

iTrader: (5)

i have seen that a blown spring in a BOV cause a rough idle before but that was is a rare case, the idle was jumping up and down pretty noticably outside the car, but i'm more leaning toward a blown engine.....

windom

iTrader: (1)

I hope not 17 on stock twins, at least with a near stock fuel system.

jonezey00

I'm thinking the only thing that is stock under the hood is the block itself. From what I can see, it has a big *** intercooler, with big piping, it's a T04S I think conversion. Dump exhaust, external wastegate, greddy intake. I will check in the morning to see what the vaccum is at idle (or close to it). All I know is... it got me home, and it still made decent power, not that I drove it hard... just felt like it was missing...

you have all been a ton of help...THANK YOU

windom

iTrader: (1)

You do know the basic maintenance for an RX-7 right? Check oil? Make sure you don't run under 1/4 tank of gas?

jonezey00

again, I'm new to the wankle, BUT, again, I'm a certified mechanic... so yes, I know what to watch for... the oil was checked recently, and the oil pressure was fine.... I'm beginning to think it was just too much boost on pump gas... I was planning on getting an EGT and wideband real soon, but I guess I'm too late... and yes... as with all turbo cars, never had under a quarter tank

jonezey00

ok... so I just went out and started it, and it is idleing on it's own now. Still missing, but doesnt sound completely horrible. It was idleing right around 950, and the vaccum was semi pulsating inbetween 14 and 15lbs. If I revved it up to around 3k, it sounded almost normal, and if held at 3k, was holding 19lbs of vac steady.

someone at my shop was talking about apex seals getting stuck sometimes??? And speaking of squirting some ATF in the spark plug holes like an old car that's been sitting. Any thoughts?

dgeesaman

iTrader: (7)

I wouldn't waste my time until the compression check results are in.

The only thing to check first is the MAP sensor connection, which sits above the brake booster on the firewall. Sometimes that hose pops loose and causes blown-engine-like symptoms.

Dave

GoodfellaFD3S

iTrader: (213)

Hopefully the motor is fine, you may have just chipped a seal.

windom

iTrader: (1)

If he chipped a seal, wouldn't the motor be damaged then? I assume it's still driveable and boostable correct? Just an inconvenience?

GoodfellaFD3S

iTrader: (213)

Sorry, I worded my last post kind of funny.

I meant to say, I hope the motor is fine, but if you did hurt it, then it sounds like just a chipped seal. This means you still need a rebuild but the internals won't be too damaged. He is still making ok vacuum. I would NOT boost the car with a chipped seal, and drive it as little as possible.

jacobcartmill

iTrader: (6)

chipped seal is a nice way of saying you're up **** creek with no ***-paddle (someone already used the *** paddle and paddled your sorry *** for rolling into 17psi in 5th gear at low RPMs)

but yeah, unfortunately, i think you blew your motor, my friend.

RotaryResurrection

iTrader: (8)

Vacuum is a reflection of compression...changes in vacuum usually reflect changes in compression.

mad_7tist

nothing like flooring the car in 5th at like 2k or so to see how well things are put together.....

jonezey00

It doesnt acheive 17 until about 3500... and anyway.. GOOD NEWS... 110psi constant on both rotors, so I guess the seals are fine. Getting new plugs and wires today, one of the plugs looked rather shitty. I just still dont understand how a no fire miss would make the vaccum tick like that... oh well

keep you updated

dgeesaman

iTrader: (7)

That is good news.

Dave

Joe Geiman

If it "chipped" an apex seal, the piece would exit the hotside of the turbo possibly damaging the exhaust impeller.

Good news about your compression test though.