cerm78

Hi guys/gals...

Mazda RX7 Convertible 1991 NA. 160k+ miles

Last weekend I was taking my girlfriend's cousin for an ice cream. Car running great as always, not pushing it in any way (kid's afraid of speed hehe). Exactly on a non-stop left turn car starts to behave weird. At first I only noticed lack of power. Few seconds later I knew it was running on one rotor only.

I crawled it to the POPS (ice cream store) and went for the so beloved choco-chips special. After the ice cream, it started with difficulty and crawled back home.

I have an A-F sensor installed and when the fault started, it went completely lean (18+) and will not hold idle nor pull strong and if I floor it, the only firing rotor will ping badly. I haven't checked yet but that makes me think the problem is fuel related.

Today I tried to start it and even harder than before, it did. But this time there is a strong fuel smell even when the A-F is lean as before. Now I'm doubtful.

I'll try to convince my girlfriend to assist me so I can at least start to test things:
- Check if spark plugs get spark (easy)
- Check if injectors get signal (damn primaries are almost inside the engine)
- Check if injectors get proper fuel (in fact I have to change filters a long time ago )

I think it's worth mentioning that it's been some time since I noticed that when doing hard lefties the engine cuts for a while. As long as I know, that can be caused by a dirty fuel pump sock filter (which I has neglected)

Any thoughts or advice?

Thanks god I'm working 8 blocks from house, because it was my daily driver.

Regards,

K-Tune

iTrader: (26)

Check compression. With an actual compression gauge. Then check the other things...

cerm78

Since one rotor is not firing, it makes no sense to warm it up prior compression test. Is it okay to test it cold?

K-Tune

iTrader: (26)

Yep, you will still be able to know if the engine itself is okay or not. It will be very obvious if there is a compression problem.

cerm78

Thanks, I haven't had chance to start troubleshooting but definitely I'll start this weekend... Thanks good I can go walking to work... how's really missing my 7 is my girlfriend... or maybe not that much... she always get rain over her due to top leaks...

OT: someone knows how to stop conv roof leaks?

BomberMan

iTrader: (4)

Well if one of your rotors went out it wouldn't necessarily be running lean since there is still fuel being injected. The bad news here is that you floored it on an engine that was running lean, and pinged your engine. If there was any engine damage it likely happened here. Either way, it sounds like you are on the right track to diagnosing/fixing your problem.

duo2999

iTrader: (1)

@ cerm78, have you tried adjusting how the roof is when closed? i adjusted mine to close tighter and i have no leaks now.

cerm78

Hi BomberMan, well I hope it wasn't that much. I know rotaries are very sensitive to pinging but remember it's an NA an it was just a split second... I'm crossing fingers and really hope it to be a bad injector or something electrical... worst case being the ECU toasted... it gets as much wet as my GF does due to the roof leaks...

Thanks duo2999... I have tried adjustments and what I have is more water in hehe... May be the seals are not good anymore... and I don´t know if they can be replaced (front window frame mainly...)

Regards,

gear_grinder

iTrader: (4)

if you've totaly lost a rotor when you go to crank it up it will cranked "loped" due to the lack of resistance on the one rotor without compression.

cerm78

Well, diagnostic was faster then I thought, but the problem was also bigger than I thought...

According to my "ear" compression test, the result is: blown apex seal (whosh, whosh, whosh, zzzz, whosh, zzzz).

According to my normal compresion tester, front rotor has 75psi max (cold engine) and the only chamber working at the rear... 25psi...

So I'm in the worst scenario of all of them... because I have little money right now...

Before dismantling everything to assess the damage, I'l take a peek at the exhaust port to have an idea of the extent of it...

The incident was very quiet... never thought it has internal damage, but well... rotaries are mechanically very quiet anyway... hope the apex seal did little damage to housings and plates... I'm sad...

nycgps

iTrader: (4)

if you're really lucky it could just be a "cracked" apex seal"

again, if you're lucky