hello guys, i have a 1988 10th anniversary fc with 114k miles.

im encountering some rough idling problems once the engine is warmed to operating temp. also if i shut off the engine, the car wont turn back on until it gets cold again. what could be the problem?

i did a compression test and it shows 85 psi in the leading rotor and 58 psi in the trailing, seems to be blown apex seals. could this be causing the idling and starting problem??

is there a way i could fix these problems at least until i rebuild the engine.

thank you very much for your time guys any advise would be greatly appreciated.

 

Generally a blown apex seal will result in two faces of a rotor not making compression so on the tester, you would see one bump, a pause then another bump instead of three even bumps.

The easiest way to tell is likely sound:
http://www.aaroncake.net/rx-7/blown.htm

Sorry, if it is a broken/chipped apex seal, then the only way to fix it is to rebuild the engine.

 

Thank you so much for your kind help.

 

I had a similar issue with rough idle and starting. Not sure what my compression but I rebuilt the carb and no longer have the issues. I knew I needed a rebuild so I never got to check the compression. However, there is some good information on the forms that will tell you what blown seals sound like. I believe it is under the FAQs

 

Hello,

I did a compression check last week on my 86 NA, so the procedure is still fresh in my mind.

First of be sure you have done the test correct. The first time I did one, I got small numbers too.
Would be a bad idea to junk/rebuild an engine with good compression due to a wrong comp test.

I read that a flooded engine can decrease the compression numbers seriously.

I noticed that I had not tightened the tester enough (hard without tools).
Be sure to put some engine oil or other lube on the tester thread and seal (Oring)
It is generally recommended to do this test with the engine at operation temp.

Pull both EGI fuses in the engine bay fuse box (EGI comp, EGI inj). So the engine wont
dump fuel in and does not fire the coils. Be sure your Battery is in good condition.

Remove the leading (lower) or trailing (upper) plug on both rotors.

Screw your tester in and floor the gas pedal, try to start the engine and hold the key for about 10 seconds.

Check your reading and go on to the next rotor, If you have doubts on the reading
do the test again.

If your numbers are still too low then there might be too much seal wear or seal failure. (Others have to chime in and list what could be wrong)

Remember that this test does just test the overall compression on one rotor, it cannot
(afaik) detect a broken seal.

You might want to remove all the spark plugs (and egi fuses, same as comp test) and crank the engine with the pedal
floored and listen to the sound it produces.
You want to hear a serie of even strong pulses, kinda like: ZASH ZASH ZASH ZASH ZASH ZASH
If anyone of them is not as loud as the others or there is a gap then there might be something wrong.
This test can indicate apex seal or side seal failure.

Additionally you can spray some wd40 or equivalent in the spark plug holes to lube
the rotors and maybe improve the compression numbers on the test.
To do so remove all plugs and turn the engine over by hand and spray the stuff
in with those small tubes that come with the can, be sure not to hit the apex seals with it while turning over.
Repeat compression test.

This will improve the sealing of the rotor face and generally produce higher comp numbers.
(mine jumped from 110 PSI to 120 PSI with lube)
If it doesnt improve there might be something wrong.

For the idle and startup problem, there might be a large range of causes, I never had that problem but read a lot of it. Generally check grounds, plugs and injectors.
Leaking injectors can give you a hard time starting. They can be send of to be cleaned and flow tested. Usually no need to replace.
Remember you have 4 of them (2 Primaries and 2 secondaries) Secondaries are supposed to kick in at 3800 rpm. You might have felt it while accelerating.
witchhunter.com has a good reputation over here and I will do same with mines, just in case...


Regards
Steven

Ps that was a longer text then I initially wanted to write, but once started its hard to stop lol

 

^yeah.... that was long...the procedure is written elsewhere ya know... ya could just link it.

Anyway my opinion is that with compression numbers at 85 and 58 you're lucky it starts at all. Before my rebuild I had 105 and 85 and the only way I could start is was by putting 20w50 in the spark plug holes. If you have to drive your car until you have time to rebuild it I recommend you keep a wrench and a bottle of oil in the car. Either way, we feel your pain man

 

Thank you guys for your help and greef lol. This is my first rotary i have somepne helping me build it might even add a few goodies to it. I will try to upload pctures when its done.

 

People who know nothing of how a rotary works reflexively blame the "apex"seal.
To me it sounds like the engine is simply worn out. Worn housings, hard seals, hard seal springs or a combination.

 

to the original poster:
soaking the engine in solvents or steam cleaning may help to extend your time, but it would seem to me that a rebuild is inevitable.

i agree on both points. it appears that many people unwittingly condemn apex seals, sometimes for things as simple as a tuneup. coincidentally, the last 2 engines i pulled apart both had very low compression and neither of them had damaged apex seals. instead, the side seals and corner seals were all carboned to hell.

 

Im hoping the Turbo2 Im about to buy that reportedly has a blown engine due to apex seal failure isn't actually blown and the girl is wrong because she doesn't know rotaries too well

 

do the seafoam treatment to it and see if the number increase. highly carboned engines seem to have low numbers, can not hurt to try. may save you a rebuild. if you do not know the process, search seafoam

 

I have heard of that process before along with a few others like wd40, or atf. I am going to try compression testing it once I get it home but the engine may actually be blown because it has 180,xxx miles on it and its a Turbo2. The engines in them usually blow well before 180 thousand miles from what Ive read. Hopefully if it is blown everything will still be reusable during rebuild time. Still wont hurt to test it so I most definitely am going to try out the seafoam treat before hand. Thanks snively

 

Cabon removal is best accomplished via carb cleaner in through the exhaust ports. You can get access to every apex seal just by lining it up with the port.

 

I agree Arron, but it does nothing for corner seals. I know, they do not make compression, but as you know are every bit as important as the apex seals to make the engine run properly and gain compression on a worn engine. just my .02 worth. my thought as to do a total decarbonization on the engine and see is comp number come up, if not then a rebuild is in order.

my 6 port broke apex seals and damaged the rotor and housing last month at 2k rpm in 1st to 2nd shift, ran fine until the carnage......so anything is possible, we estimated the engine to be at 180k milage as the apex seal groves in the rotors were worn out and the seals had wear in the center section. op is probable dealing with a worn out engine as i was.

 

As I was reading I read that high milage rotaries usually do have the worn down side housings from being run for so many years. So Im just hoping that the engine from the T2 Im going to buy does not have a blown apex seal, blown engine period actually and if it does that I can reuse the rotor housings, rotors and side housings. Thanks for the tip Aaroncake I am going to try that out for sure too.

 

I used carbon cleaner in the lower spark plug holes, it worked awesome. The engine was alot easier to turn by hand and I shined a flashlight into the holes and could literally see the apex seals and sides of the rotors get cleaner. I noticed while cleaning and shining the light in the holes that the sides of the rotor in the first housing is kind of pitted up a bit. Hoping it will run fine but should because doing a poor mans compression test out of the car all of the rotor chugs were even and strong.

 

i hope your motor is ok but if not do i hear possibly Street port :-)

 

Thanks man and this is engine for my 86' base model project so its an N/A 6 port. If it is blown Ill either sell it, get it rebuilt, or rebuild it myself. If it gets rebuilt no matter what it will be half or full bridge ported and if I feel like doing the work then the na to turbo conversion. It will probably need at least 1 new rotor by the looks of it. Weird thing was the apex seals were all fully intact from what I coud see.