xflashjr

This rx-7 is a 91 convertible 5 speed with 68,000 original miles.

The only known upgrades are a new exhaust system, with new cats. The previous owner thought the problem had to be with the cats so thats why the exhaust was replaced.
The car starts right up (after being jumped battery was dead) and will idle perfectly. The engine can be reved throughout the rpm range with no problem. When we drove the car it ran fine, until the car got up to temp and then it felt like the car just ran out of gas. We called to get help, but by the time the other party came, the car started right back up and we drove it back to the house.

I am not extremly familiar with rotary's as I race miata's so if anyone can understand the problem as something common please let me know.

thanks Stephen

xflashjr

bump

goblues24

had a similar problem with my old 86 once...came with other symptoms later which included replacing the radiator and still adding coolant often..about twice a month...not soon after the engine blew.....i think there is a thermostat problem that prevents the car from starting when a relay triggers due to the heat factor...i really wish i remebered the specifics..but try looking in the direction of the water pump/thermosta..and the signals it sends to the ecu when it doesnt function properly..im very vague because i dont remeber exactly what it was that caused this problem..but it had something to do with what i am saying...something in the thermostat and the way the 13b deals with it not functioning correctly....

hope this helps you

xflashjr

Thanks for the reply, I was thinking it had to be some type of relay or switch. But now I'm wondering if the switch has just gone bad or there is a problem with to much heat building up. I guess I should change the thermostat, relay, flush the collant system and start from there.
Hopefully it won't be too much of a hassle, once agai nthanks for the reply and if anyone has any more info let me know
Stephen

xflashjr

Well just to update, i went to the lot and found oput some more info. They said that a freind of his from the mazda dealership said when he looked at it, it was an internal oil pump. I understand how a rotary works but can someone explain to me if this makes any sense, especilly on a car with this low miles? Please let me know

Daedalus

I am most likely mistaken, but if the car senses a failure in the oilpump (or OMP), it'll either go into limp mode or turn off all together. Oil is the life blood for a rotary, and without it, it'll die? Hows your oil pressure?

xflashjr

oil pressure seemed to actually be rather good. I'm it is nothing major as I can just get my boss to take a look at it and hopefully fix it without tearing aprt the engine. Still hopeing it has something to do with a thermostat relay or soemthing

goblues24

i hope its not your omp...its a pricey fix..seeing as you have relatively low mileage..and ive had a few 7s that went over the 130,000 mile range..and never was the fault of the omp...yet ive experienced some of your symptoms...and still replaced an engine..without replacing the omp..and i tracked the other seven taht i sold which died around 140,000..and he never had to replace the omp...i think the thermostat sends false signals to the ecu and that triggers a limp mode or it triggers some sort of diferent fuel sending ratio..i do know this...i used to drive the car to work or wherever...with no probs...but once i turned it off...that is when the trouble with starting happened...basically id crank it for a while..then wait ten minutes...then cuss and swaer and try again..then cuss and swear in the heat stranded late for a party..then after about 20-30 minutes..id just try it for the hell of it...and it would fire right up..which sounds similar to what you are saying with the many failsafe relays that the rotary has its hard to track...the one thing i can say for sure is that i never got my problem resolved..which included filling the add coolant requirements a whole lot...and bottom line i was stupid...and my engine blew very soon after...within a year..as far as my specific problem..now that i have the internet and so much more info...i really attribute it to the thermo pellet failing..and letting coolant burn inside the engine causing seal failure..apex that is..so dont just do like i did in college and keep driving it..spend half as much as a rebuild to track that problem down..and your engine will last alot longer..and you will be much happier.

BadBoy

it definitely sounds like the omp...try checking for the codes...i had the same prob with my 90 vert with only 42k miles on it. replaced the omp and it never happened after that.

Fred

xflashjr

Right now I'm leading towards it being the omp. Especilly sense the used car lot mentioned something about it being an oil pump problem. I actually hope it is the OMP because my buddy who just blew his 91 gtu engine told me I could have his old one from his block. He told me that on the 90-91 engine the omp changed from being mechanical (on the earlier cars) to electronic to these cars and that is why the 90-91 can be somewhat tempremental.
For anyone who has changed there own OMP, is the job extremly difficult? I have worked on race cars for a while so I know my way around a car, and will ask some help from a few friends with rx-7's but just wondering how difficult it is.

One last thing, there was mention that the thermo pellet could fail ( i have no clue what this is) but I'm guessing it regulates coolant to some extent. This sounds like it could be a possibility but the only thing that does not register is this happened when you stoped your car. My problem happens as soon as the car warms up, meaning as soon as oil gets up to temp. So I'mw hoping my problems can be sovled by a quick fix.

Thanks
Stephen

Daedalus

If you continue to drive the car, you should probably premix your gas as a precaution. I can't tell you the details, but you can search on the topic.

Good luck.

goblues24

the thermo pellet is part of the cold start thing...basically it prevents coolant from water cooling the engine or something like that...letting the engine warm up faster, once the engine is warmed up the pellet moves to allow coolant to enter the engine..if its busted then there is not a good seal..which allows coolant to always enter the engine..at any time

as far as the omp system..the earlier system was mechanical i think and the later was electric...they did this to make it more efficient and reliable..so you have a 91...yours should be more reliable..and the two different ones dont mix and match..

when i was speaking of the car not starting after driving and stopping...it was because the car was obviously warmed up..then i parked the car..later came back to drive it..and it wouldnt start..i only said this cuz i thought that was what you were saying might have been happening to your car....what you are saying is that while continuously driving it begins to lose performance without turning off the car?...you may try to figure how much gas you have in the car..and then calculate the correct ratio of oil to gas as per a premix configuration...i think its like 100:1..in my 2 stroke applications it is 60:1 ratio..meaning 60 equal parts of gas to 1 equal part of 2 stroke oil...if you go to the store and buy some tcw-III type of 2 stroke oil..this is what you would use in a premix scenario...

if you arent familiar with the way a rotary engine lubricates it internals...it is not like a normal piston engine..where oil is distrbuted throughout the internal workings via an oil reservoir which is seperate from the combustion chamber...in a rotary engine there are internal workings and seals that need to be lubed..and can only be acheived during the cycle of combustion/exhaust/intake..because unlike piston engines the internals are actually lubricated inside of the combustion chamber..with piston engines the equivallent parts are lubricated outside of the combustion/exhaust/intake process...in the valves,crankshaft, barings etc...and is done with normal oil that does not burn away cleanly if it is involved in lubricating during the combustion cycle of the engine...2 stroke oil is different in the sense that it is designed to lubricate effectively..and at the same time burn away cleanly..and not leave deposits...the normal oil you put in a piston engine..has properties that are specific to its application..to lubricate moving parts..without much consideration for how cleanly it burns when it burns..becuase its not designed to do this..

if you look at a jet ski or an outboard boat motor..or most older motorcycles..you have to use a different type of oil that is designed specifically for the application of a 2 stroke motor which provides lubrication inside of the engine during combustion..etc..because it is a completely different type of engine all together...than a normal car/piston engine..whereas a rotary shares both properties of cooling with oil...

given this info i would think that if your vert will run in a premix type scenario..that would leave you to believe that the omp was the problem...so try and add some tcw-III 2 stroke oil to your gas..and see if the car does not begin to run better..cuz that would provide the rotary with the lubrication it needs while the omp is not functioning properly...but at the same time..with all of the failsafes invilved in the 13 b..if your omp is not functioning properly..it will send out an s.o.s. to your ecu as a preventative measure to keep you from blowing the engine...due to improper lubrication.

i know its a boatload of info..that most everyday guy doesnt comprehend..so best bet is to find a reputable rotary guy in your area..if you start calling most mechanics..once you say rotary..they usually stay away from your business..cuz its like speaking a different language..if you cant speak spanish..you dont move to spain...you just wont make it unless you understand what they are saying...mechanics usually have tried the rotary and have lost alot of time and money...cuz they just dont understand whats going on..it is a completely different animal..than what they are used to dealing with..piston engines...

a rotary specific mechanic will 99% of the time be the best money spent to resolve the problem..cuz they know whats going on...and will spend less labor hours( 60 bucks an hour out of your own pocket) doing trial and error gimmicks and such..usually having to send out to a rotary expert to eventually resolve the problem..at the expense of your dime!!

xflashjr

goblue24 thank's for the long post, as it was quite informative. Well I'm not as ignorant to how rotary's work as I might have led on. My dad owns a 94 R2 and I have helped my buddy take apart a few S4 and s5 13b's. At the same time this does not make me out to be any type of rotary expert and I greatly appreciate the info that was given.

I understand the technicalties of how a 4 stroke and 2 stroke engines work. Therefore the rotary behaves simliarly to a 2 stroke in that sense. Even though I will put some premix into the gas tank, hopefully the omp does not still send a signal to the ecu causing the car to go into some type of limp mode.

After working at a race car mechanic shop for 1.5 years I have learned the value of a good mechanic. I think I will try a new OMP myself but if that does not fix it I'm goign to bring it to my old shop and get my boss to check it out.

I will try the new omp, premix and other maintance this weekend and post the results of them. Hopefully it will end up allright.

Thanks again
Stephen

Leigh Adams

"Informative" is not the word I would use...


THIS is what the oil thermal bypass pellet does, and what happens when it fails.


He's calling it a 'valve,' but we're all talking about the same thing. And it clearly is NOT the source of your problem.


I also don't understand why goblues24 is telling you to add premix. Is the OMP supposed to detect the premix and send a signal to the ECU that everything is okey-dokey again? Because it won't. I suspect that goblues24 believes that a lack of lubrication at the apex seals is resulting in increased friction that is 'slowing down the motor.'

It doesn't work that way.


If the OMP on your s5 had failed, your ECU would have gone into Limp mode and the car would have become nearly undriveable, meaning that while it would run, it wouldn't respond to more than about 20% throttle (and if you did give it more than 20%, she would sputter and hesitate.) It would NOT have died on you like it did.


While I don't know what is causing your problem, I am certain that you are about to head down the wrong path in trying to correct it.

Give us some more information:


You said that when the car reached operating temp, "then it felt like the car just ran out of gas." Was it a gradual power drop over the course of a minute or two, or did she pretty much just drop dead, if you know what I mean?


How long did the car sit before you tried to start it again? What did the temperature gauge show after you started it this 2nd time?


Did the car quit again just as you got home, or did she seem normal right up until you shut off the motor?



goblues24 - I don't want to be the troll under the bridge or anything, and I'm not flaming you. It just makes me nuts when information is posted that is howlingly wrong. For what it's worth, I've done the same thing myself serveral times.


(This is Amur_ - I'm not at home tonight. )