Hi!
I bought a 93 rx-7 this week, and i bought it with a fault. The engine revs fine up to 4500-5000 rpm, then it cuts and starts backfiring. Almost like a rev limiter.
And after 5 minutes of driving it starts to go really bad. Like one of the rotors doesnt get ignition. As a result of this, the cat heat lamp starts glowing too.. Previous owner suspected a blown coil.. What do you guys think?

The engine is completely stock.

 

does it rev in neutral?does it seem to lack power going into 4th gear? if so you could have one or two blown apex seals . pull the plugs and see if there is excessive oil onany of the plugs(prolly T2 and L2)if so there is prolly your problem

 

It runs very smooth in all the gears and in neutral. No smoke, and it runs fine up to that rpm. So im sure its something with the ignition system..

 

I would also check into the afr's.. Make sure it isn't lack of fuel

 

I would think that a bad coil would be a problem throughout the rev range.

At about 4500 RPM, the secondary injectors start to activate. Is the car stock? Potential things to check:
- check to see if secondary injectors are the original 850cc or if someone installed larger injectors or bored out stock injectors
- check the wiring to the secondary injectors
- check the ecu to see if it is stock
- check the wiring harness at the ecu to see if there are any clipped wires there.
- check the chassis grounds in the engine bay

what you are describing with the cat glowing makes me think that fuel is being dumped in large amounts and being passed through to the exhaust b/c it can't be burned. Chances are the cat has been melted during this ordeal as well.

 

You can certainly begin by removing the coils and testing resistance. However this does not catch all failed ignition coils, so you might spend a little money to buy a set of good used coils. They are not too expensive in the US, hopefully you can find or borrow a set.

Also be sure it's not a plug wire or plug, I would replace all plugs and wires.

Unfortunately this also sounds like it might be a fuel injector issue. This is not a fun problem and can also follow your symptoms.

If the cat is in question you must remove it and inspect it for clogging.

David

 

Thanks for the answers all!
The plugs looked horrible! Some were even leaking out between the isolation and metal. I checked the spark with a spark indicator. And i got a nice spark in all 4. So coils looks fine..
New plugs arrive tomorrow.

 

That was probably the knock sensor leaking and dripping down onto the plugs

 

Did you fix the problem mate? I ask because i have the same issue

 

Do you really plan on bumping every thread you find on secondary boost issues?

It will be far more productive if you follow the troubleshooting steps I advised you to in your original thread. Sitting in front of a computer won't help you. Getting under the hood and following the troubleshooting steps will. Yes it is a pita but you can't get around that.

 

Actually no, just 3.

 

Sorry not updating this thread as solved. The problem was the crankcase censor wheel was damaged so it was bendt out of shape in one place. Took it off, straighten it with a hammer, put it on and it revs fine now

btw, this had nothing to do with boost. Just the ignition breaking up.

 

i have that exact same problem with my 1983 rx7 will go nice but slow up to 50 then wont go any faster in neutral revs but wont go over 5k new plugs new wires new cap..someone told me the motor is blown but the guy is a idiot..would like second oppinion

 

my s8 fd has a similar prob, it will run fine for ages then for no reason it will not rev under load. the problem comes and goes and the plugs are all new.

 

Are you on the stock ECU?

 

could it be a blown turbo because from the engine its smoking near the turbo area

 

Smoke coming from around the area of the turbos is usually a result of an oil line or turbo coolant hose leaking onto a hot surface. It doesn't directly affect engine performance but should be fixed asap. Either one can start an engine fire.

 

Smoke can also come from cracked gaskets on the hotside , helps with fire ***** .

 

Im getting mine into the shop tomorrow... same exact thing

 

what kind of ignition systems being used?

 

yeah stock

 

Check AFR

 

Have any of you guys tried removing the Cats, from whats been said sounds like you might have a plugged cat,or, you might have plugged screen on your fuel pump( intank),or plugged air filter, if the engine sevice light comes on it may have a faulty oil injection pump,and its going into limp mode...Hmmmmmmm.......all the best.......

 

Need to take it off limp mode....