1985 Series 3 RX7 not running properly
 

Hi there,

I've had a 1985 Series 3 RX7 for about a year now.

It is fully stock with the original 12A engine. It has been running perfectly until now.

What happens is that it often stalls when warming up and feels like it is missing every now and then. Once the car has warmed up, it runs perfectly on the road except when idling it has this weird miss every now and then and the car shakes. The idle speed is now at about 600rpm depending on how hot the engine is.

The engine still produces excellent power.

I have changed the spark plugs and fuel filter. The engine is still running on the on its original leads.

Im not sure if this is helpful, but i have noticed that coolant gets spilled out the top of the radiator cap every now and then, and im regularly toping up the reserviour.

any help appreciated.

cheers

Rob

Any green residue on the spark plugs, or white smoke (not blueish but pure white) out the exhaust?

Make sure the radiator is topped up too, not just the reservoir. How old is the radiator cap? If you don't know how old it is, replace it. They're cheap enough.

Vacuum leaks are not uncommon, especially the big hose that goes from a valve at the back of the carb down under the intake manifold. That can cause idle problems when it cracks from exhaust heat.

the spark plugs were ok. there is only the usual steam white cloud when the car is being warmed up on a cold day.

the contacts on the inside of the rotorcap look quite eaten up.. but i thought that probably was ok since the car seems to run ok when im driving it at speed.

Rob

Obviously an Aussie
 

It probly has something to do with the carby. You sure the fluid leaks out of the cap? It often comes out of that stupid level sensor in the middle top of the radiator. its only the rubber seal if thats the case...whatever it is buy a new cap or seal from Mazda. Hard to tell exactly what the idle problem is without looking at it but yeh vac leaks make it feel rough like that.

ok. ill go buy a new cap on monday. i dont think that is the cause of the rough idle.

when i changed the spark plugs they were quite shiny with oil and black after about a 20km drive.

Turn the idle up, readjust the carb. Also check your plug wires. 900-1000rpm works nice. Thats after you cure any vacuum leaks if you have any. Check the coasting valve too. Caused mine to stall in wet weather warm up.

I wouldn't adjust anything on the carb until you verify that there are no vacuum leaks. Carbs don't just fall out of adjustment. If you screw with the carb to compensate for a vacuum leak it won't run any better, and it will need to be re-adjusted when you finally fix the vacuum leak.

If you read I said after you fix any vacuum leaks.

I have a similar problem with my 13B, when cold idles rough at 700rpm and misses a bit, and unless i keep my foot on the accelerator a bit it dies. Once warm idles at 900rpm. I think this is prob also due to the fact that the choke is not hooked up :)