I have a 1994 FD RX7 13b twin turbo running standard boost, new rebuilt engine ported and doweled has only done 6000km and is missing and dumping black smoke out the exhaust but only after its been sitting at traffic lights or when idling for a short period of time. Around 4000rpm it will start missing.

Fitted a new Apexi power FC still does it, replaced alternator was stuffed still doing it, replaced battery one cell was bad still doing it, running out of money and patience.

Please help any advice would be great!

 

Are all your sensors hooked up correctly and in proper spec?

 

Missing at the top of the rev range typically suggests a ignition issue. I'd check the plugs and wires first and work your way back through the system until you find the culprit. The other possibility is that its related to your other issue (eg. black smoke, usually fuel related). Couple of questions:

Was the car tuned prior/after the rebuild? Were you having any issues like this before the rebuild? How was everything during the break-in period? What was your procedure for break-in? What kind of condition were the injectors in during the rebuild? Were they sent out for a clean and flow test?

Sorry for all the questions, but it'll help out with the diagnosis.

 

Don't the secondary injectors come on at around 4,000 RPMs?

 

Car was not tuned prior to rebuild it had a stock ecu and was not ported, I had it rebuilt with a mild porting and was doweled, the turbos were ok a few electrical issues after they put the motor back in .Break in period was good no problems didn't drive it on long runs.

Then I noticed on longer runs it was getting hot around 110C and running real rough took it back they said the thermostat was stuffed but I find that hard to believeit wasn't that old, the radiator was 40% blocked and was rebuilt, the car started playing up not long after that they told me I had to put in a aftermarket ecu hence the new power fc, they tuned it, they said it was fine i picked it up did the same thing again, took it back they said alternator, replace it and the battery. Still doing it as far as I know the injectors were not cleaned or flow tested.They also replaced the fuel pump due to it leaning out a bit at the top end.

The missing is not there when I first take it for a drive, I warm the car up then drive it everything is fine, give it a little so second turbo comes in it pulls hard, then I come to some traffic lights it sits away idling take off around 4000 revs starts missing badly black smoke poring out the exhaust.

 

Black smoke=RICH. Take it to a tuner who will safely take fuel out of the maps. Most likely not an ignition problem. Most likely a rich mixture miss issue.

 

The high rev missing is probably due to plugs being fouled due to the rich mixture.

Since it only occurs after a prolonged idle, I would suspect an injector sticking partially open, and gradually over-richening the idle.

 

Only when I've been eating bean burritos

I'd take it to another rotary shop, sounds like this one is throwing parts at it and costing you a fortune.

 

^ I agree. Throwing parts at a problem hoping it fixes it is BS. Take it to someone that knows how to troubleshoot and diagnose a problem - and be willing to pay for their time.

 

The only problem is the people giving me advice on what to replace are Rotary and motorsport businesses but I suppose its an ellimination process to find the culprit.

Its going on the dyno hopefully tonite or tommorrow so I'll let you know how we go.

Cheers
Viper_D1