My (fairly new to me, first rotary) 88 nonturbo vert needs an injector cleaning, leaking badly leading to running rich and flooding after shutdown (bandaid fixed with fuel cutoff switch).

With the cold weather, it's developed a behavior I'm curious about since I'm trying to understand the motor better.

When cold starting in colder (< ~60 deg F say) weather, the motor is rough and super rich. It basically behaves as though it's running on one rotor.

As it warms up a bit, say in a minute of not touching the throttle, it coughs as though the second rotor fires up and smooths out.

Alternately, if I slowly build revs in neutral to 2500 rpm it does the same thing with the second rotor kicking in feeling, always exactly at 2500 rpm. Right before the 2500, it sort of flattens and doesn't want to rev anymore but will with effort, then kicks off at 2500.

Anyway, that's the long background to my basic question of is there something that happens at the 2500 rpm that could be a clue for me to better understand what's going on? For example, a sensor that sends a signal at that rev point to the fuel or ignition system?

 

Timing and the rate the motor spits out the fuel is most likely why.

 

Timing huh? So here's another question.. when setting timing, my leading mark is spot on when checking leading wire, while my trailing mark is nowhere to be seen when checking trailing wire. Adjusted TPS per manual.

 

You need to use the front rotor 's trailing plug wire (Connected to T1 coil) to check trailing timing. Make sure your trailing wires are connected to the correct plugs, too. That could cause your stumble.

There is a water temperature switch on the bottom of the s4 radiator. It runs one rich fuel map below ~60deg F. Page 4A-46 of the FSM is you're interested. Above ~60, it runs a leaner different map. It's normal and is supposed to make starting easier and cat light-off faster.

 

That's good info on the temp switch, thanks for that. On the timing, wires and are routed correctly. Any other explanation for trailing mark to be so far off? It's not even visible from above?

 

did you get your problem fixed ? Im having the same problem with my 87 na.

 

No I haven't. Need for find the time to troubleshoot it all. Haven't been able to find more info on my leading / trailing timing discrepancy. It is running extremely well otherwise in the cold weather we've been having in my area though.

 

Induction style timing guns are real finicky on the plug wires on these engines..the clip has to be "just so"...Or nothin shows.

 

^+1

The trailing timing isn't adjustable if the leading timing is correct. The Ecu just makes it happen. Well there is one way: If the trailing wiring/ plug wires are crossed.

The covers that say T1 and T2 on the trailing coils are easily swapped if someone is careless. Do either of the trailing wires fire at the correct time? If so, that's T1. Or even disconnect your trailing wires and see if it runs differently.

Overall, there really isn't anything that is supposed to change ~2500 rpm on an NA. Suggestions from left field without being able to work on your car.
-Maybe your 5/6 ports are opening due to excessive exhaust backpressure caused by a clogged cat.
-Maybe your leaky injector is finally within the 'correctable' range of the ecu so it runs better.