Celica Forums Classic Generations 6th Generation Celica 6th Gen rough running/stalling

Hi all! 

Long time lurker here. I've had a my Gen 6 (ST202, 3SGE) for a few years- and have learned a hell of a lot about repairs along the way. This one has me stumped though. I was wondering if anyone could point me in the right direction!

The symptom has developed since it first appeared as a no start. I can now start and idle smoothly whilst stationary (seemingly without problem for a long time)- but as soon as I try to move anywhere the engine starts to run very roughly and then cuts out. 

The diagnostic throws up a 1 - 4 (Ignition). It has done that every now and again for as long as I've had it (with mild versions of these symptoms- a rougher run than usual) but has usually sorted itself out quickly. Some time ago I stripped down and cleaned the throttle body and intake manifold, and cleaned through and replaced the seals on the injectors. This seemed to almost totally fix the long-standing problem (perhaps just luck?). 

At first I thought that this current issue was something totally different- so when the no start first arose I thought 'fuel'- replaced the fuel filter and pump. There are no leaks in the fuel system. No change. I also checked the distributor and the spark plugs.

So now I think that the ignition fault code is the overarching problem and that some part/sensor/connection has now almost totally failed. 

My thoughts at this point are... 
1. Crankshaft position sensor worn out- feeding incorrect positions back to the ECU and registering as an ignition fault. Where is it in an st202? Integrated in the distributor?
2. Camshaft position sensor worn out- I'm less sure about what this does (timing data again?) or whether the ST202 has one.
3. Ignition coil assembly worn out- potentially it's working fine during idle then as it heats up a bit a connection is becoming loose. Long shot?

Anybody got any thoughts on where I should be looking/testing/replacing? 

If you haven't swapped out the PCV valve in the last 3 years, you might try it and see if it helps -- even a little. My new-to-me 1994 Celica had low idle problems to the point it flat out died at a stop sign idle on time.

The PCV valve and its gasket were pretty obviously damaged (rocked all over the place indicating no real good seal). I replaced it with new parts for less than $10, and the fix was quick and easy. Just install the PCV valve into the gasket before installing both into the valve cover.

I also cleaned out the MAS sensor and air intake using MAS sensor cleaner for both.

It idles much better now. It has about 335,000 miles on it, and wasn't exactly maintained very well as indicated by the clogged PCV sensor and oil caked all over the underside of the vehicle, but she still runs pretty good and might have a few years left in her if given some TLC.

It would be nice to get it to at least 400,000 miles.

I just replaced a fuel filter with a Wix filter (from China). If I were to do it again, I would go with a Toyota part purchased for the best price online.
The washer connection surface was painted on the Wix, but was metal on the Toyota part. In addition, the Wix had only two washers for the top bolt attachment and none for the lower nut attachment. I have a slight leak with the Wix.
Another tip is to spray any really tight fuel line nuts with upside down compressed air to cool down the nut and break up enough rust to allow the nut to give a little. My fuel filter nut went from "going nowhere anytime soon" to "let's get loosened" in about 2 seconds of "wrenching" after the upside down can of compressed air application.

I do have question, though. How did you get the fuel pump to stop pumping gas? in my case, gas flowed for about 20 minutes. Maybe longer. It did eventually stop. I took out the EFI relay, but I'm not sure that was sufficient.