Fuel pump - validated pressure and performed the system speed check.
Fuel filter - installed a new Mazda filter during the rebuild
Gas Cap - removed cap and there was positive pressure in the tank after running
Electrical connections - went through all of the critical ones (crank angle sensors, spark box, coils, TPS, MAP)

 

Update:
Drove it about another 10 miles on and off of boost simulating the previous times when it stalled. It did not stall. I even put in the clutch from a 4000 RPM cruise and it still settled down to idle.

I let it idle for about 45 minutes in the shop to get a lot of heat in it. Shut it off and restarted. No problems, started every time.

Took compression readings right after shut off.
Front is up to 99 from 88
Rear is up to 105 from 97

 

Hey, I have an odd question. What kind of gas do you run? Have you recently changed? I wonder if you ran a bit of bad gas?

 

I assume all three faces of each rotor are fairly equal? (i.e. the peak doesn't really matter if they aren't fairly equal) Did you mention how many miles were on the engine? I saw where djseven asked, but I assumed you talked it over with him offline. If it's a new rebuild with low miles on it still, I would keep running it around the block and short trips to put miles on it and see if the compression keeps increasing (as long as the car isn't stalling any longer).

 

cpneeda - Great queston - but running the same premium 10% max alc that I have been running for the last couple of years. I did fill it up however right after I got it running again.... I think the fuel if bad would affect the all around perf. and cold starting but not the compression.

Mahjik - All three faces indicate exactly the same pressure for each rotor. Needle bounce is all around higher than originally taken.

Right now there is about 30 miles on it.

I'm going to get some miles on it today and tomorrow then take another set of compression readings. Thinking that the ALS seals, Cermet coated housings, and Mobile 1 oil is requiring break-in time to really seat the seals.... djseven is very interested in the data gathered so I'll continue to provide.

BTW Mahjik, I'm glad I ran all of the diag's again on the systems (including PRC); it removes any questions or asumptions.

 

There you go! As I initially thought, the stalling was a symptom of low compression. Another clue was the low vaccum readings.

I think all you were seeing was low compression from not being run enough. That, along with the porting, gave too low peak pressures at idle to keep running or restart hot. That would explain why the stalling happened early on, but not recently. This also corresponds with the compression increasing with further running.

I think you are home free!

Dave

 

my 94 fd does the same thing it dies when rolling to a stop after being warm.. but it starts back up every time, unlike ttomtt were it wont start after staling.

also if i step on the brakes pedal while idleling the idle will drop very low

 

Put another 70 miles on it today

Compression:
Front 103 (90-90-90) up from 99
Rear 110 (90-90-90) up from 105

Idle holding at 900 with vacuum at 13 inches.
Tried to set the idle at 1000 but the ECM doesn't deal with it too well.....

No stalling

Things are looking up

 

oh yeah, sounds like you're good to go

 

Update
Compression is still comming up but I simply cannot get the idle right.

First the compression taken cold with 130 miles on the engine is:
Front 110 with 100-100-100
Rear 107 with 100-100-100

Idle:

• The Throttle body is set exactly correct and to the OEM specs. Both plates are fully closed and the cold start is set for Florida.
• TPS narrow band is 1.00 volts with the cold start cam not engaged. Wide band is in spec. Both narrow and wide track correctly and the full throttle output is per spec.
• Took the entire top end apart and there is nothing connected wrong or leaking.
• Bypass screw has to be out about 5 or six turns to maintain idle; Don't know why this is.
• ICS solenoid is functioning correctly, however, don't know what the stroke of the plunger is or should be but when 12 VDC is applied it solidly clicks to full open. At idle without the intake elbow installed there is about a 120hz hum from the ICS port indicating to me the system is working. Finger on the hole will cause the solenoid to open fully.
• Again, the injectors were cleaned and flowed by RC
• No codes being displayed
• Vacuum at 900 RPM is between 10 and 12 inches
• Fuel pressure at idle is 40 psi

Idle is rough and varing in RPM by +/- 100. Sounds like the thing has a high overlap cam.
Exhaust tends to irritate my eyes.
When I did an electrical load test the rear window de-ice raised the RPM's by about 100 and kinda smoothed the idle out. When I turned on the AC the RPM's went up about 150 and lasted about 5 to 10 seconds then the idle went to crap and the engine about died. This can be repeated. Load test with the lights was like the rear window de-ice.
The idle is not "hunting" just really rough and not stable.

I just bought a PFC, Datalogit and PLX WBO2 but I don't want to install until I figure this out.

A couple of things:
Are the injectors at a constant duty cycle at idle and the ICS and timing controlling the RPM?

Off Idle, cruise, and boosted load is smooth, predictable, and perfect; the problem is only with idle.

I'm thinking about hooking up the PFC, Datalogit, and WBO2 simply to get visibility into what is going on....

Your insight here would be greatly appreciated....

 

Street port with a basically stock ecu, keep in mind my streetports are usually larger than the standard "medium streetport". My newer engines have much smaller ports as it is much easier for customers to get the car to idle smoothly with stock or remapped ecu. With that compression and streetport you should be seeing around 13-14 inches of vacuum around 850-950 rpms. Possible small vacuum leak maybe. I bet if you install the pfc with the base map the car will run leaner/cleaner at idle and you will be able to get the idle to smooth out much easier.

 

the stock ECU, while a capable unit hardware-wise given its age, is not calibrated for the way you are running it.

RECALL that the stock idle timing is mostly fixed at -5 leading, -20 trailing depending on accessory load.



This is not ideal for a streetport. I have done extensive tests on idle ignition timing, and I can tell you that -5 -20 will result in a more unstable vacuum signal if you have a street port.



This was done with a Power FC by switching between fixed ignition timing and closed-loop ignition timing (toggling Idle IG control under etc.--> function select). Idle speed was 850, but I still think it illustrates the problem with running stock idle timing on a car with a streetport.

The reduced engine vacuum will also result in a richer mixture as higher MAP tells the ECU to deliver more fuel.

Read through this very thoroughly: https://www.rx7club.com/3rd-generation-specific-1993-2002-16/how-make-your-untuned-pfc-basemap-safer-idle-better-no-datalogit-needed-841706/ . The idle related stuff is mostly in the very beginning and at the very end (2nd page). Since you have a Datalogit it will be a lot easier to diagnose idle issues.

 

Agreed especially after reading arghx's reply following. What I think none of us really know is how the M2 Stage III ECU mapping was done in the idle areas. I wouldn't have thought that they would change idle settings for the mods they did on the car; speculation on my part. I do have a stock ECU that I could plug in just to see if any different.

arghx - I did read that post some time ago but it met little to me until I got the PFC and began to understand it all. Thanks for bringing it up.

OK tomorrow the PFC and commander and get it through the idle learning process. If all goes well next week the Datalogit and PLX WBO2

 

Got the PFC and commander up and running. Like day and nite compared to the M2 ECM. Idle is very stable under all load conditions. Found someone cut one of the Air Pump wires under the relay - fixed that now the air pump operates correctly. Vacuum is still off the mark. Pictures are during stable idle.

 

364mm is 14 inches. that doesn't sound too off to me if you have a significant street port. Granted, that number will change a little if you recalibrate the MAP sensor, but still it's nothing unusual. That's about what I get on my big street port which idles 900-950rpm fully warm.