Hey,

So I just finished getting the engine in the car (couple weeks ago, other issues delayed me...) so here is a list of the setup so everyone is familiar when helping troubleshoot.

Brand new engine from Mazda
Full Non-Sequential setup, followed the guide here: http://www.rotaryresurrection.com/3rdgen/tech_fd_emiss_remov_nonseq.html
Vacuum diagram followed is this one: (minus PCV Valve and Boost Controller)

Brand new Supra Fuel pump
New Fuel Filter
New plugs
New wires
New Battery
JDM UIM and LIM
No emissions (as the non seq removes everything)
Power FC with "Base Map"
GM 3 Bar Map Sensor
HKS Downpipe
RX7Store high flow cat
Cat back exhaust
Thermowax is still on

So that should be enough info on what is bolted on, there is no rats nest, no solenoids, no air pump. I have ID'ed all of the connectors (wiring harness) and ensured that all the ones still needed (minus emissions, rats nets, turbo control, pre control, etc) are plugged into the correct locations, I double checked all the ground locations, all are good, tested trying to fire up the car with a stock ECU (thinking it was the PFC) same behavior.

So here's what happens, when you crank the car, it fires right up, revs to 2K then just shuts off. To me feels like it fires up fine, then it just cuts fuel, though thats just my feeling. If I pump the gas pedal, it will stay running but wont rev past 3K, I can keep pumping the gas and the car stays running, but as soon as you let off the gas it dies.

I have tried setting the PFC idle IG setting to "off" set the "sequential" setup to off, and also turned off the "O2" feedback to see if that would help, but no luck. I have triple checked all vacuum lines left, (Fuel pressure regulator, Turbo to UIM, and on top of the engine block to the Y-pipe) Checked the TPS, its within range, I've swapped UIM, I've swapped Throttle bodies to test still ends up with the same result.

I've done a ton of searching and most of the time comes back with "vacuum leak" or "Blown engine" neither of which apply here, (or at least that I can see). any help would be appreciated, thanks!

 

First, it's most likely not going to be anything vacuum line related. As long as the MAP sensor is hooked up and you are getting a good vacuum reading on it you're fine there.

You have a 3 bar MAP sensor, is the PowerFC set up for it? You have to let the PFC know what MAP sensor you have. Could also have something with the wiring to the GM sensor. If possible it could be worth plugging in a stock MAP sensor just to get it running and troubleshoot.

The 2000 RPM isn't too out of the ordinary if you have the ISC and Thermowax.

Big thing here is finding out what's cutting off - is the fuel pump turning off or ignition? What is going away? You've got compression so that isn't an issue. It's fuel or spark.

Dale

 

So by pumping the gas, it would at least tell me that the fuel pump is still functioning... (at least logic would say that ) the Map sensor is not setup in the PFC, if I recall correctly I need a datalogit in order to set that.

I thought about the stock map sensor test, called Mazda to see if they had one in stock that I could quickly return (since they cost $530!!!) but they would have to order it. might have to grab one for sale here to test, though I thought if the Map sensor was disconnected, it would idle rough but at least start? I tested the coils (resistance) and they are within the Mazda spec (per the FSM).

Maybe I'll put more gas in it, I dumped 4 gallons in, so I don't think it's short on that... it would be funny if thats all that was...

 

Not necessarily running out of gas but the fuel pump could be cutting out. Also, if the fuel lines are hooked up backwards sometimes you'll get something similar to this where you just get a little trickle of gas getting backwards through the FPR to the rails.

You can jumper the fuel pump test connector to force the fuel pump to run full time to see if something is trying to cut it off.

Yeah, if you don't have a Datalogit you'll need to hold off on the 3 bar MAP until you can set the PFC up properly. Just buy a used MAP sensor, should be like $30 or so. Or go get a Datalogit to properly set up the PFC.

Dale

 

Thanks Dale, I will look for a stock Map sensor around here, and also try to jump the connection to the fuel pump to see if something is trying to shut it off.

 

I'd check voltage at the fuel pump, the high speed voltage circuit functions for a few seconds after start, then steps down to the lower voltage via the speed relay which could be why your car seems to run okay for a few seconds. You have a Supra pump, they draw more current so if you have a weak relay or some other high resistance your voltage could be lower than it needs to be.

You might also want to put a fuel pressure gauge on the supply hose and make sure pressure is in spec. after making sure you have decent voltage at the pump.

 

Thanks for the tip JZA80, so I pulled the IAC plug and the car wanted to idle but it was too low for it to stay on. so I pumped the gas for about 5 minutes to keep it running so it came up in temps (thinking it was maybe a cold start thing).

Well now that it has warmed up, the car just cranks and cranks (not sure if it has anything to do with it being warm or not) so its looking more and more like the fuel pump might be where the issue is. I can test bypassing the really by jumping the connection on the fuse box in the front of the car (from what I searched and found here) updates to come.

 

UPDATE: I replaced both fuel relays with brand new ones, (had purchased just not tried it) it catches (barely) then shuts down again, with the IAC disconnected it never jumps to 2K just tries to idle at 700 to 800 for just a few seconds, then dies.

Also noticed that the Cat was unusually warm... which indicates failing leading spark. though I have tested the coils (resistance) and it checks out fine, its got new wires, so maybe its the spark that is failing? though I think If that was the case when I pump the gas it should die... hope the ignitor is not shot.....

 

I'd still check the voltage at the pump and fuel pressure.

 

Quick update:

Voltage on the pump checked out, as I was getting ready to call it quits I thought let me unplug the MAP sensor (from the vacuum line, left it plugged into the harness) and just see what happens... sure as **** car starts up, and idles just fine at 850 RPMS!

Looks like my culprit is the MAP sensor and the PFC not knowing its there, so looks like I'll be getting a datalogit so I can add it manually before I get the car tuned. I let the car run for a good 20 minutes to properly warm up. The water temp gauge came up to the mid point but the PFC told me it was only 26 degrees Celsius.... seems like it should have been warmer than that after 20 minutes. the fans come on at 90 degrees right? No glowing cat, or hot exhaust so ignition seems to be working and the MAP sensor was causing all the issues...

I'll just need to let it run longer to see how long it takes for the fans to come on, want to make sure that is working right. I hope when I add the MAP sensor in everything should be good. I could rev the car up and everything, stumbled on the rev a bit (pretty sure its too rich) but didn't die on the rev down. now it starts! Well I hope when I walk into the garage tomorrow and try it, it still starts....

 

When you left the MAP sensor plugged in but disconnected the vacuum line, you let the sensor see atmospheric pressure, but it was still giving data to the ECU. So, IMO, the issue MAY NOT BE THE SENSOR, but the line to it or the filter in the line could be plugged, giving a false manifold pressure to the sensor, and a false reading to the ECU. So, IMO, see if fixing any line/filter blockage affects the issue.

If it's not that, then its calibration to the ECU could be way off, and that's screwing things up. If neither of those is the issue, it could still be a bad sensor.

 

thats what I was thinking too. I’m getting an datalogit so I can tell the PowerFC it’s a 3 Bar MAP sensor, which probably would resolve the issue, will update the thread once I make the adjustments and get results, thanks for all the help.