BuffNStuff

My freshly tuned sc is hard starting and will stall for what seems to be no reason. My tuner has spent 5 hours already driving and fine tuning the car and cant figure out why it stalls. He thinks it is something wiring related, or sensor related. Also my ac is low on freon and the compressor will click on and off a lot as a result. Dont know if this could cause stalling or not.

My question is, what are the sensors or components that can cause a sudden random stall? I know the CPS can cause stalling but it seems like a bad CPS would cause the car to run horribly. When driving, the car feels amazing. Pulls hard and smooth, will catch falling rpms, great drivability on power, just while idling and starting are concerned, there are issues.

I did not have this problem when I had the TT ecu mod. But since then I have changed some parts out so I am trying to narrow down ny search off possible **** ups I may have done.

Since switching to AEM:
IAT sensor
6an braided fuel lines to the tank
Walbro 450lph e85 pump
840cc injectors
OBD1 lower intake manifold (for injectors)
Full EGR delete
Canister delete
Silicone vacuum lines
12v fuel mod
Oil catch can
New valve cover gaskets
Phenix fuel pressure regulator at 42psi
New ebay is300 coil packs
Bkr7eix spark plugs gapped at .028


My 1997 sc300 is running is NA-T and running an AEM V2. I was previously running a V1 but my issue remained when I switched to a V2. Before that I was running the TT ecu mod on an OBDII supra ecu. When I switched to a standalone, the only wiring that was changed was for the IAT sensor. I also rewired my MAP sensor because I needed to change its location in the engine bay. I am also leaking power steering, but it is coming out of the resovoir cap. Its like boiling or bubbling and forcing its way out.

Thats everything that I can think of. Any ideas on the stalling issue? My tuner is going to be out of town for the next MONTH so I would like to check things other than the tune right now. Especially since he has tuned over a thousand cars and is well renowned in the Tucson area. He also tunes cars that compete in the Pirelli World Challenge so I believe him when he says he doesn't think it is tune related.

GTX580

iTrader: (3)

Check your grounds on your harness, I had a similar issue when i replaced my power steering pump and i accidentally loosen up one of the ground on the intake manifold. Just throwing it out there.

BuffNStuff

You had stalling issues? Which ground was it? I think theres a couple on the intske mani.

lexforlife

iTrader: (7)

Double check your integrated iacv and make sure working correctly

BuffNStuff

I pulled it off and cycled power through it and it definitely works. The pin moves in and out with ease.

Ali SC3

iTrader: (10)

that would be a common assumption that is both misleading and incorrect. the CPS uses variable reluctance, meaning that it ouputs a certain voltage everytime the gear passes by the magnet. The amount of voltage depends directly on the speed at which it passes by the magnet, meaning that at higher rpm's the CPS signal is the strongest or highest voltage, whereas at lower rpm's (starting rpm's is generally around 300-400 which is the speed of the starter) the cps puts out a fraction of the voltage, as in its very very hard for the ecu to read this signal compared to the high voltage one.

so why was this problem not there with the stock ecu? the stock ecu is designed to pick up that specific CPS sensor and was designed to amplify the signals perfectly so that the ecu can pick up even the weakest of signals even with background noise (quite impressive actually) in all RPM ranges, not just the higher ones where its easy to read. the stock system is built around the fact that the VR sensor is not linear, which is why the stock ecu picks it up perfectly on distributors that cannot even start an engine on an aem box.

the aem is designed to work on a multitide of cars, so they design the base circuit to be able to "read" "most" types of VR sensor ranges, and on the v1 they change resistors on the board to fine tweak it. thats why you have a specific box for honda's and toyota's they both use VR sensors but the sensitivities vary alot and will not run each others engines that well in all rpm ranges.

on the v2 they made it more adjustable in the software instead of messing with resistors but it doesn't mean its been perfected. if you look at how the AEM was designed from the very start, it was designed to use Hall effect sensors which are digital and read perfectly, as in a hall effect sensor has its own power source and therefore always outputs the same amount of voltage no matter what the RPM is (think square wave versus the old bell shaped wave), making it the most precise way to measure an engines rotation as you don't have to mess with the complicated post calculations involved when using a VR sensor. so what the aem does for our cars is take our VR sensors and estimate a hall output and uses that signal from there. as you can imagine there is alot of stuff going on so it needs a strong signal to work with.

So the problem is that the 2jzge distributor was made with non-adjustable VR sensors. they cannot be adjusted cause they are molded in place.
thats an issue because the gap between the VR sensor and the gear also effects the strength of the signal. the smaller the gap the larger the signal.

If you look at a 7mgte CPS, you will see each of the VR sensors has 2 screws on it and can be adjusted up and down in its slot. moving the VR sensor closer to the gear makes the CPS signal stronger, and moving away makes it weaker. when its weak you get hard starts or no starts often until you jump it off another car, and if you ever wondered why connecting your car to a running car makes your distributor work better, its because when cranking alone you normally bring your batter down to like 11-12v during cranking and the dizzy is on the lower side of its readable range. when you jump it off a running car which is at 13.5 charging voltage, its usually enough to get a clean signal to the AEM and it will start much easier and quicker.

to confirm just stare at the stat sync variable, if it takes forever to come on and if the timing error count increases, then you have a dizzy problem. Sure its not in the tune but it should be obvious to the person looking at it on the laptop.

short answer is I would try a spare distributor or even swap to a known working 7m cps and close the gaps on the 7m cps as much as possible. at least the 7m is adjustable but they are older so the chances of just finding a used one and it working is pretty slim unless you know someone who has one. the stock distributor would have to be replaced for another if you went that route, I once had one that had trouble starting and eventually it wouldn't go past 2200rpms. changed out for a 7m cps and was back on the road till I downgraded to a 2jzgte ecu, at which point I went back to a spare distributor.

BuffNStuff

If I swapped the distributor out for a 7m cps, would I need to rewire anything? Would the tune need to be adjusted? Or is it just a simple swap? So the random stalling at idle would NOT be a result of a weak signal from the stock cps to the AEM V2? At least the hard starting would go away, thats the most annoying part.

BuffNStuff

Also, are there supposed to be any wiring differences between the tt ecu mod, and the aem v2 wiring? I am using a supra v2 on my sc.

It sounds like my hard starting is the result of a weak cps signal because it takes a few tries, and I have to hold down like 1/3rd throttle to get it to start, and then hold it at like 2k rpms for 20sec until it settles and it feels like the ecu will not let it stall.

Ali SC3

iTrader: (10)

you would need to rewire the plug on it and change a few things in the settings, not the main tune. it could be that issue or it could be something else I would hook up the laptop and look at the settings while trying to start, it will show up if that is the issue cause it wont get stat syncd and it needs that to start. if you are just trying without the laptop you wont know what its doing at all. you should check before replacing it. if its getting that and its not starting then its something else.

are the vaccum lines for the power steering switch thing under the reservoir still hooked up to your intake manifold?
if that switch fails it can suck power steering fluid into the intake or push it out under boost, which is kinda what it sounds like, just thinking of why your ps fluid would be doing that.

BuffNStuff

If it does get stat synced with the stock cps, does that mean I would not benefit from the 7m cps? Because it does start, but it takes forever and can be really difficult. So long that its not really practical to drive it and its not fun.

BuffNStuff

I did notice in my research that people have been doing this swap for a while. Is this a common thing for people to do with AEMs? Almost like a necessity?

BuffNStuff

Im thinking as a back up plan, Ill swap the injectors out an use an aristo ecu instead, as long as I dont have to put my EGR stuff or all the vsv stuff back in, or put a stock fuel pump back in.

SCereal

iTrader: (4)

I was going to suggest trying an aristo ecu to see what happens. If successful, you eliminate mechanical causes. You wont need your EGR stuff, JDM stuff doesn't have it nor will you need all the vsvs, I don't have any of that and mine runs great. (or rather would if the fuel system upgrades were done).

Ali SC3

iTrader: (10)

if its getting stat syncd then the cps is being read properly at least for starting. so your distributor sounds like its doing its job. the next thing in the startup sequence is the "initial crank pulse" under advanced engine start. this is the one parameter that will give you a good start or give you a terrible start. the amount of fuel injected to start the motor is directly this parameter, there are no other modifiers. this should be tuned and even the best of tuners don't spend a lot of time here, cause when they sit down if your car starts they assume its good or they make a small tweak and set it. Tuners also usually only get 1 good cold start, after that the engine starts easy so its hard to tune as well. if its not very close to the exact amount it needs to be, you wont start when its too hot, or too cold, basically in the different conditions.

so you need to play with that variable and move it up for more fuel and down for less fuel.
not enough fuel and a cold motor wont start, too much fuel and you wash down the plugs.

on the aem, everytime you turn the key to crank it injects the initial crank pulse. lets say you started cranking for a sec and stop, then start cranking again you just got double the initial crank pulse.

so cars that are hard to start on the aem are often getting too much fuel where it washed out the spark, and every time you turn the key it keeps washing it down. if you find you can start it with modulating the throttle, try backing off the fuel some in that cell.

if you find you can't start it at all, likely too little fuel and then try adding some.

its a little guess and check but once it starts off decently on the first try (take several mornings cause they should be tested on first cold starts) then note where the values are and then only fine tweak it. this is how you get it starting up well in summer and winter, it takes time.

its like a personal choice, but the 7m cps is slimmer and always has a billet aluminum cap.
nowadays the stock dizzy has a billet cover for it, but its alot taller and sticks out further.
on standalone you can choose, on tt ecu mod you need to use dizzy.
But if you are getting stat sync's even when it doesnt start every time then don't worry about it, dizzy is fine then, but if you loose stat syncd when its not starting thats the dizzy.

Not a bad idea. you can run it without the egr stuff or vsv's, and even an aftermarket pump. I have a walboro. if you have a tt denso just make sure its wired right, the stock fuel pump ecu cant always handle the power of a denso tt unit and should be bypassed. can cause some funny issues where the pump wont run at certain speeds.

BuffNStuff

Im running a walbro 450lph because it was rated for e85 and I upgraded my whole fuel system around e85. I already bypassed the fuel pump ecu because the car would not stay running because the pump wasnt getting enough power. I just need to wire in a relay to cut power when the engine is off because it is constantly priming unless the key is off.

My tuner is coming back into town for a couple days on monday and he said he will datalog it. Hoping he finds the issue.

I think you are right about the powersteering issue. I may have reversed the vacuum lines. Ill probably just delete that anyway because people say they dont really notice or mind it being gone.

I'll report back when I hear more from the shop.