SpeedOfLife

iTrader: (16)

I've considered the tach out of calibration theory, but it doesn't hold up considering that it's clearly accurate everywhere else (like when the secondary injectors start opening).

The alternator should be good, as with this new battery it's been starting like a champ and when I initially installed it, it was pushing 14V while running.

I've considered the tach out of calibration theory, but it doesn't hold up considering that it's clearly accurate everywhere else (like when the secondary injectors start opening).

The alternator should be good, as with this new battery it's been starting like a champ and when I initially installed it, it was pushing 14V while running.

Ok, so I set up a voltmeter on the pump today, ran it to 6500RPM, hit the wall and NOTHING. I still had 12.5+V. The lowest the pump sees is about 11.2V with the heater and headlights on at idle. Now, my idle is kind of fudged by tensioning the throttle cable, but it does idle at a minimum of 650RPM, usually that minimum is 750, but occasionally it goes lower than that when I pull back on the accelerator pedal.

Plan B, anyone? I know to look at the injector electrical system, but I know nothing about it. Anyone have any relevant information or links to some?

I picked up a timing light today with a tach built in so I set my timing, which was way off (several degrees advanced). It was not, however, the cause of my 6500 RPM wall, but at least that's ruled out now. It's so much smoother than it was before though... Wow, what a difference, I think it's even a little quieter when cruising.

Just to make sure no one read that wrong, I'm still having this problem, I was just commenting on how nicely it drives after resetting the timing.

blwn rtr 89'

iTrader: (5)

whats left in the fuel system that has still yet to be checked?

SpeedOfLife

iTrader: (16)

The signals controlling the injectors. How would I test that? Otherwise I don't know what else I could test.
I checked the voltage to the fuel pump, wouldn't that be low if the ground was poor? I checked using the ground that the fuel pump uses by hooking up a spare fuel pump harness with terminals on the power and ground lines so I could easily run voltage checks while driving.

Can what the ECU sees from any sensors, specifically the ECT sensor, make it decide to cut fuel? edit: I know that when it's too cold I face this same exact problem, but at 5500RPM instead.

Also, how can I check the wiring to my secondaries? I will look for the answer on my own, but in case I can't find it I'll ask now.

I'll list what I know and what I've tested so far:
-There's a wall to acceleration under load at 6500RPM, this does not occur when revving in neutral.
-Air filter is still fairly clean, plugs and wires are new (as of maybe two months ago), the 550cc primaries are fairly new (they look it, too), and the 720cc injectors are in decent shape. HOWEVER, the only things out of those that wasn't replaced since I bought the car are the primary injectors.
-Gas tank was cleaned and fuel filter replaced within the last several thousand miles by the PO.
-The problem can't be in the ECU, as the problem has followed two different ECU's.
-I have a 255lph fuel pump in there now, which still has full electrical power supplied when the lean condition occurs at 6500RPM.
-I readjusted the TPS yesterday to refine the light throttle response, this did nothing to aide this RPM wall though.
-The load at which I hit 6500RPM makes no difference, I can crawl up to it or boost hard up to it, either way I still hit the wall at the same RPM.
-I reset the timing last night and installed a TII BAC valve instead of the NA BAC valve I installed a couple months ago.
-I worked on the engine grounds a while back, but recently learned what 'dielectric' means (including that dielectrics have insulating properties). I think I used dielectric grease on the grounds I worked on, possibly voiding the cleaning I did. I had forgotten about this, maybe this is my problem...
-I still get the secondary staging stumble, but it does not lean out as hard as it did before (this is after I installed the Rtek 1.7 stumble fix chip)
-In addition to the ground lines that the ECU uses, I ran all ground lines from the ECU to the body as well.
-The exhaust is straight through and much less restrictive than stock. I gutted the crappy muffler that serves as a midpipe.
-The alt, starter, and battery have ALL been replaced twice since I bought the car.
edit:
-I tried holding the gas down after hitting the wall, it just churns and runs really lean, sounding like it's just pushing air around. It maintains 6500RPM, however, it does not fall below that if I'm still holding the throttle open.

NoDOHC

Hey, two things more to check, connections to MAP sensor and AFM. When my NA missed at high revs I cleaned both these connections and it fixed it.

The cold conditions reminded me of the scenario on my car.

Basically, the air is more dense at low temperatures, so the engine sees the same air flow at 5500 on a cold day as 6500 on a warm day.

Seriously, take the connectors off on the MAP and AFM and clean them very carefully, then put dielectric compound on the connections.

You might also want to ground the MAP sensor.

SpeedOfLife

iTrader: (16)

w00t, new ideas FTW. Thanks! I'll get back with info once I've done those things.

edit:
http://en.wikipedia.org/wiki/Dielectric

So do you mean to apply dielectric grease around the connections or in the connections? Because I don't think it belongs in them.

NoDOHC

I just talked to one of my friends and he told me that I also cleaned the AFM and adjusted it to be more level at the same time. I didn't remember that part the first time.

I just thought that I had better include all the details of what fixed mine.

I called it a miss, not a wall, but I bet it is the same thing.

I sure hope this fixes the problem.

SpeedOfLife

iTrader: (16)

These are things I noticed while looking through the FSM, and I'm wondering if any of them might be able to cause my problem (yes, some have already been mentioned):
-AFM, and its failsafe: "Maintains basic signal at preset value." <-- what does that mean?
-Water thermo sensor (I assume the ECU may not know if it's reading a little off, however I think mine is working properly judging how the temp gauge works, and I replaced the thermostat a while back and observed positive changes)
-Water temp switch (same question as with the thermo sensor, but doesn't one or both of them control the overheat warning light?)
-Atmospheric pressure sensor

I'm not even sure what these do:
-Heat hazard sensor?
-Intake air temp sensor (on AFM and air intake pipe)?



edit: NODOHC, thanks for the additional info

blwn rtr 89'

iTrader: (5)

^ you can eliminate the IAT sensor from your list, that would not cause this problem.

if you AFM is getting messed up readings, or you are out flowing its capacity it could definitely do something like this at high rpms .

i not that familiar with the sensor reading order for the 7 just yet, but a low reading pressure sensor could also cause the car to shut off injectors at high rpms.

if your coolant temp is high enough to do this there would be other things happening as well equally bad.

ive poped about 5 water pumps for a water to air i/c setup ive done on another car because of a bad grounding location, if all else fails you might wanna look into a new fuel pump.

if you buy one of those LED light curcit tools you should be able to chech the injector plugs to see if the are activating at the correct time and also how they behave at the 6500 wall.

this is all ive come up with for now, im very curious to see what it actually is.

alexdimen

iTrader: (13)

Do the injectors have the proper impedance for the system? My money is on secondary injectors.

They will burn out if you use low imp injectors on this system w/o resistors.

hhn2002

fuel pressure regulator was mentioned a while back but not addressed. get the fuel pressure tested. and also make sure the vac line to it is good. i am no guru but just thought it'd might also be another good suggestion if maybe a tad bit far fetched.

i am eager to see you bury the hatchet and find the final solution as i am sure many here are.

SpeedOfLife

iTrader: (16)

link? I'm not sure what tool you're talking about.

blwn rtr 89'

iTrader: (5)

http://www.beachtradingco.com/servlet/Detail?no=16302

alexdimen

iTrader: (13)

If you're suggesting using this like I think, this would only tell you if the injectors were getting current from the ECU. They can get current and still not work if they're burned out.

It's a good idea, but if that lights up it doesn't necessarily mean his injectors are opening.

You would also have to test while driving in high RPM, since the secondaries don't work at idle.

SpeedOfLife

iTrader: (16)

If that were the case it would mean that at least one of my old 550cc injectors AND at least one of my recently installed 720cc injectors were burnt out at the same exact point. What are the odds?

Besides, it looks like it's a basic circuit tester with some extra features of working on different voltage systems. If that's all I need to use is a 12V LED then I can hook that up myself... But I would be hesitant, as I'm betting in series the current would blow the LED and thus open the circuit, and in parallel I would probably need a resistor many times higher resistant than the injectors for the LED, no?

blwn rtr 89'

iTrader: (5)

^no that tool should be fine in it self

i did not read one thing that suggested the injectors bad them selfs.

you said something referring to checking the harness plug for a signal.

i do not think its an injector issue, unless your running a high or low impedence with the wrong plug as said before.

my bet is on AFM either being outflowed, or defective


(edit) what are you using for tuning??

SpeedOfLife

iTrader: (16)

I don't think it is either, I was just explaining why.

I can't tune anything really, I'm running the Rtek 1.7 with 720cc secondaries, a 255lph fp, and a manual boost controller. I have an after market boost gauge and A/F gauge hooked to my O2 sensor for monitoring purposes. I modified the lid of my air filter box the other day, and despite claims from reputable people here that it increases air flow, I think it has done the opposite. Regardless, I should still be able to redline if I can fix the original source of this problem.

blwn rtr 89'

iTrader: (5)

well now that i have read about the rtek 1.7, i would say that it is your problem, how do you tune?

SpeedOfLife

iTrader: (16)

Recall that this problem was no different when I still had the stock ECU installed...

blwn rtr 89'

iTrader: (5)

what exactly can you control with the Rtek, as far as fuel, and can you log any data?

SpeedOfLife

iTrader: (16)

The Rtek 1.7 is just a drop in chip, there are no additions that let you monitor data in any different ways than you would be able to with the stock unit. The Rtek 2.x series is a whole new animal, acting much like a standalone, but with conveniences for the RX-7 and limitations in that you can only do so much in terms of injector load and maybe some other things.

alexdimen

iTrader: (13)

I was just pointing out that it doesn't eliminate the injectors as a possible failure. You're right, it is unlikely, but stranger things have happened.

He still hasn't responed whether or not he has the right impedance injectors or simply pulled the plugs off and checked if the coil is good and what resistance it has.

blwn rtr 89'

iTrader: (5)

do you have a spare AFM?

MazdaMike02

iTrader: (4)

Pull ECU plugs, ohm out each pin...its most likely a frayed or broken wire...the exact same thing happened to a friend of mine.

SpeedOfLife

iTrader: (16)

Sorry, they're the right impedance. I checked the resistance before installing them and they were within spec for... high impedance IIRC. The stock injectors for my car are purple topped, I think the first half '87 TII's used the low impedance tan ones. The FAQ says, even though the part numbers are the same... Again, I should be having much worse problems if any of my injectors were the wrong impedance.

I don't have a spare AFM.

I'll work on these things, and checking the ECU wiring will be on that list. Do you happen to know if the FSM has a procedure for that? I've looked through the engine electrical about 1.5 times and didn't notice anything to that effect, but that doesn't mean I couldn't have missed it.

I would have been doing some of this tonight, but it's 0-5*F out, and my garage is unheated, uninsulated, and not attached to anything that is. sigh.

edit: I'm aware that stranger things have happened, I just want to tackle the much more likely causes first.

alexdimen

iTrader: (13)

The reason I suggested it is because I've seen secondary injectors cause the exact symptom you describe because they were the wrong impedance.