Need help from the T2 FB guys, not running very well
07-06-09, 07:32 PM
#1
Need help from the T2 FB guys, not running very well
Ok I'll try to be as detailed as I can without typing too much extra stuff. The car is a 83 that I've swapped a full JDM S5 T2 engine into. Its running the S5's N374 ECU with full emissions, along with a custom made "left side" harness to run the coils, fuel pump resistor and circuit opening relay. The Car has been on the road over a year and has beautifully until this weekend. It is running incredibly rough, spits and sputters, and struggles to get moving, once it does it has very little power, yet still try's to build boost. It rev's freely with no load, but with a load it can barely make it to 3k, defiantly not over 3k rpm.
In their infinite wisdom Mazda didn't give the JDM engine a check engine light and I'm not currently able to check codes (I have a thread in the FC section for help with that) but I've got quite a few spare sensors and parts and switched everything I could think of, MAF, TPS, OMP to no avail. I've also checked for spark (it has it) and fuel (pressure is a bit low at 30psi, but the battery isn't 100% full due to constant starting and restarting) so I'm lost. As soon as you kind of get moving it like the brakes are locking up and its fighing to stay moving (the brakes are fine)
I'm at wits end and don't know what else to check, anyone have any ideas?
Any help is appreciated.
Thanks
Sean
In their infinite wisdom Mazda didn't give the JDM engine a check engine light and I'm not currently able to check codes (I have a thread in the FC section for help with that) but I've got quite a few spare sensors and parts and switched everything I could think of, MAF, TPS, OMP to no avail. I've also checked for spark (it has it) and fuel (pressure is a bit low at 30psi, but the battery isn't 100% full due to constant starting and restarting) so I'm lost. As soon as you kind of get moving it like the brakes are locking up and its fighing to stay moving (the brakes are fine)
I'm at wits end and don't know what else to check, anyone have any ideas?
Any help is appreciated.
Thanks
Sean
07-06-09, 07:42 PM
#2
Sounds like it is going into limp mode. You should be able to check the codes for the ECU with a test light. You have a green 6-pin connector and a green single pin connector on your 'left side' harness, correct? If so, the procedure should be the same as any s5 USDM test.
07-06-09, 08:55 PM
#3
Yes I have the 6 pin and the 1 pin, If I hook up LED's to the 6 pin (which only has 3 wires, I always found that kind of odd) and turn on the key they both light up and stay lit, if I ground the 1 pin connector they both go out and one relights, and stays lit, they never pulse like they should. It's possible I have something wired wrong, I guess I'll have to retrace my wiring harness....
07-07-09, 09:28 AM
#4
That is quite strange. Just to be clear, between what wires in the connector are you connecting the LEDs? Maybe list wire colors or a diagram..just to make sure something isn't strange there. It is possible that the wire colors may differ from the USDM models, put the pin positions should remain the same (so the same testers can be used).
Is the harness also JDM S5 T2? Could be a compatibility problem if it isn't.
As far as it having 6 pins, but only using 3 wires, car companies do that sort of thing quite a bit. First they try to make sure that you can't easily plug in the wrong connectors together. They also will try to arrange the wires in the plugs as to not cause damage if they have to use 2 similar plugs in the same area. The other reason can be cost related. Maybe the RX-7 uses 3 wires in that connector, but maybe they were building other cars at the time that used the same green connector, but it used more wires.
Anyway, I hope you can get the code checker to work. That would tell you if there was some sensor causing the ECU to go into limp mode. There are only a few things that will cause limp mode (and you have already checked a few of them). If you had enough spare parts, you could just try to swap all things that could cause the limp mode (if that is what is going on). You might have to resort to that if you can't get the code checker worked out.
Is the harness also JDM S5 T2? Could be a compatibility problem if it isn't.
As far as it having 6 pins, but only using 3 wires, car companies do that sort of thing quite a bit. First they try to make sure that you can't easily plug in the wrong connectors together. They also will try to arrange the wires in the plugs as to not cause damage if they have to use 2 similar plugs in the same area. The other reason can be cost related. Maybe the RX-7 uses 3 wires in that connector, but maybe they were building other cars at the time that used the same green connector, but it used more wires.
Anyway, I hope you can get the code checker to work. That would tell you if there was some sensor causing the ECU to go into limp mode. There are only a few things that will cause limp mode (and you have already checked a few of them). If you had enough spare parts, you could just try to swap all things that could cause the limp mode (if that is what is going on). You might have to resort to that if you can't get the code checker worked out.
07-07-09, 09:55 AM
#5
This has me in quite a funk so sorry I didn't post more specifics, I should have. The wires on the 6 pin connector are large black w/white tracer, a yellow (I think there isn't a tracer on that one) and then another yellow with a tracer (green I think, but I can't recall, I'll look tonight) As I said both light up if the 1 pin connector is not grounded, once its grounded only the led on the yellow (no tracer) wire lights up and stays lit, the other just goes and out and stays out.
Tonight I'll attempt to read codes using the same method on my NA FC just to make sure I'm doing it correctly (typicaly I read codes on my FC with the check engine light method, not the 6 pin connector)
Oh and its a JDM ecu and engine harness, the "left side" harness is made from pieces of a USDM harness, although I'd find it hard to believe that the pin outs on that 3rd yellow gang plug would differ, but I guess it could.
The part that really confuses me about this whole thing is A) how sudden it came on, was fine one day and the next as soon as I started it was not running right, got progressively worse, to the point where i cannot drive it up the driveway, forget the road, and B) the fact that it still makes boost, I would think that limp mode would prevent this and just leave the wastegate open.
With all the problems my FC, and now this FC engine have been giving me lately I'm starting to think I should go back to carb's lol, I'll see if I can post more details later tonight when I get home.
Thanks again for your help
Tonight I'll attempt to read codes using the same method on my NA FC just to make sure I'm doing it correctly (typicaly I read codes on my FC with the check engine light method, not the 6 pin connector)
Oh and its a JDM ecu and engine harness, the "left side" harness is made from pieces of a USDM harness, although I'd find it hard to believe that the pin outs on that 3rd yellow gang plug would differ, but I guess it could.
The part that really confuses me about this whole thing is A) how sudden it came on, was fine one day and the next as soon as I started it was not running right, got progressively worse, to the point where i cannot drive it up the driveway, forget the road, and B) the fact that it still makes boost, I would think that limp mode would prevent this and just leave the wastegate open.
With all the problems my FC, and now this FC engine have been giving me lately I'm starting to think I should go back to carb's lol, I'll see if I can post more details later tonight when I get home.
Thanks again for your help
07-07-09, 11:12 AM
#6
I'll see what I can think of.
You'll want to check out section 4B of the S5 FSM. It is possible that one or both of the wires at the test connector has a short or some other problem (check terminals 3X and 3Z at the ECU). However, since that one LED goes off and then comes back on, it doesn't seem like a wiring problem.
Did you try to ground the test connector before turning the key on? I don't think it matters, but that is how the FSM says to do it. To test your FC, maybe just unplug the CAS or something to force a code.
From the codes, it looks like these would cause the poor running:
knock sensor : fixed timing
AFM : fixed timing and basic injection
OMP: fixed timing and basic injection
It doesn't look like it holds the wastegate open for any codes as far as I can tell. The other codes will either cause it not to run at all (CAS codes) or will go to some default value (coolant temp, etc.) where it shouldn't cause much of a problem.
Anyway, if you can get the code tester to work, then we can find exactly what the problem is and how to maybe fix it (if there is a code). If there is no code, then we can look at things outside of what the ECU monitors that could cause poor running (bad fuel pump, clogged filter, etc.).
I'll look more at the test plug wiring and see if there is something that would cause the strange behavior for your code checking.
You'll want to check out section 4B of the S5 FSM. It is possible that one or both of the wires at the test connector has a short or some other problem (check terminals 3X and 3Z at the ECU). However, since that one LED goes off and then comes back on, it doesn't seem like a wiring problem.
Did you try to ground the test connector before turning the key on? I don't think it matters, but that is how the FSM says to do it. To test your FC, maybe just unplug the CAS or something to force a code.
From the codes, it looks like these would cause the poor running:
knock sensor : fixed timing
AFM : fixed timing and basic injection
OMP: fixed timing and basic injection
It doesn't look like it holds the wastegate open for any codes as far as I can tell. The other codes will either cause it not to run at all (CAS codes) or will go to some default value (coolant temp, etc.) where it shouldn't cause much of a problem.
Anyway, if you can get the code tester to work, then we can find exactly what the problem is and how to maybe fix it (if there is a code). If there is no code, then we can look at things outside of what the ECU monitors that could cause poor running (bad fuel pump, clogged filter, etc.).
I'll look more at the test plug wiring and see if there is something that would cause the strange behavior for your code checking.
07-07-09, 12:21 PM
#7
Ok cool thanks! I'm not sure how much time I'll have tonight, but some other "external" things I was thinking I should check is the cat to make sure its not clogged/melted (I doubt it, as its not that old) and as you said the fuel filter, although I checked the pressure with a cheap pressure gauge and it was around 30psi, this was with teh engine off and my battery is probably not totally full because of all the starts and stops it's been putting up with.
I should also probably check compression while i'm at it, just to rule that out, and I already did some quick checking for vaccum leaks and haven't found any major/obvious ones.
Given how quickly it went downhill it almost has to be a bad sensor, I'm not sure the fuel filter would clog so quickly etc
I should also probably check compression while i'm at it, just to rule that out, and I already did some quick checking for vaccum leaks and haven't found any major/obvious ones.
Given how quickly it went downhill it almost has to be a bad sensor, I'm not sure the fuel filter would clog so quickly etc
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07-07-09, 01:21 PM
#11
Also, if you go looking for a clog, your best bet is a volume test or measure the fuel pressure while driving. I helped someone on here with his GSL-SE. The car would start and idle great, but would fall on its face even driving up the driveway. Did a pressure test and it was okay. However, the fuel pump was a little louder than normal and the pressure buildup was a bit slow. Did a volume test. The SE pump should flow about 0.5 gallons per minute. After 1 minute, we had maybe 6oz or so. Turns out the pickup and return were packed solid with crap. Only enough fuel could get past to idle and nothing more. If we tried to move the car with the tester attached, the pressure would go from 30psi down to below 10psi and the car would then die.
I doubt this is the problem since it happened so rapidly, but something to keep in mind..just because the pressure is okay doesn't mean the fuel system isn't all clogged up.
It is an easy test to perform. Just need a gallon jug and a watch. Probably not the problem, but it is easy enough to check to cross it off the list.
I doubt this is the problem since it happened so rapidly, but something to keep in mind..just because the pressure is okay doesn't mean the fuel system isn't all clogged up.
It is an easy test to perform. Just need a gallon jug and a watch. Probably not the problem, but it is easy enough to check to cross it off the list.
07-07-09, 06:29 PM
#12
Update: not sure if its good news or bad, but I used the 6 pin connector on my FC to check for codes just to make sure I was doing it correctly (i unplugged the intake air temp on the intake manifold to trip a code) and sure enough it works just like the check engine light method where you ground the 1 pin green connector and count the blinks.
I then cleared the code and checked again and it does the same thing that my T2 FB is doing, they both light up, then go out and only one lights up and stays lit. Just to make sure I wired those 2 connectors correctly on my FB I unplugged the TPS and checked for codes, sure enough codes 12 and 18 come up, plug the tps back in, clear it and check again, and no codes!
So the good news is I can check for codes, the bad news is there are no codes! Guess I'll have to start searching elsewhere, unless its something that isn't right, but not off enough to trip a code or something... Very Strange.
I'll have to check the fuel system volume later on, not sure I'll have time to do that tonight...
I then cleared the code and checked again and it does the same thing that my T2 FB is doing, they both light up, then go out and only one lights up and stays lit. Just to make sure I wired those 2 connectors correctly on my FB I unplugged the TPS and checked for codes, sure enough codes 12 and 18 come up, plug the tps back in, clear it and check again, and no codes!
So the good news is I can check for codes, the bad news is there are no codes! Guess I'll have to start searching elsewhere, unless its something that isn't right, but not off enough to trip a code or something... Very Strange.
I'll have to check the fuel system volume later on, not sure I'll have time to do that tonight...
07-08-09, 07:38 AM
#13
Btw, thanks Dave for those links, some of them gave me a few things to check/try, but most of them seem to refer to the typical "3800 stumble" Whereas with mine I'm not even getting anywhere near that, the highest it can get (with a load on it) is 3k, and even getting there is a struggle, again though its trying to boost which still makes no sense to me.
Anyway, in one of those threads the guy disconnected his battery to reset everything and it started working, since thats the easiest thing to try I think I'll do that, if its still faulty I'll do a compression test, then the fuel volume test. I guess just to rule it out I'll pull the cat to make sure it hasn't melted or something. If I'm still not getting anywhere I'll start buying up all the spare S5 T2 sensors (and a N374 ECU while I'm at it ) I can and start switching them until it does something lol.
Anyway, in one of those threads the guy disconnected his battery to reset everything and it started working, since thats the easiest thing to try I think I'll do that, if its still faulty I'll do a compression test, then the fuel volume test. I guess just to rule it out I'll pull the cat to make sure it hasn't melted or something. If I'm still not getting anywhere I'll start buying up all the spare S5 T2 sensors (and a N374 ECU while I'm at it ) I can and start switching them until it does something lol.
07-08-09, 09:10 PM
#14
Another quick update, had a few minutes to work on this tonight so I did a compression test (piston tester) and sure enough its got 3 even, strong pulses on both rotors, and overall compression of over 100 psi on both, so clearly the block is still good. Ran it long enough to reach full operating temp, and again it was very hard to start, ran very rough, very rich and backfired like mad when revved (when it would rev without stumbling)
Also just for kicks unhooked the battery for a while to reset everything and it still does it, and still no error codes.
My plan of attack is to check all the sensors with a multimeter. If nothing comes of that I guess its time to pull the UIM and take a look at the injectors/fuel rails. I never sent them out to be cleaned, might as well do it now, might spring for new rails too, who knows what kind of shape the regulator and pulsation dampner are in...
Oh and still have to make sure the cat is ok, and check the fuel volume.... Anybody have any other suggestions on what I might check while I'm at it?
Also just for kicks unhooked the battery for a while to reset everything and it still does it, and still no error codes.
My plan of attack is to check all the sensors with a multimeter. If nothing comes of that I guess its time to pull the UIM and take a look at the injectors/fuel rails. I never sent them out to be cleaned, might as well do it now, might spring for new rails too, who knows what kind of shape the regulator and pulsation dampner are in...
Oh and still have to make sure the cat is ok, and check the fuel volume.... Anybody have any other suggestions on what I might check while I'm at it?
07-09-09, 05:28 AM
#16
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Sean;
Good news with the compression check.
Just as a thought starter, are you absolutely sure everything is OK with your leading ignition. I know you said that you are getting spark, but when I megasquirted my 7, my leading ignitor was failing and it ran like yours did at higher rpm, until it failed totally.
It sounds a little like you are firing only on the trailing plugs.
An easy check is if you have another leading coil, swap it out and try again.
Good luck. Hope you find the problem and its easy to fix.
RXDad
Good news with the compression check.
Just as a thought starter, are you absolutely sure everything is OK with your leading ignition. I know you said that you are getting spark, but when I megasquirted my 7, my leading ignitor was failing and it ran like yours did at higher rpm, until it failed totally.
It sounds a little like you are firing only on the trailing plugs.
An easy check is if you have another leading coil, swap it out and try again.
Good luck. Hope you find the problem and its easy to fix.
RXDad
07-09-09, 07:27 AM
#17
It's probably something to consider, I do have a few spares, as well as the one on my FC, I could easily switch and try them. Not sure if I mentioned this in my previous post, but the rear leading plug looked wet, while the front did not when I pulled them for the compression test, its possible its not firing, or firiing strong enough, although its also possible the injector has failed and is giving it too much fuel.
Btw, sorry my posts are getting long winded, just trying to provide as much detail as possible, maybe once I actually fix this, it will be some kind of reference for others. I'll post results if I find any tonight.
Btw, sorry my posts are getting long winded, just trying to provide as much detail as possible, maybe once I actually fix this, it will be some kind of reference for others. I'll post results if I find any tonight.
07-09-09, 05:47 PM
#18
Not a whole lot of time for this tonight, but did switch the leading ignition and no change, also tried switching the fuel pump resistor/injector relay assembly out of my FC, again no change. Tested the MAF with a multimeter and assuming I'm reading it right (not too experienced with electronics) its within spec. I guess my next step would be to pull the upper intake a take a close look at the injectors and fuel rails....
07-09-09, 06:25 PM
#20
Yea I will, probably get to it tomorrow night, if not then Saturday sometime. I'll also have a friend who is better with electronics double check my work with that multimeter then i'll go over all the sensors just to make sure they are ok.
07-11-09, 09:37 AM
#21
Did some more checking with the multi meter, had my Dad double check my work, and they all seem to be in spec. Pulled the UIM off, pulled the fuel rails and ran the fuel pump to see if maybe the injectors were stuck open and flooding the engine, they aren't, they are dry as a bone.
Checked fuel pressure again, still hovering under 30 psi although it starts to drop slightly after a few seconds, but I believe this is due to a slight leak on the pressure gauges hose (I can't get it to stop leaking, its from Harbor Freight so I guess no shock there)
Guess my next step would be the fuel volume test, or maybe to send the injectors out to get cleaned I don't know, I'm getting sick of working on this car, I'm obviously missing something, but I've been at this for a week and its starting to wear on me... Sorry for the rant guys...
Checked fuel pressure again, still hovering under 30 psi although it starts to drop slightly after a few seconds, but I believe this is due to a slight leak on the pressure gauges hose (I can't get it to stop leaking, its from Harbor Freight so I guess no shock there)
Guess my next step would be the fuel volume test, or maybe to send the injectors out to get cleaned I don't know, I'm getting sick of working on this car, I'm obviously missing something, but I've been at this for a week and its starting to wear on me... Sorry for the rant guys...
07-11-09, 11:28 AM
#23
Decided to put the engine back together and try the only spare ECU I have which is off of a S5 NA, figured if nothing else it would check another thing off the list and IT RUNS!!! Didn't drive it because I don't want to risk damanging anything since the N351 has no provisions for boost etc, but it started right up and seemed to run normal. I'll post a wtb thread for a new N374 ecu and hopefully that will do it. I'll post once I get a new ecu with results.
