Can't get error codes on S4 FC3S
 

So the other day I was going along the freeway and my 1986 GXL (Auto transmission) RX-7 decided to go into what I can only assume is limp mode. Stuttering, sounds rather like a ported rotary, no power, when I shut it off, would start fine, but resume doing so after a short time of driving. Ended up getting it towed home, and am trying to figure out what the problem is.

I followed the directions as close as possible on FC3SPro but can't seem to get the error codes. Now, the one place I deviated from the instructions in making the tester is that the lights I got had no apparent indication of negative or positive wires, but they're LEDs so I don't think that should matter a lot?

Anyway, putting the tester in, the only way I can get any light to light up is with the spade that should be in the ABR plug (The one with two wires connected) plugged into DCC2 and the light that will light up is the one that gets its single plug plugged into the ABR spot. I can't find a combination that will make both lights light up, but that's rather useless anyway since if they're not plugged into the correct spots, I won't really be getting the right reading anyway.

Any thoughts on what's going wrong here? I even tried messing with the tester and swapping which two wires were connected together with no effect. Any help would be appreciated, I own 3 cars and yet I'm still having to borrow one from a friend at the moment as the GXL was my DD. :blush:

Thanks in advance!

-Ernesto

There is no such thing as limp mode for S4s. If your symptoms are no power and a rough idle, the first thing you should check is compression. As for checking codes, LEDs are polar, so you have to be sure they're hooked up properly.

Odd, could have sworn I read a post from somewhere that said the S4 had a limp mode. I guess I was mistaken. I don't think it would be compression, considering that it's not at all consistent (As well, that would be horrible as the engine has ~10,000 miles on it)? It starts up fine, will run just fine for a while (varying amounts of time, seems to run longer the longer I let it sit, almost as if something internally is cooling down, but it doesn't seem as if it's the engine itself, as the temperature gauge is pretty much where it usually is, though it could be wrong), then start bucking and stuttering. The idle on startup is perfectly fine and smooth, only after the stuttering starts is the idle rough). And by no power I mean I step on the gas pedal and while the RPMs will rise in average somewhat while bouncing all around, zero power is actually transferred to the wheels.

I'll mess about some more with pulling the codes and see if I can get the tester hooked up correctly.

Check your vacuum lines as well. Could be pinched or unplug any of various reasons of that

So RPMs will increase, but you don't get moving? That would suggest your clutch is slipping. Normally, that should be something that happens under any conditions, but clutch hydraulics can be affected by temperature change under the hood. My clutch likes to act up and chatter after awhile, but engages perfectly smooth when cold.

But would the clutch make the engine itself stutter? If so, how would I go about checking the clutch on an automatic?

I'll go look at the vacuum lines and see if anything is amiss. I had another suggestion from someone that it could have something to do with the EGR valve getting warm and sticking? Is that a possibility?

I also have some squeaky belts, could that be a hint to anything? Whether it is or not, any suggestions for a brand of belts that are as quiet as possible? Planning on swapping them out soon as belts that consistently squeak louder than the exhaust is loud is quite annoying.

Still can't get the engine tester to work, might have to go pick up some different bulbs...

Thanks for your help so far!

You don't have a clutch, but a torque converter instead. You'll also have a Vacuum Diaphragm on the driver side of the transmission housing. There is a vacuum hose connected to it. If the hose were disconnectted there would be only air in the hose and not fluid. If there is fluid present then the diaphragm needs to be replaced.

Also check the voltage reading at pin 2I at the ECU as this is where the Water Thermosensor connects to and it helps govern the amount of fuel dependent upon engine temperature. W/key to on it should read 2 to 3 volts cold engine and close to .5 volts w/a fully warmed engine.

Lastly, w/an engine warmed up to the max and w/key to on check the Green/Red wire at the TPS and see if it registers 1 volt. If not adjust the adjustment screw(located near the TPS and is housed within a spring) til it does.

I checked the vacuum hose on the side of the Vacuum Diaphragm, only air, no fluid at all, so that seems fine. Checking the voltage reading on the 2I pin at the ECU yielded 2.13 with a cold engine and .6 with a fully warm engine.

I've searched through the FSMs for quite a bit and embarrassed to say I can't seem to find the TPS. I know I found it once a TurboII but I believe they're different on NA/TII models. I did some searching but only managed to find pictures of Turbo2 TPS'. It would be helpful if you could give me some pointers on that. :)

Could it be the fuel system? I wouldn't think so though I wouldn't know so because it would seem that it would have been more consistent if it was fuel, rather than starting back up perfectly almost 100% of the time when attempting to limp it home.

It's just so confusing and frustrating with this because the car starts absolutely fine, perfect as normal, will idle forever (at least until the gas is out, I reckon, I left it idling for 30 minutes yesterday had no issues at all). I haven't taken it out on the road again since I had to get it towed home, but even if it somehow didn't do anything, I'd be completely nervous about it acting up again.

Thanks for the help and ideas!

The TPS is bolted to the front of the throttle body and near a bunch of linkage that has a part that rests against the plunger tube of the TPS. Also has a short pigtail harness w/three wires.

Alrighty, I will try that tomorrow, going to work now. Speaking of which, I decided to leave an hour and twenty minutes early for my fifteen minute drive to work, in the RX-7, to see what it did.

Well, about a minute into the drive, I felt a hitch and turned straight around, halfway back it had another weird hitch (hitch meaning it felt like it lost power for a second, like it did the first time). However, except for those two hitches, everything else was fine. I put it into third gear to about 4k RPMs, then into 2nd gear all the way to 6k RPMs, revved and responded fine, exactly like normal. Right as I pulled into my driveway it went into its 'stutter mode' so I ran inside and grabbed the camera. This might provide some inside?

This video shows what it sounds like when it's stuttering, I put gas into it (not all the way down, perhaps about halfway) twice in the video, and when it hits the 2k mark, it's not stopping because of me. I kept it in for a little bit, then when I let it out it would rev up sounding normal again, then go back to idling terribly.

Note, when I started the car it started perfectly and when I pulled out of the driveway and drove it drove perfectly, nothing at all amiss that I could tell/feel, and except for those two hitches, it was also fine till it started stuttering like this.

Video: http://www.youtube.com/watch?v=85Tea0T6Rno

Hope that helps a little.

Okay, so was away for a week, but now back to work.

I tried to check the TPS using the Ohmmeter method, as it seems to be the generally agreed on as most accurate, but either my TPS was ridiculously perfect, or I was doing it wrong, because the digital reader stayed at '1', which I would be surprised at.

I'm led to believe that this thing here is the TPS itself? And if so, which of these things do I need to test? Though, even if it is one or the other, I attempted to test both and got nothing.

The procedure is to warm up the car, turn it off, unplug the TPS, then test (and adjust if needed) correct? I guess I'm doing something wrong...

However, while I'm not any sort of expert, TPS issues seem to generally be more reliable in terms of, you have an issue when you turn on the car. Is that not correct? When my car turns on it appears to have no issues, and it takes a while of driving or a long time of idling to have the issue spring up.

Perhaps another clue, the other day I couldn't get it to start, and I knew the spark plugs were a bit old, so I swapped them out for brand new NGKs. For one, it seemed like it was flooded, so whatever the issue is, it seems to aid in flooding the car. After swapping out the plugs, it started right up, idled for about 20 minutes with no problems. I drove it up and down the road, probably about 7 miles, trying normal driving and driving in high RPMs. It's running a bit warmer than usual (The weather is also warmer, though I will be checking the cooling systems), but it didn't have any issues crop up.

The next day I took it out, drove for 15 minutes to a friend's house. No problems. It sat for I'd say about 30 minutes. Started driving it back, probably about 8 minutes, started having the same issue, pulled over, turned it off. It was flooded, wouldn't start, had to tow it home.

It seems like some sensor is going wonky and therefore the mixture is too rich? I don't know, I'm just grasping at straws here. If anyone has anymore ideas, I'd very much appreciate it.

As it's going, if I can't fix it in a short amount of time, I'll probably have to sell it as is, which I'd like to avoid. :(

Measuring ohms on very old wiring can give you faulty readings. The ECU is supposed to see 1 volt at the Green/Red wire as stated by the FSM. The plug is supposed to be connected during the test.

Okay, so maybe this is a hint? But an odd one. When I connected the reader it read ~3.83v on the Green/Red wire of the TPS. However, remember, it's idling perfectly at 750 RPMs. Therefore, when I tried to adjust the voltage down, the engine would start to idle lower and die.

On the other hand, figured out the ohm method, and though it may be a faulty reading, it's at 1056 ohms while warm and idling.

The ohm method is done w/the plug disconnected and the engine not running. You are not supposed to check for ohms w/the key to on or you risk doing damage to the electrical system as this is a no no. If you do the ohm method remember to disconnect the plug and check to see what the ohm reading is and when you did it previously what did you mean when you stated it "stayed at one." Not sure what this means.

As far as the voltage method the engine needs to be as warmed up as can be. Was it completely warmed up when you did this test? The engine can actually be running when doing the voltage method. The red meter terminal goes to the G/R wire and the black meter lead to a suitable ground such as the alternator casing/housing or the negative battery terminal and the key to on.

Those are both the methods I did. I'll retry the voltage one with a different ground spot as it's possible it was incorrectly grounded though I'm not sure how I got the voltage I did as such. Stranger things have happened, electrical systems hate me.

When I said it "stayed at one", when the dial is set to Ohms on my digital multimeter, it reads '1' by default.

Unfortunately I'll have to try again tomorrow as I have to go to work right now. I'll post results in the morning. Can I ask again why the TPS though? If it idles at 750 RPM perfectly with no fluctuations at start, how could it affect what the engine would do later during driving?

1 is usually infinite or open circuit, need to select a higher range when it says that.

I don't have much to add for the running problem though.

The TPS doesn't change the idle speed specifically as it is used to smooth out fluctuations in the idle mode and can affect other RPM ranges because it provides the ECU with voltage input based upon how far the plunger sticks out and this input data from the ECU helps the ECU coordinate the various sensors so they work in unison as opposed to against each other.

When using the ohm aspect of the multimeter you're suppose to turn the meter to the ohm setting then touch both leads together and the meter should read 0 ohms before measuring for ohms. If it reads otherwise, the meter is not calibrated properly.

I rechecked using the voltage method, it reads 1.19 volts fully warmed up. Rechecked the ohm method as well, still hovers around ~1050, so I would hazard to say the TPS is okay?

Use the spring encased screw near the TPS to bring it to 1 volt. 1.19 is a bit high.

Okay, I'll do that. Do you have any suggestions on how I could try and trigger the problem to see if it still manifests so that possibly I could figure it out in my driveway instead of driving around nearby and possibly needing to be towed?

If you keep the rpm level while driving below 3800 or so does the problem occur or does it only occur after the car is driven above 3800 rpm. If the Boost sensor vacuum hose is removed and plugged, and the TPS pigtail is also disconnected then this creates load on the engine so that the car's secondarry injectors, which only come online w/the car under load and rpm at 3800 rpm or higher will fire. While sitting in the driveway these injectors won't fire unless the car is tricked into being under load as suggested by doing as stated above.

It occurs under 3800 RPM as well as above 3800 RPM. As I mentioned above, once before did it begin misfiring (I think that's what it is, not entirely sure though) while just sitting idling in the driveway. But I didn't do anything different to it that changed it. That was with the previous plugs.

As this seems like it could be an electrical issue, it may be relevant that it's possible something is odd with the alternator. When I engage an electrical system in the car, such as turning on headlights, or changing the suspension from normal to sport, the voltmeter will bob down for a second before returning to its normal position. Currently with the car on and warm, the voltage at the battery is reading 14.96, though on the voltmeter in the car it looks more like it's around 13.8. So it could just be the voltmeter itself. I'm trying to enlist someone's help to read if there's an actual change in voltage using a meter. Though, it may be irrelevant.

The FSM says that misfiring can be caused by failing of the coilpacks. Despite the intermittent nature of it, is there a way to test to see if one is starting to fail?

EDIT: I should mention that the volt bouncing thing has happened since I got my alternator rebuilt about 4 months ago, but other than that, I haven't had a problem with it previous to now. Although, when it does bounce on the voltmeter, the RPMs dip a slight bit (while idling) so there must be something actually happening and not just the built in voltmeter being screwy.

The Black cable/wire bolted to the alternator is the output wire and you can measure the voltage on this wire while the car is running to see if the voltage is actually jumping around. The voltage should not be higher than 14.4 volts or so while measuring the output wire of the alternator and the voltage at the battery should be less.

Ah, wow. The alternator is putting out about 15.75v and now the battery while the car is on and idling is at 15.5v, but at 14.4v when the car is off. Also tested the 'dipping' and when I press the suspension changing buttons it goes down to 14v for a second.

Sooo, the alternator has an issue. I have a spare one that I believe is okay that I can try out. I have a couple of days off after today that I'll be able to spend messing around with this.

Then the voltage regulator in the alternator is acting irregularly, but make sure the two wire plug at the back is plugged in properly. The B/W wire in the plug should be on top while the W/B wire would be on the bottom of said plug.

Well my 'weekend' didn't go as planned, but finally got the different alternator in, it's working at 14.4v. The other was plugged in properly and everything, must've just had a bad voltage regulator. I was always a bit suspicious about it after I got it rebuilt a few months ago.

After putting the new alternator in, I took the RX-7 out for a drive, and at the very least, it went 17 miles without even being overly hot on the temp gauge like before. Last time I took it out it went about 10 miles before having an issue, if I remember correctly. So it's not a certain fix.

I'm kind of confused. I'm going to try taking it out for a longer drive soon hopefully, but I'm not really sure how this could have been the root of the problem? Or do you think there's something else that just hasn't resurfaced yet?

Figured I might as well resurrect this thread since I'm still experiencing the same problem, no point making a new one.

Went through a number of alternators, found out that the tester was incorrect in the first place, alternator was fine (Go figure, spent an annoying amount of money on 'alternator issues' before finding that out), and of course, after finding that out, a day after throwing a working alternator on, original issues resurfaced.

I did a compression test, engine is very healthy as I suspected seeing as it has about 12,000 miles on it. Both rotors above 110 PSI, all even bounces using a piston compression tester. Set the TPS first using voltage method, then fine tuned with resistance method.

My guess right now is leaky injector(s). By all appearances it's choking itself out on too much fuel. I'll start it, leave it idling, and after a while it will start to lope, sounding like it's misfiring. There's a strong smell of fuel, and sometimes it will backfire (either when pressing the accelerator, or trying to start it again). Pressing the accelerator will result in it attempting to rev higher, generally will go no higher than 3-4 thousand RPM and sounds absolutely terrible doing it. After a while of loping it will eventually kill itself. If trying to restart it seems flooded, but also very difficult to restart. I have a fuel cut off switch, and if I shut off the pump, it will start on what fuel is left in the chambers, but if I switch fuel on again, it usually dies again without actually starting and running.

Any other thoughts besides injectors? I have a set of 86 TurboII injectors that I believe are okay that I'm going to clean up and throw in to try, in theory it would use more fuel but, if they work, won't exhibit the same problem, correct? If that did work I'd send off the original injectors to a cleaning shop and put them back in when they got back.

Or could it be the fuel pump? I also have a spare TurboII fuel pump I can try, or if there's a test with a multimeter I can do that.

Never did get to test out the fuel pump unfortunately, for which I am kicking myself now.

I'm fairly certain it has something to do with the fuel system, and at this point I've saved up a bit of money and I'm going to start replacing things. I replaced the fuel filter a little while back and it definitely ran better... For a little bit. Then back to same old. Next step I'm going to replace the fuel pump with a new Bosch pump with fuel sock. If that doesn't work I'll remove the injectors and send them off to get them flow tested and cleaned if necessary (I do suspect if it's not the fuel pump it might be an injector stuck open).

If it's not THOSE... Well, I'll cross that bridge when I get there.

Unless there's any other suggestions? I'll hold off on ordering a fuel pump until mid-day tomorrow to see if anyone has ideas. :)

You can always secure the injectors to the fuel rails, unbolt the fuel rails (Put something under the fuel injectors to catch any fuel that may spew while performing this test.), jumper the fuel check connector near the passenger side strut tower, turn the key to "ON"... Not to "START". You'll be able to hear the fuel pump running. Check to see if there is fuel spewing out of your injectors. If so, your injectors are stuck OPEN. (There is a great example of this in the FSM. Fuel and Emission Control Systems E.G.I. > Section 4A - Page 70.) -> 1988 FSM: N/A Fuel and Emission Control Systems

I tried to do that but my fuel lines were too short to move the fuel rail with the injectors on them... I may have been doing it wrong, and may be worth another shot after today.

So now have a brand new fuel pump and fuel filter and still the same problem. Does injectors sound like it could even be the problem? It seems to encounter the issue pretty much once it's fully warmed up.

Check the voltage of ECU pin 2I, Green/White wire, which is the Water Thermosensor. It should be 2 to 3 volts cold and .4 volts fully warmed. Sensor helps to decide how much fuel is required relative to the engine temp. More for a cold engine, less for a hot one.

Finally got out there to check it. We may have a culprit?

At key to on, it was 2.8V, which is above FSM specs. Then started, it was 2.8V, which was okay, then it jumped to 4.95V for a second, went back to 2.8, started lowering as it got warmer, occasionally spiking to 4.95V, finally went back down to 1.2V as it was about halfway warm, spiked to 4.95V again, went slowly down to 4.8V and then sputtered and died.

Cold engine will be between 2 to 3 volts. Secondly, if it jumps to 5 volts then it's likely that either of the two wires in the plug are pulled back and not making good contact w/the sensor.

Kind of confused. Is this the water thermosensor? (not my engine, found this picture on the forum)

https://www.rx7club.com/attachment.p...1&d=1288745469

If so it's only got one black and green wire coming from it. I can't trace where it goes, as the engine is hot at the moment and it disappears into a bundle of other wires.

Nope, but it's close. It's located on the backside of the water pump almost underneath the alternator. It has a plug which looks like an injector/BAC plug (this is the dead giveaway). G/W and a Black ground wire.

Ah, found it. It was actually very slightly unclipped. I pushed it firmly back in, but the voltage still ended up going back to 4.6-4.8 and dying. The wiring to the sensor is in a rubber cover though. Unfortunately it's dark and raining outside so can't do any more tonight. I guess next step would be to remove the plug and clean off the contacts?

There are two contacts inside and make sure that both are not recessed/pulled back as this is likey the cause, and occurs fairly often it seems. And the plug could be as snug as possible, but that doesn't mean that one of the wires is not pulled back in the plug.

I popped out the sensor today, and the contacts inside were fine. No play, not recessed. A tiny bit grungy, so I cleaned them off, put it back on, clipped on the plug, and while it seemed a little better, as it got down to .67V while warming up (though flashing to 4.95 twice again), at .67V it went up to 4.95 for a third time and chugged and died again.

If the plug connection is good and the sensor was good, which you can test using the method in the FSM, then the possible cause would be the G/W wire is damaged as it meanders its way back to the ECU or the ground wire is faulty. And when you say the contacts inside were fine are you referring to the plug or the sensor?

You can take a ohm/resistance reading on the G/W and see what that reads and this is done w/no key. You can also turn the key to on and measure the voltage on the ground and w/respect to the ground you can also place one meter lead on the ground wire and the other meter lead to a good ground and w/the meter set to ohms see what you get as it should be a rather low reading and this is also done w/no key. You can also jiggle the wires that this harness runs to when taking these measurements to see if you get a range that would indicate that it is okay at one moment but not another.

I can't test the sensor yet, I'll see if I can pick up a thermometer tomorrow (Sadly don't have one lying around), but I did get the resistance/voltage readings.

I had the setting on the multimeter at 200 ohms, wasn't quite sure if that was correct, but it provides reference.

G/W resistance: 1.2
Ground resistance: 1.2
Ground voltage: .02

Also just to make sure, to get the ground voltage I put one end on the ground tab then the other on a good ground with the multimeter set to volts, correct?

Wiggling around the wires made it vary between 1.1 and 1.2 occasionally.

In the meantime you can try starting the car and as it warms up and gets close to .5 volts on the G/W wire before it konks out disconnect the plug to the Thermosensor and the ECU should default to a warm engine temp and this should allow the car to run properly w/o any interference from the ECU. The sensor in a normal situation sends a resistance reading to the ECU which reduces the voltage on the wire and the ECU then uses this reading to help identify how much fuel is needed based on the engine temp. Now the ECU uses a voltage signal sent to a group of sensors such as the TPS and AFM for example and it's referred to as the voltage reference or Vref which should be 5 volts. You might want to measure pin 2A (should be a Brown based wire) w/key to on and while running and see if it reads 5 volts.

Alright, so I started the car, couldn't actually tell when it got to .5 because it leaped to 4.95 in about a minute and then slowly went down to 4.76 and died. It fortunately started right back up with no chugging (pretty rare for it to do that), unplugged the the sensor, and it's been running a good 20 minutes now and is still running, at full warm temperature.

The brown wire read 4.95 the entire time.

As long as the engine is close to warm the car won't really need the sensor, but it might run a little rough after starting a cold engine and the car could easily have a difficult time starting if the engine is cold to begin with w/o the sensor. You'll want to still test the sensor itself, but could you explain the method used to test the resistance on the G/W wire?

I backprobed the G/W wire on the ECU, then ran the other end to the plug under the hood. Since it was covered I couldn't actually tell which was ground and which was the G/W wire, but I guessed that since only one gave me a reading when plugged to the ECU, and one gave a reading when grounded, that signified which was which.

Not exactly an expert electrician so hopefully doing this correct. I'd definitely welcome advice on how to do better.

The plug to the ECU, housing the G/W wire, needs to be disconnected before measuring the resistance on the G/W wire that is backprobed.

Okay, I went out and did it again with the ECU plug disconnected but it still registered as 1.2.

And if you want to make sure you are measuring the correct wire on both ends then you can do a continuity test and if it rings out you then know you have identified both ends to a segment of wiring.

I'm kind of confused. Is a resistance test the same as a continuity test? It rather looks like that from what I've been reading.

Going to try and get my hands on a thermometer to test the thermosensor tomorrow. I'm also kind of confused on that as well though. When this first happened and a few times after that as well it was on a fully warm motor. The first time it happened I had been driving g for 40 minutes. If it should sword to different sensors when warm is there something that could make it swap back to the thermosensor which seems like it's having issues?

Not sure what this means. And the ohms test is a bit different and uses a different setting on the meter. Ohms would normally have the Omega symbol which looks like an upside down n w/feet and the continuity symbol is usually a sound wave looking image (V shaped like a tornado).

EDIT: If you place both meter leads together while set to continuity, the meter will emit a solid beep. And when using the ohm setting it is normal to first touch the meter leads together to reset the meter to 0 ohms.

Wow, autocorrect messed that sentence up and I didn't notice. What I meant to ask was "If the car switches to a different set of sensors when warm, what could make it swap back to using the thermosensor which seems to be having issues and thus causing the issue?"

Also my multimeter doesn't appear to have that feature. It's a pretty simple one, AC, DC, and Resistance.