Randomly as I drive, the car will develop a terrible sputter, that gets worse the more throttle I give. Lots of backfiring, and a very rough idle. But then the problem seems to magically go away, IE park it at night barely running, turns on fine the next morning. It comes and goes and will drive fine for a week, then do this for a week. Been dealing with this problem for around 2 months now. Seems to happen more when its hot, but recently has been pretty much all the time, to the point that I can no longer drive the car. Changed/checked spark plugs, and wires but the old stuff seemed fine, if not very fouled. New plugs seemed to fix it for around 2 days, then the problem came back. Also swapped coil packs, which did nothing.

Leaky injector maybe? Seems to have a fuel smell in the engine thats stronger than I would expect.

JDM S4, intake, exhaust, rtek 2.1.

Video shows how it is currently running....or not running...

 

disconnect the trailing coil and see if the issue is the same , suspect it may not be toggling between T1 and t2

 

CAS set properly?

 

I doubt it is the cas, or it wouldn't be intermittent.

I did a road rally in feburary and just beat the ever living snot out of my car. When the race was finished I shut my car down for about an hour. When I started it back up it started doing what your car is doing in that video but was able to get it running with some fancy footwork with the gas peddle.

It never has done that before and hasn't done it since, so I never figured out why that happened.

 

jjwalker, thats half the problem, is that it just clears up sometimes for pretty extended periods of time. Got another video of it actually idling I am going to put up.

 

Pardon the "me talking over the idle like an idiot"

 

Wow, that sounds more like a lawnmower than a 13B

If I'm reading this correctly, it is intermittently flooding itself silly right? Intermittent funkiness usually points to a sketchy ground connection.

Proper RX-7 Grounding Procedures

There are 4 grounds I'd suspect, given the symptoms: Main ECU ground (under the UIM), MAP sensor ground, the Main Ground and the Coils' grounds.

The strange thing about the coils' is that their ground comes from being bolted to the inner fender, which is a painted surface and most likely not the greatest conductor. While it works fine when the car is new and clean, 25+ years of gunk can make all sorts of weirdness come out as you've experienced.

I'd suggest giving every ground a good cleanup per Aaron Cake's article. As for the coils' grounds, adding a redundant ground to the Main Ground point would be a good idea and should rule out any ignition sketchiness in the future.

To make it easier to attach the negative cables and the new coil grounds, put the main ground bolt in from the wheelwell side.

 

Is your charging system up to par? You might want to try to jumpstart the car to see if a low voltage output situation is causing the problem.

 

could try driving with a timing light hooked up. see if the ignition is cutting out. it's usually good practice to get a general idea of where the problem is stemmng before further diagnosing and zeroing in on the culprit. ie, start by determining whether it's fuel or ignition related. then once that's figured, further testing to narrow it down to the culprit.

heck, try checking codes first. i know these obd systems were in their infancy, but it may throw you a bone. always check codes first

 

Is your car an S5? If so, than you might want to check your AFM. When my 90 GXL was several months old (yes, I am the original owner), I had an intermittent problem where the car would sputter like it were running out of gas or sometimes just quit but would usually start right up and run fine. Took it back to the dealer and after a week of troubleshooting, they found that the temperature sensor in the AFM was defective. This might be something you want to check out.

 

Quick update on this while I wait for another video to upload.

I have performed the following:
Checked all grounds, wirebrushed, brake cleaned, and replaced with new hardware, as well as adding a massive cable from the airpumb bracket to the strut, just to be sure.

Charging system is just fine, have an FD alternator in the car, but this problem was happening before that was in there anyway. It was just way more intermittent back then. Had kind of hoped it was some kind of voltage drop.

Have not checked codes, Im dumb and forgot to do that today.

Not a S5, but when it IS idling, the car dies as soon as the maf is unplugged, and also does the same thing when its idling like crap.


I also worked on the TPS today. When plugged in, my stock unit got 1k ohm at idle, but as soon as I touched the throttle, it dropped down, till it was full throttle sitting at around .5k ohm. Thinking this was the issue, swapped in a new one, that bench tested fine at 1k ohm to 5k ohm. Plugged it in, and got hte same readings. Im 99% sure that whatever is causing this is the issue. Any ideas what would change the resistance?

Forgot to mention, also swapped injectors with known good units, and eliminated the FPD, but this changed nothing at all.

 

I don't think your TPS is the issue here. Generally speaking, most TPS's resistance decreases the more you open the throttle. Another way of explaining it is that at idle, the TPS wire to the ECU will read 0v, while at WOT it will read 5v.

If your TPS's resistance is INCREASING as you open the throttle, it is wired incorrectly. This would result in the ECU believing the engine is at WOT and dumping in ludicrous amounts of fuel accordingly.

 

I was just going off of this guide FC3S Pro v2.0:&nbsp TPS adjustment for 1986-1988 RX-7 Turbo II models

So I thought it was supposed to go from 1k ohm to 5k ohm, which my tps does outside the car, but once it is wired in place, stock plugs an everything, it goes from 1k ohm to 1/2k ohm.

I completely agree that it something to do with the tps, I just dont get why I would get completely different readings when its plugged in VS outside the car.

 

You cant check resistance plugged in. It does weird things in a circuit and finds other ways to do things. If you go by resistance, you must unplug the connector. You have Rtek 2.1, what does it say the reading of the tps in the ecu is?

Listening to it running, its not hitting on one rotor. I had a similar issue when an injector harness broke. And at idle it only runs the primaries. Easy way to tell which injector harness to go after is when its running like that, remove a plug wire and see how it runs. No change then you found the rotor to look at, changes, then you known its the other you need to look at... It will take some digging, but if its not broke it could be shorted in the harness or in the ecu. Do you have a stock ecu that you can plug in and test with?

 

Holy crap, Im stupid hahaha. I totally missed that he had it unplugged, thank you for pointing that out. Let me check the reading on the TPS at the rtek real quick.

I do have a stock ecu to plug in, however this issue was happening when that was in as well. No real change in it with the rtek or the stocker.

I will also check the plug wires.

 

which harness are you using? It sounds like its only running on 1 rotor, either because of lack of fuel or spark.

 

So unplugging the wires just kills it, either rotor.

Checking the rtek tps reading, it goes from 19-96 depending on throttle. Idle is at 17-20, but for the most part reading at 19.

 

Not sure what you mean by what harness am I using, just the stock 87 turbo harness. If you are asking if I have a swap or something, its just the stock Japanese car.

 

Is it jumping from 17 to 20 while idling? Not very steady if so. May just be cause by your shaky engine though

 

No not when its actually idling. Just when I go from full to idle. Kind of like it goes a little more closed sometimes than others. But its usually for a split second, then goes back to 19/20

 

takes 2 minutes to check codes. could save you a lot of time and energy. and it gives you a good foundation to begin your diagnosis. instead of blindly shooting in the dark hoping to hit the target. which is what you're doing

 

Just finished checking the codes, and didnt get anything back.

 

TPS is not your problem. an easy way to troublshoot tps problems is simply unplugging it, it should idle and drive fine without it, its mostly just used for fuel cut when decelerating

its probably not related to your ignition, since you unplug either wire and the engine dies. seems fuel related.. You tried different primary injectors, so probably not stuck injector.

It could be a vacuum leak, get some starting fluid spray, and while its idling, spray aroudn teh intake manifold. If the idle changes at all (or dies), its a vacuum leak.

The next thing i would try is swapping the AFM. Or you could try sweeping it with a meter. THe voltage on the signal pin should go from 0V to 4V, close to open, if i remember correctly. the AFM pinout is in FSM. You can test it off the car with a 5V power supply, or by backprobing the ECU connectors with ignition key on. Check the engine section of the FSM for which pin to check at the ECU

if all that checks out, check for 12V on each injector wire at the ECU, or you can do a continuity check from each injector back to the ECU

 

While I was replacing my clutch line, I found a solenoid opening and closing all on its own, key in the on position but not started. Its hte grey solenoid on the rack on the US drivers side. Disconnected it and just by-passed it to see if it would make a difference, but it sure didnt seem to.

Weirdest thing though, is I got it to start up, and kept it revved to around 3k, until it smoothed out. Once I did that, it will idle down to ~700, and slowly but surely die out, smelling richer and richer. I raised my idle to around 1100, and now it seems to be alright. Drove to and from work today with basically no big issues. Couple sputters but thats it.

 

That is the switching solenoid, and it shouldn't be clicking with just the ignition on. It tells the ACV to direct air to either the exhaust ports or the split air pipe.

Sounds to me like you are having some sort of electrical problem at this point, but without further research on your part, I am not sure what advice to give at this point in time.