I have an 87 NA, and am having an issue with it. I've just replaced and set the TPS on it, and I think it has solved my issue with the car not wanting to idle, but am now having a revving problem.

In neutral, if I stop on the gas, it revs nicely up to about 3000 RPMs (not quite 3800 unless my tach is wrong), and then it just cuts out completely. It's almost like a slow rev limiter, because if I rev it up slowly, I can go over 3000 RPMs no problem. When it cuts out and revs drop, it will start back up and rev up to 3000 again, repeat.

So what could be going on here, I need some help. It does not sound like the 3800 rpm hesitation, because it not hesitating, it cutting out.

 

If this problem didn't exist before installing the new TPS, I would suspect it as being the cause. What happens if you unplug it entirely? The car can run without one; it just won't run all that smoothly.

 

agreed ^

 

Update, I took your advice and did a little troubleshooting around the new TPS I put in. In short, it didn't make a difference. Here's exactly what I did:

- Started the car as is with TPS in it, it idled at 3000-3500 RPMs for about 30 seconds, then droped down and eventually stalled (my stalling issue is not yet fixed). I didn't touch the gas.
- Unplugged TPS started the car, revved it up WOT. It revved past 3000 this time, but this time it didn't rev past 4000. This time it did NOT act like a rev limiter, but more like an ignition problem, it just started running rough, and wouldn't rev up any more.
-Plugged the TPS back in, and did the same thing. This produced the same exact symptoms as the last test.

So what could this be?? Timing? Battery/alternator? 3800 rpm hesitation??

 

is the motor hard to start hot? have you checked basic things like plugs/wires and compresson

 

I'm not really sure if its harder to start when it is hot. If it is, what would that indicate?

It's got new plugs an wires, so that should be good. I checked the compression, and it was low, but even. There were a lot of things that could contribute to it reading low, so I'll test it again to be sure.

 

hard starting is a symptom of low compresson. how low is low? my turbo2 is running like 35psi and still pulls 10 psi so how low is urs

 

Now that I think about it, it does start fine when warmed up. When I tested it, it was reading about 55psi across the board. It sounded like the gauge wasn't making a perfect seal though... and I'm in Colorado, and the engine has a street port, and the engine was cold.

 

Have you checked your boost sensor and since you are in a high altitude environment how about the atmospheric pressure sensor as well?

 

I have an NA, so I don't think I have a boost sensor. Is that the equivalent of the pressure sensor on NAs that is the little black box next to the passenger side strut tower?

I do not know what the atmospheric pressure sensor is, can you explain?

 

Same thing.

The atm. pressure sensor is located behind the passenger side kick panel and the service manual describes how to check it although I would focus the attention to the boost/pressure sensor first.

 

OK, I will try to check the boost sensor tonight then. I assume the service manual explains how to do that.

 

Pay attention to post #3 in the link included except for the Br/R wire should read 3.5 to 4 volts for an N/A. Also, you could remove the vacuum hose, plug it, remove the TPS sensor plug and try to rev it over 3000 RPM.

https://www.rx7club.com/showthread.p...t=boost+sensor

 

My gxl would do the same thing. Found out it was a faulty AFM or the flapper on it was stuck and wouldn't open correctly. I just lubed it and it worked great after that. You can check just by taking off the air intake and looking at it while someone else revs the gas. Just my exp

 

Thanks for the info, I'll check it out tonight.

Great, I'll check that out too. Just curious, but did that also cause cold idle problems for you?

 

This a 87 engine in a 85 car? Using the 87 ECU?

Won't rev over three grand in the driveway..............does it just sputter when doing that or die?

Can you backprobe the 87 ECU pin 2G and see if its' reading approx 1vdc at idle with a fully HOT engine. Should. All elect plugs connected when doing so.

Then backprobe pin 2B for the boost/pressure sensor and write down its value. IF the reading is say.............4.5 to 5vdc.......the wiring is open b/t the sensor and the ECU and is part of the driveway problem.

And while you there, go to the small plug on the ECU and with key ON engine OFF, see if you have batt voltage on the light green/white and light green/red wires or not. Your allowed to remove the small plug from the ECU and probe those two wires IN the elect plug while it's not connected to the ECU.

And while your there, go to 2I on the middle plug and see if the green/white wire in that socket is reading approx a half volt with a HOT engine. Like 0.4 vdc to 0.5vdc. Plug MUST be connected to the ECU and engine fully warmed up/hot.

Almost sounds in some ways like you have your fuel rails connected up WRONG. Or in this day and age WRONGLY. FPR is the LAST thing in the system before the fuel goes back into the fuel tank to be recycled. Yep. Fuel lines on wrong at the PD and FPR and rail ends. Yeah. Solved that baby. Gone.

 

Thanks for the info. Its more of a sputtering (now). For clarification, its an '87 GXL. I'll update my sig...

Hmmmm... you might be onto something. I thought the fuel lines seemed wired up kind of weird from the PO. Anyone have a simple diagram of how they should look?

 

I remember it running correct just not revving over 3k. Good luck

 

The best I can do for routing of the fuel lines is the jpg attached. Fuel comes out of the fuel filter...........gets connected to the hard line on the engine........goes to the primary fuel rails front end which has the PD on it............goes thru the primary fuel rail......exitst the primary fuel rail and goes to the aft end of the secondary fuel rail.........goes thru the secondary fuel rail and exits the fwd end of that rail where the FPR is............leaves and goes back to the fuel tank in a continuous cycle as long as the pump is running.


The 86-87 FSM had a procedure for check to see if the secondary injectors were working at 3800 rpm. They had you remove the TPS connector and unplug the vacuum line on the pressure sensor and plug that vacuum line.

Then you rev the engine over 3800 rpm and listen to the secodary injectors with a listening device to hear them start to click at over 3800 rpm. Personallly I found that when you rev the engine over thirty eight hundred rpm, that the secondarys would come online and the engine would sputter for a while at just over 3800 rpm. ................which brings me back to my last post where I asked what the TPS voltage is AT the ECU and what the voltge is for the pressure sensor at the ECU. If I found both missing............that might be the cause of the problem.

 

since no one said anything i will 55psi is wayyy low and out of spec. spec is 85 on a hot motor. it will still redline and should not sputter with compresson that good just stating that its very low and that wont last long

 

Okay, my fuel lines generally look like that... except for one important difference... My main fuel line coming out of the filter, and the fuel return line, are both T'd off, and are directly connected to eachother! That seems like it could cause low fuel pressure.

Is there a good reason to set it up like this... or is this a big WTF for the previous owner??