Good day all!
I have searched the forums and haven't found my specific problem so here I am.

I recently purchased a 1989 RX7 GXL. It has about 25k miles on a rebuilt engine (reputable company, new rotor housings etc.) with a small street port, corksport intake, and corksport "power series" header and exhaust. No catalytic converter. It is running a stock ECU. The air line that normally goes into the exhaust is zip tied out of the way and I'm not sure what the story on O2 sensor is. (Isn't that in the exhause somewhere?) Also has an aftermarket clutch (forget the brand) a racing beat flywheel, and a short shifter.

The car starts up fine, idles great, and runs up to redline willingly. The problem occurs when under light load, such as cruising down the highway at a constant speed. It starts hesitating or misfiring, and the power surges cause the car to lurch. Floor the throttle and it is smooth again all the way to redline. Or push in the clutch and it drops down to a smooth idle.

Having just got it I have only changed the oil and oil filter, and the spark plugs so far. I am away from home for the next six days but when I get back I am going to change the air and fuel filters, as well as the transmission and differential fluids. I haven't cleaned the grounds but at a glance they look good. I have a Haynes manual for it as well.

Any ideas whats wrong????

Thanks in advance.

 

You will want to check the voltage on the Green/Red wire at the TPS w/key to on and the engine at operating temperature (completely warmed up) and the voltage should be 1 volt. Report back w/your findings eventually. And at what engine speed is this hesitation problem occuring?

 

It does it a varying rpm, just always under partial throttle. I've probably seen it between 2500 and 6000 rpm. I should also mention that it is intermittent. When I test drove the car it was fine. . .

TPS is throttle position sensor, correct?
Do I check the TPS voltage with the car idling? Or do I warm it up, turn off the engine, turn the key back on then test?

 

[QUOTE=flying_goat92;11097353]It does it a varying rpm, just always under partial throttle. I've probably seen it between 2500 and 6000 rpm. I should also mention that it is intermittent. When I test drove the car it was fine. . .

TPS is throttle position sensor, correct?
Do I check the TPS voltage with the car idling? Or do I warm it up, turn off the engine, turn the key back on then test?[/QUOTE]

Either way will work.

 

I finally got around to adjusting the tps on my car.

I warmed it up fully, then uplugged the six pin connecter and put an ohm meter on the black/red and green/red wires. Showed approx 1700 ohms with the throttle at idle. Adjusted the screw until I got 1000 ohms. To get there I had to screw the adjustment almost all the way in. Drove the car and it was still running exactly as before.

Tried adjusting the tps again, this time by using the three pin connecter behind the air box. Adjusted the screw until only one side of the three pin connecter had voltage with throttle at idle. Test drove and same old problems.

Am I adjusting the tps correctly?
Are there any other things I should be looking at?

I still haven't changed my fuel filter. . .

Thanks

 

Have you checked for codes. On your S5 there is a Green check connector near the leading coil which has just an Orange wire to it. Ground this wire to the negative battery terminal and w/key to on any codes should be displayed.