RenoCYM

It's a '93 R1, totally stock under the hood - no mods at all to engine, intake, turbos, ECU, etc. Has 59,400 miles on it. I'm about to park the darn thing with the keys in the ignition in the worst part of town and just be done with it.

I've had a rough idle for quite awhile, smooths out under load, but with a light load or at idle it's rough. Also, I noticed that when I floored it (WOT) in third or fourth gear above 4K rpms nothing happened, as if I'd already run out of throttle travel. After a couple really disastrous trips to the Mazda dealer to try and fix it, it actually got worse, so I decided to try and fix it myself. Reading up it sounded like perhaps the TPS needed to be adjusted.

Checking the manual I found the TPS was on back wards, with the plug pointing towards the engine. The dealer said it didn't matter, but I figured it might be 180 degrees out of phase, so I took it off (nasty job!) and put it back on the correct way. I was going to set it according to the method described in many threads here: using a multimeter and a safety pin; but no matter how I probed, stuck, mashed that safety pin in there I can't get a reading. Just .2 V, that's it, and no change with full throttle, so either I'm not doing it right or it just doesn't work.

Anyway, since I had to just "eye-ball" the TPS adjustment I started with it in the middle of its adjustment range and started the car. It went right up to 5k rpm before I switched it off. I rotated it all the way clockwise, started the car and once again the revs shot through the roof before I keyed it off at 7K. So, I kept rotating it counter clockwise trying to get the idle down, and ended up at the end of its adjustment range counterclockwise. The lowest I can get the idle now is 1200, no amount of adjusting the AAS screw or the two adjustment screws on top of the throttle body will lower it past that. In fact, they all increase the idle, especially the AAS. And now the air pump is cycling on and off; about one second on, about 5 seconds off, at idle causing the idle to surge up and down with the air pump. Under a load or on the road, it does have better throttle response, though. And instead of the revs dropping like a rock as soon as I push in the clutch to shift, the revs hold for just a beat - making shifting easier than it was. And it doesn't seem to want to stall when slowing for a traffic light, but that could just be because the idle is so high.

And, now the Check Engine Light is on. In the 10 years, and many boost and vacuum problems I've had with the car, I've never seen the CEL. What could I have messed up with the TPS that would trigger this? I've tried resetting it with the battery cable trick, but it comes right back on after a few seconds of idle.

Help. This geezer is getting pretty frustrated with this car, and I'm a long way from any competent RX 7 shop.

Prophet7000

I don't understand your explanation of how the TPS was on. Is it turned with the plug side towards the passenger side of the car? As far as testing goes, I didn't need a paper clip. I just pushed the probes on my cheapy rad shack multimeter in there. If you're sure you're getting a solid connection at the TPS plug and you're sure that the ground you're using is actually a ground, then I'd suspect a TPS issue. They've been known to have the contacts go bad. Oh one last thing, when you mounted the TPS back on did you make sure that the metal tabs from the TB are touching the FLAT sides of the plastic tabs on the TPS?

ArmitageGVR4

iTrader: (13)

It's not uncommon to flip the TPS 180 degrees in order to get more clearance for an aftermarket (GReddy or the like) oil filter sandwich. However, based on what you're saying, if you can't get ANY reading at all then maybe the TPS is completely dead. You really have to poke the safety pin through the wire insulation to get a reading though, and of course the vehicle power must be on. Yes, a bad TPS calibration or failed sensor would cause the CEL to come on. You can verify this by jumpering the diagnostic block and reading the CEL flashes on the dash.

Don't despair though, it sounds like you know exactly where the problem lies and fixing it isn't that bad of a job.

RenoCYM

I'm just frustrated, I guess.

Yes, the TPS was on backwards, with the plug on the engine side of the TB, I rolled it back to where it's suposed to be (just like the picture in the shop manual). By "touching the flat sides of the TPS" do you mean inside the little notches? The TPS had two little nooks, notches, whatever you call them, and I fit them OVER the metal tabs in the TB, so they would catch the tabs and move them when I adjusted the TPS - is that right?

I will try again to stick a pin into the wires through the insulation and get a reading. And yes, I've had the ignition on when I've tried to get a reading at the TPS, to the last click before starting. I feel better knowing that the CEL is caused by the TPS. One more question; would the car still run if the TPS has gone completely Tango Uniform (**** up)?

However, since I"ve already run the gamut of its adjustment, from one extreme to the other, I'm not sure I can get it any better. It's already as far to the "slow" idle adjustment as it will go, there's no more movement left in that direction, and the other way just increase idle to a high rev.

Prophet7000

Nope. The metal tabs go on the flat side of the plastic tabs not in the notches.

mad_7tist

did u just twist the tps while it was in contact with the throttle body? or did u un bolt it turn it 180,and then engage the tabs?? souds like the tps is holding the throttle open a bit

RenoCYM

I completely removed it, then mounted it as it should go.

Okay, I'll take it off and make sure the metal tabs from the TB go on flat side - opposite side of where I have them - of the notches in the TPS. Thanks, maybe that will fix everything? It does seem that the throttle is being pushed open by the TPS, and maybe that's the reason.

Prophet7000

Yeah, you won't get the correct voltages with the metal tabs on that side. The tabs just move away from the TPS tabs with throttle also. Get those set right then check your voltages and adjust.

RenoCYM

Thanks, I'm hitting the garage tonight as soon as I get home from work.

RenoCYM

Prophet7000, I can't thank you enough. You were right, I had the tabs on the wrong side, such a little thing to cause such a big difference. That's something that isn't mentioned in the shop manual or anywhere, and another example of answers that can only be found on this forum. Thanks again.

I took the TPS off, made sure I had the tabs in the right position, and remounted it. I got some hex head bolts the same size as the screws (Home Depot!) and while I had it loose I buried a safety pin up to the hilt in the second wire. Voilą, voltage! With the hex heads it was much easier tightening and loosening to do the adjustment, and with the voltage within spec the car idles right at 800, and there's not as much roughage or missing. And, of course, no CEL either. The next step is to take it out and hit the highway for a high speed road test and see if my throttle response has improved above 4K.

Prophet7000

Hey man, just glad I could help.