Th0m4s

I've got a very strange problem. I believe fixing it can't be a big deal but i've got no clue where to start searching.

My RX7 runs very good till round about 4000 rpm. At 4000 rpm it's bucking one time and accelerates very slow for about 1 sec. It's like the turbo stops turning but the stock gauge shows no difference in pressure at all and i still can hear the turbo spinning. The car is also missing much power at high rpm. I can't even get it higher than 7000 rpm in fourth gear anymore because of the missing power and it's only running 190 km/h (120 mph).

What is really strange is that when i took a test drive it strarted acting normally after 30 minutes of driving for about 10 minutes. I even was able to accelerate to 240 km/h (150 mph) without any problems but 10 minutes later everything was like before. No power and so on.

You should know all vacuum lines have been exchanged (not by me) because of some leaks. I also got new spark plugs and my injectors were cleaned because they were clogged. The compression is good and there are no problems with the coolant gaskets.

I guess something is stuck but what could it be? Where should i start searching?

Aaron Cake

iTrader: (1)

Check your grounds:

http://www.aaroncake.net/rx-7/grounding.htm

Did someone install larger secondary injectors at some point? They should be 550CC. Larger injectors without some way of tuning them will run quite rich until the engine reaches an RPM/boost point where that fuel can be burned.

Th0m4s

I allready read through your side and checked all the grounds and regrounded the 2 wires from the ecu because they looked bad.
All 4 injectors are the original 550ccm ones. I pulled them out and cleaned them because the secondary ones were not opening correctly and the primary ones weren't closing. Now everything is ok with the injectors.

By the way i just tried to set the idle speed because it didn't go below 1500 rpm even if the engine was 100% warmed up. I used the factory manual for that but had strange problems. The previous owner was playing around with the idle air adjust screw and the variable resistor for the fuel. I guess he did that because of the vacuum leaks.

I drove the car for about 30 minutes (idle was at 1500 after that), then shut the engine down, connected the 2 ports of the initial set coupler with eachother, started the engine again ( it went up to 1500 again) and tried to set the variable resistor first like the manual said. (I also checked the TPS some days ago. Everything ok there.) Now matter how far I turned the potentiometer to L or R there was no response of the engine. It was also missfireing all the time. At least it sounded like that. The engine was shaking sometimes and you could hear muffled explosions while standing behind the car.
I shut the engine down again, waited 2 minutes and tried again. Now the idle speed immediately went down to 1000 after I started the engine and I was able to adjust the resistor. I turned it up till the engine didn't run faster anymore. After that I set the idle speed to 750 with the air adjust screw.

Somewhere I read that if you screw the air adjust screw completely in the engine should stall. Mine didn't. It was still running at about 560 rpm. A bit rough but it ran.
Could that be a sign for another small vacuum leak or even 2 mixed up vacuum lines? I should have done the vacuum line thing on my own. At least than i would have known what was done to the car.

satch

iTrader: (1)

I wouldn't worry about the engine not stalling w/the idle adjust screw all the way in. There are other factors in setting idle that if any of these were altered a bit it would likely cause the the adjust screw you mentioned to respond differently then if everything was set to spec.

Th0m4s

I just rechecked everything again and took a long test drive i think Aaron was right. There must be some grounding problem. That bucking at 4000 rpm seems to be that famous 3800 rpm hesitation.

My only problem now is that it can't be the ecu grounding anymore because it's new. Could it even be the main grounding on the backside of the engine?

By the way: My oil pressure gauge is showing weird values. They are much too low (0-2). The water temperature gauge is also showing a much too low temperature (about 40-50°C). Should be at least 65°C when fully warmed up, right? Are they using the engine grounding, too?

Thanks for helping me that much Aaron and Satch.

Oh and by the way i guess my precat is glowing when the car is idleing. Too much fuel i guess. Maybe the grounding problem, too...

satch

iTrader: (1)

I think a glowing cat can also be caused by incorrect timing.

The engine ground is the ground that supplies the ECU. If it is poor then the grounds at the ECU would be in the same boat. You could address this situation by either redoing the ground on the engine manifold, regrounding the four ECU grounds by adding an additional ground to each of the four wires or pulling back the harness tape on the emissions harness as it comes out of the ECU and checking the condition of the staples which combine some of the ground wires as these could be faulty.

Disconnect the plug/connector to the oil pressure sender and clean it as this could prevent the sender from transmitting the proper signal to the gauge. You can ground the single wire to the sender w/key to on and the gauge needle should climb to the top of the range. Do this just briefly to check the viability of the gauge so as to prevent from damaging the gauge itself. If it works and the cleaning of the connector does not work then you likely need a new sender.