Th0m4s

I got a RX7 TII S4 from 1988 some weeks ago. It's not really in a perfect condition but the engine is running without any smoke, the coolant isn't leaving it through the gaskets, there is an even compression on al chambers and i didn't find any rust.

There is only a strange problem with my idle, my warm start, when i raise the rpm and put my foot away from the pedal and when i raise the rpm to 5000+.

My RX7 idles quite normal, at least when it comes to rpm, but it's bouncing around a little bit. There's no change in the rpm but the whole car start shaking a bit every few turns. It only does this when the engine is more or less hot.

Second strange thing is cold start works really good. It only needs about 1 sec to start and moves up to round about 2500 rpm for the first few seconds like it should but when I try to start the engine again when it's hot it only starts when i press down the accerlator a bit. Otherwhise it starts, goes up to round about 1000 rpm and stalls immediately.

The third small problem is that the engine starts shaking when it goes back to idle speed. The shaking starts at round about 3000 rpm and won't stop till idle speed. When I rev it up there's no problem from 750 till round about 6000 rpm. From 6000 till 8000 it starts vibrating really fast.

I guess there could be a problem with the fuel injection maybe but i'm really not sure about that. Where should i start searching in your opinion?

There are also 3 little electrical problems.
The oil pressure gauge shows much too low pressure all the time according to the users manual but I don't think it's really that low. It shows 0 at idle speed and round about 2 Bar ( 30 psi) at 4000rpm.
The temperature gauge shows the same strange behavior. It never goes higher than 60°C (140°F). That's only about one third of the gauge.
The fuel gauge isn't showing any fuel at all and the fuel warning light goes on after driving round about 5 min but i guess the probe is simply stuck in the tank.

I guess these are all my problems for the moment. Would be great if you could help me out a bit. Sorry for my English. I guess it's not that good because I'm from Germany but i hope you can understand me.

RotaryRocket88

iTrader: (7)

1) A bouncy idle can be TPS or vacuum leak related.

2) If the engine is shaking at certain RPMs, an engine mount may be broken. The passenger-side mount takes a beating from all of the heat put out by the turbo. It can also be hard to tell if the rubber has separated from the metal, but a well placed jack can see if lifting one side is possible with the mount bolted in place.

3) The low oil pressure could be a damaged front cover o-ring, but it could also just be a false reading from the oil pressure sender. I have yet to see an original sender that will read higher than 45-50 psi above 3000 RPM. The factory spec is about 65-70 psi @ 3000+ RPM, and something like 25 psi at idle.

4) A stock S4 temperature gauge should sit at around the 1/4 mark, which is about 180*F. 1/3 of the way is closer to 200*F, which can be reached on hot days.

5) Your fuel level sender and low fuel sender are probably broken. Removal of the fuel pump assembly would be the only way to check out what's going on back there.

Th0m4s

Thanks for answering. Helped a lot allready. It looks like there's really a broken engine mount.

If the front cover o-ring would be broken wouldn't the oil run out of the engine or into the combustion chamber? Because I didn't recognize any higher oil usage and there's no blue smoke coming out of the exhaust like once when my old car had a broken gasket. Also the engine is completely dry from the outside.

I heard rumors about those strange S4 temperature gauges some time ago but couldn't believe it. It sounded somehow strange because i know no other car that runs with such a low water temperature but I'm relieved to hear that it's really that way.

Only problem left is that I still don't know what's wrong with my hot start. I guess it's not the normal behavior that i have to push down the accerlator a bit in order to keep it alive for the first few seconds.

Could it be that the weird oil pressure and that hot start thing have to do something with a bad mass connection on top of the engine? Because i also got that famous 3800rpm hesitation...