Lack of power (most of the time)
 

Hi there,
I have 1989 FC3S Turbo II which I bought a year ago but haven't had much time to work in it, since it needs some body work - nevertheless the car seems to have a good engine, but some weeks ago I decided to compare it with an Audi A3 (turbo diesel engine) with around 160 bhp and I couldn't pass him.

There's a bridge on that road, going uphill where I usually take a look at the speedometer and I couldn't believe I was going so slow (140 km/h) which is slower than a 150bph Alfa Romeo I had.

Well (I though) the engine lost it's power, or there's a turbo issue with this baby...

After 3 or 4 passes I stopped the car for about 30 minutes and after chatting with that friend (who actually owns half of the RX7), I went back home and suddently I noticed that the car was delivering more power. A lot more!

I drove again on the same road and the car was FAST then. Under that bridge I got 180km/h and I can tell you, those 200bhp were definitively there!



So now I'm wondering what that could be. I had some problems with idling, and it was a spring that pulls back the accelerator cable which is located under the intercooler. That was fixed. When engine starts, it goes as normal, to 3000 rpm, and then drops but on the first few miles it still idles high as 2000rpm. Then when it's warm, it gets normal idling.

What kind of thing can take away such amont of power? It doesn't look like a turbo issue, but on the other hand, when I'm driving at full acceleration, sometimes the rpms go up a bit then get to normal, just like if the clutch is slippering... can it be that - i don't think it is the cause of the problem...

Can it be the TPS?

Or the air measure unit?

My friend got fed up about the car's power and he wants to sell it, but I think this is probably a very small issue and easy to fix, so I am asking for your help!!!

Sounds like the engine needs a tune-up. You can download the Factory Service Manual. Go through the Fuel&Emissions section of the FSM; there's a troubleshooting section that can get you pointed in the right direction. Don't forget to change fluids and filters if that hasn't already been done.

Well, I gave a look at the Factory Service Manual, and as I am not very used with "messing up" with engines I got a little afraid of doing things wrong. When I bought the car there were some things I changed: oil and oil filter, radiator fluid, brake pads, air filter... The only thing I think I may have missed was the fuel filter but I am not really sure about that.

I guess the problem is the same that causes the rpms to be a bit inconsistent. When engine is not yet at operating temperature, the rpm goes to 2000, and even when engine is hot, it doesn't always behave the same: sometimes the rpms are around 1000, sometimes 1500rpm and sometimes going up and down between both. Maybe the cable that sits below the intercooler, but I can't guess if it's that.

Yesterday I noticed that when I fully press the accelerator there's a whistle probably from the turbo but the rpms don't go up immediately (turbo lag maybe) - and the strange thing: rpms go up a bit, then go down by 100, 200rpms maybe and only then they start climbing until the redline. I can almost bet that it's a cable or electric stuff but I don't know where to begin... and I don't want to spend too much money before being sure it has nothing to do with the engine!!... in Portugal I guess theres isn't a single mechanic who can rebuild a wankel engine... unfortunately :-( (oh yeah, and the same apply to Mazda dealers!! they just don't know how to...!!! - unbelievable isn't it?)

Hell, good Wankel engine techs are hard to come by even in the states!

I am just lucky I live 15 minutes from Rotary Performance. :)

I do most of the work on my car myself, but sometimes I just don't want to and would rather pay.

You could have some poor electrical grounds, possibly a clogged catalytic converter. If you gained a lot of power though I wonder if you blew out your clogged cat so it's now less restrictive.

About the RPM issue, I'd bet it's your clutch slipping and not an electrical problem.

Really good thing to do once in a while and ESPECIALLY right after you buy the car is check it for vacuum leaks. Don't dick around with spraying flammables anywhere around the engine, get one of these, it's by far the best way (if you have access to an air compressor).
http://boostpro.net/prodtester.html

\/\/\/ this is the one you'd want, you can stick it in the turbo inlet duct.
Single Pop (Gauged)
With Male Compressor Coupler
$20 + $4.60 shipping

The weird thing is that once, and only once I felt that the car had the right power. Is not normal to be beaten (or almost) in a straight line by a diesel engine that would make at most, 170 hp.

The situation is this: I have driven that car about 15 times, and only in of of those 15 times the car had power as I think it should have. It would be, let me say, on the 14th time, but after that, the car got back to the usual "underpowered" thing. Those revs are not climbing up fast, no easy rear wheel spin... nothing.

Do you think that there could be a clogged catalytic converter? it's kinda weird that, only once the car had a different (good) behaviour and then got back to (not) normal.

Going to check that fuel filter and try to find the vacuum leaks - but I still suspect that it has something to do with those unstable engine RPMs...

By the way, can't i try to figure out the leaks by using some kind of baby powder? I guess this could sound stupid but as my friend wants to sell the car I don't want to be spending money in buying a vacuum tester because if that's not the cause I won't have any use for it.

Thank you once again !!!

Sounds like a possibility.

Check out the set of secondary throttle plates.

The outter ones should go full open. The inner secondary ones open with a bit of a delay.

The delay is caused by the Black cam/damper.

If the cam and damper are not in good shape and binding that could cause the secondary inner to not open all the way. Not opening causes..........loss of power.

I had this problem when the black cams cracked and finally fell apart. The black cams plasctic is riveted on the last time I looked.

This outfit is located on the front side of the throttle body. Look for the damper with its piston resting on a thin black cam outfit.

Do you understand what I'm talking about? IF not, write and say so and I'll try once more.

Hey there. It's a nice piece of advice. I don't know exactly what this means since as I said, I'm not very used to deal with engines (but I like them a lot so i always like to learn!) - what i am going to do is to take a good look at the service manual and discover where the black cam / damper is. Only thing is that i am not American and sometimes you give slightly different names (or abbreviations) from the user manual. I will check it out anyway since I'd really like to learn a bit more. Hope i can give you feedback soon, and meanwhile if you can help me by using the service manual, it should be on Fuel and Emission Control Systems section (4) around F2-34, F2-35 or something...

This is a side view of the throttle body. Notice the double butterfly valves on the bottom, there is another set just like it behind them and the two sets are linked. Hailers sounds like he might be on to something, I would definitely check that out.

http://fc3spro.com/TECH/HOWTO/TBM/tb09.jpg

A cam? plastic? Hell maybe mine is gone. On my S5 there is a metal "ear" that engages the secondary throttle plates at a certain point. If there is supposed to be a piece of plastic on that thing, let me know so I can fix it.

See the attached jpgs. You might follow the words on the jpgs.

When the black plastic cracks and falls off............all that is left is the metal plate and that's not good enough. I had the plastic crack and hold the throttle wide open. Not really a good way to drive down the hwy. It jammed the throttle linkage. Prior to that I'd had problem similar to the thread owner. So I messed with the damper setting and probably screwed it tooooo much which caused my black plastic cam failure.

Wired the item open as shown in the jpg and the lack of power problem disappeared altogether. The suckers had been jamming shut and not opening except when they felt like it.

Goofy answer but the secondarys not opening was my lack of power periodically.

A lot of people remove the secondary set of plates anyway... can't remember if I've done this yet, I should if I haven't. If you want to do it though SEARCH first, there are pros and cons to doing it.

The inner set can hang up if the cam/dashpot etc are ??? corrupt. Not only the outter set.

That's what the cam/dashpot are all about...........delaying the opening of the secondary inner set of plates.

Well, even not knowing if i will discover the trouble with this operation, i can't thank you enough for trying to help!
Tonight I hope I will have some time to go to the garage and give it a try. Not really sure how much time it will take me to get to the inner of the throttle body but the car is parked so i can do this with enough time. I'm looking forward to give you an input really soon!

Hmmm, I have no cam, it's all done with linkage. Is the plastic cam S4 only?

Edit: Nevermind, I am thinking of the actually secondary throttle plates. I don't have the "engine cold" restrictors to even worry about.

With a huge lack of time, I only removed the intercooler yet (well, not fully removed - still have some pipes attached. As far as I know, the throtle body is below the intercooler, but it's still in the middle of a huge amount of cables and other stuff. I'm not sure if I feel comfortable to open it. Do I have to fully remove it before opening? Or is it possible to take a look at those butterflies without removing the whole body from the car?
I know this may sound a bit silly but i am not very used to work with engines (you see, my daily work with computers doesn't give me much space to really be a car mechanical !)...

All you really need to do is remove the large black intake tube running to the throttle body from the air box. This will give you a birds eye view of the throttle plates just like in the pics provided in this thread.

Well after all, today I checked the engine and saw that one of the sparks didn't had the cap right in place. Tried the car after that and well, I kinda discovered the root of the problem: clutch. I picked up my mobile to shoot a small movie and pressed the pedal when running in 4th gear at around 3000 rpm. It was the end of that clutch. Had to drive home carefully and now I really feel that I'm in trouble now because it's an expensive repair...