You can have all the required sounds but have uneven compression on 2 of the faces. This is why I don't recommend this test, but do recommend using a piston compression tester. Your test will show you if you have a really bad failure on a rotor, but it won't let you know if you have damage, but just not a complete seal failure.

 

So, it is ok to start the car then (for, say, a compression test)? Are there any precautions I should take?

 

Nope. If the motor is already damaged, doing a compression test isn't going to really make anything worse or better. If it's not, you'll just get confirmation that its not. That doesn't mean it won't be low compression. Generally, if you have shaking at the idle, you'll have compression on all 3 faces, but two of them will be lower (i.e. exposed to each other).

 

Great thanks! I'll definitely report back if any of the suggested answers work out. Well, frankly, I'll report back either way.

 

I suppose the experience can vary from blown motor to blown motor, but when I blew an apex seal, the only sign was a loping idle--flub flub-flub flub. At normal driving rpms, the engine ran smooth, just down on power. So if the engine is shaking at higher rpms, you may be talking about a different issue than a blown motor. I'm thinking ignition as someone suggested or a motor mount as someone else suggested. But if everything else checks out, definitely do a compression test.

 

You don't start it for a compression check, you just use the starter to crank it to get the readings.

Dave

 

Great thanks again, guys. I think the first step is taking it to GroundZero and letting them give me some input since they have the lifts/tools that I don't have.

 

check your O2 sensor...

 

I just had it replaced a couple weeks ago. Maybe a faulty one? How would the O2 sensor cause the symptoms? I'm pretty ignorant.


Also, one thing I forgot to mention is that my car has been hesitating for the last few weeks (kind of like the 3k hesitation, but at different RPM). It particularly seems to dislike slow (and no) constant acceleration. As if erratic throttle prevents the hesitation. Perhaps the things are related?

 

Might be throttle position sensor out of adjustment...

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/fixed-my-idle-problems-backfiring-bucking-more-170731/

Dave

 

Ok, so I've gathered a little more information about my car's symptoms.

First, when I started the car, it seemed like it had a little bit of trouble. It's hard to explain, but it wasn't like it was turning over and not catching. It was more like it started up right away, but had difficulty getting up to idle (it was a smooth climb, but seemed labored).

Second, the idle was a little high, but constant for the short time I watched it (it certainly wasn't choppy). I started the car in first in the attempt to bypass the 3k, and it was idling at 1100 RPM.

Finally, the engine does seem to be shaking more than normal (I can honestly say I never made a mental note of engine shakeage). In fact, while idling, the engine shake was causing my door to shake as well. I don't know if any internal engine issues would cause any shake.

I used my digital camera to try to capture some of the engine's motion, but I don't know how well it comes through on the video.

http://s124.photobucket.com/albums/p...rrent=RX-7.flv

And the engine noise at the beginning of the clip is from a passing truck, not my car. Only the last 2 seconds or so are my idle sound.

It is definitely a strange issue, and I'm probably going to have to go get the compression tester tomorrow.

 

In my experience, engine shake usually equals broken apex seal . I hope your compression check comes out ok.....a longer video letting us hear the exhaust note (with no trucks tearing down your street, lol) would be helpful.

 

Hah... yea... stupid truck. I didn't even realize it had ruined the video until I got home and watched it.

I have to agree... after doing a lot of forum reading here, engine shake is not the good news I was looking for. It is indeed a sad day. I will post with any compression results I get.

But... in the meantime, it seems really coincidental to me that I JUST had my check engine light go off (we assumed due to a faulty O2 sensor, which I got replaced) and then a couple weeks later -- POP. My question is, since the 'Feedback system' code can indicate a lean mixture, is it possible that I was getting a warning of the impending doom ahead of time? Perhaps it wasn't the O2 sensor at all?

Well, I'm just trying to reconstruct the 'what went wrong' of this engine since (supposedly) it was just a teenager still.

 

Check engine light and engine failure are not really related in these cars.

 

Heh, well the way these things fall apart all the time, it's a good thing one doesn't imply the other.

But I just mean... isn't the Feedback System code indicative of either a) a bad O2 sensor OR b) the car running lean/rich? Maybe I misunderstood it. But I thought lean RX-7 = boom.

 

On most cars a bad O2-sensor will cause the engine to run too RICH, which is sort of a fail-safe.

I don't know if the FD does that as well. Anyone ?

Good luck,

:-) neil

 

You can also tell just by cranking the motor over and listening to the pulses, if they sound even and uniform, then the motor is most likely ok. If it skips eradict, then you most likely have a blown seal. Just a quick test.

 

Unless you know 'exactly' what you are listening for (i.e. you work on a lot of cars/engines so you can tell the good from the bad), that test isn't going to help. For 99% of the people on this forum, that test just isn't going to be conclusive.

 

to an untrained ear, it shouldnt be too hard, but its worth a try.

pull your EGI relay off (yellow relay next to your battery, box says EGI MAIN)

You want to have your window open or something so that you can hear your starter. Also, have someone at your exhaust pipe if you can, so they can hear the "pulsing".

Turn your car over, and make sure the pulsing is consistent. it should sound like put put put put put put. if you hear a put put put swoosh swoosh put from the exhaust pipe, then you most likely have a bad apex seal. It will probably be hard to tell, but like i said, the main thing you are looking for is consistency of the pulsing sound of your starter and coming from your exhaust.

Your starter makes a higher pitch noise when there is no (or very low) compression.

A compression check would be the definitive answer though.

 

Hah... it's a good thing I can have a sense of humor about this whole situation...

I went to take my car to get the compression test (the shop is literally about a 10 second walk from where my car came to rest), and the damn thing won't even start now! It wasn't turning over, but it also seemed to try a bit (I've had a completely dead battery and it wasn't like that). It was a click, and it almost seemed like the engine was caught on something. Starter perhaps?

So now, I'm paying for .5 hr labor and hoping a mechanic can get it started and THEN get a compression test.

 

^ bummer....it will be worth it to know that there is compression.....or no compression. hopefully, for the sake of your wallet there is. good luck!

 

Well, they couldn't get it running to go test the compression (I don't think... more on this later). As I thought, the mechanic said the starter was no good (just grrrrreat timing, really). When I spoke to the guy who schedules appointments and talks with the mechanics (he seems more like a mechanic than just a suit), he said that since they couldn't get the car running, they didn't do the compression test, but that the mechanic was convinced by the sound of the motor trying to run that in fact it was blown.

But let me quote part of the invoice:


Which makes it sound like they did a compression test.

Oh well... my fears are confirmed. I look forward to the fresh start I'll get with a new motor (who knows when that will be unfortunately).

Thanks for all the responses guys.

Fd2blk is going into observer mode once again.