SlickArrow

Hello everyone,



I'd like to start by thanking you for taking the time to read this post. Although I would love the "magic answer" (who doesn't), that is not what I am expecting. All I am hoping for is to be pointed in the right direction by those with much more rotary experience than I.



My Story:



I recently purchased my buddy's 1993 RX-7 (Yellow Mica). She is mostly stock. While I was completely aware of some of her "issues", I knew it was an opportunity, with the right help, to get her running great again.



What I'm looking for:

I'm hoping I can list as much information as possible and hopefully get some direction on what to check etc..



Here's the info:

1993 RX-7

stock motor and tranny

140000 miles on body- engine replaced due to previous owner seeing the RED coolant light, what do they call it?...the "'replace engine light"

slotted brake rotors





Details / History:

- My mechanic did a compression test on the engine and that passed.

- Both turbos were confirmed to spin

- Replaced wires and plugs

- Since the front cat was completely blocked it has been "Hollowed out" and now has a tiny leak. This had restored the power that was missing. ( this was done prior to me, not sure if the leak or hollowed cat is not providing enough back pressure though)



Symptoms I am seeing:



Issue 1) Loss of power (feels like the mixture is not right, like the engine's being flooded with fuel) - Although this symptom is not consistent, to reproduce it, I get on the highway, get her in 5th gear and then slow down to the point where I really should down shift to 4th, but I don't. Then I hit the gas and the engine RPMs actually go down a tiny bit.. This causes the car to "coast" for lack of a better term and begin to slow down. I let up on the accelerator and try to feather the gas. It is inconsistent, but usually the engine will "recover" and then take off like a rocket. The O2 sensor was my first thought, and then I thought of the exhaust leak. I have had the O2 sensor replaced as it was not showing the proper readings. I will be testing her later tonight but wanted to run this by the experts as I certainly am not one.



From how I understand a rotary, it is more dependant upon the back pressure of the exhaust than a piston engine, similar in the way a 2 stroke is.



My question: Could a tiny exhaust leak in the cat produce such an inconsistent and noticable lack of power. Is there a control module that needs to be checked for certain values? BTW: I checked for engine codes and none were found.







Issue 2) When there is any type of significant electrical load on the system, and I have the car in 1st with the clutch down (like when at a red light) the car will begin to drop RPM in a "bouncing way" and eventually stall. (Electrical load such as: rear defroster on, or headlights on, or the heater fan above '2'. ) If I do not have the clutch in and the car in 1st it will not stall. Again, there are no codes in the system, and the engine seems to idle fine when not in gear.



To reproduce, I put the car in gear and at idle I move the fan switch from 2 to 3, as soon as the idle begins to fluctuate and starts to stall I put the swtich back down to 2 and it is fine. Now, as I mentioned, this happens with the rear defroster by itself, or simply with the headlights on at night. (Obviously shutting the headlights off at night while at a red light isn't cool)...



My workaround has been to just not leave it in gear, but this can be troublesome on hills.



On this one, I have no clue.



My question: Any ideas at all?







Sorry for the lack of technical information in this post, but if you can't already tell, I'm not that mechanical.. All repairs are being done by my friend who is a great piston engine dude.



Any suggestions you can provide will be greatly appreciated.



thank you for your time in reading this post.



- J

amp

post some pics of the cym...

quick comment on the precat... their cheap enough these days not to just go grab a downpipe..

your lack of power could be a number of things... from boost leak.. double throttle issue.. to a failing turbo...

grab a boost gauge and monitor the readings and report back...

Signal 2

Agree with amp, remove the gutted pre-cat and get a decent downpipe. Examine your main-cat as well. When the pre-cat collapsed, junk may have gone downstream and plugged that as well.

If you haven't already, put a fresh set of plugs on it, a boost gauge, and downpipe. Check ALL the couplers for leaks, especially the one at the top of your 'Y' pipe leading to the bottom of the intercooler. Run some good fuel system/injector cleaner through it, I like the Chevron stuff myself.

dblboinger

Being relatively new to FD's myself, my first advice is get a copy of the factory service manual. You can also download it at http://www.wankel.net/~krwright/cars/rx7/93_manual.htm , but I'd still get a hard copy too, available at Mazdatrix for around $100. I look everything up in the hard copy, then print off a copy of the pages I need when I do the work. That way the hard copy doesn't get all dirty.



Also check out this link http://www.autosportracetech.com/RX-7/Turb...bleshooting.htm

SlickArrow

Thanks so much for all the suggestions.



I'll throw a boost guage on it and check out what will need to be done to the exhaust system.



I'm assuming you want the results of the boost guage just before, during, and just after I experience the loss of power issue.



thanks again!!

Signal 2

If it helps, here is what you should see as far as a boost pattern. http://www.autosportracetech.com/RX-7/Boos...malBoostPattern

SlickArrow

UPDATE:



OK, so my job leaves me little time during the week to mess with her, so I will be following all of the great suggestions and advice this weekend.



However, as an update to the situtation, this is what happened today on my way to work:



She ran great!



There was no loss of power at any gear. Curioiusly, the stalling issue when stopped and in first gear, at a red light, disappeared as well. In addtion to that, the engine seems to be running and idling much smoother, not like it was before ( Previously when experiencing the issues, it sounds like a 2 stroke idling ).



When idling at a red light this morning and Out-of-gear, she idled between 600 and 700 RPM, when I put her into first while waiting at the red light, she increased to 900 RPM steady as a rock. (Typically, putting her in gear at a stop will make her idle bounce between 1000 RPM and eventually 0, which then stalls her ).



Anyway, this has got me thinking of it possibly being some sort of sensor or faulty control module...



I am sure her "Issues" will return very shortly. I am just adding this info to this post in the event that it may help narrow down the possible causes.



I am still planning on executing the tests and reporting back the results as requested, I just wanted to post an update underscoring the inconsistent behavior.





thanks again for your time and suggestions

GreyGT-C

where are you located? Might get lucky and live near some of the FD savy crowd.....

SlickArrow

nice rex!



North East of the country -> Massachusetts



Hard to find a rotary guru, at least where I've been looking.

SlickArrow

She needs a bath really, really bad, but here are some quick pics. It's overcast here so the pics don't do the paint job justice.. but w/e ..