Hello! I just recently purchased a '93 RX-7 touring (with R1 spoiler added) with only 47k miles for $17.5k. It's in really good shape on the outside. Its black paint is nearly flawless.



I have had a couple of mechanics look at it, and they say that it is A-OK (needs only a few minor fixes - thermostat, oil metering pump, the usual). However, it seems to idle kinda rough, especially during a morning cold start, or when it gets down close to 750 rpm. When it's idling at around 900-1200 rpm with the AC and/or lights on (after warmup), it seems smooth.



It also often lets out one really mild, muffled "poof" from the exhaust when I shut it off.



One mechanic who recently tuned it up said it probably just needed to be driven on the freeway for a bit before it smoothed itself out, since it was in storage on and off for several months. He also happened to find some water in the fuel filter (common for a car that's been sitting).



So, per his advice, I've been adding ISO-Heet gas dryer to the tank during recent fillups to get the water out....



Still, I've put about 1500 miles on the car now, and it hasn't really improved.



Are these cars known to idle rough normally? What should I expect and/or what can I do?



Thanks in advance for any info!

How old is the gas?

Just filled up this weekend (I've filled up several times since buying the car)....

how are the spark plugs and wires ?

Just had the plugs and wires replaced

i'm gonna say a solenoid or check valve has gone bad. best bet is to take it to rotary specialist. luckily in cali you have a ton!



http://www.mazdatrix.com



http://www.rx7fashion.com



a few more if need be

Those are pretty easy fixes, no?

How does it drive?

Those shops are both in Southern CA, and Mazdatrix is ALWAYS backed up. He'd probably have to wait over a month just to get an appointment.

It drive just fine. It's got the typical 3k RPM hesitation occasionally, but it feels pretty healthy (everyone who's driven it says so).



As far as shops, I've been talking to the guys at Mazda Masters in Sunnyvala, CA a lot.

Does a check valve or solenoid cost lots to fix, and does it tak much time?

It depends on which one it is, but it's pretty straightforward.

Okay. I'll have the Mazda Masters guys take a look and tell me what they think, and let them know about the check valve and solenoid possibility you mentioned....



So far, everybody keeps telling me it's fine and just needs to be driven, but I'm afraid to keep putting miles on it if turns out there is something wrong. Tough situation.



Oh, and sometimes I need to give it a little gas to get it started... Not sure if that's related to the other stuff.....

If it had bad gas in it originally you might want to think about having your injectors cleaned. This may solve your problem.

Yeah, I've been thinking about that, but the Mazda Masters guys said that sending them out to get cleaned gan be risky, because some places may clean them thoroughly, but they may wind up causing leaks a few miles down the road.....



Plus, he said it can be expensive to take them out and put them back in, and could be only worth it in case they need replacing....

try runnin redline fuel additive for the next couple of fills and run her hard....

I had my injectors out and new o rings all round after one sprang a leak.

Must have been easy enough as it was all done (by the workshop) in a few hours.

I did try running Techron concentrate through the system a couple of weeks ago (of course, I also had a gas dryer in there at the time)....



Would it hurt the car to run more fuel additive through there?



I have a bottle of octane boost, which is supposedly OK to run at every fillup....



Should I try redline, even though I already tried Techron?

That sounds like a bunch of crap to me.

Give it a little gas on start-up...when my engine blew...it did that...



CRAZY idea, but have you checked the compression?

i think it might be time to ATF the engine !

I second that...atf...The engine may be carbon locked due to it sitting for so long https://www.nopistons.com/forums/pub...DIR#>/wink.png

I had what may be the same problem. The cure for me was as simple as replacing the oxygen sensor (about 25 bucks at Autozone, about 225 from Mazda.) That was 5 years ago, and smooth as silk ever since. Good luck!

Compression check comes out fine. Hydrocarbon check in coolant comes out fine...



Just noticed something else... When I turn on the AC full-blast, the bad idle smoothes out completely (and not just due to the increase in RPMs - I checked that).



Any ideas?

Okay, at least we're dealing with a good engine. Have you tried adjusting the throttle at all? I did that this weekend and it made a world of difference in idle.

Yeah, adjusting the throttle body can sometimes help alot.

Is the O2 sensor even doing anything at idle? A friend of mine mentioned that typically O2 sensors are not really doing anything until the car is moving?



Would the O2 sensor actually affect the idle on an RX7?



Man, today it started up rough, and it's been running rough all day. I had a guy check the idle and mixture, and everything looks fine.



Every time I turn it on after it's warm, it kinda goes "va-va-va vroom" instead of smoothly getting up to idle speed.



Sheesh, this is getting frustrating. <_<

just stick w/ it. one you solve this problem u wont be able to stop smiling, Esp. since ur driving a 3rd gen. Keep Ur Head Up

Is the O2 sensor even doing anything at idle? A friend of mine mentioned that typically O2 sensors are not really doing anything until the car is moving?



Would the O2 sensor actually affect the idle on an RX7?



Man, today it started up rough, and it's been running rough all day. I had a guy check the idle and mixture, and everything looks fine.



Every time I turn it on after it's warm, it kinda goes "va-va-va vroom" instead of smoothly getting up to idle speed.



Sheesh, this is getting frustrating. <_<[/quote]

The ECU uses O2 sensor input at idle and cruise conditions for fuel economy purposes.

God I want to get this fixed. What exactly are the other symptoms of leaky or bad injectors? What about a bad O2 sensor? Does it show up in exhaust mixture? This was checked and looks good. What about a vacuum leak or bad seals (apart from the obvious smoking)? Shouldn't this be ruled out by a hydrocarbon check and a compression check?



So what's left that it could be? Dingy coils? Bad grounds? Man, you'd figure that at least one of the 2 mechanics would've picked something like that up, especially since 1 is an "RX-7 expert."



Is it possible that I'm just stuck with a car that idles and starts sloppy? That would suck.

Leaky injectors will usually cause flooding and hard starting. A bad O2 sensor may hurt your throttle response and make you run rich at idle. A vacuum leak could be the culprit, but it will take a good once over to find it.

especially being a 3rd gen isn't it quite possible that a vacuum line popped off. I've heard that's a common problem on the FD's, positive intake manifold pressure popping vacum lines off and introducing leaks (boost). Isn't there an infamous one that runs under the upper intake that the dealers were always missing which is directly related to the control of the turbos?

Yeah, that's what I'm thinking. If he doesn't figure it out soon I'll be by to check it out. https://www.nopistons.com/forums/pub...DIR#>/wink.png