ozman08

I have an 88 fc convertible that i picked up a while ago. It has 220,000 miles and i bought it used with this mileage. Old guy treated it as a normal car(honda, ford, toyota, etc.). the only maintenance he did was oil changes, and his last was with synthetic which ate up the gunk and destroyed the original seals, gaskets and hoses. I replaced most of the parts and inspected the others. A line from the engine to the tranny fell off(screws to bottom driver side) and it wont go back on(fell off while driving). I recently did a catless performance exhaust and the car was beasty for 2 weeks befor i hit overheating problems. found some new leeks took care of it. I found out that the mass airflow was no good so i removed it and replaced the whole system with a high flow cold air system.

So this leaves us with my new and current problem and some questions. It starts and revs to 5k rpm and then dies. What can be causing it? Can anyone help me with this problem? And finally, Do i need a mass airflow sensor and does that hose to the tranny have to be installed? Any and all help will be much appreciated and i like my rx very much and dont wanna have to get rid of it. Also, i never messed with the timing on the engine in any way so i know this has nothing to do with that.

RotaryRocket88

iTrader: (7)

Well, it's never supposed to rev up to 5k RPM on startup. 3K RPM when cold, yes, but not 5k. If it's going that high, you've probably got a big vacuum leak. If not a vacuum leak, a bad AFM (air flow meter) can also cause a similar problem, since it contains a fuel pump switch. Are you sure the "new" one is any good? The FSM has some resistance values you can compare to test it.

For your other questions:

1) Yes, you have to use the AFM. If you remove it, the engine will run horribly.

2) What is this line on the transmission you're talking about? Is this an automatic? On a manual transmission, there are only a few things connected to it: 2-3 sets of wires for switches & the speedometer cable.

Another thing for you to consider with a catless exhaust, is that the aux. ports will no longer be functional. Exhaust pressure normally opens these at ~3800RPM, and contributes to a lot of the engine's top-end. Without them working, you're down about 25hp. You can read up on the ports and the AFM on this site:

http://mazdarx7.iougs.com/intakeair.shtml

ozman08

about the exhaust part, i took the vehicle to a rotary only shop and the mechanic said that catless is best and that the setup will give a total of 45hp. his dyno sheet showed an increase of about 32hp for my car.
And as for the afm, i removed it completely, so if i replace that, will that take care of my problems.

RotaryRocket88

iTrader: (7)

Well, opening up the exhaust will produce hp gains (though 32whp is an extreme claim), but you still need to inspect the aux. port actuators. If someone "wired" them open, you'll have the same top-end, but low-end torque will suffer. But if they're not working at all, then the additional intake ports (it's a 6-port engine) will not be used at all. A common way to actuate them after removing exhaust restrictions is to use an electric air pump & an RPM switch. I used this sort of setup on my old NA engine.

I'm not sure why you thought removing the AFM was ok to do. All fuel calculations are based on measured air volume. Replace it and your problem should magically disappear.

ozman08

the reason i removed the afm was because i pulled it apart to inspect and 2 of the conectors were missing and the others were either busted or corroded. The afm was no good and was giving no signal(no voltage). and i know someone who has a rx(same engine) and no afm on his and it runs just fine. so thats why i thought, but he must of found an override. besides, i didnt have 350 for a new one. as for the hp gain from my exhaust, the gains are true with the header and full setup, but like u said my torque seemed to drop a bit. on take off the car is slow and sluggish, but once i hit 3600rpms, all my torque is back and the vehicle flies. It usually takes a couple seconds to hit 3600rpm but once it does my rpm just flies from 3600 to 8500 like nothing and my shifts are 1st gear at 8300(drops to 3800) and 2nd and 3rd run up just as fast, i believe my total recorded times were 0-20 in 3sec(no bottom end torque/also thats up to 3600rpms.) and 0-57(top of first) is just under 6 where my 0-108(top of third) is at about 12sec. measured them with a stop watch and on a trck my quarter was 13.2 at 117mph. and that was with a really good launch(reved at 2500 before releasing clutch, to help build bottom end torque. but if i wire the aux open, will that take care of my troque prob or what?

RotaryRocket88

iTrader: (7)

Again, your performance claims are impossible. 117mph trap would be in the 12 second range, and an NA convertible is not getting anything better than ~16 seconds. You'd need a lot of nitrous to get into the 13s. And 8500 RPMs, huh? Redline is at 7k, and an S4 NA won't make any power at all beyond that. You're either trying to destroy the engine, or you're just BSing. Either way, I could care less.

Re-read my previous posts. Wiring open the aux. ports causes a LOSS of low-end torque.

There is no "override" for the AFM. The ONLY way to remove it is by using a standalone EMS in place of the stock ECU.

RTRx7

iTrader: (2)

rotaryfreak7

hey guys whats goin on i was not sure how to start a forum for this so yeah. but anyways i got this 7 and it will start for 2 or 3 seconds then it will die sometimes it wont even start some times when it does start it runs pretty bad for those 3 seconds but im getting sparks and its getting fuel but i think the injectors might be bad can i get anyones input on that?? or hear what anyone thinks and answers would be greatly appreciated i have not even gotten to drive it since i bought it thanks alot

Aaron Cake

iTrader: (1)

The RX-7 is a normal car.

Modern synthetic oil does not do this. This was only an issue with very old synthetics that reacted poorly to the gasket material used at the time. Also, rotary engines do not really "gunk up" in their oil passages like piston engines.

Automatic? There is no line from the engine to the transmission in the manuals, and any line from the engine to transmission in the automatic would cause major problems if disconnected.

Big vacuum leak.

Yes.

Take a picture of the hose and post it.

If you have disassembled the AFM, it might now be out of calibration. Just replace it, because you will not be able to get it back into spec.

He is running a full standalone EMS system. Most standalones are run without an AFM.

Your aux ports are not opening, or are wired open, or are sticky.

Bullshit.

Please post in your own topic.

ozman08

rx7's are anything but normal cars. a normall car in the US anyway is a gasoline engine vehicle with pistons(therefor rotary is not normal.) And this is a manual trans and the engine and car is not completely stock(high flow injectors, high density plugs/wires, header and catless race exaust). just found the slip and time in 1/4 is 13.62. AFM is shot(missing and corroded conectors, not giving any signals) And no vaccum leaks with this vehicle. and the line to the trans looks like some kind of hose line about 1/4 inch thick and screws into place on driverside bottom of the tranny. oh yeah, as a lube tech and someone who does research on oil, synthetics were designed to destroy(break up) engine gunk, and the seals on a rx are supposed to be replaced every 50,000 thousand miles according to mazda.