Rotary engine help

[cs]

Need a little advice here. I've asked on the RX-7 fourm and thought I would ask here also.

Last week my car decided it didn't want to idle. I mean it runs fine at speed, but once you stop it dies. And it runs rough up to about 1500 RPMs. After that it runs fine. Now I've changed the air filter, put in new plugs and changed the fuel filter. I've added fuel injector cleaner and octane booster to the tank, all to no avail. Now I know that the usual suspects would be a vacum leak, but I ain't found one yet.

So, whatcha say?

Chad

[Mrleft8]

Arthritis. Try glucosimine tablets. :D

[Matt Middleton]

That sounds like a vacuum leak to my amateur ears- they are hard to find. The old hoses can crack and split, but you'd never see the problem. Vacuum hose is pretty cheap, and it may be worth replacing it all just so you can totally eliminate it as the source of your problem, before you move on to the more expensive fixes. And you just might fix the problem in the process. :cool:

Good luck!
Matt

[cs]

Matt you wouldn't believe the number of vacum lines on this thing and than there is all the electronic sensonrs and valves and all that good stuff. Oh, how I long for the days of the simple V8 with the carborated fuel system.

Chad

[Wayne Jeffers]

In the old days, I figured on replacing all the vacuum lines after 5 years. At that point, they were living on borrowed time.

Of course, in those days engines ran hotter so the lines didn't last so long, and there wasn't quite as much vacuum line to replace as there is now.

Wayne

[Matt Middleton]

Hey Chad- I know what you mean. I'm not sure how familiar you are with the twin turbo version, but that engine has something like 72 vacuum lines to operate the valves and other gadgets associated with the sequential operation of the turbos. Can you imagine chasing down a pinhole leak in one of those?!?

Let us know when you have it pegged.

Matt

[Noah]

Another trick that I've heard is using an un-lit propane torch. Move it along the vacuum lines, and when the engine rpm's increase you have found your leak.

But it's good practice to replace all of the vacuum lines with Silicon tubing. I have a turbo Charged 2.3 liter 4 running around 250 hp, and vacuum lines are crucial to to the whole engine. I have replaced all of them, and check them regularly.

All in all, it's pretty easy to do, and well worth it.

Noah

[cs]

The only problem with using these methods to check for a vacum leak is the car has to be able to idle. Right now I can't even get it to idle. It runs fine above 1500 RPM but not below.

Chad

[Noah]

Was it a sudden problem, or gradual?

Any lights on the dash? Do those things have a O2 sensor on the exhaust? That could be shot, but that would probably set off the check engine light.

How about Air Intake Sensor? How does the car measure the amount of air coming into the car? If it is failing it could be causing this problem at low idle. Saying the car has less air than it does...

Generally the air mass meter and the O2 sensor work together. At higher RPM the O2 sensor could be the one taking the readings and the air mass meter isn't used. Or the other way around. I don't really know much about the Rotary's...

Good luck

[cs]

That is the problem, this car has so many sensors, vacum lines, air control valves, by-pass air control valves and the list goes on and on. You could spend a year just tracking it down. I'm scheduled to put her in the shop on Thursday, but I was hoping to fix it before I had to pay somebody. Guess I'll keep looking using your suggestions.

Chad

[Noah]

Well Sheesh, you gotta learn how the darned thing works...Sounds like fun to me. It couldn't be too much more complex than my Saab with the turbo, and it only took me 6 or 8 months to figure that system out...

Noah

[cs]

Two things work agaisn't me taking my time and figuring it out myself.

One it is my primary source of transportation.

Second it takes time away from working on my boats.

Chad

[John Bell]

I onece had an early 80's Toyota that had about a mile of vacuum hoses. When I got fed up with niggling vacuum leaks, I went out and bought a big 'ol spool of hose and spent a 'happy' afternoon replacing each hose one-by-one. It's not that much fun, but not that bad either.

One scary thought: Have you checked your compression lately?

[Matt Middleton]

I'm still thinking like John Bell- go get some hose and spend some quality time with your car. Who knows, maybe your baby is misbehaving to get your attention? ;)

My truck actually has a foam earplug stuffed into the counterbored hole where the idle mixture screw resides- enough air gets sucked past that screw to kill the engine at idle if the hole isn't sealed. Your symptoms sound just like mine, before I found the problem. So that's why I'm guessing it's a vacuum leak.

I wouldn't expect an O2 sensor to be bad, based on your symptoms- cars with 1 wire sensors run off of a preprogrammed map until the exhaust heats the sensor to operating temp, so your car idles without the sensor every time you start. It going bad shouldn't cause a rough idle.

Anyhow, I hope you get it going before Thursday.

Matt

[cs]

John I wouldn't even have a clue about compression on a rotary engine, but I don't think that is it. She still runs like a scalded dog with not blue smoke trail.

As far as ideling when started these cars (by design) idle up to about 2000 grand when starting and than idle themselves down. So it starts fine but dies as it starts to idle down. It takes enough time to idle down that I can get out of the car and adjust the throttle rod under the hood.

Chad

edited to add: It was a sudden problem

[ 09-30-2003, 04:57 PM: Message edited by: cs ]

[Noah]

It still sounds like a vacuum leak, but I also say air mass meter failing.

Good luck and have fun with some new tubing. It will save you problems in the long run anyway.

Noah

[Gary E]

If it's that big of a leak, why not try pulling off and capping each one. Then as you plug in each line the leaker should show up.

Get an American car if that fails.

G

[Oyvind Snibsoer]

Have you checked the other parts of your ignition system, such as the coil?

[High C]

I once had a Hyundai that had a rather large hose that went to something on the fresh air intake side that came off and caused the same symptoms you describe.

If it's a vacuum leak, the mechanic should be able to diagnose it very quickly. But it could take forever to find. Maybe if you get the vacuum diagnosis you could take it home and replace them ALL yourself. Sure sounds like a BIG vacuum leak. Sometimes you can hear the big ones, a loud sucking sound, duh.

Good luck...

[cs]

Originally posted by High C:
Sometimes you can hear the big ones, a loud sucking sound, duh.

Your right I should be able to hear a big vacum leak, but I can't hear any sucking or wheezing. The more I think about it the more I'm convinced that it is something to do with the air control valve or the bypass air control valve. Guess I'll let the mechanic ponder on it awhile.

BTW I got a good mechanic that does not take advantage of you and does outstanding work.

Chad