TypeSL_T

Today as I was getting on to the interstate, I was changing gears between 3rd and 4th and it started to backfire as if I had just started it and ran it up to 7k and just let the throttle pedal go. My gauges all looked fine so I did not worry about it, but when I got to my exit about 6 miles away, I stopped and my car idled WAY high, just like I had my choke out. I checked but of course I didn't and that was when I started to smell a horrible burning smell. Unlike any of the other burning smells I have encountered. I turned the car off, but it didn't necessarily want to turn off, but eventually did. I then started it back up and proceeded to drive it home because I was only 3 minutes away. I parked it and let it idle while I popped the hood and walked around it. Everything looked and sounded ok except it was still idling really high (1800-2000rpm). And then I started hearing a wooshing noise coming from the exhaust pipe, which I found out were fireballs shooting out of my pipe. I turned the car off and THEN it started to smoke like it was on fire. I looked under the car and the cat was the brightest color orange I have ever seen and smoke was coming off of it like it was on fire, but it wasn't. Any ideas?

It is an all stock 1983 12a. I have done nothing to the car except regular maintence which was done about 2 months ago. Not quite time for my oil change. The car has 51000 miles on it. Any other info you need let me know. I have seen this happen before in the video where they run the 2nd gen and it just starts burning the back bumper.

James

85 FB

Sounds like a classic case of backed up/clogged catalytic converter. I've heard many a horror story about those things getting clogged and glowing a bright orange. On a 2nd Gen, a guy had a similar problem of a glowing orange catalytic but turned out it was his fuel pressure regulator. I'm not sure how to check a clogged cat other than just having it replaced. Any other reasons why, I cannot offer as I have no prior experience with 12As. Hope this little bit of info helps.

MattG

iTrader: (2)

You need a new cat, it is clogged! No biggy, just anohter great part of owning a 7!

85 FB

Yes, welcome to the club! You'll get used to it sucking your wallet dry. My most recent repair bill (two days ago) was $927. No matter what I'm originally quoted, the price always jumps. Oh well, I'm just glad to have my 7 back. Hopefully, it won't cost you that much just to replace a catalytic.

WARNING: Purchasing, owning, and driving an SA/FB is extremely addictive. Be sure to consume in high doses until satisfaction is reached. After complete satisfaction, continue to consume the rotary goodness.

Rfarrow2005

LOL i love the warning.

TypeSL_T

I would have to agree with the warning. Would the clogged cat cause my idle to run high?

MattG

iTrader: (2)

I dont see why it would, but I havent had a cat in so long I couldnt tell ya.

Here is one with only a 1000 miles on it for 60
https://www.rx7club.com/showthread.php?t=521181

Found it while I was looking for a stock carb, I just just read your thread, so id figure id share with ya

BTW: is that Murfreesboro TENN? By any chance?

Kentetsu

No, I don't believe that it would. Start by verifying that you still have spark on your lower (leading) spark plugs. If that checks out, post back and we can go from there. When's the last time that you checked your timing? Is there any chance that your distributor is loose enough that it could have turned a little and self adjusted the timing? A sudden advance in timing will increase your idle speed and heat up your exhaust system in a hurry....

cdrad51

Actually, retarded, not advanced ignition is what will cause a glowing exhaust. And no leading ignition would create the same effect since trailing ignition only is the equivalent of a very retarded ignition. It would definitely create backfiring too.

I don't know about the timing though. Retarded ignition wouldn't raise the idle, but advancing it would not make it idle at 1800-2000 rpm either.

Kentetsu

Good catch man. I meant retarded would heat the exhaust, but advance would increase the idle some... How about a big vacuum leak?

cdrad51

A big vacuum leak would only make it a rough idle. But it'd be hard to tell if there is a vacuum leak with a 2k rpm idle - that's just out of the carb's idle circuit range.

TypeSL_T

I heard that the carb may need a rebuild because 2 of the 4 barrels could be stuck open. I am not with the car right now, so I can't go look at it. I am trying to get my other car running so that I have a means of transportation. Could the carb be the problem?

85 FB

Perhaps, if they're stuck open.

Rx7carl

Agreed with you guys. Since it happened all of a sudden I'd check that the ignition sys is functioning as a starting point. Put a timing light on all 4 plug wires and see that your getting spark. Also your carb could be flooding (not likely with the symptoms, but easy to check). Shine a light in the barrels and see if either pair are open, and check float levels on the windows on the front and rear of the carb.

Clogged cats usually show a big drop in power.

cdrad51

On the sudden high idle, the only thing I can think of is either a) your hot start assist went completely nuts or b) the throtle linkage is binding somewhere. Follow the 4 cables that go into the carb throtle linkage and make sure none of them is stuck for some reason. If one of them is stuck, my bet would be the choke's. In that case of course, the choke's butterflies would be partially closed, making the mixture too rich, and thus maybe causing some of the symptoms you describe.

I would check on the above after checking ignition.