Hey all, i've got a S1 RX-7 with the standard 12a N/A. I've just had a new exhaust system installed, i got the car back & it drives but the idle speed is poorly low and sometimes conks out, it also knocks & misfires now which makes the car really jumpy when driving, and it stutters on constant throttle untill i back off. I've taken it to the local rotary mechanic, and he said the carb needed to be rebuilt. After having the carby rebuilt, it still made no difference. I've attatched a few pictures of where the new extractors are, and what looks to be a clamped off air valve?

Can anyone help me?
Any help at all would be great, cheers - Sam

 

Hey welcome to the forum. Firstly, It looks like you don't have any of the hoses connected to the carb that should be. Did the mechanic leave it that way? The clamped off pipe is weird also, not a real big help though, someone else will chime in. If you have no hoses connected to carb either like the idle compensator hose and you will have a bad idle. Sorry, not a big help on the carbs. Check out the faq page, archives and the search button is your friend. God bless

 

Those clamped off hoses are a result of running an aftermarket header, it's also part of removing the rats nest and emissions, check the FAQ for info on that. The after market parts weren't designed for the air injection (for lack of a better word) that the stock systems use to improve emissions performance.

I think knocking is a sign of detonation so you may not want to drive it until you have this problem sorted out, otherwise you'll end up doing a rebuild from destroyed seals.

It sounds to me like whoever did the exhaust didn't know what they were doing and missed something minor that's causing the problem. I've read a couple of times that stuttering and backfire is a result of a vacuum leak somewhere. At this point, you might as well go through the rats nest removal tutorial.

 

Deffinately sounds like a vacuum leak. I wonder if where those pipes are pinched shut if there might be a poor seal. When I isntalled my header, I put in a block off plate where that whole assembly is (of course, mine's a '79 US model, so it may be different). Also, if those blue tubes into the air box are inside the diameter of the filter, you might want to block those off to prevent sucking crap into your engine.

 

Your mechanic is hack to do that kind of work piching off the air tubes. Get a proper block off plate and then check for vacuum leaks. I make my own block off plates out of 1/4" aluminum.

 

Did your mechanic do the rebuild on the carb?

 

Hey guys, thanks for your replys. The exhaust shop guy is the one that pinched off those air tubes (he also had to remove the intake manifold to fit the new headers). As soon as i got it back from theexhaust shop it was running badly. The rotary mechanic did rebuild the carb yes, and it made no difference whatsoever. Any ideas on what it may be?

 

Vacuum leak. Either the intake manifold is not sealed correctly or there is a leak around the carb.
Recommend spraying carb cleaner around until you find it.

Also recommend that you go back thru and verify all vacuum hoses are routed correctly.

 

Well i just got it back from the mechanics, and guess what the problem was? A vacuum leak! Also the o-rings had cracked, so they have been replaced along with everything properly sealed and a rebuilt carby. It runs way smoother now! Thanks guys so much for all the help, come say g'day if you ever visit South Australia!

Cheers - Sam

 

They should be ashamed of themselves for not replacing those o rings when they pulled the intake manifold off in the first place...

 

I wouldn't be too harsh on the exhaust guy, he's not a mechanic and probably didn't know about what was required to reseal properly. Whoever he got the intake gasket from should of supplied him with the o'rings or told him about them.

Now, your mechanic is another story. They all too often jump on the bandwagon when there is a idle issue that the carb is the source of the problem. And after he made his generic statement that it was the cause and rebuilt it. If it was not the problem he should of found the problem for free and fixed it. Put that's just my opinion and all the years in the Automotive field.