I've got a stock '84 GS. My car was idling poorly (stalling occassionally while stopping). I found a decent sized vacuum leak around the back of the engine, passenger side, and this raised my idle to 1000-1100 rpm or so when fixed. Turning the idle speed screw on the carb does nothing.

Now that the leak is fixed, my car backfires loudly on upshifts whenever I have the choke pulled out even a little bit (raising idle and richening mixture). When fully warmed, it will backfire on WOT shifts. I had the leaking exhaust flanges replaced this weekend, but now it just backfires straight through the muffler instead of through the holes in the exhaust. The exhaust shop said the baffling in my cats and exhaust manifold were blown out and any noise I'm hearing is related to the blown baffles in the manifold.

Is Meineke full of it? How can I solve the backfire blues?

Kev

 

baffles in the manifold??? well sounds like your running rich or exhaust leak but you said u kinda ruled it out or your not getting good enough spark???timing maybe?? check all that. the baffles being blown out sounds normal. if i were you i would go over every inch myself, i dont trust anyone workin on my car unless its a person who specializes in rotarys or has a good rep with them. i dunno maybe im missing some wait for trochoid to reply.

 

Definitely check your timing. Also, have you adjusted your carb with the change in weather? It could be running richer now that the weather has cooled off so much. Check both of those things like Rolf said.

 

The timing has never been touched to my knowledge. In fact, I don't think the PO knew how to to advance/retard it, and neither do I lol. I know piston motors, but rotaries still baffle me at times.

The only thing touched with the carb was when I tried to turn out the idle speed screw to lower the idle, which didn't do anything. The idle mixture screw has that funky emissions cap thingy on it I think. I doubt it would effect backfiring while shifting though??? Wouldn't it still be running on the main circuits for that .2 seconds it drops 1000 rpm or so?

I think I might still have a small vacuum leak somewhere (undetectable with the carb cleaner technique). That would cause the raised idle speed I think.

Kev

 

if you had a proper idle before and now all the sudden you find a vacuum leak, plug it, and the idle raises you KNOW someone fiddled with the idle speed or timing to accomodate.

 

It was idling really low before. Like down to 500 rpm or so when braking. I've heard of small vacuum leaks raising the idle from stock by introducing extra air into the engine. Others have told me the reason I can't lower the idle with the carb is because of a leak somewhere.

Kev

 

do you have a timing light?

 

Yes, of course. Just haven't opened up the Haynes manual to figure out how to time it with the silly leading/trailing set up on these cars.

Kev

 

Anybody else have any suggestions?

Kev

 

UPDATE:

This weekend I checked the timing. Leading is dead on yellow, trailing is dead on red. I again tried to mess with the idle speed screw, but it didn't do anything. I can hear something on the passenger side of the engine compartment clicking. It sounds like a solenoid. The engine has a tiny miss when I hear the clicking noise. I couldn't locate it with a piece of hose as a stephoscope, but I believe it's towards to back of the engine, where the two vaccuum canisters are in the back of the Nikki. It may also be one of the 8000 solonoids on the side of the engine.

Any ideas?

Kev

 

If turning the idle screw does not change the idle, check the tension on the other cables, throttle, choke, hot start and cruise. If those are loose like they should be, then you probably still have a vacuum leak. Make sure you have all the hoses that connect to the air cleaner connected and tight.

 

Anyone have a diagram pic of the nikki showing the location of the cables? The stock Nikki is really hard to work on because of the 8,000,000 hoses and crap around it.

Kev

 

In my sig line is a link to the online FSMs, one of which is the factory carb manual.

 

Ah, right. Thanks Thochoid.

kev