I have an 85 gs (stock carb and engine) and wanted to see what my issues could be. When in neutral, just idling, I step on the accelerator and when I hit about 4,000 it starts to bog and choke (pedal all the way down). When I let off the pedal (just a touch) it runs fine. Does the same thing under load on the highway, 5th gear, full pedal.

One other issue is backfiring/stumbling when car is taken out of gear and runs down to idle. I've adjusted the idle and fuel mixture 1000 times but to no avail.

The car is slow either way (100 hp stock back in '85 doesnt translate to much now) but I feel that this could be something like a shutter valve, coasting valve, exhaust leak (maybe at manifold?) or possibly the anti afterburn valves.

let me know what you guys think...thanks

 

When was the last time you changed the fuel filter?? This should be an annual event. Amazing what problems it solves...
Stu Aull
80GS
Alaska

 

Changed it about 20k ago...maybe it will help to change it

 

Those stock filters are good for about 5 - 10k miles, depending on the quality of gas and the condition of your tank and lines. Definitely start there.

You can verify the position of the shutter valve by looking at the position of the arm below the carb (driver's side). Not sure which position is open though. But once you figure that out, you can even wire it open for testing purposes.

If that doesn't clear up things, then consider rebuilding the carb.







.

 

I will be changing the fuel filter soon, but as far as anything else goes like backfiring, I may have to replace the exhaust at the manifold. Would an exhaust leak cause this?

 

How many lines are there on the carb? (stock nikki) I believe there is two lines bringing fuel in, but I want to double check.

thanks

 

one supply line, one return.

 

for the mildly ignorant....is the line closer to the left front the supply? as for the return, what does that actually do for the system...other than its name? In other words, what is its purpose?

much appreciated

 

Supply is the larger diameter, return is smaller. A return line is so that the fuel pressure can stay constant under different fuel demands.

 

very good, thanks!

 

Looking at the carb from the driver's side.

LEFT LINE (smaller of the two) is your RETURN (has a check valve in it, if not, it has been removed and ya might want to put it back if your running stock nikki).

RIGHT LINE (larger of the two) is your SUPPLY line.

Hope that helps

 

Exhaust leaks are the most common cause of backfiring. Fresh air enters the system and ignites any unburnt fuel. BANG!

 

An eventful day it was today. Changed the fuel filter, added a 2nd filter near the carb, ran the car for about 15 minutes (got a few miles down the highway) and then lost 50% of what little power I had.....

I figured it was yet another cheap coil gone bad (recently bought factory one to replace a bad one 3 days ago) seeing as how all of a sudden at idle the car was running at about 400 rpm. I unplugged the old coil and this did ABSOLUTELY NOTHING...so either those 2 plugs are shot or its the coil. Limped back on two plugs (surprised I made it) and put in a freshly bought coil....didn't fix the problem much. Changing the plugs tomorrow along with wires.

Told the woman that if I have to replace one more coil or spark plug with this car I will just have to use it for storage (5th and 6th coil and will now be my 5th set of plugs in 3.5 years).

Added bonus for the day...all kinds of smoke coming out by the manifold....at least I know where my backfiring problem is coming from. Has to be unspent gas cuz the plugs are'nt firing.....what a day.

carb has been adjusted real nice....and will be again after plug change...so thats not whats causing my ignition issues.

 

85 gs carbureted...relatively stock. Replaced faulty coil 3 days ago and took the car about 60 miles round trip no problems.

Yesterday...about 5 miles down the road I lost a good amount of engine power...could barely do 50 on the highway and VERY slow when accelerating. So I replaced the other coil, ran it a bit...and the new coil cleaned up the plugs pretty good so I took it out again. 2 miles later something let go and the same problem again.
Maybe a ground for the coils? Maybe a bad plug wire? All I know is I have 4 new plugs and 2 new coils and it seems only one wants to fire at a time.

I'm on my 3rd set of coils and 4th set of plugs in 3.5 years....something is amiss. Any suggestions are helpful...thanks guys

 

Did you check the ignitors?

 

No sir...where are they located?

 

I was able to locate them. I am going to test both of them tomorrow. As for reference, is it worth it to buy new ones or better off with GOOD used ones? For example, $90 used and $160-$190 new. Seems to me that it would be worth it to buy used, maybe even a spare set.

 

as long as they work, used is fine. and i've seen used a lot cheaper than 90 bucks.

 

Figured out my issue....coil wires weren't secured well, needed new connectors. Runs great now, but may consider new ignitors in the future.

thanks guys!

 

moderator please close thread, thanks